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The Technical and Economic Feasibility of
Siting an Anaerobic Digester at UCD
Luke Martin
A thesis submitted to
University...
i
Abstract
The major research institutions of Ireland have a key role to play in the modernisation of
the country’s infras...
ii
Contents
Abstract.........................................................................................................
iii
3.3.1 Societal Benefits..................................................................................................
iv
6.2 UCD Campus Scenario ..................................................................................................
v
Acknowledgments
I would like to thank all those whose help and support have contributed to this thesis. In
particular, t...
vi
List of Acronyms
Technical Acronyms:
AD Anaerobic Digestion / Anaerobic Digester
BMP Biomethane Potential
BOD Biologica...
vii
Organisational Acronyms:
CER Commission for Energy Regulation
DAFM Department of Agriculture, Food and the Marine
DoEL...
viii
List of Figures
Figure 1: The four stages of anaerobic digestion (Al Seadi et al., 2008)................................
ix
List of Tables
Table 1: Optimum system type for each scenario.............................................................
1
CHAPTER 1
Executive Summary
UCD has the potential to become the Irish centre of excellence for anaerobic
digestion. This...
2
The cost-benefit analysis revealed that the construction of a digester both on the
UCD campus as well as on the Lyons re...
3
CHAPTER 2
Document Overview
2.1 Purpose of this document
The purpose of this document is to present a clear and concise ...
4
popular has suggested that lack of stakeholder and investor awareness in AD coupled
with uncompetitive REFIT rates are k...
5
CHAPTER 3
Background of Anaerobic Digestion
3.1 Anaerobic digestion: the process
Anaerobic Digestion (AD) is a biochemic...
6
Each one of these stages are intrinsically linked however bearing in mind that this
is a biological process, each of the...
7
The most popular reactor type is a single stage tank reactor. In this configuration, all of
these stage occur in the sam...
8
these temperatures year round can reduce the economic feasibility of the plant (Patterson
et al., 2009). In addition the...
9
Hydraulic Retention Time (HRT)
This is the average amount of time that any given substrate resides in the digester. This...
10
adequate compromise to suit both aspects of the mixing regime. Water is sometimes
added to the process to ease mixing.
...
11
3.1.2 Feedstock Characteristics
Upon analysing the parameters of AD it quickly becomes clear that feedstock type
is the...
12
Agricultural residues arising from arable crops, highlighted in green, have slightly higher
methane yields than slurrie...
13
among farmers in particular; is that these requirements are a hindrance and discourage
uptake of the technology (Bywate...
14
suppliers. Of course if a potential investor manages their own waste streams, such as a
farmer or a food processing fac...
15
Figure 3 is depicted from Pöschl et al (2010) and illustrates the distances for which
transport of various feedstocks r...
16
3.1.4 AD Technologies
Figure 4 is a simpler schematic of a typical full-scale biogas plant in Europe. It is included
he...
17
This schematic uses the example of a continuously stirred, single stage tank
reactor usually made from concrete or stee...
18
The biogas can be used for a number of post-production applications. The
simplest application is to burn the gas in a m...
19
3.2 Legislation and Policy
Given the aforementioned potential for AD to contribute to a variety of different areas, it
...
20
Broadly speaking, Kyoto protocol and the EU 20-20-20 targets acted as
precursors to the energy white paper. The Kyoto p...
21
3.2.2 Renewable Energy Feed-In Tariff (REFIT)
This legislation is currently the only major, monetary incentive for an o...
22
3.2.3 Animal By-Products
This legislation is as complex as it is stringent. Granted the size of the Irish
agricultural ...
23
Table 5: Summary of the main regulations from ABP legislation (EC No. 1774/2002)
Waste Type Minimum
Treatment
Constrain...
24
Category 3 wastes are also expected to contribute to the feedstock of the
proposed AD in all scenarios of this study. T...
25
3.2.4 Nitrates Directive: Directive 91/676/EEC
This directive was conceived in an effort to minimize pollution to water...
26
3.2.5 National Waste Management Policy
Council directive 1991/156/EC was essentially the beginning of reform of
Europe’...
27
With higher levels of OFMSW being diverted from landfill, technologies such as
composting and AD, along with thermal tr...
28
 Landfill levy: S.I. No 194 of 2013 amended the landfill levy from €65 per tonne
to €75 per tonne from 1 July 2013 fur...
29
Table 7: Cost of waste permits for a bio-degradable waste facility
Intake per year Application fee
Class 11 (Part II) <...
30
3.3 Advantages of Anaerobic Digestion
It is important to realise that anaerobic digestion will never contribute to the ...
31
Achievement of 2020 Targets
Looking at the more immediate future, Ireland is expected to fall short of its 2020
renewab...
32
3.3.2 Agronomic Benefits
Slurry Management
Under the nitrates directive, farmers are obliged to have storage capacities...
33
3.4 Barriers to AD
3.4.1 Complex Legislation
Section 3.2 highlighted the fact that in order to get an AD project off th...
34
few kilometres North in Co. Down. The DCENR must assign tariffs that are at least in
line with the rest of Europe.
3.4....
35
3.5 Vision for Ireland
Ireland currently meets its energy requirements by importing in foreign oil and
gas, burning it ...
36
the right incentives were in place, the private sector fabricated technologies to take
advantage of them. Wholesale upt...
37
The key question is how can Ireland realise this vision of implementing AD in a
way that benefits its surrounding commu...
38
project and apply it to anaerobic digestion. Such a project can allow stakeholders to gain
a direct insight into the te...
39
CHAPTER 4
Objectives and Outcomes
The fundamental objective of this project is to determine whether it is feasible unde...
40
general public could be coaxed into engagement with this industry within the cosy
confines of the campus in Belfield.
T...
41
CHAPTER 5
Scope and Methodology
5.1 Methodology
This study was carried out in accordance with the prescribed methods
re...
42
per kilowatt data for these case studies allowed an appropriate figure be assigned to any
given biogas scenario for UCD...
43
Upon compiling all this data; the results suggested that the economies of scale
could be improved even more. The possib...
44
5.1.5 General Business Costs
The smaller scale scenarios, utilising indigenous wastes were considered to be
rather easy...
45
5.4 Assumptions
Despite minimal correspondence from the appropriate agencies, for the most part, it was
possible to “re...
46
CHAPTER 6
Cost-Benefit Analysis
6.1 Rationale of Inputs
6.1.1 Investment Costs
Table 9 summarizes the capital costs of ...
47
Table 9: Economics of biogas plants in UK, Germany, Denmark and Ireland
Facility Feedstock
(t/d)
Output
(kW)
Capital Co...
48
Table 10: Break-down of investment costs for each scenario
Break-down Method of Estimation
Overall Capital Cost 5500-75...
49
Table 11: Characteristics of feedstocks considered for every scenario
Feedstock Quantity (t/a) Biogas Yield
(m³/t)
Dry ...
50
competitive gate fee to entice the company into cooperation. Tipping fees were set at 80
€/t in this scenario. Digestat...
MSc_Thesis_Luke Martin
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  1. 1. The Technical and Economic Feasibility of Siting an Anaerobic Digester at UCD Luke Martin A thesis submitted to University College Dublin in fulfilment of the requirements for the degree of Master of Science College of Engineering and Architecture School of Biosystems and Food Engineering Supervisor: Dr Kevin P McDonnell Head of School: Prof Colm P O’Donnell August 2015
  2. 2. i Abstract The major research institutions of Ireland have a key role to play in the modernisation of the country’s infrastructure. Piloting an innovative renewable technology such as an anaerobic digester at UCD will have a combined effect of determining the feasibility of the technology whist simultaneously providing a template for prospective commercial stakeholders to assess. A technical and economic feasibility study carried out on anaerobic digestion discovered that the construction of a digester at UCD is not only feasible but is also a financially attractive investment. Projected payback periods were estimated at 5 years for the campus scenario and 8.5 years for the Lyons estate scenario.
  3. 3. ii Contents Abstract............................................................................................................................................i Acknowledgments.........................................................................................................................v List of Acronyms..........................................................................................................................vi List of Figures.............................................................................................................................viii List of Tables ................................................................................................................................ix Executive Summary ......................................................................................................................1 Document Overview ....................................................................................................................3 2.1 Purpose of this document.............................................................................................3 2.2 Multi-functional technology .........................................................................................3 Background of Anaerobic Digestion..........................................................................................5 3.1 Anaerobic digestion: the process .................................................................................5 3.1.1 Parameters of AD...................................................................................................7 3.1.2 Feedstock Characteristics ....................................................................................11 3.1.3 Logistics of AD.....................................................................................................13 3.1.4 AD Technologies..................................................................................................16 3.2 Legislation and Policy..................................................................................................19 3.2.1 National Renewable Energy Drivers .................................................................19 3.2.2 Renewable Energy Feed-In Tariff (REFIT) .....................................................21 3.2.3 Animal By-Products.............................................................................................22 3.2.4 Nitrates Directive: Directive 91/676/EEC......................................................25 3.2.5 National Waste Management Policy ..................................................................26 3.3 Advantages of Anaerobic Digestion..........................................................................30
  4. 4. iii 3.3.1 Societal Benefits....................................................................................................30 3.3.2 Agronomic Benefits .............................................................................................32 3.4 Barriers to AD..............................................................................................................33 3.4.1 Complex Legislation.............................................................................................33 3.4.2 Non-competitive Incentives ...............................................................................33 3.4.3 Stakeholder Uncertainty ......................................................................................34 3.4.4 Lack of Access to Capital....................................................................................34 3.5 Vision for Ireland.........................................................................................................35 Objectives and Outcomes..........................................................................................................39 Scope and Methodology.............................................................................................................41 5.1 Methodology.................................................................................................................41 5.1.1 Estimation of Investment Costs.........................................................................41 5.1.2 Estimation of Biogas Input Data .......................................................................42 5.1.3 Determination of the Cost of Biomass .............................................................43 5.1.4 Revenue Streams and Finance Plans..................................................................43 5.1.5 General Business Costs........................................................................................44 5.2 Site Selection.................................................................................................................44 5.3 Constraints....................................................................................................................44 5.4 Assumptions .................................................................................................................45 Cost-Benefit Analysis..................................................................................................................46 6.1 Rationale of Inputs ......................................................................................................46 6.1.1 Investment Costs..................................................................................................46 6.1.2 Biogas Input Data.................................................................................................48 6.1.3 Cost of Biomass....................................................................................................49 6.1.4 Revenue Streams and Finance Plans..................................................................49 6.1.5 General Business Costs........................................................................................50
  5. 5. iv 6.2 UCD Campus Scenario ...............................................................................................51 6.3 Lyons Estate Scenario .................................................................................................53 6.4 Sensitivity Analyses......................................................................................................56 Options and Alternatives ...........................................................................................................59 7.1 UCD Campus Scenario ...............................................................................................59 7.1.1 Technical Description..........................................................................................59 7.1.2 Implementation at UCD......................................................................................61 7.1.3 Advantages ............................................................................................................62 7.1.4 Disadvantages .......................................................................................................63 7.2 Lyons Estate Scenario .................................................................................................64 7.2.1 Technical Description..........................................................................................64 7.2.2 Implementation at UCD......................................................................................66 7.2.3 Advantages ............................................................................................................66 7.2.4 Disadvantages .......................................................................................................67 Project Timeframes.....................................................................................................................68 Risks ..............................................................................................................................................71 9.1 Planning Permission ....................................................................................................71 9.1 REFIT Alternative.......................................................................................................72 9.3 Competition..................................................................................................................73 Recommendations.......................................................................................................................74 Conclusions..................................................................................................................................75 References ....................................................................................................................................76 Appendix 1 - Waste Management Methods for European Countries .................................84 Appendix 2 - Detailed Calculations of the Lyons Estate Scenario.......................................85 Appendix 3 - Detailed Calculations of the Campus Scenario ...............................................86
  6. 6. v Acknowledgments I would like to thank all those whose help and support have contributed to this thesis. In particular, there are a number of people to whom I owe special thanks: Firstly, my supervisor, Dr Kevin McDonnell, for his guidance, support and encouragement throughout the duration of my Masters. Despite his hectic schedule he has always had time to discuss my work and provide assistance. An hour spent in his office was more valuable than a day spent in the library. It is baffling how one person can have so much knowledge in the field of sustainable energy. He has been an excellent mentor and to him, I express my most sincere thanks. John O’Halloran, from the UCD School of Chemical and Bioprocess Engineering for his invaluable advice on the intricacies of anaerobic digestion. It is always excellent for the creative process to have somebody to bounce ideas off and John, given his extensive knowledge on AD was the perfect person for this. Gary Smith, from campus services his assistance in retrieving waste management data from the UCD campus. Tom Canning, from ESB international for his explanation on the grid connection process. Ann Gallagher, a sustainability architect for her generous support and for her assistance in outlining the planning process. Hannah Martin, for proof reading the first draft and extended thanks goes to the rest of my family for their support and encouragement along the way. Finally, I would like to dedicate this thesis to my mother Mary Martin, for without her support throughout this intensive year of study, I would not have been one tenth as successful.
  7. 7. vi List of Acronyms Technical Acronyms: AD Anaerobic Digestion / Anaerobic Digester BMP Biomethane Potential BOD Biological Oxygen Demand CHP Combined Heat and Power CSR Corporate Social Responsibility GHG Greenhouse Gas GW Gigawatt HRT Hydraulic Retention Time I-SEM Integrated Single Electricity Market kW Kilowatt kWh Kilowatt Hour MEC Maximum Export Capacity MSW Municipal Solid Waste OFMSW Organic Fraction of Municipal Solid Waste OLR Organic Loading Rate PEIO Primary Energy Input Output ratio PSO Public Service Obligation MW Megawatt REFIT Renewable Energy Feed In Tariff RES Renewable Energy System
  8. 8. vii Organisational Acronyms: CER Commission for Energy Regulation DAFM Department of Agriculture, Food and the Marine DoELG Department of Environment and Local Government DCENR Department of Communications, Energy and Natural Resources DPER Department of Public Expenditure and Reform DIT Dublin Institute of Technology DSO Distribution System Operator EC European Commission EPA Environmental Protection Agency ESB Electricity Supply Board EU European Union HEA Higher Education Authority (of Ireland) IEA International Energy Agency OGP Office of Government Procurement SEAI Sustainable Energy Authority of Ireland TSO Transmission System Operator UCD University College Dublin
  9. 9. viii List of Figures Figure 1: The four stages of anaerobic digestion (Al Seadi et al., 2008).............................................................. 6 Figure 2: Benchmark methane yields of organic waste types (Preißler et al., 2007) ........................................12 Figure 3: Primary Energy Input/ Output ratio of AD supply chains (Pöschl et al, 2010).............................14 Figure 4: Schematic of a typical biogas plant with a single-stage digester (Blogspot.ie, 2013)......................16 Figure 5: Waste Management Hierarchy (DoELG, 2004)...................................................................................26 Figure 7: (a) Projected vs Empirical biogas production; (b) Projected vs Empirical biogas production. ...57 Figure 8: Flexibuster mobile AD (Innovation Showcase, 2015)........................................................................60 Figure 9: Plan view of proposed AD at Lyons research farm ............................................................................65 Figure 10: Effect a reduction of electricity price will have on profitability of an AD at Lyons Estate. ......72 Figure 11: Influence of gate fees on profitability of the propose AD at Lyons Estate..................................73
  10. 10. ix List of Tables Table 1: Optimum system type for each scenario.....................................................................2 Table 2: Common temperature ranges for AD.........................................................................7 Table 3: Pre-treatment methods for feedstocks (Zhang et al., 2014)....................................13 Table 4: REFIT rates applicable to AD (DCENR, 2015) .....................................................21 Table 5: Summary of the main regulations from ABP legislation (EC No. 1774/2002)...23 Table 6: Fertilizer and storage capacity regulations (DAFM, 2006).....................................25 Table 7: Cost of waste permits for a bio-degradable waste facility ......................................29 Table 8: Irish feed-in tariff rates compared to the rest of Europe (Caslin, 2013)..............33 Table 9: Economics of biogas plants in UK, Germany, Denmark and Ireland .................47 Table 10: Break-down of investment costs for each scenario...............................................48 Table 11: Characteristics of feedstocks considered for every scenario................................49 Table 12: Cost-benefit of UCD campus scenario...................................................................51 Table 13: Cost-benefit analysis of Lyons Estate scenario......................................................53 Table 14: Food waste generated by UCD, TCD and DIT per annum ................................54 Table 15: Energy characteristics for UCD on campus scenario ...........................................62 Table 16: Timelines required for each planning parameter ...................................................69 Table 17: Timelines for construction and consultancy ..........................................................70
  11. 11. 1 CHAPTER 1 Executive Summary UCD has the potential to become the Irish centre of excellence for anaerobic digestion. This technology; which utilizes local wastes as a resource to generate renewable energy is on the brink of penetrating the Irish market on a significant scale. The key barrier to overcome is uncertainty amongst stakeholders which is inhibiting any major investment in the technology. Complex legislation, uncompetitive government incentives and unfamiliarity with the technologies associated with the AD process are thought to be the causes of such uncertainties. By building an anaerobic digester at one of its premises, UCD can demonstrate to all the relevant stakeholders, the many benefits of this technology and alleviate any of their concerns. This report describes and evaluates the possible AD systems and supply chains which could be readily integrated into either the college campus at Belfield or the research farm at Lyons Estate. As a bare minimum, any scenario was expected to utilize the organic wastes generated by UCD annually. Potential co-substrates were then considered in an effort to boost technical and economic performance. Scenarios were assessed on a cost-benefit basis initially using the “Big-East” biogas calculation tool. Any system configuration which proved financial feasible was outlined in greater detail.
  12. 12. 2 The cost-benefit analysis revealed that the construction of a digester both on the UCD campus as well as on the Lyons research farm were economically feasible. Table 1 summarises the key results from each scenario. The Lyons Research Farm scenario considered the co-digestion of 8000 t/a of slurry produced on the farm along with 2800 t/a of organic waste sourced from the UCD campus and a potential commercial partner from the food processing industry. The campus scenario considered the treatment of organic municipal waste originating from UCD and as the possibility of importing additional feedstocks to improve the system’s performance. Table 1: Optimum system type for each scenario Lyons Research Farm UCD Campus System Type CSTR Flexibuster by SEaB Energy Investment Cost €1.15 Million €424,000 Electrical Output 173 kWe 28kWe Annual Turnover €132,368 €86,000 Payback Period 8.5 years 5 years Despite having a longer payback period, the Lyons research farm scenario was recommended as the most ideal scenario for UCD. This recommendation was based on the fact that it engaged more of the stakeholders relevant to the AD industry in Ireland hence would be more beneficial to the AD industry as a whole. It is anticipated that the successful implementation of this system will provide a valuable template for potential investors to work off; will pave the way for new research avenues and add an extra level of prestige to the UCD School of Agriculture and Food Science.
  13. 13. 3 CHAPTER 2 Document Overview 2.1 Purpose of this document The purpose of this document is to present a clear and concise evaluation of the options available to UCD for the implementation of an anaerobic digester at one of its facilities; either on campus at Belfield or on the college research farm at Lyons Estate Co. Kildare. 2.2 Multi-functional technology Anaerobic digestion (AD) is the breakdown of organic material in oxygen-deprived conditions. The products of this process include biogas, which can be used to generate heat and power, and digestate which can be used as a soil conditioner and fertilizer, offsetting chemical fertilizers. Although AD does not contribute to the field of sustainable energy in a massive way, compared to RES such as wind or hydro, when the vast spectrum of additional benefits are taken into account, the installation of such becomes a worthwhile venture. Despite its potential of contributing to slurry management, waste management and sustainable energy production simultaneously, the uptake of AD in Ireland has been extremely limited. Research carried out on countries where the technology is more
  14. 14. 4 popular has suggested that lack of stakeholder and investor awareness in AD coupled with uncompetitive REFIT rates are key factors inhibiting this technology from taking off. By building a fully functioning digester at one of its facilities, UCD can aid the stimulation of stakeholder interest in AD by demonstrating the massive potential this technology has.
  15. 15. 5 CHAPTER 3 Background of Anaerobic Digestion 3.1 Anaerobic digestion: the process Anaerobic Digestion (AD) is a biochemical process involving the breakdown of complex organic matter into simpler molecules under oxygen starved conditions by a variety of anaerobic microorganisms. These ‘simpler molecules’ form the basis of two valuable end products in the form of biogas and digestate. The biogas production process involves four distinct stages, outlined in figure 1. As illustrated, hydrolysis is the first stage in the process in which the initial feedstock of complex organic matter is broken down into simpler molecules by hydrolytic microorganisms (Al Seadi et al., 2008). These simpler molecules of fatty and amino acids along with glucose (sugar) are then acted upon by fermentative bacteria in the acidogenic phase to form methanogenic substrates. Certain molecules are more difficult to break down and must undergo acetogenesis in order for the methanogens to act upon them. Methanogenesis is the final step in the process, yielding the desired end product biogas, predominantly composed of methane and carbon dioxide along with traces of other gases.
  16. 16. 6 Each one of these stages are intrinsically linked however bearing in mind that this is a biological process, each of the respective organisms have differing optimal environments. According to Al Seadi et al., (2008), methanogenesis is a particularly sensitive step which is influenced by operating conditions such as temperature, pH, organic loading rate and the composition of the feedstock. Organic Matter Fats, Proteins, Carbohydrates Soluble Organic Molecules Fatty Acids, Amino Acids, Sugars Acetic Acid, CO₂, H₂, NH₃, NH₄, H₂S Carbonic Acids, Volatile Fatty Acids, Alcohol Methane and Carbon Dioxide BIOGAS Hydrolysis Methanogenesis Acetogenesis Acidogenesis Figure 1: The four stages of anaerobic digestion (Al Seadi et al., 2008)
  17. 17. 7 The most popular reactor type is a single stage tank reactor. In this configuration, all of these stage occur in the same environment. The key here is to find a happy medium by creating an environment in which all microorganisms can be productive (Azbar et al., 2001). Other system configurations such as a two-stage digester have two reactors in sync with one another; the first optimized for hydrolysis and acetogenesis while the second has favourable conditions for the more sensitive methanogenic bacteria (Nizami et al., 2009). 3.1.1 Parameters of AD It is useful to point out that the AD process occurs naturally in the stomach of a ruminant. An important difference however between a cow and a metal tank is that the cow’s system is regulated by homeostasis to ensure favourable methanogenic conditions. Homeostasis essentially needs to be mimicked artificially in the metal tank reactor to ensure maximum biogas production. There are many parameters which need to be maintained such as temperature, pH, hydraulic retention time and organic loading rate (Abu-Dahrieh et al., 2011). Temperature Table 2 highlights the three temperature ranges which are applied to AD. The temperature range selected will have a bearing on the retention times of substrates in the digester. Table 2: Common temperature ranges for AD Process Temperature Min. Retention Time Psychrophilic <20°C 70 to 80 days Mesophilic 30-42°C 30 to 40 days Thermophilic 43-55°C 15 to 20 days Obviously the lower the retention time, the more productive a biogas plant can potentially be. The thermophilic range with the lowest retention time is also most efficient for the reduction of pathogens and weed seeds enhancing both biogas and digestate produced. The low retention time is a result of methanogenic bacteria’s preference for higher temperatures; hence more substrate is digested, enhancing biogas production (Angelidaki, 2004). The disadvantage of this range is the cost of maintaining
  18. 18. 8 these temperatures year round can reduce the economic feasibility of the plant (Patterson et al., 2009). In addition the AD process tends to be more unstable at higher temperatures, increasing maintenance costs and plant downtime. The mesophilic temperature range can be maintained without the use of additional heaters in warm climates however in Ireland, a heater will most definitely be required. The retention times associated with psychrophilic ranges are usually considered too lengthy to justify the AD process from an economic perspective. pH Value pH values within the digester affect the growth of microorganisms and the dissociation of ammonia and hydrogen sulphide (Comparetti et al., 2013). Methanogens prefer a pH value of 7.0 (Lee et al., 2009) but can maintain activity between 5.5 and 8.5, while the optimum pH for hydrolytic and acetogenic microbes are in the 5.5-6.5 range (Kim et al., 2003). This reaffirms the importance of gaining a happy medium especially with single reactor configurations. The substrates fed into the digester obviously have a significant influence on the system pH. This parameter can be controlled either by carefully managing the substrate going into the reactor or by installing ‘bicarbonate buffer system’ (Al Seadi et al., 2008). Co-digestion of different feedstocks can also have a stabilising effect on the overall reaction (Cuetos et al., 2008). Organic Loading Rate This is the amount of feedstock fed into the digester per unit volume of the digester per time, typically expressed as kg VS m³ d. This rate is limited by the amount of time required for the microorganisms to decompose the substrate. Considering the dynamics of microorganism duplication rates it is generally uneconomical to design a system aiming for total substrate decomposition (Al Seadi et al., 2008). BR = m * c / VR BR organic load [kg/d*m³] m mass of substrate fed per time unit [kg/d] c concentration of organic matter [%] VR digester volume [m³] Equation 1(Al Seadi et al., 2008)
  19. 19. 9 Hydraulic Retention Time (HRT) This is the average amount of time that any given substrate resides in the digester. This parameter is correlated to the reactor volume and the organic loading rate (Al Seadi et al., 2008). Equation 2 suggests that HRT is determined by the size of the reactor and the rate at which fresh material is loaded into the reactor. HRT = VR / V HRT Hydraulic retention time [days] VR Digester volume [m³] V Volume of substrate fed per time unit [m³/d] Equation 2 (Al Seadi et al., 2008) This equation is an over-simplification; HRT must be greater than reproduction rates of the slowest growing bacteria involved in decomposition in order to maintain digestion rates. Veeken & Hamelers (1999) identify hydrolysis as the rate limiting step in AD. If the feedstock is ejected quicker than the microorganisms can multiply and spread, there may be insufficient microbes to act upon the next batch of fresh material (Friehe et al., 2010). Furthermore some substrates are more susceptible to decay than others. A feedstock containing mostly fats and carbohydrates will require a low retention time as they degrade rapidly. Feedstock high in cellulose, are tougher to break down, hence require a longer retention time. For these reasons it is necessary determine if a constant and uniform feedstock is available during the preliminary stages of a biogas project as it will have a profound impact on the choosing a suitable digester type. There is a close correlation between OLR and HRT. Solids Content This parameter affects the mixing regime within the digester. Postel et al (2010) maintains that the optimum DM content of the feedstock in a typical wet digester is 12% for ease of “pumpability” of the medium. Mixing ensures even heating of the substrate, uniformity of the substrate composition and prevention of a scum layer and solids deposition (Igoni et al., 2008). Excessive mixing can lead to shear forces, which are detrimental to the productivity of acetogenic and methanogenic microbes which prefer calmer conditions (Friehe et al., 2010). A system of slowly rotating agitators is usually an
  20. 20. 10 adequate compromise to suit both aspects of the mixing regime. Water is sometimes added to the process to ease mixing. Toxic Substances It is impossible to deprive the digester of oxygen totally as molecules of this element are released from the chemical reactions occurring inside the digester. Methanogenic bacteria are completely intolerant of oxygen however their coexistence with oxygen consuming bacteria from previous stages of the AD reaction ensure their survival (Friehe et al., 2010). Considering the common substrates to a digester tend to originate from farms, it is not uncommon for pesticides or herbicides to infiltrate the system. These antibiotics along with heavy metals can inhibit microorganism productivity, halting the biogas process (Al Seadi et al., 2008). Friehe et al (2010), report that a number of inhibitors such as; Ammonia, Hydrogen Sulphide and volatile fatty acids, can arise from the fermentative process itself. The most effective control mechanism for this parameter is careful selection and quality assurance of feedstocks. This may require an alteration of practices upstream which in turn calls for increased awareness throughout the supply chain. C: N Ratio The carbon nitrogen ratio is important to the growth and performance of the micro- organisms involved in the AD process. Carbon acts as the energy source for the microbes while nitrogen enhances their growth rates. Igoni et al (2008) reports that excess nitrogen not used by the microorganisms can lead to excessive levels of ammonia gas while carbon is consumed up to 30-35 times faster than nitrogen is converted; hence this study calculates the optimum C:N ratio to be 30:1. Other reports suggest that in a co-digestion scenario, C:N ratio can be ideal at a lower value of 15:1 (Zhang et al., 2013). This study concludes that optimum C:N can vary between feedstock type and inoculum used.
  21. 21. 11 3.1.2 Feedstock Characteristics Upon analysing the parameters of AD it quickly becomes clear that feedstock type is the single most important factor to consider during the preliminary design phase of a biogas project. Feedstock type will influence the technology type deployed, the size of the reactor and the biogas potential of the facility. It is important to secure a constant and reliable source of substrate for the biogas plant at an early stage of the planning process as it will influence a lot of decisions further on in the project. Gavigan (2014) describes the two main sources applicable for treatment in a biogas plant; I. Products from agricultural:  Animal slurries  Harvest residues  Grass / maize / cereals II. Products from food processing  Meat/fish processing waste  Dairy waste  Brewery grains  Vegetable waste  Food factory waste  Sewage Sludge  OFMSW Figure 2 shows the approximate methane potential originating from a number of feedstocks potentially available to a digester sited at UCD. The livestock wastes highlighted in orange have significantly lower biomethane potentials per tonne of dry matter than other feedstocks. This is partly explained by the high water content of slurries (Asam et al., 2011) and by the fact that a significant amount of the energy content has already been extracted from these wastes as they pass through the animal’s digestive system. Despite their lower methane yields, these wastes are very popular in AD due to their cheap cost to obtain and their natural content of anaerobic bacteria, minimizing the need for expensive pre-cursors (Al Seadi et al., 2008).
  22. 22. 12 Agricultural residues arising from arable crops, highlighted in green, have slightly higher methane yields than slurries. Nizami et al (2009) report that ensilage of such residues; especially grass, can enhance their biomethane potential even further. Figure 2: Benchmark methane yields of organic waste types (Preißler et al., 2007) Flotation sludge and cooking oil, due to their concentrated nature along with their high lipid and protein contents, tend to have the most favourable biomethane yields (Al Seadi et al., 2008). The various types of food wastes (blue) also tend to have higher methane yield compared to wastes of agricultural origin. It is important to note that these are benchmark values; there are a lot of variables which can raise or lower the biogas yield of every feedstock on this chart. Once a project hits feasibility stage, empirical testing will have to be carried out on the actual feedstocks available. This usually involves the use of a eudiometer, a device which measures the change in volume of a gas mixture following a physical or chemical change. As well as securing a sufficient amount of feedstock, it is also crucial to ensure the quality of the feedstock coming in. This should involve legal agreements with feedstock suppliers to ensure they take appropriate action to limit contaminants or unsuitable materials. Certain feedstocks are subject to stringent government regulations which require pre-treatment before being administered into the digester. The general perception 0 100 200 300 400 500 600 700 MethaneYield(m³/toDM) Waste Type
  23. 23. 13 among farmers in particular; is that these requirements are a hindrance and discourage uptake of the technology (Bywater, 2011). On the contrary to this view, Zhang et al (2014) found that some of these pre-treatment methods (listed in table 3) increase gas yields to a level that the added revenues of such justify their inclusion in the biogas system. Table 3: Pre-treatment methods for feedstocks (Zhang et al., 2014) Method Raw Substrate Results Key Mechanism Microwave (145°C) Food waste Increased biogas production Increased solubilisation Thermal (120°C for 30 min) Food waste Increased biogas production by 11% Increased solubilisation Freeze-thaw (-80°C - 55°C) Food Waste Increased biogas production by 23% Cell wall disruption Pressure-depressure (10 bar to 1 bar) Food Waste Increased biogas production by 35% Cell wall disruption 3.1.3 Logistics of AD The next most important factors in designing a biogas plant are the economics. The simple fact is that organisations are not going to build these facilities solely for the sake of environmental protection. In order to secure funding to finance these expensive projects, stakeholders are going to need to see a return on their investment usually by ensuring optimum methane production (Walla and Schneeberger, 2005). For these reasons it is necessary to take the following measures to maximise the profitability of a biogas plant. Uniformity of feedstock: In order to size the digester correctly it is imperative to secure a constant, reliable and uniform source of feedstock for the life time of the system. In order to maximise biogas output and by extension; profits, it is in the operator’s interest to have the plant running at full capacity for as many hours as possible throughout the year. Otherwise the operational costs out-weigh the revenue streams and the plant operates at a loss. Al Seadi et al (2008) stress the importance of securing long-term contracts with feedstock
  24. 24. 14 suppliers. Of course if a potential investor manages their own waste streams, such as a farmer or a food processing factory, this is less of an issue. Co-Digestion Studies have shown that the co-digestion of different wastes can have synergistic effects on each other. Macias-Corral et al (2008) has demonstrated that co-digestion of OFMSW and cattle manure can lead to a more favourable pH value, hence a more stable reaction within the reactor and enhanced methane yields compared to these substrates being digested individually. More specifically, Zhang et al (2013) have shown that co-digestion of food waste and cattle manure at a ratio of 2:1 can improve methane yields by 41.1% in batch reactors and 55.2% in semi-continuous reactors. At biogas enhancement rates like this, it can prove very lucrative for a facility to practice co-digestion. Operators can also gain additional revenue streams by charging gate fees for the treatment of particular types of waste (Braun and Wellinger, 2002). Minimization of transport: Transport of feedstocks or the products of digestion is a very costly process. It is also likely to involve use of fossil fuels, which is counter intuitive to one of the main reasons for deployment of AD. The most logical solution here is to build the digester at the source of the predominant waste type. However in a centralised facility or a co-digestion scenario; some degree of transport is unavoidable. Figure 3: Primary Energy Input/ Output ratio of AD supply chains (Pöschl et al, 2010) Cattle Manure Sludge Food Residues Grass Silage Corn Silage Straw 0 10 20 30 40 50 60 70 80 90 100 0 20 40 60 80 100 120 140 PEIOratio(%) Transport Distance (km)
  25. 25. 15 Figure 3 is depicted from Pöschl et al (2010) and illustrates the distances for which transport of various feedstocks remains energy efficient. This was calculated on the basis of primary energy input/ output ratio (PEIO); calculated on the presumption that biomethane yields would over-compensate the fossil fuel energy input into the system. A low PEIO ratio is indicative of a highly energy efficient system chain. Figure 3 shows that straw and silage tend to have lower PEIO ratios meaning they can be transported great distances whilst still maintaining the energy efficiency of the supply chain. At the other end of the scale, with a particularly high PEIO are cattle manures. The PEIO ratio of these feedstocks becomes negative at just 21 km hence it is not feasible to transport these feedstocks even over short distances. According to Pöschl et al (2010), this disparity between feedstocks is largely to do with their differing energy densities and by extension dry matter contents. It is possible to improve the PEIO ratio of certain substrates using pre-treatment methods which separate feedstocks into solid and liquid fractions. Asam et al (2011), report that this technique, can significantly improve the methane potential per unit volume of substrate. This research provides an excellent technical basis for centralised AD or co-digestion plants to work off.
  26. 26. 16 3.1.4 AD Technologies Figure 4 is a simpler schematic of a typical full-scale biogas plant in Europe. It is included here as a visual reference to accompany the technical description of a biogas plant below. Figure 4: Schematic of a typical biogas plant with a single-stage digester (Blogspot.ie, 2013) The process begins with the intake of feedstocks such as organic waste, animal slurries and crop residues (a, b and c) into the pre-storage pit (d). In Ireland animal by-products legislation (S.I. No. 187, 2014) dictates that all food waste must be pasteurised at 70°C for one hour prior to entering the digester. These types of wastes must strictly segregated at the reception station from regular farming activities and must also be kept separate from non-hygienically problematic waste streams before entering the primary digester (Postel et al., 2010). However it is reasonable to assume a facility could charge considerable tipping fees for these waste types hence the costs of implementing pasteurisation can be offset. This step, although not illustrated in fig. 4 would be included at this point in the system. Feedstocks are then fed into the digester (e) via pumps or a screw press depending on the solids content of the feedstocks. Water may also be pumped in at this stage to attain an optimal DM content (Knitter, 2011).
  27. 27. 17 This schematic uses the example of a continuously stirred, single stage tank reactor usually made from concrete or steel in an up-right cylindrical position. According to Nagao et al (2012) 95% of all full-scale plants in Europe utilize this type of digester. The key characteristics of this technology type are that all four micro-biological stages outlined in figure 3-1 occur within the same, gently stirred reactor. The substrate is stirred either mechanically by agitators or by pumping some of the biogas produced back into the substrate. The popularity of this configuration is largely due to its cost-effectiveness at sizes greater than 300m³ and due to the fact that it can usually be serviced without the need of emptying the digested, minimizing downtime (Postel et al., 2010). Two-stage reactors consist of two separate tanks in phase with one another. The basic premise of this configuration is that the first reactor is optimised for hydrolysis and acidogenesis while the second is optimized for the methanogenic stage (Abu-Dahrieh et al., 2011). The key advantage of two-stage digestion is that higher organic loading rates can be achieved due to the shortening of the rate-limiting hydrolysis stage (Nizami et al., 2009). In a situation where a facility has an abundance of feedstock, this would be advantageous for the overall productivity of the facility. Both this and single stage designs are generally suited to farm or centralised scale facilities where sufficient economies of scale can be achieved. Another AD technology which has recently reached commercial maturity is batch- process digestion. This system consists of placing the raw biomass inside a concrete or metal container and sealing it air-tight (Postel et al., 2010). This type is particularly suited to substrates with a high DM content such as maize or grass silage. There are a wide variety of other reactor types which UCD could consider however a detailed discussion of such is beyond the scope of this pre-feasibility study. The AD process creates two key products; biogas (f) and a solid residue called digestate (g). Digestate is pumped into an effluent storage tank. It is common to apply solid/liquid separation techniques to the digestate such as belt filter presses or screw separators (Postel et al., 2010). The liquid portion can be applied to arable land using conventional spreading techniques while the solid portion acts as an excellent soil conditioner.
  28. 28. 18 The biogas can be used for a number of post-production applications. The simplest application is to burn the gas in a modified natural gas boiler. This process, not shown in figure 4 is most common in the developing world in subsistence digestion systems however there are a few circumstances this method is used in the developed world. The Camphill Community biogas facility in Co. Kilkenny had in its initial plans to include a CHP unit to combust the gas. However following difficulty in obtaining a power purchasing agreement from CER, the operators had no choice but to utilize biogas boilers (SEAI, 2005). The most efficient application is utilise a CHP unit (i). In this scenario, biogas is combusted in a specialised engine such as a Stirling or Jensbacher engine. These engines are robust enough to combust the biogas in its raw form and are used to run an electricity generator while the heat is channelled for use either on-site or at nearby locations. Such configurations can achieve efficiencies of up to 90% (Al Seadi et al., 2008). While CHP is the most desirable end-use application, there is not always a sufficient demand for the heat generated. As an alternative the biogas can be cleaned and pressurized to upgrade it to biomethane (k). This involves the removal of impurities such as hydrogen sulphide and carbon dioxide via various adsorption and scrubbing techniques (Al Seadi et al., 2008). Once upgraded, the biomethane can be pumped into the natural gas grid (l). Patrizio et al (2015) has shown that considerable subsidies which are not currently in existence would be required to make this option economically viable. In countries such as Sweden and Austria, upgraded biomethane is utilised as vehicle fuel (k) (Murphy & Power, 2009). At Linkoping Biogas plant, Sweden biogas is upgraded to be used in buses and cars. By 2005, 64 buses were running completely on upgraded biomethane (IEA Bioenergy Task 37). According to the Swedish Gas Association a three pronged approach of energy taxation regulations, electricity certificates and investment supports for agricultural facilitated an innovative project like this. Today there are now 47,000 vehicles running on biogas in Sweden. It should be noted that Sweden has a number of car manufacturers such as Saab, Volvo and Scania to build such vehicles. While Ireland is without this luxury, this is still an excellent example that shows when the incentives are attractive; the private sector will develop a solution.
  29. 29. 19 3.2 Legislation and Policy Given the aforementioned potential for AD to contribute to a variety of different areas, it is also liable to adhere to a variety of different legislations. This has been highlighted as a major barrier to the wholesale uptake of the technology as opposed to a driver, as it breeds confusion and uncertainty into the relevant stakeholders (CRÉ, 2011). This section reviews the legislation which is currently pertinent to the construction of a biogas plant, with the intention of presenting it in a simplified and relevant manner. 3.2.1 National Renewable Energy Drivers Speaking at a seminar introducing the upcoming white paper at Dublin Castle, Minister Alex White stated the following; “The impact of global warming demands that we put sustainability at the very centre of our energy policy” DCENR (c), 2015 In his speech, Minister White also acknowledged the fact that gas and coal must be replaced with renewable energy sources within 35 years and that policy must ensure certainty, stability and affordability, in making the transition to a low carbon future. Unfortunately this white paper isn’t due to be published until later this year so for the purpose of this feasibility study, the previous white paper will have to suffice. The Government White Paper – Delivering a sustainable energy future for Ireland 2007- 2020 lays down the strategies which are designed to ensure Ireland honours its international and European commitments. This document centres around three pillars:  Ensuring the security of the country’s energy supply,  Promoting the sustainability of the country’s energy supply,  Enhancement of the competitiveness of energy supply. Section 3.4 of this document, “enhancing the diversity of fuels” highlights the government’s disapproval of Nuclear energy being added to the energy mix meaning hydro, wind and biomass technologies were forecasted to play a major role. Section 3.10 provides a general outline of measures to accelerate growth of the renewable energy sector.
  30. 30. 20 Broadly speaking, Kyoto protocol and the EU 20-20-20 targets acted as precursors to the energy white paper. The Kyoto protocol mandated Europe with the task of collectively reducing its GHG emissions to 5% above 1990 levels (EPA (a), 2015). This prompted the EU to forge the 20-20-20 Policy targets which are as follows:  20% reduction in GHG emissions to that of 1990 levels  20% of electricity sourced from renewables  20% improvement in European energy efficiency It was recognised that some EU countries had a greater capacity to achieve these targets than others. Burden-sharing agreements in which some countries aim for tougher targets to offset those which can’t achieve their own were put forth to overcome this. Under EU directive 2009/28/EC, Ireland has been set a specific, legally-binding target of 16% of energy across all sectors generated from renewable energy sources by 2020. Article 3 and 4 of this directive provides a common framework to assist member states form their own policies on the promotion of renewable energy. The National Renewable Energy Action Plan (NREAP) was published in response to this directive. It set interim targets to achieve and segregated renewable targets into the following sections:  40% electricity generated from renewable energy (RES-E)  12% heat supplied from renewable sources (RES-H)  10% of the transport ran on renewable power. (RES-T) The National Bioenergy Action Plan was published by DCENR around the same time as the white paper. This document outlined the key strategies to develop the Irish bioenergy sector. This strategy prompted the expansion of the REFIT programme to include waste-to-energy projects such as AD. The strategy acknowledged the amount of government departments with a stake in the bioenergy sector and envisaged the development of a cross-agency information and education programme to facilitate joined-up thinking on the subject. The plan put the onus of this task on the SEAI and enterprise Ireland.
  31. 31. 21 3.2.2 Renewable Energy Feed-In Tariff (REFIT) This legislation is currently the only major, monetary incentive for an organisation to construct a digester in Ireland. The REFIT scheme is funded by the Public Service Obligation (PSO) which is a levy imposed on all electricity users (DCENR(a), 2015). The purpose of this scheme is to stimulate the development of renewable electricity and to ensure Ireland meets it 2020 electricity targets of 40% coming from RES. The basic premise of REFIT is that a minimum floor price for electricity is guaranteed for a period of 15 years after a RES is energised. Different prices are offered to different forms of generation technologies. AD comes under the REFIT 3 scheme which opened for applications in 2012. The current rates offered for anaerobic digestion are illustrated in table 4. Table 4: REFIT rates applicable to AD (DCENR, 2015) REFIT 3 2014 (€/kWh) 2015 (€/kWh) Large AD Non CHP (>500kW) 10.48 c 10.50 c Small AD Non CHP (<500kW) 11.53 c 11.55 c Large AD CHP (>500kW) 13.62 c 13.65 c Small AD CHP (<500 kW) 15.72 c 15.76 c As illustrated in this table, higher tariffs are awarded to AD plants which include a CHP unit and rightly so as this is a more efficient use of the biogas produced. The larger scaled plants are awarded lower tariffs as it is estimated that economies of scale make such installations more profitable. The closing date for new applications to the REFIT 3 scheme is the 31st of December 2015. What’s more is that applications are required to be at an advanced stage to qualify for the scheme by this date. This essentially rules this particular project out of the running for REFIT 3. The DCENR have indicated that a new support scheme for renewable electricity projects will be available in 2016 however have not yet published any detailed information on what this might be.
  32. 32. 22 3.2.3 Animal By-Products This legislation is as complex as it is stringent. Granted the size of the Irish agricultural export market, it is within the country’s interest to keep the sector disease free. As AD is applicable to a vast spectrum of organic wastes there is cause for concern that the application of digestate containing animal by-products poses a risk of spreading disease (EPA(a), 2006). Introduced in 2002, this legislation regulates how animal by- products are disposed of and processed. The consequences for non-compliance of these rules are extreme, with any person found in breach of them liable to 3 months imprisonment and/or a €250,000 fine (S.I. No. 187, 2014). Hence these regulations have major implications for biogas plants. Article 2 part 1(a) of this legislation gives a holistic definition of animal by-products: “Entire bodies or parts of animals or products of animal origin referred to in Articles 4, 5 and 6 not intended for human consumption, including ova, embryos and semen” These by-products are categorised based on the potential severity of the threat they pose to the bio-security of the agricultural industry. Table 5 summarises the main conditions any biogas plant commissioned at UCD must adhere to when dealing with these wastes. Category 1 waste is completely off limits for this project. The School of Veterinary Medicine and the School of Chemistry and Chemical Biology are the only locations this type of waste may arise from. These schools have their own waste management plans hence it is unlikely that this waste would end up in any feedstock streams for a potential AD at UCD Category 2 wastes are expected to constitute a large proportion of the feedstock stream for at least one of the scenarios proposed in this study; the siting of an AD at Lyons Estate. The ABP legislation requires that waste in this category are pasteurised and macerated to a maximum particle size prior to AD treatment. Manure and digestive tract content are however exempt from this rule meaning an AD dealing with this feedstock is not required to include expensive pre-treatment processes in the system.
  33. 33. 23 Table 5: Summary of the main regulations from ABP legislation (EC No. 1774/2002) Waste Type Minimum Treatment Constraints Category 1 (Covered under article 4)  Animals suspected of being infected by BSE and their by-products.  Animals other than farmed animals.  Catering waste of international origin.  Experimental Animals  Incineration or co-incineration.  Burial (household pets only) This category is completely off limits for inclusion in an AD Category 2 (Covered under article 5)  Manure & digestive tract content.  Animals that die other than being slaughtered for human consumption  Manure/gut contents can be treated by AD or spread directly onto land.  All other wastes suitable for AD following pre- treatment.  Must be pasteurised @ 60°C for 48 hours prior to being fed into AD.  Must be macerated to a particle size of >400mm  Manure/ digestive tract content requires no pre- treatment. Category 3 (Covered under article 6)  Former foodstuffs of animal origin.  Domestic catering waste  AD following pre-treatment.  Must be pasteurised @ 70°C for 1 hour prior to being fed into AD.  Must be macerated to a particle size of >12mm
  34. 34. 24 Category 3 wastes are also expected to contribute to the feedstock of the proposed AD in all scenarios of this study. These wastes include catering waste, a considerable amount of which is produced by UCD every year. Any digester which processes this type of waste must include a pasteurisation and maceration process in its design adding to the overall capital cost of the project. The inclusions of such pre- treatment steps are usually justified by the fact that food waste has a much higher biomethane potential (BMP) than animal slurries, hence the enhanced revenues from the higher biogas production more than cover the added capital cost. Article 7 of this legislation outlines how animal by-products should be collected, transported and stored. ABP can only be transported by a license haulier. Annex II dictates the following:  ABP shall be transported in sealed packaging or covered by leak-proof containers.  Reusable equipment used to facilitate the transport must be cleaned and washed after each use and be dry before the next use.  Appropriate temperatures must be maintained. Conveniently for UCD, category 3 catering waste is exempt from these conditions; however if such waste is to be transported off campus, a licensed haulier must be used or alternatively UCD must seek the appropriate license from the DAFM to transport the feedstock itself. S.I. No. 820/2007 sets out the legislation which must be adhered to in order for such a licence to be granted. Offaly county council is the administrative agency which issues these permits. This permit costs € 1000 per region waste is collected from and must be renewed every five years at a cost of half the initial amount paid. Processing time is estimated at 40 days. There are also a number of rules related to plant layout outlined by DAFM (2009). The digester receiving off farm wastes must be must be separated from other premises on the farm by permanent, animal-proof close meshed fencing whilst also maintaining a minimum of 5 metres from livestock. A way around these restrictions is to pasteurize such wastes prior to reaching the farm. There might be some merit for UCD to pre- pasteurize food waste before exporting it off campus in one of the digester scenarios outlined in chapter 6.
  35. 35. 25 3.2.4 Nitrates Directive: Directive 91/676/EEC This directive was conceived in an effort to minimize pollution to water courses originating from agricultural sources. Under article 3.2, Ireland was obliged to designate zones which are particularly vulnerable to water course pollution. Article 4 of this directive prompted farmers to establish good agricultural practices. This prompted the Department of Agriculture, Food and the Marine to divide the country’s agricultural land into three zones based on rainfall, type of soil and duration of growing season. In each zone there are different capacity requirements for the storage of manure (DAFM, 2006). Table 6 highlights the outcomes of this directive. Farmers are required to store any slurry produced at sensitive times of the year and are restricted. In addition to these regulations, the National Nitrates Action Programme limited the application of over 170 kg of nitrogen per hectare per annum. Table 6: Fertilizer and storage capacity regulations (DAFM, 2006) Zones Storage Capacity Required Prohibited Application Periods (Weeks) Chemical Fertilizers Organic Fertilizers Farmyard Manure A 16 15 Sept -12 Jan 15 Oct – 12 Jan 1 Nov – 12 Jan B 18 15 Sept -15 Jan 15 Oct – 15 Jan 1 Nov – 15 Jan C 20 15 Sept -31 Jan 15 Oct – 31 Jan 1 Nov – 31 Jan C* (Cavan and Monaghan) 22 15 Sept -31 Jan 15 Oct – 31 Jan 1 Nov – 31 Jan These regulations should in theory, complement the growth of AD. With it now being a requirement to store slurry and other agricultural residues, it seems only logical that a farmer should be able to heat these products and recover energy for them. What’s more is that the spreading of digestate is safer for the environment than that of raw slurry (Holm-Nielsen et al., 2009).
  36. 36. 26 3.2.5 National Waste Management Policy Council directive 1991/156/EC was essentially the beginning of reform of Europe’s waste management practices. Figure 5 outlines the hierarchy put forth by this directive, which member states are expected to adhere to. In Ireland, this prompted the publishing of many documents such as “Waste Management Changing Our Ways (1998)” and “Waste Management: Taking Stock and moving forward (2004)” by the department of Environment and Local Government. The aims of such documents were to outline methods and strategies, to steer Ireland towards a more sustainable waste management system, one which didn’t revolve around dumping multiple waste types in a landfill. The council directive 1999/31/EC (known as the landfill directive) imposed strict operational regulations on municipal waste landfills, in order to minimize the multitude of negative effects this archaic disposal method had on the environment. This legislation focuses on the management of the organic fraction of municipal solid waste (OFMSW). Ireland was assigned the following targets for the diversion of biodegradable municipal waste going to landfill.  25% reduction of 1995 levels by 2010  50% reduction of 1995 levels by 2013  65% reduction of 1995 levels by 2016 Figure 5: Waste Management Hierarchy (DoELG, 2004)
  37. 37. 27 With higher levels of OFMSW being diverted from landfill, technologies such as composting and AD, along with thermal treatment techniques were expected to become more prevalent. These technologies occupy a more favourable positions in the waste hierarchy illustrated in figure 2. Anaerobic digestion sits between the recycling category and energy recovery category on this chart. A well-managed system can extract nutrients from the waste to facilitate nutrient recycling; whilst simultaneously recovering energy from the same material. Under article 5 of this legislation, member states were obliged to establish a national strategy, with a view to achieving the landfill diversion targets. In accordance with this rule; and probably most pertinent to the AD industry, the National Strategy on Biodegradable Waste was published in 2006. A study carried out on behalf of the European Commission revealed that the source separation of MSW into recyclable and organic waste streams and subsequent treatment of these streams individually leads to the lowest generation of GHG’s compared to other treatment scenarios (Smith et al., 2001). Paper, metals and plastics are to be recycled while degradable wastes are to be treated by composting or AD. Based on the findings of this repost along with an assessment of other European country’s waste regimes, the action plan recommended Ireland adopted the following measures to achieve the national waste targets:  Source separation of MSW: This has been relatively successful in the Dublin region at least, with every household subject to a 3-bin collection system (Dublin City Council, 2012). The dry-recyclable “green bin” had been in place prior to this repost and the brown bin for food waste followed shortly after.  Introduction of legal measures to control waste collection and disposal practices: S.I. No. 191/2015 has reinforced the regulations associated with the collection and treatment of food and bio-waste. Under Part II, paragraph 4 of this legislation, food waste may only collected by licenced hauliers and treated at authorized AD or composting plants. Part III of this instrument extends these regulations to householders stating that it is now an offence to place food waste with non-biodegradable materials. According to Part IV, paragraph 14 of this legislation, any person found in breach of these rules is liable to a maximum fine of €500,000 and/or 3 months in prison.
  38. 38. 28  Landfill levy: S.I. No 194 of 2013 amended the landfill levy from €65 per tonne to €75 per tonne from 1 July 2013 further discouraging waste collectors from disposing waste at these facilities.  Producer Responsibility Agreements: industries with high levels of a particular waste develop their own waste management practices on site. Coillte for example, stockpiles thousands of dry tonnes of biomass per year, with the intention of supplying customers with woodchip boilers or CHP installations. This initiative began with the view to treating waste wood in a more sustainable manner however the company now seeks biomass from sources other than their own as the demand for woodchip increased throughout the country (Coillte, 2015). Large enterprises such as Coillte have sufficient access to capital in order to finance such projects. Such ventures benefit the overall market as it stimulates interest in the sector and creates demand and supply scenarios.  Market Development: It is envisaged that, after implementing the aforementioned strategies successfully, the end result will be a market where demand for biodegradable waste is strong; and revenues are sufficient enough to offset the costs of the collection and treatment of bio-waste. The report recommends cooperation with authorities from Northern Ireland to facilitate the development of synergies and cater for improved economies of scale along the entire biomass supply chain. Before a biological waste treatment facility can become operational, it must satisfy the regulations set forth by the myriad of waste management acts between 1996 and 2008 along with the Protection of the Environment Act: S.I No. 27/2003. These instruments define the standards of practice any given facility must aspire to for the sake of minimising negative environmental impacts. This area is regulated by the EPA hence any organisation intending to operate a waste treatment facility must apply for a waste permit. S.I. No. 86/2008 outlines the different categories various waste treatment plants fall under and the regulations which apply to such. The third schedule of this act outlines the regulations with respect to a biological treatment facility such as a biogas plant; the costs vary according to the amount of waste intake per annum as outlined in table 7.
  39. 39. 29 Table 7: Cost of waste permits for a bio-degradable waste facility Intake per year Application fee Class 11 (Part II) <5,000 tonnes €300 Class 8 (Part I) <10,000 tonnes €1,000 Class 10 (Part I) >10,000 tonnes €10,000 Paragraph (d) of S.I. No. 283/2012 insists that a completed Environmental Impact Statement (EIS) must accompany any prospective applications to the EPA in search of a waste permit. An EIA must be completed by a licenced professional hence outside consultancy is required for any AD project in Ireland.
  40. 40. 30 3.3 Advantages of Anaerobic Digestion It is important to realise that anaerobic digestion will never contribute to the field of renewable energy generation as much as wind, hydro or even solar in Ireland. Even if the a thousand 380kW AD plants were built over night, maximising the potential of the available agricultural land space; this would equate to a contribution of only 6.5% towards Ireland 2020 renewable energy targets (JCCENR, 2011). However what AD lacks in energy potential, it makes up for in versatility and reliability as the following section will show. 3.3.1 Societal Benefits Renewable Energy Source AD utilizes biomass, in a variety of forms as a feedstock. Producing energy from biomass is considered an (almost) carbon neutral process as the CO₂ released during combustion of the biogas was previously removed from the atmosphere via photosynthesis (SEAI, 2013). The AD process also reduces methane emissions in the sense that energy is recovered from the gas before it is release into the atmosphere during combustion. Energy recovery offsets the use of fossil fuels improving the country’s energy security and assisting in the attainment of 2020 targets. AD contributes not only by electricity generation but also by heat generation when the biogas is used in a CHP unit. Furthermore AD holds a significant advantage over the likes of wind power as power output is relatively constant hence it acts as an excellent complimentary RES. Energy Security Fossil fuels accounted for 93.2% of Ireland overall energy usage in 2013, the majority of which are imported (SEAI(b), 2014). Being on the periphery of Europe; puts Ireland firmly at the end of a long and volatile supply chain. The country’s thirst for Russian gas and Libyan oil is an unsustainable habit. As political tensions rise and fossil reserves wane Ireland will be at the mercy of the markets and will have to pay exorbitant energy prices in the near future. At present there is simply no back up plan in place. The country needs to do everything in its power to wean itself off fossil fuel and realise the vast potential of its natural resources. AD however minor a contribution needs to be rolled out on a massive scale.
  41. 41. 31 Achievement of 2020 Targets Looking at the more immediate future, Ireland is expected to fall short of its 2020 renewable energy targets by between 1-4% which could possibly result in fines of between €140m and €600m a year to the exchequer (DPER, 2014). Wall et al (2013) has estimated that the construction of 170 farm-scale digesters treating silage and slurry can exceed the 10% of renewable energy supply in transport target should the gas be upgraded into a biofuel. Whether the industry follows this path or not is irrelevant, the simple fact is that AD can make some contribution to all three 2020 targets of electricity, heat and transport. Job Creation in Rural Areas Decentralisation has long been an objective high on the government’s agenda. The rolling out AD on a large scale is calculated to create 7800 jobs in construction, farming and manufacturing predominantly in rural areas (JCCENR, 2011). The average age in the agricultural sector is 54 according to a CSO agricultural census carried out in 2012 (Murphy, 2012). This is no surprise considering the mass exodus of young Irish people to foreign countries in recent years. The implantation of AD can breathe much needed youth into this sector. Waste Treatment In the AD process, waste is viewed as a resource; utilising locally produced waste materials to generate localised power (Asam et al., 2011). Ireland has been slow to adopt a modernised waste management system compared to its European Counterparts. Despite the ban on landfills, 43% of Irelands waste was still going to these facilities in 2012 (Appendix 1). It’s no surprise that the best performers in waste management are also highest achievers in the field of AD with Sweden and Denmark achieving diversion rates of 99% and 97% respectively. Zhang et al (2014) identifies AD as the best treatment method for biodegradable wastes due to their high water contents rendering them inefficient for thermal treatment. In addition food wastes can boost biogas production and lead to a more stable process when co-digested with agricultural slurries (Nizami et al, 2009).
  42. 42. 32 3.3.2 Agronomic Benefits Slurry Management Under the nitrates directive, farmers are obliged to have storage capacities for animal slurries for at least 20 weeks of the year. AD essentially carries out the same function whilst simultaneously deriving energy from the substrates. The solid substrate remaining after treatment is free from pathogens and has a higher nutrient content per unit volume that of raw slurry making it safer to apply to land. Furthermore the digestate has a lower biological oxygen demand making it less potent to aquatic environments should it reach them due to run-off (Holm-Neilsen et al , 2009). Odour Reduction The AD process reportedly reduces odour by 80% (Al Seadi et al., 2008). The resultant digestate after AD treatment has a much less pungent smell than raw slurry hence when it is applied to land there are less nuisance odours emitted to the surrounding countryside. Additional Revenue Streams When a CHP unit is deployed in conjunction with AD, electricity and heat can be generated on site. This can act to either offset electricity and heat use on-site, resulting in energy savings or alternatively electricity can be sold to the grid by securing a power purchasing agreement. In some countries, incentives are provided for the sale of heat however no such incentives exist in Ireland as of yet. It is also common practice to charge gate fees for any organic wastes the AD receives from off site. In Ireland the current rates are particularly lucrative with a tonne of food waste obtaining rates of ~€110. Digestate Replacing Chemical Fertilizers Digestate is rich in Nitrogen, Phosphorus, Potassium and other micronutrients. It also has an improved fertilization efficiency due to the improved homogeneity and a more favourable C:N ratio following AD.
  43. 43. 33 3.4 Barriers to AD 3.4.1 Complex Legislation Section 3.2 highlighted the fact that in order to get an AD project off the ground it is necessary to engage with or seek approval from no less than six governing bodies including, DCENR, DAFM, DoElG EPA, the local County Council and the national waste permit office. The sheer thoughts alone of dealing with so many bureaucratic agencies are likely to be too overwhelming for the average farmer. Every application costs a significant amount of time and money and in some cases, after investing such considerable amounts of time and effort; the project might not even gain approval for planning permission (Bywater, 2011). This necessitates that the inception of any biogas project will require consultancy from an early stage, making AD a costly affair even at feasibility study stage. 3.4.2 Non-competitive Incentives It has long been accepted that most if not all renewable energy systems require government subsidies in order to gain a competitive edge on the established fossil fuel markets. AD plants are no different; anything under the size of 1000 kW requires heavy incentives (Patrizio et al. 2015). Table 8: Irish feed-in tariff rates compared to the rest of Europe (Caslin, 2013) Country Price per kWh Germany 18-28c Italy 22-28c UK 18-25c N. Ireland 22-27c Austria 16-18c France 16c +Capital Grant Ireland 13-15c Table 8 highlights the fact that Ireland has the lowest feed-in tariff rates in Europe. A project which is marginally feasible in Dublin becomes a lucrative investment if sited a
  44. 44. 34 few kilometres North in Co. Down. The DCENR must assign tariffs that are at least in line with the rest of Europe. 3.4.3 Stakeholder Uncertainty With no platform for information to be circulated the benefits of AD are not common knowledge to many of the potential stakeholders within the sector. Reports of excessive downtime and technical difficulties are more likely to travel as opposed to a plant which has been operating successfully for extended periods of time. With the market in its infancy there is a lack of experienced contractors, planners, suppliers, maintenance companies who have worked with the technology hands on. Tying in with the complex legislation; projects in advanced stages of the planning process have been reported to be refused planning permission. 3.4.4 Lack of Access to Capital AD is an expensive investment and in almost all cases requires loans in order to finance. As a result of the banking crisis; money lenders are becoming increasingly selective on the types of projects they award loans to. The age profile of farmers in Ireland doesn’t help this situation. The average age of the Irish farming sector is now set at 54 (Murphy, 2012). It is extremely difficult for this demographic to gain access to finance because they are coming up so close on retirement age. Excessive conditions are usually necessary such as having to put forward collateral before a loan is granted.
  45. 45. 35 3.5 Vision for Ireland Ireland currently meets its energy requirements by importing in foreign oil and gas, burning it in large centralised stations and distributing it long distances to customers around the country. As fossil fuels become scarcer and scarcer it becomes less acceptable to lose so much of the energy generated due to the inefficiencies of transmission. Hence the days of the centralised grid are numbered. The future lies in a smart grid distribution system consisting of multiple smaller generators providing energy to their immediate surroundings. The beauty of this decentralised energy model is that excessive transmission losses are minimized. So how can Ireland adopt this new model and reduce its reliance on fossil fuels? At a recent conference on sustainability Brendan Halligan, Chairman of the Institute of International and European Affairs recommended (jokingly) that the best thing Ireland can to in order to modernise its energy system; is to take the Danish Energy Policy, translate it into English, and copy it down into our own legislation. (Sustainability Gathering, 2015). Despite the tongue in cheek tone there, appears to be a lot of merit in what Mr. Halligan was saying. While Ireland is struggling to achieve its 2020 targets, Denmark is well on its way to achieving their equivalent targets with renewables constituting a 28% share of their grid mix (Eurostat, 2015). Topping this list was Sweden, with a 52% share. In addition these countries currently sit at 33% and 19% below their 1991 CO₂ emissions respectively (European Commission, 2014). It is worth looking at appendix 1 to see where these countries are with respect to landfill diversion targets. It is safe to say these two countries are the over-achievers of Europe. When it comes to implementing a RES such as AD, one can safely say the Irish AD industry can take a lot away from their experiences. Both countries recognised that their respective governments had to create the appropriate economic conditions to facilitate the introduction of AD. Both the Danish and Swedish governments stimulated interest in the AD sector by imposing high taxes oil products and providing a fair feed in tariff rate for CHP installations (Raven & Gregerson, 2007; Swedish Biogas Association, 2011). Once
  46. 46. 36 the right incentives were in place, the private sector fabricated technologies to take advantage of them. Wholesale uptake of AD was just one outcome of this. Ireland on the other hand has increased its reliance on foreign fossil fuels in recent times as opposed to taxing them; while the REFIT rates are among the lowest in Europe. The government has failed to create the right environment for wholesale uptake of RES in general. This issue was raised in the House of the Oireachtas, with experts recommending a fair REFIT tariff of 19.5c/kWh for farm scale AD (JCAFM, 2010). Followed by this joint council, the refit rates were adjust only up as far as 15c/kWh as opposed to the recommended 19.5. While it is clear the government need to offer better incentives to stimulate investment, there are other factors which need to be addressed in order for Ireland to embrace AD in its full capacity. Raven & Gregerson (2007) note a key to Denmark’s success in this industry was the deployment of a “bottom-up strategy” which encouraged the dissemination of information pertinent to AD throughout all the stakeholders involved. They go on further to describe the success of a dedicated social network in enabling this bottom up approach. There are many dedicated experts conducting excellent research on this subject in Ireland however there is no dedicated social network to facilitate the interaction of various stakeholders. The SEAI is too broad, while the IrBEA are not very together as an organisation with a poorly maintained website and zero presence on social media. There is currently no institution driving this industry, no established centre of excellence. One final factor Raven & Gregerson (2007) mentions, is the willingness of small farmers to cooperate in small communities. Walker & Devine-Wright (2008) state that the practice of a large utility company building a wind farm owned by private equity firm offers no benefits to the community they are constructed in. It is no surprise that NIMBYism is so prevalent in the Irish mind-set. If however a radical technology change was implemented in which the community saw the direct benefits from such, attitudes will most definitely change. AD being the versatile technology that it is, offers many benefits to the immediate surroundings.
  47. 47. 37 The key question is how can Ireland realise this vision of implementing AD in a way that benefits its surrounding community? The general theme to emerge from the JCAFM (2010) discussion in the House of the Oireachtas is that Ireland’s principal feedstock for AD should be grass, given its relative abundance throughout Ireland. In the short term, Wall et al (2013) recommends a scenario of 170, “380kW” digesters, co- digesting dairy manure with grass silage in an effort to meet the RES-T target in 2020. This vision sees the rolling out of a RES system on a large scale whist simultaneously providing a slurry management solution to rural areas. Putting the argument that the government needs to offer greater incentives aside for the minute, what else is preventing uptake of AD? Bywater (2011) upon carrying out a review of AD in the UK identified the farmer as the most important stakeholders in AD. They are the ones taking the risks in building a digester, and they are the ones dealing with the system on a day-to-day basis. There is a common misconception among farmers that AD is only feasible at a large, centralised scale (Bywater, 2011). While it is true that the economies of scale become greater the larger a facility gets, the implementation of AD at farm scale is usually a worthwhile venture due to the multitude of other benefits the technology provides to the surrounding communities. In order to overcome this misconception, farmers need to be engaged and informed that AD is in fact feasible in their situations. This is what will drive the Irish AD forward, especially when an AD is recognised as an alternative slurry management system as well as RES. It is at this point that the country’s research institutions can step in and demonstrate, educate and inform farmers as well as other key stakeholders the key benefits of this technology. It’s useful to look at Dundalk IT as an example of what this might entail. Instead of demonstrating the key benefits of wind power in a classroom, the college went and physically built a turbine on campus. The ethos behind this project was that it was important for Ireland to expand its expertise in emerging renewable energy technologies (Ryan, 2005). With one of the most prestigious Schools of Agricultural and Food Science departments in the country, UCD is poised to emulate the ethos of the Dundalk wind
  48. 48. 38 project and apply it to anaerobic digestion. Such a project can allow stakeholders to gain a direct insight into the technology.
  49. 49. 39 CHAPTER 4 Objectives and Outcomes The fundamental objective of this project is to determine whether it is feasible under any scenario possible, to build an anaerobic digester at UCD. Within the AD industry the orthodox aims of building a digester are usually to generate an additional income or to adopt a more sustainable slurry management system. This project differs because the principle motivation for constructing a digester is to act as a template for potential stakeholders; in order to ease their uncertainties within the industry. Given the fact that UCD has one of the most esteemed Schools of Agriculture and Food Science Departments in the country, the development of a digester with which the college has complete control over can be viewed as a valuable asset to the department. It would not be unreasonable to suggest that UCD could become the centre of best practice AD in Ireland; educating and promoting sustainable agricultural practices and ensuring the industry thrives with the development of state of the art biogas plants throughout the country. As the proposed centre of AD excellence, UCD could offer the opportunity to all the relevant stakeholders, particularly farmers, to learn more about the technology, quelling the uncertainty which has so far been strangling any opportunity of the industry taking off. As well as farmers, financiers, contractors, government officials and the
  50. 50. 40 general public could be coaxed into engagement with this industry within the cosy confines of the campus in Belfield. To fulfil its objective as an exemplary technology appropriately, any proposed development must be a cost-effective, state-of-the-art technology which engages as many potential stakeholders as possible and utilizes most if not all of UCD’s organic waste. It is also envisaged that such a development will pave the way for future research. In order to determine if such a project is feasible, the financial feasibility of a number of different scenarios will be tested for both the UCD campus and Lyons Estate. The most feasible of each will then be presented in greater detail.
  51. 51. 41 CHAPTER 5 Scope and Methodology 5.1 Methodology This study was carried out in accordance with the prescribed methods recommended by Al Seadi et al, (2008) and Fischer et al (2010). A cost-benefit analysis formed the basis of the results for this project. This was carried out using the “Big-East Biogas Calculation” tool. This is a relatively detailed and robust model, recommended by the SEAI for estimating the investment costs and revenue streams of a biogas plant at preliminary project stages. Data for the following inputs were gathered in order to run the model. The projection for the best case scenario AD for Lyons estate is included in appendix 2. It would be useful to follow this whilst reading this section. 5.1.1 Estimation of Investment Costs To put an exact figure on capital costs at pre-feasibility study is next to impossible no matter how experienced the planner and consultant. A detailed interpretation of the literature pertinent to the construction of an AD in Ireland was carried out in order to determine the regulations which must be applied to the project. In order to determine the capital cost of the UCD scenarios; the approximate size of the facility required was estimated using the “Big East” calculation tool. This gave sufficient data to allow a comparison between the UCD scenario and one of the above case studies. Known cost
  52. 52. 42 per kilowatt data for these case studies allowed an appropriate figure be assigned to any given biogas scenario for UCD. Upon assigning a figure to the overall investment, it was necessary to provide a breakdown of these costs for the calculation of maintenance charges. Construction costs usually make up 30-40% while machinery makes up 10-20% of overall investment costs (SEAI, 2012). CHP was estimated at 500-1000 €/kWe (Caslin, 2013). Maintenance costs for these inputs were estimated at 5-7% (SEAI, 2012). An explanation of the grid connection process along with best estimates for the cost of such for an AD facility at Lyons estate was provided by Mr. Tom Canning B. Eng, a consultant engineer who once worked for the ESB. With respect to planning costs, Dun Laoghaire/Rathdown and Kildare county councils were contacted initially for information on planning permission however both were unwilling to provide assistance in the given time-frames of this project. Expert advice was sought from a sustainability architect, a Mrs. Ann Gallagher, M. Arch, to overcome this issue. The costs of the relevant permits were determined in section 3.2. 5.1.2 Estimation of Biogas Input Data Ensuring security of feedstock is generally accepted as the primary parameter that will determine a project’s feasibility. Initially the ideal scenario considered; involved the construction of an AD with a view to treating all the organic wastes produced by UCD. With the assistance of Mr. Gary Smith from campus services, this data was collected by liaising with the respective managers of each department. This included the student sports and leisure centre, campus services, the first restaurant at the Gerard Manly Hopkins centre, the School of Veterinary Medicine and Lyons Farm. As the project progressed another scenario was considered in which additional feedstocks would be imported in order to improve the projected economies of scale and reduce payback periods. This scenario considered the possibility of building an AD under the guise of the Higher Education authority of Ireland. Organic waste data was gathered from Trinity College by interviewing the grounds and maintenance manager who wishes not to be named. Organic waste data for DIT was readily available on its college website.
  53. 53. 43 Upon compiling all this data; the results suggested that the economies of scale could be improved even more. The possibility of importing additional feedstocks was considered. Under this train of thought, it emerged that the collaboration between UCD and a large food-processing company could prove extremely beneficial. One final scenario involved testing the feasibility of Wall et al’s (2013) vision of co-digesting grass silage with animal slurries. 5.1.3 Determination of the Cost of Biomass Waste streams indigenous to UCD were considered as a baseline feedstock for the potential AD hence there are no costs of procurement for this portion of feedstock. Given their low energy density (Pöschl et al., (2010), under no circumstance would slurry be transported in any scenario of this project. Costs associated with truck transport of food waste were derived from Blaschek et al (2010). Current costs of grass silage were estimated from Reidy (2015). 5.1.4 Revenue Streams and Finance Plans REFIT tariffs used in the model were those outlined in table 4. Income from heat produced was assigned a value recommended by the model itself as there are currently no government incentives which this project can avail of. The exact cost to UCD or Trinity for organic waste disposal was protected by commercial secrets. Estimates for tipping fees for the disposal of food waste were extracted from Creedon et al (2010). The sale of digestate was not considered in this project; it was assumed that such would be utilised by UCD directly. Typical Interest rates for construction loans were determined from The Central Bank (2015) and were applied to the project financing plan. Sources of funding are considered in chapter 7.
  54. 54. 44 5.1.5 General Business Costs The smaller scale scenarios, utilising indigenous wastes were considered to be rather easy to manage and did not consider employing any administrators or operators. Once scenarios began considering the importation of feedstocks, wages for a part-time administrator were included. The site was assumed to be rent free given the fact the land in both scenarios is owned by UCD. Costs for insurance were estimated on a per square meter basis. The cost for transporting food waste, mentioned in section 5.1.3, was included in the “other individual costs” section. The economic feasibility of each scenario was considered first using this model. The best case scenario for both the campus and Lyons estate were then considered in more detail as ideal systems for implementation at UCD. 5.2 Site Selection The selection of a suitable site was a relatively simple process given the mass expanse of land that UCD has at its disposal. Two site scenarios were considered for building the potential digester; one on campus at UCD and the other on the college research farm at Lyons Estate. 5.3 Constraints Pre-feasibility studies are generally given no funding and are usually pressed for time. Given the nature of these studies; commercial enterprises and administrative agencies are extremely reluctant to part with information especially that which involves cost. Commercial entities are generally bound by commercial secrets and are reluctant to provide detailed information to a project in its preliminary stages as they are not guaranteed to win the contract for building the project at this stage. Administrative agencies such as the county council require a clear and detailed plan of the proposed development and will only meet under the circumstances of a fee-paid pre-planning meeting. Upon contacting both Kildare and Dun Laoghaire/ Rathdown county councils; along with a number of government departments it became clear that meeting with any of these bodies would not be possible within the time-frame of this project.
  55. 55. 45 5.4 Assumptions Despite minimal correspondence from the appropriate agencies, for the most part, it was possible to “read around” the issue and obtain as detailed information required from similar case studies and best estimates from the consultants mentioned in section 5.1. It is accepted that exact figures are not usually found at pre-feasibility in any circumstance however every measure was taken to ensure the data in this study was as robust as possible. The aim was to limit the occurrence of financial surprises to potential investors for the project.
  56. 56. 46 CHAPTER 6 Cost-Benefit Analysis 6.1 Rationale of Inputs 6.1.1 Investment Costs Table 9 summarizes the capital costs of a number of biogas facilities throughout Europe and Ireland. These facilities are ranked in order of their cost per kilowatt hour to provide a template with which to estimate the investment costs for this study. Topping this list is the Lintrop facility in Denmark; one of the largest centralised AD facilities in the world. This plant treats a massive 547 tonnes of material a day. This was only included in this table to demonstrate the effect economies of scale has on the financial feasibility of AD. A facility of this scale will not be considered for implementation at UCD. Second on the list is the Ballytobin plant in Kilkenny. At first glance the economics of this facility appear to excellent with an extremely low cost per kW despite its relatively small scale. However the kW output is that of heat, no electricity. According to SEAI (2005) the facility failed to secure a power purchasing agreement from CER. The operators had no choice but to utilise the biogas in boilers for the production of heat. This is a much less efficient and less lucrative option hence payback periods on the plant are more excessive than they should be.
  57. 57. 47 Table 9: Economics of biogas plants in UK, Germany, Denmark and Ireland Facility Feedstock (t/d) Output (kW) Capital Cost (€) Cost per kW (€/kW) Source Lintrop 547 2084 kWel 5,500,000 2639 (Monson et al, 2007) Ballytobin 21 220 kWth 800,000 3636 (SEAI, 2005) Pellmeyer 55 690 kWel 3,000,000 4347 (Patterson et al, 2009) Kemble Farms 54 300 kWel 1,680,000 5600 (Bywater, 2011) McDonnell Farms 24 250 kWel 1,500,000 6000 (SEAI, 2014) Greimel 34 500 kWel 3,000,000 6000 (Patterson et al, 2009 b) Copy’s Green Farm 14 140 kWel 1,000,000 7142 (Bywater, 2011) UCD Campus Scenarios 0.34-1.2 15-28 kWel 400,000 26,000- 14,000 (SEaB Energy, 2015) UCD Lyons Estate Scenarios 22-26 200- 250kWel 1,300,000 6500-5200 The remaining five facilities appear to follow a pattern of the greater the power output, the more favourable the financials. The only exception to this pattern is the Greimel facility. Monson et al (2007) attribute the facility’s poor economic performance to complications in the construction phase, which added to the overall capital cost. Once a figure is obtained for the overall investment cost, it is necessary to determine how this is broken down for the model to accurately project maintenance costs. Referring to table 10, the top four parameters of construction, maintenance, CHP and machinery are estimated in the form of percentages recommended by the literature and vary according to the investment cost. The bottom four parameters are relatively constant throughout each scenario as they do not vary to the same degree according to investment cost. These figures were provided by the architectural and engineering consultants mentioned previously and more detail is provided on such in chapter 7.
  58. 58. 48 Table 10: Break-down of investment costs for each scenario Break-down Method of Estimation Overall Capital Cost 5500-7500 €/kW Output Construction 30-45% Capital Costs Maintenance 5% Construction Costs; 5% Machinery costs; 1% CHP costs CHP 700-1000 €/kW Output Machinery 10-20% Capital Costs Planning 8600 Permits 3000 Consultancy 45000 Grid Connection 110,000 – 427,000 Grid Connection: The proposed AD is anticipated to have a maximum export capacity (MEC) of well below 500 kW hence it is eligible for connection to 110 kV network or less. This means the project has to apply for grid connection through ESB networks. This project is most likely to go under the sequential planning procedure. Connection costs can be considerable depending on the proximity of the site to the nearest suitable connection site. According to Tom Canning from ESB international, there are an abundance of connection points at the proposed site at Lyon’s Farm while the UCD scenario will not require a grid connection at all considering the constant high demand for both heat and power on campus. The best estimates of €110,000- €427,000 are calculated from ESB Networks (2015). 6.1.2 Biogas Input Data Table 11 reveals the assumptions made related to the feedstocks available to UCD in the various scenarios. The quantities of animal slurries were obtained directly from Lyon’s farm based on 90 dairy cows, 200 beef, 150 pigs and 500 ewes. With the cap on the national herd being lifted this year; the dairy herd is set to expand on the farm while the beef herd is to be contracted.
  59. 59. 49 Table 11: Characteristics of feedstocks considered for every scenario Feedstock Quantity (t/a) Biogas Yield (m³/t) Dry Matter Content (%) Methane Content (%) Cattle/Pig Manure 3809 28 10 58 Dairy/Sheep Manure 4190 70 22 55 Food Waste 129- 2800 179 35 60 Grass Silage 4000 225 40 55 Three different food waste quantities are examined ranging from 129 t/a to 2800 t/a. The importation of grass silage is considered for one scenario. The figures associated with biogas yield, DM content and methane composition are based on estimates provided by Al Seadi et al (2008) as well as from Fischer et al (2010). 6.1.3 Cost of Biomass The majority of feedstocks listed in table 6-9 are collected at source hence there are no associated costs for the procurement of such. Food waste is calculated at 12-20 €/t assuming distances are under 50km (Blaschek et al., 2010). The current costs of grass silage are estimated at 28-32 €/tonne (Reidy, 2015). 6.1.4 Revenue Streams and Finance Plans As illustrated in table 4, every scenario studied in this project is entitled to a REFIT rate of 15c/kWh of electricity produced. The current lack of renewable heat incentives in Ireland mean any revenues from thermal energy will be minimal. A default value of 2c per kWh is assumed in this model. The current costs of disposing food waste in Ireland are estimated at €110- €185 per tonne (Creedon et al., 2010).With the exception of the “food processing company” scenario; the model used the conservative amount of 110€/t as a number of sources throughout the data collection process hinted at figures close to this amount. If UCD were to go down the route of sealing a long term contract to take waste from a processing company, it would undoubtedly have to offer a
  60. 60. 50 competitive gate fee to entice the company into cooperation. Tipping fees were set at 80 €/t in this scenario. Digestate is assumed to generate no revenue in this study. The costs of offsetting artificial fertilizers with such were also left outside the scope. An interest value of 3.8% on construction loans was applied to the financing section of this model as recommended by the Central Bank of Ireland (2015). 6.1.5 General Business Costs The smaller scale scenarios assume no operator or administrator is required. The larger scale scenarios include wages of €26,000 one employee assuming an operator/administrator role. Rent for the site is assumed to be zero considering UCD own both site being considered. Insurance is assumed at 3€/m³/yr for all scenarios based on the default recommendation of the model. Other parameters in this section are deemed irrelevant to the types of digesters being considered for this project.

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