Life Cycle Analysis of Algal Biofuel


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Life cycle analysis of micro-algae based bio-fuel production (cradle-to-gate)

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Life Cycle Analysis of Algal Biofuel

  1. 1. IndianAgriculturalResearchInstitute,NewDelhi
  2. 2. IndianAgriculturalResearchInstitute,NewDelhi
  3. 3. Introduction  With the ever growing world population and technological advances in all works of life, world energy demand is expected to rise by 44% while CO2 emissions will see an increase of 39% by the year 2035 (U.S. Energy Information Administration, 2010)  Developments of renewable source of energy  Renewable energy – solar, wind or geothermal; hard to store  Biofuel – biodiesel and bioethanol  Biodiesel advantageous over conventional diesel fuel – * 4 times faster degradation * Safer and non-toxic * Higher flash point (100-170 C) (NREL, 2009) IndianAgriculturalResearchInstitute,NewDelhi
  4. 4. Introduction …  1st generation biofuels – bioethanol produced by fermentation of starch (e.g. wheat, barley, corn or potato) or sugars (e.g. sugarcane or sugar beet) and biodiesel (FAME) produced by trans-esterification of oil (e.g. rapeseed, soybeans, sunflower, palm, coconut) and animal fats (Chisti, 2007)  2nd generation biofuels – bioethanol and biodiesel produced from the residual, non-food parts of crops (Jatropha, cassava or Miscanthus), and from other forms of lingo-cellulosic biomass such as wood, straw, grasses, and municipal solid wastes (Inderwildi and King, 2009)  Criticisms – Conversion of food crops into biofuels is unsustainable (Scharlemann and Laurance, 2008) – limited energetic and environmental benefits IndianAgriculturalResearchInstitute,NewDelhi
  5. 5. Introduction …  3rd generation biofuels – algae-derived fuels such as biodiesel from microalgae oil, bioethanol from microalgae and seaweeds, and hydrogen from green microalgae and microbes (Aylott, 2010; Dragone et al., 2010) IndianAgriculturalResearchInstitute,NewDelhi
  6. 6. Why algae? IndianAgriculturalResearchInstitute,NewDelhi  For production of 60 billion gal/year of biodiesel at a productivity rate of algae at 50 g/m2/day with 50% triglycerides, the CO2 required for necessary algae cultivation would be 0.9 billion ton/year which is 36% of the total US power plant emissions (Pienkos, 2007)  The other nutrients required for cultivation such as nitrogen and phosphorus can be obtained from organic waste from agri-food industry (Cantrell et al., 2009)  Oil yield from microalgae per acre of land used is huge Plants/ organisms Oil yield (gallons/acre) Soybean 48 Jatropha 202 Palm oil 635 Algae @ 10 g/m2/day with 15% triglyceride 1200 Algae @ 50 g/m2/day with 50% triglyceride 10000  Biofuels from microalgae are fast attracting international research interest * They do not compete for agricultural land * High photon conversion efficiency * Metabolic storage of intracellular lipids, carbohydrates and triglycerides * They produce 15-300 times more feedstock for biodiesel production than conventional, terrestrial bioenergy crops (Chisti, 2007)  Coupling photosynthetic efficiency with biomass production offers exciting prospects for producing renewable biofuels (Greenwell et al., 2010; Scott et al., 2010)
  7. 7. Hurdles  Various technological and economic issues (commercial scale deployment, cost of the biodiesel)  It is important to study in detail the environmental impacts of implementing such technologies and their sustainability to avoid „problem shifting‟ or “The displacement or transfer of problems between different environmental pressures, product groups, countries or over time”  Need for adoption of a cradle-to-grave perspective and assessment of several environmental impacts  Life Cycle Assessment/Analysis (LCA) - ISO method: it allows the detection of pollution transfer from one step to another one or from one kind of environmental impact to another one IndianAgriculturalResearchInstitute,NewDelhi
  8. 8. Life cycle assessment “Compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product system throughout its life cycle.” - International Organization for Standards (ISO, 1997) IndianAgriculturalResearchInstitute,NewDelhi
  9. 9. Types of LCA  Conceptual LCA – Life Cycle Thinking Very basic level assessment of environmental aspects presented using qualitative statements, graphics, flow diagrams or simple scoring systems which indicate which components or materials have the largest environmental impacts and why  Simplified LCA Covers whole life cycle superficially by using generic data and standard modules for energy production * Screening * Simplifying * Assessing reliability  Detailed LCA Involves full process of undertaking LCAs and require extensive and in-depth, data collection, specifically focused upon the target of the LCA IndianAgriculturalResearchInstitute,NewDelhi
  10. 10. Phases of LCA  LCA generally has 4 phases - (i) Goal and scope definition (ii) Inventory analysis (LCI) (iii) Impact assessment (LCIA) (iv) Interpretation  All phases are often interdependent in that the results of one phase will inform how other phases are completed (ISO 14040-14044: 2006) IndianAgriculturalResearchInstitute,NewDelhi
  11. 11.  Starting key step * Sets out the context of the study * Explains how and to whom results are to be communicated  The goal and scope of a LCA should be * Clearly defined * Consistent with the intended application  The goal and scope documents: * The functional unit * The system boundaries * Any assumptions and limitations * The allocation methods used to partition the environmental load of a process when several products or functions share the same process * The impact categories chosen IndianAgriculturalResearchInstitute,NewDelhi Goal and Scope Definition
  12. 12.  Defines what is being studied  Quantifies the service delivered by the product system  Provides a reference to which the inputs and outputs can be related  Enables alternative goods, or services, to be compared and analysed IndianAgriculturalResearchInstitute,NewDelhi Functional Unit  can be set to different extends depending upon the goal of the study  Variants:  cradle to grave (raw material extraction- usage of the product)  cradle to gate (raw material extraction- production)  cradle to cradle (extraction of raw material- production- distribution- usage- disposal- recycling)  gate to gate (production process) System Boundaries
  13. 13.  Involves creating an inventory of flows from and to nature for a product system  Development of a flow chart of the system to show mass and energy flows included in the processes  Compilation of the mass and energy inputs and outputs and their quantification throughout the life cycle of the system (Rebitzer et al., 2004) IndianAgriculturalResearchInstitute,NewDelhi Life Cycle Inventory (LCI)
  14. 14.  Evaluates the environmental and potential human health impacts of the system  4 mandatory elements: * selection of impact categories, category indicators and models, * assignment of the LCIA results (classification), * calculation of category indicator results (characterisation), * data quality analysis  Optional elements: * Normalization: Comparison of the results of the impact categories from the study with the total impacts in the region of interest * Grouping: Sorting and possibly ranking the impact categories * Weighting: Allowance or adjustments of the different impacts relative to each other so that they can then be summed to get a single number for the total environmental impact IndianAgriculturalResearchInstitute,NewDelhi Life Cycle Impact Assessment (LCIA) Impact categories Category indicators Classification Characterization Global Warming Potential GWP CO2 Kg CO2 eq. Acidification Potential AP SO2 Kg SO2 eq. Eutrophication Potential EP PO4 3- Kg PO4 3- eq. Ozone Depletion Potential ODP CFC-11 Kg CFC-11 eq. Photochemical Ozone Creation Potential POCP C2H2 Kg C2H2 eq. Abiotic Depletion Potential ADP Oil/mineral Oil/mineral eq.
  15. 15.  GHG emissions to the atmosphere retain heat in the Earth‟s ecosystem by absorbing reflected radiation, resulting in global warming  GWP is an index to measure the contribution to global warming of a substance that is released into the atmosphere  E1 = Σ eC1,jBj (kg) (Bj = Emission of green house gas j eC1,j = GWP factor for j)  Expressed relative to GWP of CO2 IndianAgriculturalResearchInstitute,NewDelhi Global Warming Potential (GWP) j = 1 J 1
  16. 16.  Acidification is a consequence of acids being emitted to the atmosphere and subsequently deposited in surface soils and water resulting in negative consequences for coniferous trees and the death of fish in addition to increased corrosion of manmade structures  AP is based on the contributions of SO2, NOx, HCl, NH3 and HF to the potential acid deposition in the form of H+ (protons)  E2= Σ eC2,jBj (kg) (Bj = Emission of gas j eC2,j = AP of gas j)  Expressed relative to AP of SO2 IndianAgriculturalResearchInstitute,NewDelhi Acidification Potential (AP) j = 1 J 2
  17. 17.  Eutrophication originates mainly from N and P (such as N, NOx, NH4+, PO4 3-, P and COD) in sewage outlets and fertilizers  Nutrients accelerate the growth of algae and other vegetation in water. Degradation of this organic material consumes oxygen resulting in oxygen deficiency and fish kill  EP quantifies nutrient enrichment by the release of substances in water or into soil  E3= Σ eC3,jBj (kg) (Bj = Emission of a species j eC3,j = EP of species j)  Expressed relative to EP of PO4 3- IndianAgriculturalResearchInstitute,NewDelhi Eutrophication Potential (EP) j = 1 J 3
  18. 18.  The ozone layer in atmosphere protects plants and animals from the sun‟s harmful UV radiation  Some substances in atmosphere (CFCs, halogenated hydrocarbons, N2O) make the ozone layer decline, resulting in an increased UV radiation level at ground level  E4= Σ eC4,jBj (kg) (Bj = Emission of a ozone depleting gas j eC4,j = ODP factor of j)  Expressed relative to ODP of CFC-11 IndianAgriculturalResearchInstitute,NewDelhi Ozone Depletion Potential (ODP) j = 1 J 4
  19. 19.  Photochemical ozone (ground level ozone or summer smog) is formed by reaction of VOCs and nitrogen oxides in presence of heat and sunlight  Excess ozone can lead to damaged plant leaf surfaces, discolouration, reduced photosynthetic function and ultimately death of the leaf and finally the whole plant and in animals, it can lead to severe respiratory problems and eye irritation  E5= Σ eC5,jBj (kg) (Bj = Emission of species j participating in summer smog formation eC5,j = Classification factor for smog formation)  Expressed relative to the POCP classification factor for ethylene IndianAgriculturalResearchInstitute,NewDelhi Photochemical Ozone Creation Potential (POCP) J j = 1 5
  20. 20.  ADP includes depletion of non-renewable resources i.e. fossil fuels, metals and minerals  E6= Σ Bj / eC6,j (Bj = Quantity (burden) of the resource used eC6,j = Estimated total world reserves of that resource) IndianAgriculturalResearchInstitute,NewDelhi Abiotic Depletion Potential (ADP) J j = 1 Other Impact categories  Human Toxicity Potential (HTP)  Aquatic Toxicity Potential (ATP) 6
  21. 21. IndianAgriculturalResearchInstitute,NewDelhi Life Cycle Assessment Software, Tools and Databases Understand Develop Implement
  22. 22.  Systematic technique to identify, quantify, check, and evaluate information from the results of LCI and LCIA  Interpretation should include: * Identification of significant issues based on the results of the LCI and LCIA phases of an LCA * Evaluation of the study considering completeness, sensitivity and consistency checks * Conclusions, limitations and recommendations  Helps to determine the level of confidence in the final results and communicate them in a fair, complete, and accurate manner IndianAgriculturalResearchInstitute,NewDelhi Interpretation
  23. 23.  Micro-algal biofuel production consists of 4 processes: * Microalgae cultivation * Biomass harvesting * Micro-algal oil (lipid) extraction * Oil conversion to final products (e.g. biodiesel) IndianAgriculturalResearchInstitute,NewDelhi Case Study
  24. 24. LCA goal and scope  ICES microalgae-to-biodiesel production: - From cultivation and harvesting (integrated lab-scale), - Lipid extraction (lab scale with estimated energy requirements), - Theoretical conversion (from literature), - Sensitivity analysis.  Comparison of ICES microalgae-to-biodiesel system with five other case studies For (II), comparisons will be made against ICES ‘Base Case’ and a projected ‘Optimistic Case’ IndianAgriculturalResearchInstitute,NewDelhi The selected functional unit for all cases is 1 MJ as the high calorific value of biodiesel Methods
  25. 25. It can be quantified by comparing energy inputs required in each LCA stage and compare the total required inputs with the embodied energy of that biofuel product CO2 balance It is critical to consider the total emissions from fossil energy and resource consumption Vs. the CO2 intake by the microalgae during cultivation IndianAgriculturalResearchInstitute,NewDelhi Energy balance 1 tonne of algal biomass is estimated to fix (or sequester) 1.5-1.8 tonnes of CO2 (Patil et al., 2008)
  26. 26.  From cradle-to-gate, starting from microalgae cultivation and ends with biodiesel production as the main product  The ‘cradle’ stage begins with an integrated photobioreactor- raceway system for cultivating microalgae Nannochloropsis sp. From here, wet biomass is harvested and dewatered to produce dry biomass  Lipid extraction is carried out with the use of solvents which are assumed to be fully recycled IndianAgriculturalResearchInstitute,NewDelhi Modelling parameters
  27. 27.  The production of biodiesel from lipid is carried out via trans- esterification with the help of methanol  Main energy inputs and CO2 emissions/absorption by microalgae will be included throughout the life cycle  Emissions of wastewater and other types of air pollutants are not covered in the LCA  Any by-products (glycerine) are also not taken into account  Waste (solids or wastewater) treatment is not covered in the LCA  The final heat energy content of the biodiesel product is 40 MJ/kg (base case) IndianAgriculturalResearchInstitute,NewDelhi Modelling parameters …
  28. 28. IndianAgriculturalResearchInstitute,NewDelhi ICES microalgae-to-biodiesel system
  29. 29.  Microalgae: Nannochloropsis sp.  Culturing system: Integrated PBR and raceway pond  Doubling time: 12 hours  Cell density: 0.5 g/L  2000 L culture volume needed to produce 1 kg biomass  Growth medium provided with elements (N and P) in PBR  Energy requirement for CO2 pumping (2%) for mixing: 0.0222 kWh per kg CO2 (Kadam, 2002) IndianAgriculturalResearchInstitute,NewDelhi Microalgae cultivation
  30. 30. IndianAgriculturalResearchInstitute,NewDelhi Microalgae cultivation …
  31. 31.  Coagulant: FeCl3.6H2O @ 250 mg/g biomass  Air sparging assisted coagulation flocculation (ASACF) process  Biomass content: 3%  Energy consumption in ASACF: 16.7 kJ  Dewatering by centrifugation  Biomass content: 15% energy consumption by centrifuge: 360 kJ/kg of biomass (dry equivalent) IndianAgriculturalResearchInstitute,NewDelhi Biomass harvesting
  32. 32.  Microalgae contains 15-60% lipids per dry biomass weight (Demirbas et al., 2011)  Lipid content of 25% to be extracted from the dry microalgal biomass  Solvent extraction: hexane: methanol (3:1 by volume)  Solvent-to-dry biomass: 20:1  Lipid-depleted biomass settles at the bottom  Extract was decanted and filtered  Evaporation and recycling IndianAgriculturalResearchInstitute,NewDelhi Microalgal oil (lipid) extraction
  33. 33.  Total energy demand (lipid extraction process + evaporation step): 3.8 MJ per MJ biodiesel (or 152 MJ/kg) A simple mass balance is applied as:  From the content of 25% lipid in algal biomass, 1 kg of dry micro- algal biomass can produce a theoretical maximum of 0.25 kg of lipids. This further translates to 4 kg dry biomass per kg lipid  From 1 kg lipid produced, 90% is converted to biodiesel. Therefore the total amount of dry algal biomass required to produce 1 kg biodiesel = 4.44 kg dry biomass  Heat of combustion of the microbial oils can be 38-42 MJ/kg. (Sorguven and Özilgen,2010) IndianAgriculturalResearchInstitute,NewDelhi Micro-algal oil (lipid) extraction …
  34. 34.  Chemical conversion of oil by trans-esterification  Total energy input: 540 MJ/tonne biodiesel (Janulis, 2004)  30.3 MJ of energy required to produce 1 kg methanol (methanol : lipid = 6.5:1) (Pleanjai and Gheewala, 2009)  50% methanol recycled  Total energy consumption per kg biodiesel = 0.054 MJ/kg (electricity input) + 3.15 MJ/kg (methanol input) = 3.2 MJ/kg IndianAgriculturalResearchInstitute,NewDelhi Biodiesel production
  35. 35. Preliminary energy and CO2 results Energy requirement: 0.56 MJ Energy requirement: 3.88 MJ per MJ biodiesel per MJ biodiesel Total energy demands: (0.56 + 3.88) = 4.44 MJ (13% = biomass production, 85% = lipid extraction and 2% = biodiesel production) IndianAgriculturalResearchInstitute,NewDelhi Results and discussions
  36. 36. Sensitivity analysis  Increase of lipid content from 25% to 35% and 45% Manipulation of micro-algal lipid metabolisms (i) Induce nutrient stress during cultivation (ii) Selection of species with high lipid content (Greenwell et al., 2010)  Lower energy requirements for lipid extraction by 1.5 MJ and 2.5 MJ per MJ biodiesel Nannochloropsis sp. contain very rigid cell walls (Wijffels et al., 2010) * Lipid extraction is a big challenge * Energy decrements as small steps IndianAgriculturalResearchInstitute,NewDelhi Results and discussions …
  37. 37. Sensitivity analysis  Heat of final biodiesel product value of 38 and 42 MJ/kg Energy content of biodiesel ranges between 38 and 42 MJ per kg biodiesel (Sorguven and Özilgen, 2010) IndianAgriculturalResearchInstitute,NewDelhi Results and discussions …
  38. 38. LCA comparisons with other case studies  Comparison of energy and environmental performance based on both laboratory and projected (hypothetical) industrial scale (Stephenson et al., 2010; Lardon et al., 2009) IndianAgriculturalResearchInstitute,NewDelhi Results and discussions …
  39. 39. LCA comparisons with other case studies  Parameters: (i) lipid content of 45% (ii) 1.8 MJ per MJ energy demands for lipid extraction (iii) final heating value of product 42 MJ/kg  Total life cycle energy demand for ICES „Base Case‟: 4.44 MJ per MJ biodiesel (25% efficiency)  LCA carried out by NREL in 1998 reported an input of 1.2 MJ of fossil energy to produce 1 MJ conventional petro-diesel (83.3%efficiency) IndianAgriculturalResearchInstitute,NewDelhi Results and discussions …
  40. 40. Further discussions (limitations)  Quantitative investigations of different LCA systems and results are not straightforward  Cases differ in species variation, cultivation methods, operating conditions and use of biomass to make different products IndianAgriculturalResearchInstitute,NewDelhi Results and discussions …
  41. 41. Further discussions (limitations)  No internationally agreed conclusion on the environmental burdens or benefits from this seemingly green renewable energy alternative  This case study was investigated to emphasize the main challenges of the microalgae-to-biodiesel value chain  „Base Case‟ results highlighted that the main energy burdens were from lipid extraction (primarily) and next, biodiesel production  From the „Base Case‟, sensitivity analysis was performed by making adjustments to the energy requirements, percentages of lipid contents, and lower and higher heating product value  In „Optimistic Case‟, total life cycle energy requirements dropped significantly – by nearly 60% IndianAgriculturalResearchInstitute,NewDelhi Results and discussions …
  42. 42.  LCA is used to analyse various microalgae-to-biofuel production  Main bottleneck for most systems lie in the energy intensive processes of lipid extraction, and next, biodiesel production  Highly favourable results can be generated when the energy requirements for the extraction of lipids or biodiesel production were excluded from the study  Each unique case is modelled with different LCA assumptions or conditions, making a justified comparison rather difficult  However, this does not undermine the importance of using LCA to set an overall benchmark and test the feasibility of any biofuel production system IndianAgriculturalResearchInstitute,NewDelhi Conclusions
  43. 43.  Systematically estimate the environmental consequences and to analyse the exchanges that take place to the environment and are related to the examined product or process  Quantify the emissions into air, water and land that take place in every life cycle phase  Detect significant changes in the environmental effects between the life cycle phases IndianAgriculturalResearchInstitute,NewDelhi Advantages of LCA  Estimate the effects of materials consumption and environmental emissions on human and the eco-system  Compare the consequences to human and to the eco-system of two or more competitive products or processes  Allocate the impacts of the examined product or process in one or more items of environmental interest
  44. 44.  A holistic LCA is a very data-intensive and time-consuming procedure  There is not a generally acceptable LCA methodology  The selected and analysed system in some of the studies does not include the overall life cycle of the examined product or process, but it is only confined to specific stages  The assumptions made in such studies might be subjective  The results of such studies are focused on national and regional level and they might not be suitable for local applications  The accuracy of a LCA study depends on the quality and the availability of the relevant data IndianAgriculturalResearchInstitute,NewDelhi Disadvantages of LCA
  45. 45.  LCA for algal biofuel production demand a careful design of reference system, system boundary and inventory establishment  Contemplating the next decade of LCA involves considering the dynamic processes in the human and natural environments that may drive the need for assessment of environmental burdens  Utilization of biological nitrogen, CO2 and NO2 for some special purpose  Co-products, by products and residues can enhance energy and GHG savings through substitution of fossil fuel use IndianAgriculturalResearchInstitute,NewDelhi Future prospects
  46. 46. IndianAgriculturalResearchInstitute,NewDelhi