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CAN CROP MANAGEMENT IMPROVE EMISSIONS SAVINGS?: PRELIMINARY RESULTS OF THE OPTIMIZATION OF RYE (Secale cereale L.) AS ENERGY CROP FOR ELECTRICITY PRODUCTION IN SPAIN
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CAN CROP MANAGEMENT IMPROVE EMISSIONS SAVINGS?: PRELIMINARY RESULTS OF THE OPTIMIZATION OF RYE (Secale cereale L.) AS ENERGY CROP FOR ELECTRICITY PRODUCTION IN SPAIN

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Several studies suggest that lignocellulosic energy crops for electricity production may have a better performance compared to those crops for liquid biofuels production, when assessing GHG savings …

Several studies suggest that lignocellulosic energy crops for electricity production may have a better performance compared to those crops for liquid biofuels production, when assessing GHG savings with respect to fossil references. Winter cereal residues and some annual winter grasses, as dedicated energy crops, are currently being grown in Spain and harvested as bales to be burned for electricity production in biomass power plants. Previous studies of our group analyzed GHG emissions and energy balances of winter cereals for electricity production by means of Life Cycle Assessment. We selected highly productive genotypes of three annual winter cereals (rye, triticale and oat) and compared them with Spanish electricity produced using natural gas. This paper compares effects of the use of different crop management practices for rye growing in the assessment of energy balances and GHG emissions. We analyzed the effects of six different management practices consisting of two different sowing doses (suboptimal and normal) combined with three top fertilization doses (zero, 30 and 80kgN ha-1). We made a characterization analysis of biomasses to estimate the nitrogen uptake of the crops in order to compare it with the nitrogen provided by the fertilizers. This comparison evaluates if lower fertilization doses are sustainable for the soil nitrogen stocks. Our results suggest that there is trade-off between soil nitrogen and emission savings. The use of zero or low top fertilization doses (30 kg N ha-1) improves GHG emissions and energy balances even with a yield reduction. Nevertheless the use of these doses imply an annual lose in soil nitrogen stocks for the majority all of our trials. Using suboptimal sowing doses resulted in yield decreases that did not compensate the lower input consumed.
Keywords: electricity, energy balance, energy crops, greenhouse gases (GHG), life cycle assessment (LCA), sustainability criteria

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  • 1. CAN CROP MANAGEMENT IMPROVE EMISSIONS SAVINGS?: PRELIMINARY RESULTS OF THEOPTIMIZATION OF RYE (Secale cereale L.) AS ENERGY CROP FOR ELECTRICITY PRODUCTION IN SPAIN Martín-Sastre C.1*, Maletta E.2, Ciria P2, Perez P.2, del Val A.2, Santos A. M.1, González-Arechavala Y.1 and Carrasco J. E.21 Institute for Research in Technology (IIT) - ICAI School of Engineering - Comillas Pontifical University - E-28015, Madrid (Spain). Phone: +34 91 542-2800, Fax: +34 91 542-3176 2 CEDER-CIEMAT. Energy Department. Biomass Unit. Autovía de Navarra A-15, salida 56. 42290 Lubia (Soria). Phone: +34 975281013 *Corresponding author: carlos.martin@iit.upcomillas.es Several studies suggest that lignocellulosic energy crops for electricity production may have a better performance compared to those crops for liquid biofuels production, when assessing GHG savings with respect to fossil references. Winter cereal residues and some annual winter grasses, as dedicated energy crops, are currently being grown in Spain and harvested as bales to be burned for electricity production in biomass power plants. Previous studies of our group analyzed GHG emissions and energy balances of winter cereals for electricity production by means of Life Cycle Assessment. We selected highly productive genotypes of three annual winter cereals (rye, triticale and oat) and compared them with Spanish electricity produced using natural gas. This paper compares effects of the use of different crop management practices for rye growing in the assessment of energy balances and GHG emissions. We analyzed the effects of six different management practices consisting of two different sowing doses (suboptimal and normal) combined with three top fertilization doses (zero, 30 and 80kgN ha-1). We made a characterization analysis of biomasses to estimate the nitrogen uptake of the crops in order to compare it with the nitrogen provided by the fertilizers. This comparison evaluates if lower fertilization doses are sustainable for the soil nitrogen stocks. Our results suggest that there is trade-off between soil nitrogen and emission savings. The use of zero or low top fertilization doses (30 kg N ha-1) improves GHG emissions and energy balances even with a yield reduction. Nevertheless the use of these doses imply an annual lose in soil nitrogen stocks for the majority all of our trials. Using suboptimal sowing doses resulted in yield decreases that did not compensate the lower input consumed. Keywords: electricity, energy balance, energy crops, greenhouse gases (GHG), life cycle assessment (LCA), sustainability criteria1 INTRODUCTION nitrogen balance was made to assess the sustainability of lower fertilizer doses for soil nitrogen stocks. To evaluate The climate change problem coupled with declining the effects of management practices three plots wereoil and gas reserves has led to the development of energy established for each practice in the northern of Spainsources to minimize greenhouse gas (GHG) emissions (Soria’s province). The parcels were grown by famersand expand energy supplies from solar, wind, hydraulic, using traditional management practices for cereals in thegeothermal and bioenergy sources [1]. Solid and liquid zone, except for sowing and top fertilization doses asbiofuels guarantee the energy security and reduce GHG objectives of the assessment. Farmers prepared the land,emisions when compared to fossil referecences in many pesticides and NPK fertilizers were applied, seeds werestudies [1–3] [4–6]. Several studies suggest that spread, top fertilization was made (in case it applies forlignocellulosic energy crops for electricity production the trial) and crop was harvested through mowing,may have a better performance compared to those crops swathing and baling. The system analyzed considers realfor liquid biofuels production, when assessing GHG data collection from farmers, transportation of squaresavings with respect to fossil references [7,8]. bales and a real power biomass plant for electricity Winter cereal residues and some annual winter production in northern Spain. The results were comparedgrasses, as dedicated energy crops, are currently being to electricity production from the National natural gas.grown in Spain and harvested as bales to be burned forelectricity production in biomass power plants [9].Previous studies of our group analyzed GHG emissions 2 MATERIALS AND METHODSand energy balances of winter cereals for electricityproduction by means of Life Cycle Assessment [10]. We Life Cycle Assessment (LCA) is the environmentalselected highly productive genotypes of three annual tool we selected to determine the energetic andwinter cereals (rye, triticale and oat) and compared them environmental performance of rye to producewith Spanish electricity produced using natural gas. lignocellulosic biomass for electricity generation. In this article we compare the effects of the use of LCA is a systematic set of procedures for compilingdifferent crop management practices for rye, grown as and examining the inputs and outputs of materials anddedicated energy crop for electricity production, in the energy and the associated environmental impacts directlyassessments of GHG emissions and energy balances by attributable to the functioning of a product or servicemeans of Life Cycle Assessment. For this purpose six system throughout its life cycle [11]. This environmentalcrop management practices were considered. These assessment tool is regulated by ISO 14040 [11] and ISOpractices consists of combining the use of low (24 kg ha - 14044 [12] standards, and according to this, LCAs should1 ) and typical (120 kg ha-1) seed doses with zero top follow four steps: (1) goal and definition, (2) inventoryfertilizer dose (0 kg N ha-1), low fertilizer dose (30 kg N analysis, (3) impact assessment and (4) interpretation.ha-1) and typical fertilizer dose (80 kg N ha-1). Also a Simapro 7.2 [13,14] software tool and Ecoinvent 2.2
  • 2. [15,16] European database have been selected for the Table II: Biomass productivityLCAs. Also a rough nitrogen balance was made considering Seed Top Trial productivitynitrogen supply by fertilizers and measuring the amount Crop Fertilizer (odt ha-1) Doseof nitrogen contended in the crops as the nitrogen Management Dose (kg ha-1) 1st 2nd 3rd (kg N ha-1)extracted. Prior to the description of the LCAs conducted and TSD & ZTF 120 0 9.001 10.142 7.092the nitrogen balance methodology, some methodological TSD & LTF 120 30 10.792 10.442 8.182aspects regarding the experimental design and the TSD & TTF 120 80 13.200 11.815 10.548biomass characterization and productivity are described LSD & ZTF 24 0 7.758 6.992 4.773in the two following subsections. LSD & LTF 24 30 7.860 6.447 4.4032.1 Experimental design LSD & TTF 24 80 9.045 8.099 6.087 To assess the effects in energy and GHG balances ofcrop management practices a plot of 8500 m2 was Average data about dry basis composition and netestablished to grow rye. The management practices heating value of the managment practices trials areconsist on the application of two different sowing doses shown in Table III. The net heating value at constantand three top fertilization doses resulting in six possible pressure has been calculated for humidity contents of 0%combinations. For its possible combination three trials and 12%, as 12% is the average humidity of burnedwere done dividing the 8500m2 of the parcel eighteen biomass in the biomass power plant selected for thissmaller plots. The Table I summarizes the characteristics research.of the site selected for the study as well as the conditionsof the each crop management practice used. Table III: Aerial biomass characterization Table I: Experimental design summary Crop C N NHVcp,0 NHVcp,12 1. Location Soria Management (%) (%) (MJ kg-1,db(1)) (MJ kg-1,wb(2)) 41º 36’ 40.0” N TSD & ZTF 44.8 0.84 16.70 14.40 Coordinates 2º 28’ 55.6”W TSD & LTF 45.1 0.86 16.76 14.46 Altitude 1035 m TSD & TTF 45.4 0.87 16.90 14.58 2. Experimental period 2010-2011 LSD & ZTF 45.10 1.00 17.11 14.76 Continental LSD & LTF 45.40 1.03 17.17 14.81 3. Climate Mediterranean with cold LSD & TTF 45.7 1.04 17.31 14.94 winters Average Temperature / rainfall 10.4ºC, 446.5 mm 3 RYE LCA METHODOLOGY 4. Soil type Clay (%) / Sand (%) / Silt (%) 13.56 / 80.66 / 5.09 The following sub-sections describe the methodology Texture Sandy loam Organic matter (%) 1.07 follow to conducts the rye optimization life cycle Nitrogen (%) 0.06 assessments. 5. Genotype Specie (variety) Secale Cereale (Petkus) 3.1 Goal and Scope definition 6. Plots The aim of this study is to evaluate the energy Quantity / type / size 18 / Strips / 0.04-0.05 ha balance and environmental impacts of six crop 7. Crop management practices management practices for growing rye in Spain for electricity generation and compare them with electricity Typical Seed Dose (TSD) 120 kg ha-1 generation from natural gas, as a reference for generation Low Seed Dose (LSD) 24 kg ha-1 from non-renewable fossil sources. Common Top Fertilization (TTF) 80 kg N ha-1 3.2 Functional unit Low Top Fertilization (LTF) 30 kg N ha-1 The functional unit chosen is 1 TJ of electrical energy Zero Top Fertilization (ZTF) 0 kg N ha-1 generated from rye biomass for the studied system and from natural gas for the reference system. This amount of electrical energy is a round number corresponding to 122.2 Biomass characterization and productivity In order to assess the environmental and energetic hours of functioning of the 25Mw power plant selectedperformance of rye biomass as solid fuel for electricity, for this study (see 3.3.2). The electricity production per hectare of rye trial isthe productivity of crop management trials was measured the product of the crop yield (see Table II) at 12 %(see Table II). humidity by the net calorific value at 12 % humidity (see Table III) and by the efficiency of the biomass conversion process into electricity (29.5 % for this case study). According to this, between 17 ha and 51 ha are needed to produce 1 TJ for the higher and the lower yielding trials. 3.3 Systems description The bioenergy systems analyzed includes three subsystems: agricultural biomass production, electricity generation and the transport of products and raw materials.
  • 3. 3.3.1 Agricultural system inputs consumed. This information is shown in Table IV The agricultural system could be described by the for all the crop management trials made in Soria for thecrop schemes followed, the machinery used and the rye bioenergy cropping system. Table IV: Agricultural system summary for the Soria trials. Operation Tractor Implement Inputs Operating Weight Power Type Weight Fuel consumption rate (kg) (kWh) (kg) (h ha-1) (L ha-1) Moldboard Primary tillage 5470 103 1390 1 20 plowSecondary tillage 5470 103 Cultivator 400 0.66 10Base fertilization 3914 66 Spreader 110 0.20 4 NPK fertilizer 8-24-8 300 kg ha-1 Hybrid rye seeds (kg ha-1): Sowing 5470 103 Seeder 830 0.60 8 TSD (24), LSD (120). MCPA 0.332 kg ha-1, Dicamba Herbicide Boom 3914 66 230 0.50 4 0.125 kg ha-1, 2 ,4-D 0.370 kg ha-1 treatment sprayer Calcium ammonium nitrate 27% kg Top fertilization 3914 66 Spreader 110 0.20 4 ha-1: TTF (300), LTF (100), ZTF (0) Rolling 3914 66 Roller 1000 0.40 8Mowing-Swathing 3914 66 Mower 150 0.70 8 Baling 3914 66 Baling packer 1700 0.40 4 Loading Bales 5470 103 Trailer 1870 0.40 43.3.2 Biomass power plant system 3.3.3 Transport system All the data considered to model the biomass power The transport system is summarized in Table VII.plant system are real data from a 25 MW biomass plant This table shows all modes of transport used and thelocated in northern Spain. This plant consumes biomass distances between origin and destination points for everyat an average humidity of 12% and produces electricity transport in the LCAs carried out.with a conversion efficiency of 29.5%. The plant The transportation means and distances for theconsumes natural gas for maintenance operations and transport of agricultural inputs until the regionalpre-heating and produces ashes and slag from biomass as storehouse are taken from the Ecoinvent database [17].residues. The average consumption of natural gas and the The distance from the regional store house to plots wasproductions of ashes and slag per kilogram of burned 10 km approximately. The transport of workers to thebiomass are shown in Table V. parcel has not been considered because of the highly variability of transport distances depending on cases. Table V: Biomass power plant consumptions and Biomass, ash and slag means of transport and residues produced distances were provided by company in charge of the biomass power plant. Consumed or produced Amount substances Table VII: Transport system summary Natural gas consumption 0.0342 (MJ Kg-1 Wet Biomass Burned) Material From To Distance Vehicle Slag production Processing Lorry 82.47 (g Kg-1 Wet Biomass Burned) Seed Field center 30 km 20-28t Ashes production 8.25 Processing Regional Lorry (g Kg-1 Wet Biomass Burned) center storehouse 100 km 20-28t Regional Demonstration Lorry The emissions of the plant into the air are submitted 10 km storehouse parcel 16-32tregularly to the local government. The emissions Fertilizers Regionalaccounted are only those which affect the global warming and Manufacturer 600 km Train storehousepotential (GWP). In the power plant studied these herbicidesemissions come from gas natural combustion (see Table Lorry 100 km >16tVI). Carbon dioxide emitted from biomass combustion Regional Demonstration Lorrywas not considered because it was previously fixed from 10 km storehouse parcel 16-32tthe air by the crop. Demonstration Lorry Biomass Biomass plant 60 km parcel 16-32t Table VI: Biomass power plant aerial emissions Ash and Biomass plant Disposal 37 km Lorry slag 16-32t Substance Origin Amount (g Kg-1 Wet Biomass 3.3.4 Natural gas system Burned) The natural gas system includes the gas field Fossil carbon operations for extraction, the losses, the emissions and Natural gas 1.94 dioxide the purification of the main exporter counties of natural gas to Spain (Algeria 73 % and Norway 27 %). Also includes the long distance and local transport of gas to
  • 4. the power plant in Spain, considering the energy 3.4.4 Diesel consumption and combustion emissions ofconsumption, loses and emissions for distribution. Finally agricultural machinerythe substances needed and the average efficiency of The diesel consumption of agricultural machinery isSpanish natural gas power plants to produce electricity obtained from Table V. The inventories for theare taken into account [18]. extraction, transport of petrol, the transformation into diesel and its distribution are taken from Ecoinvent [25].3.4 Life cycle inventory analysis The exhaust emissions of diesel in agricultural The inventories used to consider natural gas machinery engines are also considered [26].consumption [18] of the biomass power plant, transports[19] of agricultural inputs, and biomass and power plant 3.4.5 Agricultural machinery manufactureresidues are taken from Ecoinvent. The inventories for agricultural machinery The methods used for the inventory analysis of the manufacture are specific to the different types ofagricultural system mainly follow that proposed on Life machinery (tractors, harvesters, tillage implements orcycle inventories of agricultural production systems [17]. general implements).To consider N2O emissions we follow the formula The amount of machinery (AM) needed for a specificproposed by de RSB GHG Calculation Methodology v process was calculated multiplying the weight (W) of the2.0 [20]. This formula is basically based on the formula machinery by the operation time (OT) and dividing theproposed in the Ecoinvent Agricultural Report [17], that result by the lifetime of the machinery (LT) [17]:considers the new IPCC guidelines [21]. Also weconsider the nitrate emissions affecting to Global AM (kg FU-1) = W (kg) OT (h FU-1) LT-1(h);Warning Potential as the RSB purposes [20], making andestimation of them by means of nitrogen balance, the soil Where FU (See 3.2) is the functional unit of the LCA.and crop characteristics and the rainfall of the zone. The life time of the machinery was provided by its owners.3.4.1 Fertilizers productions The fertilizer inventories consider the different steps 3.4.6 Nitrous oxide emissionsof the production processes, such as the use of raw The calculation of the N2O emissions [20] is basedmaterials and semi-finished products, the energy used in on the formula in Nemecek et Kägi [17] and adopts thethe process, the transport of raw materials and new IPCC guidelines [21]:intermediate products, and the relevant emissions [17]. The production of calcium ammonium nitrate starts N2O=with the production of the ammonium nitrate by the 44/28∙(EF1∙(Ntot+Ncr)+EF4∙14/17∙NH3+EF5∙14/62∙NO3-)neutralization of ammonia with nitric acid. The finalproduct is then obtained by adding dolomite or limestone With:to the solution before drying and granulation [22]. N2O = emissions of N2O [kg N2O ha-1] No inventories are given in Ecoivent for multinutrient EF1 = 0.01 (IPCC proposed factor [21])fertilizers due to the amount different possible ways to Ntot = total nitrogen input [kg N ha-1]mix nitrogen, phosphorous and potassium compounds to Ncr = nitrogen contained in the crop residues [kg N ha -1]produce NPK fertilizers [22]. The modeling of NPK EF4 = 0.01 (IPCC proposed factor [21])fertilizer inventories has been approximated by NH3 = losses of nitrogen in the form of ammonia [kgcombining inventories of single fertilizers according to NH3 ha-1]. Calculated as proposed in the RSB [20] andmultinutrient fertilizer specific contents of N, P 2O5 and Nemecek et Kägi [17] methodologies.K2O, as well as the form of the nitrogen provided 14/17= conversion of kg NH3 in kg NH3-N(ammonium, nitrate or urea) [22]. EF5 = 0.0075 (IPCC proposed factor [21]) NO3- = losses of nitrogen in the form of nitrate [kg NO33.4.2 Herbicides production ha-1]. They were estimated through the RSB formula [20] The data related to emissions, energy and substance which considers nitrogen supply, the nitrogen uptake, theconsumption in the production of the herbicides sprayed soil and crop characteristics and the local rainfall.is taken from Ecoinvent [23]. The quantities of active 14/62= conversion of kg NO3- in kg NO3-N.matters considered are taken from the formulations of thecommercial fertilizers used. 3.4.7 Land use changes Direct land used change does not take place because3.4.3 Seed production the parcel selected was previously a winter cereal crop Annual cereal seeds are produced in Spain under land. Indirect land use change is a complex process that issimilar conditions compared to the operations of fertilizer not fully understood by the scientific community and soand management practices used for commercial grain or is not included in this study [1].forage cultivation techniques. Rye is frequently producedunder irrigation in high quality soils under contract with 3.5 Life cycle impact assessmentreal farmers, thus their normal operations and yield Life Cycle Impact Assessment (LCIA) is the phase inproduction were assumed to be similar to that of the local an LCA where the inputs and outputs of elementary flowscommon management practices cosidered in this study. that have been collected and reported in the inventory are Then, a grain production yield of 5.5 odt ha-1 was translated into impact indicator results [27].considered as harvest index of 35 % for Petkus variety as LCIA is composed of mandatory and optional steps.a non hybrid rye genotype. Mandatory steps of classification and characterization The energy consumption for cleaning, drying, seed have been carried out and optional steps normalizationdressing, and bag filling of the cereal seed in the and weighting have been avoided in order to make resultsprocesing plant has been estimated in 32.8 kWh t -1[24]. more comparable and to avoid introducing value choices.
  • 5. In the classification steps elementary flows shall be 80 80 Kg N ha-1 Top Fertilizationassigned to those one or more impact categories to which 70 & 24 Kg ha-1 Seed Dosethey contribute. In the characterization steps each 80 Kg N ha-1 Top Fertilization 60 & 120 Kg ha-1quantitative characterization factor shall be assigned to GWP (Mg CO2 eq TJ electrcity-1) Seed Dose 30 Kg N ha-1all elementary flows of the inventory for the categories 50 Top Fertilization & 24 Kg ha-1that have been included in the classification [27]. 40 Seed Dose 30 Kg N ha-1 Top Fertilization & 120 Kg ha-13.5.1 Environmental impact assessment method 30 Seed Dose 0 Kg N ha-1 We have selected the software tool Simapro 7.2 [13] 20 Top Fertilization & 24 Kg ha-1and the impact assessment method of the IPCC 2007 [28] Seed Dose 0 Kg N ha-1 10to assess the 100 years time horizon Global Warming Top Fertilization & 120 Kg ha-1 Seed DosePotential (GWP). 0 3000 5000 7000 9000 11000 13000 15000 Yield (kg d.m. ha-1)3.5.2 Energy assessment method In order to assess the energy consumed to generate Figure 1: Relationship between global warming potentialelectricity from winter cereal biomass and from natural of rye biomass electricity and whole plant yieldgas, we have selected the software tool Simapro 7.2 [13]and the Cumulative Energy Requirement Analysis The Figure 2 shows that the GWP savings with(CERA) [29]. This method aims to investigate the energy respect to natural gas go from 50 % to 85%. We obtaineduse throughout the life cycle of a good or service [29]. a very high amount of savings for the typicalThe primary fossil energy (FOSE) has been obtained management practices of the site (blue circles), due to theusing this method. high yields of trials for this management. All the points in red, corresponding to low sowing doses, have result in worse balances when comparing them with their4 RYE NITROGEN BALANCE METHODOLOGY equivalent management with conventional seed dose (blue points). A rough nitrogen balance was made. This estimationconsiders nitrogen supplied in base and top fertilizations 90% 80 Kg N ha-1 Top Fertilizationas the entrance of the system and total nitrogen content of 85% & 24 Kg ha-1 Seed Dose % GHG Savings (Natural Gas as reference)rye aerial biomass trials as exit of the system. The total 80% 80 Kg N ha-1 Top Fertilizationamount of nitrogen extracted and exported by the crop 75% & 120 Kg ha-1 Seed Doseharvest is calculated by multiplying the yield of each trial 70% 30 Kg N ha-1 Top Fertilization & 24 Kg ha-1(see Table II) by its respective biomass nitrogen content 65% Seed Dose 30 Kg N ha-1(see Table III). As roots remain into the soil we assumed 60% Top Fertilization & 120 Kg ha-1that all nitrogen from roots return to the soil. Therefore Seed Dose 0 Kg N ha-1 55%we did not take into account any proportion of root Top Fertilization & 24 Kg ha-1 50%nitrogen content as extracted nitrogen. Seed Dose 0 Kg N ha-1 45% Top Fertilization & 120 Kg ha-1 40% Seed Dose 3000 5000 7000 9000 11000 13000 150005 RESULTS AND DISCUSSION Yield (kg d.m. ha-1) In the following sub-sections the final results of rye Figure 2: Relationship between greenhouse gasoptimization assessments are presented for GWP, fossil emissions savings of rye biomass electricity compared toenergy consumption and balance of nitrogen. Besides we natural gas and whole plant yield.present the contribution of the phases considered in thelife cycle assessment of the systems to GWP and fossil 5.2 Rye biomass electricity energy assessmentenergy consumption of the typical management practices The Figure 3 shows that electrical energy obtained isscenario. between two and five times the fossil energy invested. The differences between results for different fertilization5.1 Rye biomass electricity global warming potential doses are lower for the fossil energy consumption than The Figure 1 shows that for all the rye managements for GWP, because N2O emissions are irrelevant forthere is an inverse relationship between yield obtained energy assessments. We have again worse results forand the GWP emissions. The results are contended in the lower sowing doses (Red points) compared to typicalinterval that goes from 20 to 75 Mg CO2 eq. TJe-1. This sowing doses (Blue points).means that every trial produce less GWP than thegeneration of electricity from gas natural in Spain, that isabout 145 Mg CO2 eq.TJe-1 [18].
  • 6. 5.4 5.4 80 Kg N ha-1 80 Kg N ha-1 Top Fertilization NITROGEN DEFICIT NITROGEN SURPLUS Top Fertilization 4.9 & 24 Kg ha-1 4.9 & 24 Kg ha-1 Seed Dose Seed Dose 4.4 80 Kg N ha-1 4.4 80 Kg N ha-1 Top Fertilization Top Fertilization & 120 Kg ha-1 Energy output per fossil energy inputs Energy output per fossil energy inputs & 120 Kg ha-1 3.9 Seed Dose 3.9 Seed Dose (TJ electricty TJ fosil energy-1) (TJ electricty TJ fosil energy-1) 30 Kg N ha-1 30 Kg N ha-1 3.4 Top Fertilization 3.4 Top Fertilization & 24 Kg ha-1 & 24 Kg ha-1 Seed Dose Seed Dose 2.9 30 Kg N ha-1 2.9 30 Kg N ha-1 Top Fertilization Top Fertilization 2.4 & 120 Kg ha-1 2.4 & 120 Kg ha-1 Seed Dose Seed Dose 0 Kg N ha-1 1.9 1.9 0 Kg N ha-1 Top Fertilization Top Fertilization & 24 Kg ha-1 & 24 Kg ha-1 1.4 Seed Dose 1.4 Seed Dose 0 Kg N ha-1 Top Fertilization 0 Kg N ha-1 0.9 0.9 Top Fertilization & 120 Kg ha-1 & 120 Kg ha-1 Seed Dose 0.4 Seed Dose 0.4 3000 5000 7000 9000 11000 13000 15000 -80 -60 -40 -20 0 20 40 60 Yield (kg d.m. ha-1) Nitrogen Balance (kg N ha-1 year-1)Figure 3: Relationship between electrical energy output Figure 5: Relationship between electrical energy outputper fossil energy inputs of rye biomass and whole plant per fossil energy inputs of rye biomass and the annualyield. nitrogen balance of the soil.5.3 Rye biomass electricity nitrogen balance 5.4 Relative contributions of the phases considered in the The Figure 4 shows that there is a trade-off between assessmentemission savings and soil nitrogen deficit. This trade-offis clear for both low and typical sowing doses (24 and The Figure 6 shows that for the typical management120 kg ha-1). For typical seed doses and zero top practices fertilizers and nitrous oxide emissions representfertilization there is an annual loss of 50 kg N in soil about 75 % of total GWP generated. However thenitrogen stocks with 85 % of savings. However with biomass power plant represent only 1.7% of GWPtypical sowing and fertilization doses the nitrogen according to our modeling.balance is neutral and the savings are lower, about 70 %. Seed and Pesticides production & GWP; 1,7% transport 90% 80 Kg N ha-1 GWP; 2,6% NITROGEN DEFICIT NITROGEN SURPLUS Top Fertilization 85% & 24 Kg ha-1 GWP; 5,8% Fertilizers production & transport Seed Dose GWP; 11,6% 80 Kg N ha-1% GHG Savings (Natural Gas as reference) 80% Top Fertilization & 120 Kg ha-1 Nitrous Oxide emissions 75% Seed Dose 30 Kg N ha-1 70% Top Fertilization & 24 Kg ha-1 GWP; 46,5% Seed Dose Field Works (Machinery amortization 65% 30 Kg N ha-1 and Diesel consumption & combustion Top Fertilization emissions) 60% & 120 Kg ha-1 Seed Dose Biomass transport to power plant GWP; 31,8% 55% 0 Kg N ha-1 Top Fertilization & 24 Kg ha-1 50% Seed Dose Biomass Power Plant (Residue disposal 0 Kg N ha-1 and Natural Gas consumptions & 45% Top Fertilization & 120 Kg ha-1 combustion emissions in maintenances) 40% Seed Dose -80 -60 -40 -20 0 20 40 60 Nitrogen Balance (kg N ha-1 year-1) Figure 6: Relative contribution of phases to Global Warning Potential (GWP) for the average of the threeFigure 4: Relationship between greenhouse gas trials with typical seed doses and top fertilization doses asemissions savings of rye biomass electricity compared to crop management practices.natural gas and the annual nitrogen balance. The Figure 7 shows that for fossil energy The Figure 5 shows the same previous trade-off consumption seed and pesticides as well as field worksbetween nitrogen deficit and fossil energy consumption, have double their importance with respect to GWPalthough correlation appears to be less strong for this impacts. This happens because emissions do not affect tocase. We find more red points generating nitrogen surplus fossil energy consumption.because the crop did not take all the available nitrogendue to the small amount of plants per hectare. FOSE, 4.1% Seed and Pesticides production & transport FOSE, 3.9% Fertilizers production & transport FOSE, 13.5% Field Works (Machinery amortization and Diesel consumption) FOSE, 25.9% FOSE, 52.6% Biomass transport to power plant Biomass Power Plant (Residue disposal and Natural Gas consumptions in maintenances) Figure 7: Relative contribution of phases to Fossil Energy consumption (FOSE) for the average of the three trials with typical seed doses and top fertilization doses as management practices.
  • 7. 5 CONCLUSIONS cropping system in southern Europe. Biomass Bioenergy 2007;31:543–55. Biomass square bales from rye grown in semiarid [5] Gasol CM, Gabarrell X, Anton A, Rigola M,regions in Spain may be used in power biomass plants for Carrasco J, Ciria P, Rieradevall J. LCA of poplarelectricity production and become a real alternative for bioenergy system compared with Brassica carinatathe replacement of electricity from natural gas as non energy crop and natural gas in regional scenario.renewable fossil reference. Biomass Bioenergy 2009;33:119–29. Typical rye top fertilization doses of about 80 kg N [6] Butnar I, Rodrigo J, Gasol CM, Castells F. Life-ha-1 (NAC 27 %) appear to be sustainable for soil cycle assessment of electricity from biomass: Casenitrogen stocks and can achieve 70 % of GHG savings studies of two biocrops in Spain. Biomass andwhen comparing to electricity from natural gas. Bioenergy 2010;34:1780–8. Although reduced and zero top fertilization doses (30 [7] Dworak T, Elbersen B, van Diepen K, Staritsky I,and 0 kg N ha-1) produce considerable deficit in soil van Kraalingen D, Suppit I, Berglund M, Kaphengstnitrogen stocks, they can achieve greater GHG savings T, Laaser C, Ribeiro M. Assessment of inter-(75-85 %). Due to this fact, if we want to obtain higher linkages between bioenergy development and watersavings, we need to combine the use of reduced availability. Ecologic – Institute for Internationalfertilization doses with some soil nitrogen improvement and European Environmental Policy Berlin/Vienna;management practices as rotation with legumes, fallow 2009.management and no-tillage farming. The use of legumes [8] Elsayed MA, Matthews R, Mortinmed ND. Carbonin crop rotations could improve the soil nitrogen stocks and Energy Balances for a range of biofuels options.from 80 to 300 kg N fixed per year [30]. The amount of Project final report. Project numberN fixed by different legumes is determined by the B/B6/00784/REP. Resource Research Unit,inherent capacity of the crop/rhizobium symbiosis to fix Sheffield Hallam University and Forest Research.N, modified by the crop’s growing conditions (e.g. soil, 2003.climate, disease), crop management and length of time [9] Maletta E. A de. V and JC. El potencial de lasfor which the crop is grown [30]. gramíneas como cultivo energético en España. Vida Other optimization in rye might be achieved through: Rural, Núm. 325. 2011.using less emitting fertilizers (e.g. ammonia sulphate) [10] Martín C, Maletta E, Ciria P, Santos A, del Val MA,instead of typical nitrogen products used for most farmers Pérez P, González Y, Lerga P. Energy andin our study region (like NAC 27% and UREA) and enviromental assessment of electricity productionsplitting nitrogen fertilizer in two applications in order to from winter cereals biomass harvested in twoincrease nitrogen application use efficiency. locations of Northern Spain. 19th European The use of lower sowing doses (24 kg ha-1) instead Biomass Conference & Exhibition:From Researchof typical sowing doses (120 kg ha-1) has produced worse to Industry and Markets, Berlin Germany: 2011.results for both GWP and fossil energy consumption. The [11] ISO. 14040:2006. Environmental management-Lifedose of 24 kg ha-1 appears to be very low and probably cycle assessment-Principles and framework.we would have obtained better balances with higher European Committee for Standardization. 2006.doses because with 24 kg ha-1 the number of plants per [12] ISO. 14044:2006. Environmental Management–Lifeha has been very low to use all the available N. Cycle Assessment–Requirements and Guidelines. European Committee for Standardization. 2006. [13] Goedkoop M, De Schryver A, Oele M, Sipke D, De6 NOTES Roest D. Introduction to LCA with SimaPro 7. Netherlands: PRé Consultants; 2010.(1) db: dry basis [14] Goedkoop M, De Schryver A, Oele M, others.(2) wb: wet basis Introduction to LCA with SimaPro 7. PRé Consultants Report 2008;4. [15] Frischknecht R, Jungbluth N, Althaus HJ, Doka G,7 REFERENCES Dones R, Hischier R, Hellweg S, Nemecek T, Rebitzer G, Spielmann M. Overview and[1] García CA, Fuentes A, Hennecke A, Riegelhaupt E, Methodology. Final report ecoinvent data v2.0, No. Manzini F, Masera O. Life-cycle greenhouse gas 1. Dübendorf, Switzerland: Swiss Centre for Life emissions and energy balances of sugarcane ethanol Cycle Inventories; 2007. production in Mexico. Applied Energy [16] Frischknecht R, Jungbluth N, Althaus H-J, Doka G, 2011;88:2088–97. Dones R, Heck T, Hellweg S, Hischier R, Nemecek[2] Yee KF, Tan KT, Abdullah AZ, Lee KT. 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