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Perennial Energy Crops For Semiarid Lands in the Mediterranean


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The aim of this report is to demonstrate and evaluate the potential of Elytrigia elongata to
avoid GHG emissions and obtain lower economic costs in marginal areas of Spain and the
Mediterranean region. Our research built scenarios based on experimental plots (2 years growth) in
three locations of Spain with very different climate conditions (provinces of Girona, Soria and
Palencia). In our experiences, we achieved an adequate establishment and biomass production in the
second year in the plots, and assumed yields until the end of the life cycle (estimated in 15 years in many
other studies in United States, Argentina and Eastern Europe). Using data from the experimental plots,
statistical information for economic inputs costs, and the scenarios built, we estimated GHG emissions
savings and compared them to the rank of biomass yields obtained from annual grasses (oats, triticale
and rye) in a large range of environmental conditions (yields of perennial grasses from 3 to 13
odt/ha.year). GHG emissions savings were calculated replacing natural gas electricity with electricity
from biomass combustion in a real centralised power plant in Spain. The assessment included GHG
emissions savings and energy balance for the mentioned yields rank, estimated economic costs for the
achieved biomass and compared with the biomass costs from the winter annual grasses of our previous
study. The preliminary evaluation results suggest that the use of C3 perennial crops, like tall wheatgrass
in marginal areas of Spain for electricity production might present a better performance in terms of
energy yields, costs of the electricity and GHG savings, than utilizing annual grasses

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Perennial Energy Crops For Semiarid Lands in the Mediterranean

  1. 1. Perennial energy crops for semiarid lands in the Mediterranean: Elytrigiaelongata, a C3 grass with summer dormancy to produce electricity in constraint environments Emiliano Maletta*1, Carlos Martin-Sastre2, Pilar Ciria1, Aranzazu del Val1, Annabel Salvado4, Laura Rovira4, Rebeca Díez3, Joan Serra4, Yolanda González-Arechavala2 and Juan Carrasco1 1 CEDER-CIEMAT. Energy Department. Biomass Unit. Autovía de Navarra A-15, salida 56. 42290 Lubia (Soria). Phone: +34 975281013 2 Institute for Research in Technology (IIT) - ICAI School of Engineering - Comillas Pontifical University - E- 28015, Madrid (SPAIN)3 ITACyL. Biofuels and Bioproducts Resarch Centre, Pol. Agroindustrial Par.2-6 (24358), Leon, Spain. Phone/fax: +34-987374554 4 IRTA, Mas Badia (17134) Girona, Spain. Phone: +34- 972780275, Fax: +34-972780517 * Corresponding author: The aim of this report is to demonstrate and evaluate the potential of tall wheatgrass (Elytrigia elongata) to avoid GHG emissions and obtain lower economic costs in marginal areas of Spain. Our research built scenarios based on experimental plots (2 and 3 years growth) in 3 locations of Spain with completely different climate conditions (provinces of Girona, Soria and Palencia). In our experiences, we achieved an adequate establishment and biomass production, and assumed a rank of biomass yields until the end of the life cycle that is usually accepted to be about 15 years in many other studies in United States, Argentina and Eastern Europe where tall wheatgrass is extensively cultivated in marginal areas for sheep livestock production. Using our experimental plots and statistical information for economic inputs costs, we built 5 different scenarios per region considering a large range of biomass yields of tall wheatgrass. The analysis included a comparison with annual grasses economic costs calculated for a wide range of biomass yields of a previous study. We estimated GHG emissions savings for tall wheatgrasses and used our previous study (which had GHG emissions savings as well). Savings were calculated replacing natural gas electricity with electricity from biomass combustion in real power plants in Spain. In a wide range of yields, the results suggest that marginal areas might present a better performance with tall wheatgrass compared to annual winter grasses (cereals whole plant cuttings), thus producing biomass yields with higher GHG savings and lower economic costs at the farm level. 1 INTRODUCTION maize) and fibre sorghum (sorghum bicolor), are now typical solid biofuels involved in private contracts In Spain, a country with more than 4M ha with potential between farmers and energy companies. These contracts for energy crops as a consequence of liberalization and often establish biomass prices as high as 85€/odt for Common Agricultural Policy reforms [1], the square bales from these annual crops [4]. Therefore many development of energy crops to produce biomass for stakeholders are developing a strong interest in new heating or electric applications represents a major perennial energy crops that could produce lower biomass challenge. The extensive semiarid rainfed areas of the costs in both irrigated and rain fed areas. Biomass yields Mediterranean require species that tolerate severe per hectare are closely linked to biomass costs since frequent droughts during late spring and summer and many areas have low yields as most Mediterranean produce sufficiently high yields to obtain biomass with extensive rain fed areas have low competitive lands low costs and high environmental benefits in relation (unfertile soils, scares rains in spring and summer, etc.). with the used inputs and fossil energy. This consideration would be fundamental in order to Economic constraints affecting renewable energies allow the economic feasibility of biomass power energy are usually cited as important barriers when developing plants in Spain. new activities in rural areas. Moreover, biomass Despite of economic considerations, energy crops production marginal costs in Spain are still a major producing liquid or solid biofuels require to produce constraint limiting the expansion of new facilities at the environmental benefits regarding global warming time that recent measures have cut subsidies and financial potentials (GWP) and greenhouse gases emissions (GHG) aid for private companies [2]. among many other impact categories often studied in Life During the last decade, in Spain some new power cycle assessments (LCA) of energy crops and bioenergy energy plants started to produce electricity from solid chains [5, 6]. Several studies have encouraged the agricultural residues [3]. Biomass bales from herbaceous research and development of perennial species as energy crops are currently used for co-firing to produce crops for marginal areas in order to produce biomass electricity in power energy plants. The first raw materials yields with high energy balances and low environmental considered were agricultural residues (mostly cereal straw impact regarding water, nitrogen use, erosion, in square bales with less than 11% humidity) and biomass biodiversity and GHG emissions [7, 8]. from energy crops were then also included. Winter In 2009, the Renewable Energy Directive (RED) annual crops like triticale (triticosecale sp.), oats (Avena established increasingly restrictive minimum GHG sativa), peas (Pisum sativum) and rye (Secale cereale) emissions savings for biofuels replacing fossil reference but also warm annual grasses like fodder maize (Zea fuels for transport. This minimums savings are 35%
  2. 2. (from 2009) and will become in 50% in 2017 and 60% metabolism pathway, usually known as “warm grasses”)from 1stJanurary of 2018 [9]. Since then, several studies these crops have yields reported to be higher than 20have provided evidences that marginal areas might odt/ha per year during their lifetime [4, ]. Neverthelessproduce also marginal biomass yields or have logistics most of them require irrigation for rhizome propagationimplications producing low or none environmental or event direct sowings in most agricultural lands at leastbenefits from feedstock, residues and energy crops [5, 8, during the establishment (spring) when drought events10]. The RED also established a methodological are very frequent in Spain limiting their viability to theapproach for LCA for biofuels, nevertheless solid irrigation arable surface. Additionally, even when theybiomass standards and a sustainability criteria for them produce much more biomass yields, in some cases have ahave not been addressed sufficiently at the time that many higher establishment cost reported to be as high asdebates, recommendations on methods and discussions 2000€/ha in Miscanthus [19, 20].on land use changes effects on GHG calculations are Perennial C3 grasses (three-carbon photosyntheticcurrently taking place [11]. Recent significant metabolism pathway) also called “cool grasses” can beadvancements have added new principles such as those established without irrigation during autumn or earlyfrom the Roundtable on Sustainable Biofuels (RSB) for spring and may produce forage in successive years withcertification schemes. The RSB included a new harvests during late summer when less precipitationcertification scheme for most biomass and biofuel occur in the Mediterranean. Forage traditional crops likefeedstock and established a calculation method for GHG reed canary grass (Phalaris sp), tall fescue (Festucaemissions from agriculture considering CO2, NOx, N2O, arundinacea) or perennial ryegrass (Lolium perenne)nitrates and Ammonia derived from fertilizers have been extensively used in Europe for livestockproduction, application and dynamics in the soil [12]. production and also as new energy crops [21]. In Spain electricity from lignocellulosic energy crops Nevertheless, in Mediterranean and semiarid areas mostmay replace electricity from natural gas, the cleanest species produce too low yields or do not re-grow after thesubstituted fossil source as suggested by RSB and RED. extreme summer drought events. Other best suited C3In Spain only few publications on LCA have addressed energy grass is giant reed (Arundo donax) with very highlignocellulosic energy crops [13, 14] and there is a lack yields but require rhizomes or shoots for propagation andof information on C3 or C4 perennial grasses scenarios even irrigation or some rains during establishment [20].producing energy. In a previous study [13], we analysed Then most of these grasses are best suited for sub-humidGHG emissions from triticale, oats and rye cultivated in areas in northern regions of Spain, not allowing most raincontinental rain fed areas in Spain in a wide range of fed low competitive cereal regions to produce biomassbiomass yields from different species and varieties. Our from perennial species.results suggested that cereal bales (grain+straw) have to Elytrigia elongata (Host) which common name isoutreach a yield of about 8 odt/ha in order to accomplish “Tall wheatgrass”, is also known as Thinopyrumsimilar sustainability criteria established for liquid ponticum (Podp), Agropyron elongatum (Host); Elymusbiofuels in the RED (from 2018, 60% of GHG savings elongatus (Host) var.ponticum. It is a summer dormantcompared to the fossil substituted reference). Therefore, cool season perennial grass native from Eurasia and hasthose results suggested to condition sustainability of been cultivated in constraints environments all over thebiomass in most agricultural arable lands in Spain that world [22]. Among many other similar wheatgrasses suchhave semiarid climate conditions and produce an average as Elymus lancelolatus, Pascopyron smithii, Agropyronnational grain yield of 1,8 t/ha; whole plant biomass cristatum, A. intermedium and A. sibericum, tallyields of 4 odt/ha considering local harvest indexes wheatgrass is probably the latest-maturing wheatgrassreported from experimental networks [15]. adapted to the temperate areas of North America and Additionally, many reports strongly suggest that Europe and probably the most productive of all [22]. TheCommon Agricultural Reforms (CAP) for 2014 health species is adapted to range sites receiving at least 300mmcheck, should encourage perennial grasses and renewable of annual precipitation and is particularly noted for itsenergy alternatives at the time cereals and dairy milk capacity to produce forage and persist in areas that arequota would have shorten subsidies for farmers [16]. too alkaline or saline for other productive crops [22, 23].Spain as one of the member countries with more Thus, it is a good source of pasture and hay during theabandoned and low competitive cereal lands of Europe late summer, when forage often is in short supply. It alsomight require new alternative crops to be cultivated under has been used successfully as a silage crop. Tallrain fed conditions and produce biomass. There is a wheatgrass has large seed that is easy to harvest andcurrent need for additional plots and LCA with perennial plant. It has good seedling vigour, and established plantsspecies suited for marginal lands or in those areas where have an exceptionally deep root system, whichtraditional agriculture and livestock production have low contributes to its resistance to drought [23]. Itsand very low competitiveness [17]. palatability for livestock is low at the same time that it Among several alternative crops, many perennial could have acceptable characteristics to use forgrasses have been studied as energy crops and may combustion in industrial boilers to produce electricityproduce high environmental benefits and low biomass power. Some recent European studies have analysed Tallcosts at the farm level that are relevant for their wheatgrass and encourage its consideration for semiaridconsideration on bioenergy chains [4, 5, 6, 7]. areas as a novel energy crop [24].Nevertheless, early autumn and spring rains in the The aim of this report, is to use current experimentalMediterranean regions are very scarce and in most plots in three regions of Spain established two (2010) andregions they limit the adequate establishment and annual three years (2009) ago for building scenarios consideringproductivity of best suited energy crops like Panicum their expected lifetime. We compared tall wheatgrass andvirgatum, Arundo donax or Miscanthus giganteum. As previously reported annual grasses performance on GHGmany other C4 grasses (four carbon photosynthetic emissions savings when producing electricity in existing
  3. 3. Spanish power energy plants and their economic costs at highest is 23ºC. Extreme temperatures rarely are belowthe farm level in a wide assumed range of yields in the 0ºC or exceed 40°C. There are generally soft winters andthree study regions. hot-drought summers, which generates a lot of accumulation of water vapor in the atmosphere which produce “cold drop” in autumn (weather phenomenon 2 MATERIALS AND METHODS associated with the Mediterranean area characterized by heavy rains, hail and electrical storms). The average2.1 Location, climate and soil of the experimental plots rainfall values are between 600-750mm. May occurused for scenarios building torrential rains in spring, but especially in autumn. This Two groups of parcels were established with tall location has less dry months than other locations of thesewheatgrass in the provinces of Girona (located in the climate characteristics. The province of Palencia, isregion of Catalonia), and Soria and Palencia (in the characterized by a Continental Mediterranean climate.region of Castilla y Leon). All plots were cultivated Rainfalls range between 350 and 600 mm, the maximumunder rain fed conditions in 2009 and 2010 (Figure 1). is in spring and autumn (minimum in winter and summer). The monthly mean temperature is between 7ºC and 19 °C with cold winters (between 5 and -10 ° C), and Girona dry and hot summers (between 20 and 27 ° C average temperature). Figure 2 shows Ombrothermic diagram – average temperature (ºC) against precipitation (mm)- from September 2010 to August 2011. Palencia Soria Girona 70 140 Temperature (ºC) 60 120 Precipitation (mm) 50 100 40 80 30 60 20 40 10 20Figure 1: Plots with Tall Wheatgrass (Elytrigia 0 0elongata) in the three study regions in Spain Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Months The experimental plots took place in very different Palenciasoils (Table 1). The plots in Soria were on a loam sandy 70 140texture soil (sand 75-85%, lime less than 10% and clay 60 120 Precipitation (mm)less than 15%) with organic matter about 0.6% and pH of Temperature (ºC) 50 1006.8. This soil is light, with good drainage. The deeper 40 80texture is sandy or sandy loam. The soil in the plots of 30 60Palencia was the richest in P with moderately high 20 40organic matter (1.37) and the highest pH (8.5). The plots 10 20in the province of Girona have highest organic matter 0 0contents (1.65%). Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug MonthsTable I: Soil characteristics in 0-30 cm layer of the three Soriasites used for scenario building in this study P K Organic 70 140 pH N (%) Texture Temperature (ºC) 60 120 (mg/kg) (mg/kg) Matter (%) 50 100 Girona 8,2 0,11 28 192 1,65 loam 40 80Palencia 8,5 0,09 50,4 0,22 1,37 Franc 30 60 Soria 6,8 0,03 6,6 61,2 0,6 sandy 20 40 10 20 0 0 Regarding climate conditions, the region of Soria is Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Augcharacterized by fairly hot summers, with temperatures Monthssometimes reaching 30 ºC, and cold winters, with Average Temperature (ºC) Precipitation (mm)temperatures falling below 0 ºC and frequent frosts; in Figure 2: Ombrothermic diagram for the period2010 the first autumn frost occurred on September 27th (– September 2010-August 2011 in all three sites0.4 ºC), whereas the last spring frost in 2011 took placeon March 22nd (–0.4 ºC). 2.2 Experimental plots used for scenario building The province of Girona is characterized by a Coastal The experimental parcels were established in autumnMediterranean climate. These characteristics give to this 2009 and 2010, and in both cases they had no harvestslocation more moderate temperatures with no prolonged during the establishment year.periods of extremely high or low temperatures. Theaverage annual temperature is between 15-16° C, theminimum annual average is 7°C and theTable II: Experimental plots from different trials (established in 2009 and 2010) in the three study regions
  4. 4. Regions Soria Palencia GironaManagement and inputs 2009 2010 2009 2010 2009 2010Experimental plot Strips Strips small plots Strips small plots small plotsPlot size (total in m2) 5000 4500 225 135 90 90Tillage operations Chisel, harrowing, rotary tillerBase (NPK in kg/ha) 350 500 noneTop fertilizers NAC27% (kg/ha) 1st year none none none Succesive years 250 300 0 250Sowing rate 40 20 30 20 20Sowing date Nov.2009 Nov.2010 Oct.2009 Oct.2010 Oct.2009 Oct.2010Herbicides pre-emergence none Glifosate none post-emergence none 2-4D 2-4D and MCPAWeed control mowings 2010 2010 2009 and 2010 2010 and 2011Cut numbers 1 1 1 1 2 (june - Oct) 1Biomass yield range (odt/ha) 2.5 - 6 4 - 10 5 - 12 5 - 12 12 - 39 10 - 40Note: Yields from 2012 were estimated before harvest (June 2012). Maximum and minimum values correspond to theextreme values of replicates in the first and second year, and in the third year in the case of trials established in 2009 Both trials (2009 and 2010) followed similar the third years were based on observations and height inmanagement techniques. Operations for tillage soil June 2012.preparation were similar to those usually implementedwith cereals and annual grasses in Spain, including two 2.3. Scenarios definitionpasses of chisel, one with harrow disks, rotary tiller andring roller. Then, a base fertilization was usually utilized Management, machinery operations and raw materialsbefore sowing in autumn except in Girona were soils arericher enough and typical management considers weed Scenarios definition followed several assumptions forcompetition as favoured when nitrogen fertilizers are the total expected lifetime of tall wheatgrass. There areapplied during crop establishment (table II). Sowing rates very few studies with evaluations of tall wheatgrass in awere adjusted in relation to the germination rates and long period of time especially without grazingseed viability from previous tests (data not shown). management (only grass cuttings). Many evaluations onHerbicides and weed control operations (mowing) during tall wheatgrass were intended for forage production underestablishment were followed when needed. extreme alkaline soil conditions that are very different from the areas under study (mostly arable lands with low cereal yields). Based on specific studies in other countries, lifetime of tall wheatgrass in this assessment was assumed to be 15 years [24]. Following this report and our experimental plots, we assumed no harvest in the first year, as well as a maximum yield after the third year to be maintained for 7 years and a progressive decrease starting after the crops has 10 years old. Before establishment, machinery labour included tillage operations and base broadcasting fertilizations with NPK fertilizer in Palencia (500kg/ha). Considering our plots in Soria, Palencia and Girona, once tall wheatgrass was established we assumed mowing operations during next spring in order to avoid weed competition which is also a recommended management to avoid excessive evapotranspiration during summer in theFigure 3: Trials plots in Soria (2009) with tall first year [22]. Thus, by letting the biomass on the groundwheatgrass during bailing in the second year in the first year no baling was considered. Machinery equipment and tractors weights and Sampling methods were used to evaluate the lifetime as well as diesel consumptions were taken fromproduction in each replicate when trials were cultivated the Spanish Ministry of Agriculture [25]. Thisas small plots (Girona and Palencia). Biomass yields information was taken into account for the LCA andincluding harvest losses evaluation were registered in the economic costs analysis considering the number of timesgrass strips of Soria by mowing and baling operations of all operations during the assumed lifetime.(Figure 2). Biomass yields reported considered the Fertilization during spring was also different amongvariation among trials and repetitions or replicates as well the defined scenarios. Based on our experience in Soria,as an estimation of the expected biomass yield to be no top fertilization in spring was done in theachieved in summer 2012. Biomass yields assumed for establishment year. Fertilization with Calcium Ammonia
  5. 5. Nitrate (CAN) 27% doses were assumed to be 300, 250 assumed to be linked with soil and climate variationsand 150 kg/ha for Palencia, Girona and Soria based on (climatic year and site dependent).the soil characteristics and yield expectancy consideringclimate conditions. Additionally, a nutrient restitution to 2.4 Life Cycle Assessment methodologiesthe soil with NPK was assumed to be 50kg/ha in Palenciaand Girona, and 80kg/ha in Soria 6 times in the 15 years Life Cycle Assessment (LCA) is the environmentallifetime of tall wheatgrass. tool we selected to determine the energetic and Other inputs like herbicides where assumed based on environmental performance of Tall wheatgrass to producethe plots of the three study regions as well. Thus, the lignocellulosic biomass for electricity generation.scenario considers a pre-emergence glyphosate (1 l/ha) in LCA is a systematic set of procedures for compilingPalencia, and broadleaf herbicides 2-4D and dicamba (1 and examining the inputs and outputs of materials andl/ha) in Soria and Palencia during the first year. A final energy and the associated environmental impacts directlyherbicide spreading (two passes) was also assumed for attributable to the functioning of a product or servicethe end of the lifetime to allow a new crop establishment system throughout its life cycle [28]. This environmental(glyphosate, 1 l/ha). assessment tool is regulated by ISO 14040 [28] and ISO 14044 [29] standards, and according to this, LCAsTable III: Machinery equipment and number of should follow four steps: (1) goal and definition, (2)operations involved in the lifetime (15years) of tall inventory analysis, (3) impact assessment and (4)wheatgrass interpretation. Weight Lifetime Palencia Girona Soria Simapro 7.2 [30,31] software tool and Ecoinvent 2.2Machinery operations for lifetime (kg) (h) (times)Chisel ploughing (50cm) 750 1200 1 [32,33] European database have been selected for theHarrowing by disks 1800 1200 2 2 LCAs.Ring roller 1500 400 1 Also a rough nitrogen balance was made consideringChisel ploughing (25cm) 750 1200 1Rotary tiller 1400 1200 2 2 nitrogen supply by fertilizers and measuring the amountBase fertilizer application (establishment) 700 400 1 0 0 of nitrogen contended in the crops as the nitrogenRestitution NPK fertilizer (spreader) 700 400 6 6 6 extracted.Sowing 810 750 1 1 1Herbicides spreader (pre-emergence) 600 500 1 0 0Top fertilizer application (spring) 700 400 15 15 14 2.4.1 Goal and Scope definitionHerbicides spreader (post-emergence) 600 500 1 1 1 The aim of this study is to evaluate the energyMowing 2400 667 15 16 15Baling (250kg bales) 9000 2308 14 14 14 balance and environmental impacts of the 15 scenariosBales loading 2500 1333 14 14 14 defined in the above sections for growing tall wheatgrassLast herbicide (End-life application) 600 500 2 2 2 as energy crop in Spain for electricity generation andTractor 1 (120HP) 4320 12000Tractor 2 (150HP) 5400 10000 compare them with electricity generation from natural gas, as a reference for generation from non-renewableYields fossil sources.In order to build scenarios assuming normal large-sized 2.4.2. Functional unitplots with tall wheatgrass in the study regions, we used The functional unit chosen is 1 TJ of electrical energythe information from our management techniques and generated from biomass for the studied system and fromresults in small and medium sized (strips) plots. Based on natural gas for the reference system. This amount ofsimilar practices and yields in other reports from electrical energy is a round number corresponding to 12Argentina [26], United States [27] and Hungary [24] we hours of functioning of the 25Mw power plant selecteddefined five yield scenarios for each region: very low, for this study (see 2.4.5).low, middle, high and very high (Table IV). These The electricity production per hectare of talldifferent yields assumed no substantial changes in wheatgrass trials is the product of the crop yield (seefertilization or cultivation techniques. Therefore we Table IV) at 12 % humidity by the net calorific value atassumed that variation in yields is mostly caused by soil 12 % humidity [27] and by the efficiency of the biomassand climate variability among years and specific site conversion process into electricity (29.5 % for this case(parcels) of each region. Yields defined in scenarios for study).large plots considered the typical differences that smallplots have because of border effects (usually large plots 2.4.3 Systems descriptionpresent 25-50% lower yields compared to small plots The bioenergy systems analyzed includes threedepending on boarders and plot shape). subsystems: agricultural biomass production, electricity generation and the transport of products and rawTable IV: Yield scenarios for the three study regions materials. Yield scenarios (mean value for lifetime) Agricultural systemRegions Very low Low Middle High Very HighPalencia (odt/ha) 4,1 5,8 7,0 8,2 10,2 The agricultural system could be described by theGirona (odt/ha) 6,2 8,1 9,5 10,9 12,8 crop schemes followed, the machinery used and theSoria (odt/ha) 2,4 3,9 5,0 6,1 7,0 inputs consumed. The three agronomic management patterns (one per Biomass power plant systemregion) and five yield levels of our three regions reportedthen a total of 15 scenarios for which economic and LCA All the data considered to model the biomass powerwas carried out. The five yield levels reflect variations plant system are real data from a 25 MW biomass plant
  6. 6. located in northern Spain. This plant consumes biomass Biomass, ash and slag means of transport and distancesat an average humidity of 12% and produces electricity were provided by company in charge of the biomasswith a conversion efficiency of 29.5%. The plant power plant.consumes natural gas for maintenance operations andpre-heating and produces ashes and slag from biomass as Natural gas systemresidues. The average consumption of natural gas and the The natural gas system includes the gas fieldproductions of ashes and slag per kilogram of burned operations for extraction, the losses, the emissions andbiomass are shown in Table V. the purification of the main exporter counties of natural gas to Spain (Algeria 73 % and Norway 27 %). AlsoTable V: Biomass power plant consumptions and includes the long distance and local transport of gas toresidues produced the power plant in Spain, considering the energy Consumed or produced consumption, loses and emissions for distribution. Amount substances Finally the substances needed and the average efficiency Natural gas consumption 0.0342 of Spanish natural gas power plants to produce electricity (MJ Kg-1 Wet Biomass Burned) are taken into account [35]. Slag production 82.47 (g Kg-1 Wet Biomass Burned) 2.4.4 Life cycle inventory analysis Ashes production 8.25 (g Kg-1 Wet Biomass Burned) The inventories used to consider natural gas consumption [35] of the biomass power plant, transports The emissions of the plant into the air are submitted [36] of agricultural inputs, and biomass and power plantregularly to the local government. The emissions residues are taken from Ecoinvent.accounted are only those which affect the global warming The methods used for the inventory analysis of thepotential (GWP). In the power plant studied these agricultural system mainly follow that proposed on Lifeemissions come from gas natural combustion (see Table cycle inventories of agricultural production systems [34].VI). Carbon dioxide emitted from biomass combustion To consider N2O emissions we follow the formulawas not considered because it was previously fixed from proposed by de RSB GHG Calculation Methodology vthe air by the crop. 2.0 [12]. This formula is basically based on the formula proposed in the Ecoinvent Agricultural Report [34], that considers the new IPCC guidelines [37]. Also weTable VI: Biomass power plant aerial emissions Substance Origin Amount consider the nitrate emissions affecting to Global (g Kg-1 Wet Biomass Warning Potential as the RSB purposes [12], making and Burned) estimation of them by means of nitrogen balance, the soil Fossil carbon and crop characteristics and the rainfall of the zone. Natural gas 1.94 dioxide Fertilizers productionsTable VII: Transport system summary The fertilizer inventories consider the different steps Material From To Distance Vehicle of the production processes, such as the use of raw Processing Lorry materials and semi-finished products, the energy used in Seed Field 30 km center 20-28t the process, the transport of raw materials and Processing Regional Lorry intermediate products, and the relevant emissions [34]. 100 km center storehouse 20-28t The production of calcium ammonium nitrate starts Regional Demonstratio Lorry 10 km with the production of the ammonium nitrate by the storehouse n parcel 16-32tFertilizers neutralization of ammonia with nitric acid. The final Regional product is then obtained by adding dolomite or limestone and Manufacturer 600 km Train storehouse to the solution before drying and granulation [38].herbicides Lorry No inventories are given in Ecoivent for multinutrient 100 km >16t fertilizers due to the amount different possible ways to Regional Demonstratio Lorry mix nitrogen, phosphorous and potassium compounds to 10 km storehouse n parcel 16-32t produce NPK fertilizers [38]. The modeling of NPK Demonstratio Lorry fertilizer inventories has been approximated by Biomass Biomass plant 60 km n parcel 16-32t combining inventories of single fertilizers according to Ash and Lorry Biomass plant Disposal 37 km multinutrient fertilizer specific contents of N, P 2O5 and slag 16-32t K2O, as well as the form of the nitrogen providedTransport system (ammonium, nitrate or urea) [38]. The transport system is summarized in Table VII.This table shows all modes of transport used and the Herbicides productiondistances between origin and destination points for every The data related to emissions, energy and substancetransport in the LCAs carried out. consumption in the production of the herbicides sprayed The transportation means and distances for the is taken from Ecoinvent [39]. The quantities of activetransport of agricultural inputs until the regional matters considered are taken from the formulations of thestorehouse are taken from the Ecoinvent database [34]. commercial fertilizers used.The distance from the regional store house to plots was10 km approximately. The transport of workers to the Seed productionparcel has not been considered because of the highly Tall wheatgrass seeds can be produced in Spain undervariability of transport distances depending on cases. similar conditions compared to the operations of fertilizer and management practices used for forage cultivation.
  7. 7. Tall wheatgrass seeds are frequently produced under land. Indirect land use change is a complex process thatirrigation in high quality soils under contract with real is not fully understood by the scientific community andfarmers, thus their normal operations and yield so is not included in this study [43].production were assumed to be similar to that of the localcommon management practices considered in this study. 2.4.5 Life cycle impact assessment Then, a grain production yield of 0.8 odt ha-1 was Life Cycle Impact Assessment (LCIA) is the phase inconsidered as suggested by other studies [25,26,27]. an LCA where the inputs and outputs of elementary flows The energy consumption for cleaning, drying, seed that have been collected and reported in the inventory aredressing, and bag filling of the Tall wheatgrass seed in translated into impact indicator results [44].the processing plant has been estimated in 32.8 kWh t- LCIA is composed of mandatory and optional steps.1 [40]. Mandatory steps of classification and characterization have been carried out and optional steps normalizationDiesel consumption and combustion emissions of and weighting have been avoided in order to make resultsagricultural machinery more comparable and to avoid introducing value choices. The diesel consumption of agricultural machinery In the classification steps elementary flows shall bewas obtained from the Spanish Ministry of Agriculture assigned to those one or more impact categories to which[25]. The inventories for the extraction, transport of they contribute. In the characterization steps eachpetrol, the transformation into diesel and its distribution quantitative characterization factor shall be assigned toare taken from Ecoinvent [41]. The exhaust emissions of all elementary flows of the inventory for the categoriesdiesel in agricultural machinery engines are also that have been included in the classification [44].considered [41]. Environmental impact assessment methodAgricultural machinery manufacture We have selected the software tool Simapro 7.2 [45] The inventories for agricultural machinery and the impact assessment method of the IPCC 2007 [46]manufacture are specific to the different types of to assess the 100 years’ period horizon Global Warmingmachinery (tractors, harvesters, tillage implements or Potential (GWP).general implements). The amount of machinery (AM) needed for a specific Energy assessment methodprocess was calculated multiplying the weight (W) of the In order to assess the energy consumed to generatemachinery by the operation time (OT) and dividing the electricity from tall wheatgrass biomass and from naturalresult by the lifetime of the machinery (LT) [34]: gas, we have selected the software tool Simapro 7.2 [45] and the Cumulative Energy Requirement Analysis AM (kg FU-1) = W (kg) OT (h FU-1) LT-1(h); (CERA) [48]. This method aims to investigate the energy use throughout the life cycle of a good or service. The Where FU (See 2.4.2) is the functional unit of the primary fossil energy (FOSE) has been obtained usingLCA. The life time was obtained from the Spanish this method.Ministery of Agriculture (see Table III) [25]. 2.5. Comparison between tall wheatgrass and winterNitrous oxide emissions cereals from previous studies The calculation of the N2O emissions [12] is based A previous study data and results from twoon the formula in Nemecek et Kägi [34] and adopts the experimental plots with triticale (Triticosecale sp.), oatsnew IPCC guidelines [37]: (Avena sativa), lopsided oats (Avena strigosa L.) and rye (Secale cereale) was utilized in order to makeN2O= comparisons with tall wheatgrass scenarios performance.44/28∙(EF1∙(Ntot+Ncr)+EF4∙14/17∙NH3+EF5∙14/62∙NO3-) The 15 scenarios of tall wheatgrass were based in a similar range of biomass yields compared to the citedWith: research in which GHG emissions savings whenN2O = emissions of N2O [kg N2O ha-1] substituting natural gas electricity by combusting biomassEF1 = 0.01 (IPCC proposed factor [37]) in a 25MW boiler. The mentioned study considered twoNtot = total nitrogen input [kg N ha-1] sites with experimental plots located in two SpanishNcr = nitrogen contained in the crop residues [kg N ha-1] provinces in Castilla y León (Soria and León). The powerEF4 = 0.01 (IPCC proposed factor [37]) energy plant and transport systems cited in tables V andNH3 = losses of nitrogen in the form of ammonia [kg VI, were the same for both studies [13].NH3 ha-1]. Calculated as proposed in the RSB [12] andNemecek et Kägi [34] methodologies. 2.6 Economic costs at the farm level14/17= conversion of kg NH3 in kg NH3-N In order to calculate costs for biomass production atEF5 = 0.0075 (IPCC proposed factor [37]) the farm level, the 15 scenarios defined for tallNO3- = losses of nitrogen in the form of nitrate [kg NO3 wheatgrass in above sections were analysed together withha-1]. They were estimated through the RSB formula [12] the winter cereal trials analysed in previous studies [13].which considers nitrogen supply, the nitrogen uptake, the Winter cereals costs included two regions as defined insoil and crop characteristics and the local rainfall. our previous study (Soria and León) which were assumed14/62= conversion of kg NO3- in kg NO3-N. to explore enough yield and be management representative for typical cereal areas in central Spain.Land use changes Rental land costs in Soria were assumed to be 90€/ha per Direct land used change does not take place because year when cropping Tall wheatgrass. Winter cerealsthe parcel selected was previously a winter cereal crop rental land costs were assumed to be an average value for
  8. 8. the region of Castilla y León (119€/ha.year). Both tall Total mean costs per hectare considering 15 yearswheatgrass and winter cereals used economic data from lifetime of Tall wheatrgrass, were much higher thatMARM (2012)[25] and local information for fertilizer, winter cereals in all scenarios (Table VIII). The higherherbicides and tall wheatgrass seeds prices. costs of winter cereals might be explained mainly because of a higher contribution of establishment (machinery2.7. Nitrogen balances operations, base fertilization and sowing). Rental lands A rough nitrogen balance was made. This estimation contribution, top fertilization and harvest operationsconsiders nitrogen supplied in base and top fertilizations (mowing, baling and loading) are major costs affectingas the entrance of the system and total nitrogen content of Tall wheatgrass.rye aerial biomass trials as exit of the system. The totalamount of nitrogen extracted and exported by the crop 3.2. Global warming potentialharvest is calculated by multiplying the yield of eachscenario (see Table IV) by its respective biomass Increasing yields reflect a remarkable reduction innitrogen content [27]. As roots remain into the soil we GHG emissions when producing electricity in a powerassumed that all nitrogen from roots return to the soil. energy plant. Nevertheless, winter cereals had higherTherefore we did not take into account any proportion of GWP at similar yields at the farm level compared to Tallroot nitrogen content as extracted nitrogen. wheatgrass. As reflected with mean production costs, lower yields achieved higher GWP per TJ in winter3 RESULTS AND DISCUSSION annual grasses compared to Tall wheatgrass (Figure 5).3.1 Economic assessment 120 Oat 100 Lopsided Oat Costs at the farm level resulted to be much higher for GWP (Mg CO2 eq TJ electrcity-1)biomass production from winter cereals compared to Tall 80 Ryewheatgrass (Figure 4). Triticale 60 Tall wheatgrass (Soria) 240 Tall wheatgrass Palencia Tall wheatgrass 220 40 (Palencia) 200 Tall wheatgrass Soria Tall wheatgrass (Gerona) 180 20 Tall wheatgrass GironaMean biomass cost (€/odt) 160 Triticale 140 0 Rye 2000 4000 6000 8000 10000 12000 14000 120 Oat Yield (kg d.m. ha-1) 100 80 Lopsided Oat Figure 5: Global warming potentials as function of 60 biomass yields per hectare in winter cereals and Tall 40 wheatgrass scenarios. 20 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 90% Oat GHG Savings (%) Biomass Compared to electricity Biomass yield (odt/ha.year) 80% Lopsided Oat from Natural Gas as fossil referenceFigure 4: Biomass costs production at the farm level in 70% RyeTall wheatgrass and winter cereals 60% Triticale 50% Tall wheatgrass (Soria)Table VIII: main costs for biomass from three scenarios 40% Tall wheatgrassof Tall wheatgrass and for winter cereals considered in 30% (Palencia) Tall wheatgrassthis study (Gerona) 20% Tall wheatgrass Winter cereals Tall wheatgrass (€/ha.y-1) €/ha.y-1 10% Regions/inputs Palencia Girona Soria (Soria and León) 0% 2000 4000 6000 8000 10000 12000 14000Field works 19 18 16 164 Yield (kg d.m. ha-1)base fertilization 13 0 0 157Top fertilization 70 54 35 70 Figure 6: GHG emissions savings of Tall wheatgrass andPre emergence herbicides 1 8 13 0 winter cereals producing electricity from biomass as aReposition fertilization 8 2 0 0Post emergence herbicides 1 2 1 51 function of biomass yield.Final herbicides 2 2 2 0Rental land 119 174 90 119Mowing, baling and loading 156 153 153 163Seeds 5 5 5 114Total 393,58 418,53 314,18 838,00 Considering the biomass yields explored range in ourscenarios, Tall wheatgrass produced lower costs at allyields but differences were higher (as much as 124€/odt)when biomass yield was lower (below 4odt/ha). Highestyields showed a lower cost for Tall wheatgrass (around36€/odt) suggesting that more productive areas may bealso better suited for the perennial grass.
  9. 9. 0,6 wheatgrass biomass used for electricity might be suitable Palencia 2,3 5,2% 1,5% 0,2 0,4% for areas with lower potential yields achieving similar limitations stated in the sustainability criteria established 3,5 for biofuels in the RED. 8,0% As shown in Figure 7, most important inputs causing GWP are fertilizer production and those derived from fertilizer use (nitrous oxide), accounting in total for 21,7 50,2% 89.9% in Palencia, 78.4% in Soria and 80.7% in Girona. 15,0 Differences are linked to the nitrogen fertilizer doses for 34,7% each case (see table II). 3.3. Energy balances Seed and Pesticides Fertilizers Energy yields increased significantly with biomass Nitrous Oxide Field Works production per hectare as most inputs variation is lower Biomass transport Power Plant Operation than outputs, suggesting that specific conditions could be (yearly climate differences or soil variability) could 2,3 0,6 1,8% 0,2 0,6% Soria generate different energy balance scenarios. Therefore, climate and soil conditions determining yields might 6,4% cause large variations on energy balances as well. Tall wheatgrass originate a similar response compared to 4,6 winter cereals, but with a parallel higher response when 12,9% 14,5 correlating energy yields at the power energy plant with 40,8% biomass yields in the field (figure 9). 8,0 Oat Energy output per fossil energy inputs (TJ electricty 7,0 13,4 Lopsided Oat 37,6% 6,0 TJ fossil energy-1) 5,0 Rye Seed and Pesticides Fertilizers 4,0 Triticale Nitrous Oxide Field Works 3,0 Biomass transport Power Plant Operation Tall wheatgrass (Soria) 2,0 Tall wheatgrass 0,6 0,1 1,0 2,3% 0,4% Girona 0,0 (Palencia) Tall wheatgrass 2000 4000 6000 8000 10000 12000 14000 (Gerona) Yield (kg d.m. ha-1) 2,3 8,0% Figure 9: Energy ratios for electricity production from 2,4 8,6% biomass of Tall wheatgrass and winter cereals scenarios 12,8 as a function of biomass yield 45,3% The scenario for the region of Soria clearly has a higher energy yield at similar biomass yields in the farm 10,0 35,4% probably explained by lower fertilizer uses (figure 10). Most important fossil input contributions were fertilizers. Fossil energy inputs were mostly caused by Seed and Pesticides Fertilizers fertilizers: 46%, 59.8 and 50.7 in Soria, Palencia and Nitrous Oxide Field Works Girona respectively. Secondly, machinery fossil inputs Biomass transport Power Plant Operation and raw materials (pesticides and seeds) were affecting energy ratios as well.Figure 7: Different contributions to the global warmingpotentials for tall electric production (TJe) from biomass 3.4. Soil nitrogen balanceof wheatgrass in the three study regions Nitrogen balances in the soil changed dramatically in the scenarios assumed for tall wheatgrass as a function of Higher yields produced a higher emission reduction biomass yield (Figure 11). A clear negative relationshipwhen comparing GWP of electricity from biomass in the between soil nitrogen balance and biomass yield seems to25MW power energy plant, with natural gas electricity in be explained as nitrogen fertilizer uptakes are higher toSpain (figure 6). As suggested in previous studies, winter nitrogen applications then suggesting a necessarily soilcereals low biomass yields at the farm level determine nitrogen extraction from the soil nitrogen stock. Ashigher GWP and lower emissions reductions replacing management scenarios defined in this study consideredthe fossil reference. Even under extremely low yield same nitrogen doses for five different biomass yields,scenarios (below 4odt/ha) calculated GHG emissions higher biomass yields imply a higher nitrogen uptakesavings were always higher than 50% and low and compared to lower yields (figure 12). This result suggestmedium yields scenarios in both Palencia and Soria, were that yields between 6 and 8 odt/ha resulted in assumed noalways above 60%. These results suggest that Tall changes in soil nitrogen.
  10. 10. 0,002 60 0,011 5,0% 1,0% Soria Tall wheatgrass Nitrogen Balance (kg N ha-1) 40 (Soria) 0,035 20 Tall 16,5% wheatgrass (Palencia) 0,098 0 46,0% Tall -20 wheatgrass (Gerona) -40 0,067 31,5% -60 -80 Seed and Pesticides Fertilizers 0 2000 4000 6000 8000 10000 12000 14000 Field Works Biomass transport Yield (kg d.m. ha-1) Power Plant Operation Figure 11: Soil nitrogen balances in the three regions 0,011 0,002 scenarios as a function of its biomass yields. 4,4% 0,8% Palencia As mentioned in above sections, obtaining high GHG 0,035 emissions savings would probably mean that Tall 14,4% wheatgrass had enough high biomass (energy output) and energy yield, compared to the GHG emissions incurred for crop and post-harvest transport and processing 0,051 producing electricity. Nevertheless, our results indicate 20,7% 0,146 that producing more biomass implies more nitrogen 59,8% uptake and a potential excessive soil nitrogen depletion that should be addressed in a bioenergy sustainable production. In Girona for instance, only very low yields extracted less nitrogen than that supplied to the crop. Seed and Pesticides Fertilizers Highest GHG emission reductions coincide with soil Field Works Biomass transport nitrogen depletion suggesting that an adequate nitrogen Power Plant Operation management should be consider (more nitrogen fertilizers 0,001 may cause higher fossil inputs and lower emission 0,7% reductions but may allow soil nitrogen stability). Girona 0,011 6,4% 90% NITROGEN DEFICIT NITROGEN SURPLUS Tall 85% wheatgrass GHG Savings (%) Compared to electricity from 0,035 (Soria) 21,0% 80% Natural Gas as fossil reference) 75% Tall wheatgrass 0,085 70% (Palencia) 50,7% 65% Tall wheatgrass 60% (Gerona) 0,036 55% 21,3% 50% 45% Seed and Pesticides Fertilizers 40% -80 -60 -40 -20 0 20 40 60 Field Works Biomass transport Nitrogen Balance (kg N ha-1) Power Plant Operation Figure 12: GHG emissions savings as a function of soil nitrogen balances.Figure 10: Different contribution for energy fossil inputsper TJe in the three study regions with Tall wheatgrass
  11. 11. 4 CONCLUSIONS Available (in Spanish) at: From the results obtained under the trial conditions, it 2012-1310.pdfcan be concluded that: [3] IDAE, 2010. National Action plan for renewable Tall wheatgrass has good prospects for energy in energies in Spain (Plan de Acción Nacional deview of the amount of biomass produced in less fertile Energías Renovables de España, PANER) 2011-areas without too many inputs. 2020. Instituto de la Diversificación y el Ahorro According to the obtained results, the mean Energético (IDAE), Ministery of Industry andproduction costs of Tall wheatgrass at the farm level commerce. Madrid. Spain. Available at: www.idae.esranged from 40-60 €/odt for low and medium yield [4] Maletta E. A de. V and JC. El potencial de lasscenarios (5-7 odt/ha.year). These costs are lower than gramíneas como cultivo energético en España. Vidathose of winter cereals that should have maximum yields Rural, Núm. 325. order to obtain similar biomass costs. Considering a [5] Fischer, G., S. Prieler, H. van Velthuizenet, S. M.price of 75-85€/odt for square bales at the farm (loaded Lensink, M.Londo & M. De Wit. 2010. Biofuelon the truck), wheat grass have a potential profitability at production potentials in Europe: Sustainable use ofleast for the scenarios defined in this study. This suggests cultivated land and pastures. Part I: Land productivitythat Tall wheatgrass could be suitable to supply power potentials." Biomass and Bioenergy 34(2): plants in Spain. [6] Fischer G., S. Prieler, H. van Velthuizen, G. Berndes, Considering the explored range of crop yields and A. Faaij, M. Londo & M. de Wit-2010. Biofuelmanagement conditions, GHG emissions savings when production potentials in Europe: Sustainable use ofusing Tall wheatgrass biomass for producing electricity cultivated land and pastures, Part II: Land useare significantly higher (50-90%) of those of winter scenarios, Biomass and Bioenergy, Volume 34, Issuecereals (5-70%). Energy yields of electricity production 2, A roadmap for biofuels in Europe, February 2010,where clearly higher when biomass was obtained from Pages 173-187perennial grasses (2.5-7.5) compared to those of [7] Lewandowski, I. J. M. O. Scurlock, E. Lindvall y M.electricity from winter cereals biomass (1.5-3). Christou, 2003. The development and current status These results suggest that TW can have a significant of perennial rhizomatous grasses as energy crops inpotential as energy crop in marginal lands in Spain. the US and Europe, Biomass and Bioenergy, Volume Nitrogen fertilization have been observed to be the 25, Issue 4, October 2003, Pages 335-361.most important input to be considered when producing [8] EEA, 2006. How much bioenergy can Europeenergy from the species under study. This is because produce without harming the environment? EEAnitrogen fertilizer production requires a large amount of Report No 7/, causing greenhouse gas N2O emissions and [9] EC 2009. Renewable Energy Directive 2009/28/EChaving a significant negative impact on CO2 balance. of the European Parliament and of the Council of 23 Another sustainability indicator considered in this April 2009 on the promotion of the use of energystudy was nitrogen balance that was linked with GHG from renewable sources and amending andemissions savings of electricity from biomass in Tall subsequently repealing Directives 2001/77/EC andwheatgrass. As management techniques regarding base 2003/30/EC. Available at:fertilizers (NPK) and top fertilizer applications in spring ammonia nitare, 27%) were different in each able_energy/en0009_en.htmsite and the production was assumed to vary in five [10] Petr Havlík, Uwe A. Schneider, Erwin Schmid,scenarios, an impact on the soil nitrogen balance suggest Hannes Böttcher, Steffen Fritz, Rastislav Skalský,that soil must be considered when looking for Kentaro Aoki, Stéphane De Cara, Georgsustainability of perennial grasses. It would be important Kindermann, Florian Kraxner, Sylvain Leduc, Ianto consider no only energy crop fertilizing and its impact McCallum, Aline Mosnier, Timm Sauer, Michaelon biomass quality and emissions but also economic and Obersteiner, Global land-use implications of first andenergy balances. Moreover, the interest lies on obtaining second generation biofuel targets, Energy Policy,maximum yields with a minimum emission impact, so it Volume 39, Issue 10, October 2011, Pages 5690-is recommended to improve the efficiency in the use of 5702.nitrogen by adjusting the dose, the optimal timing of [11] T.D. Searchinger, S.P. Hamburg, J. Melillo, W.application, the type of fertilizer, etc., or the inclusion of Chameides, P. Havlik, D.M. Kammen, G.E. Likens,alternative crops like nitrogen fixing species (legumes) or R.N. Lubowski, M. Obersteiner, M. Oppenheimer, G.pasture mixes. Philip Robertson, W.H. Schlesinger, G. David Tilman. 2009.Fixing a critical climate accounting error. 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