Applied Energy 92 (2012) 92–98

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Applied Energy

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A life cycle assessment of derived from the ‘‘niche filling’’ energy in the USA ⇑ Brian J. Krohn , Matthias Fripp

Oxford University, Environmental Change Institute, School of Geography and the Environment, South Parks Road, Oxford OX1 3QY, UK article info abstract

Article history: Camelina sativa (L.) is a promising crop for that avoids many of the potential pitfalls Received 19 July 2011 of traditional , such as land use change (LUC) and food versus fuel. In this study the environ- Received in revised form 30 September 2011 mental viability of camelina biodiesel was assessed using life cycle analysis (LCA) methodology. The LCA Accepted 14 October 2011 was conducted using the spreadsheet model dubbed KABAM. KABAM found that camelina grown as a Available online 29 November 2011 niche filling crop (in rotation with or as a double crop) reduces greenhouse gas (GHG) emissions and fossil fuel use by 40–60% when compared to petroleum diesel. Furthermore, by avoiding LUC emis- Keywords: sions, camelina biodiesel emits fewer GHGs than traditional and canola biodiesel. Finally, a sen- Life cycle assessment sitivity analysis concluded that in order to maintain and increase the environmental viability of camelina Camelina Biodiesel and other niche filling biofuel crops, researchers and policy makers should focus their efforts on achieving Land use change satisfactory yields (1000–2000 kg/ha) while reducing nitrogen fertilizer inputs. Biofuel Ó 2011 Elsevier Ltd. All rights reserved.

1. Introduction To address these two issues a variety of alternative biofuel feed- stocks are currently being researched. Niche filling crops show po- Due to a persistent and growing awareness of the negative so- tential in avoiding the two major issues of food vs. fuel and LUC cial, political, and environmental impacts of fossil fuels over the because they are crops that can be grown during fallow periods last two decades there has been a constant push by governments, or mixed into the traditional agricultural system. [8–11]. Camelina industry, and citizens to develop alternative energy sources that sativa (L.) is a niche filling oilseed crop that shows potential as a fu- are both domestic and renewable. In the US are predicted ture feedstock for biofuels, specifically biodiesel [12,13,13–17]. to make up 80% of the growth in liquid fuels between 2010 and Camelina is a notable potential niche filling crop because com- 2035 [1]. Biofuels from traditional food crops such as corn, soy- pared to current oilseed crops, specifically canola, it requires lower beans or canola, however, have two significant drawbacks. First, agricultural inputs, is more tolerant of cool weather, has a shorter the high demand for biofuel crops may result in direct or indirect growing season, and is more efficient in its water use [14,18–20]. changes in land use on a domestic or international level [2,3]. Land Due to these unique properties camelina is well suited to fill fallow use change (LUC) is a considerable issue when land with a large periods in dryland wheat farming or to be grown as a double crop amount of stored carbon, such as forests or peat bogs, is converted with short season or sunflowers [18,21–23]. Before con- into land with low amounts of stored carbon as is the case for most siderable acreage is devoted to camelina, however, it is important agricultural land. The resulting conversion releases sequestered to assess its environmental viability. In this paper we assess the carbon into the atmosphere creating a ‘‘carbon debt’’ that may take fossil energy consumption and greenhouse gas (GHG) emissions the biofuel years if not hundreds of years to pay off [2,4,5]. The sec- of camelina biodiesel using life cycle analysis methods. ond issue for biofuels is the dilemma between food and fuel [6].In 2006/2007, food prices around the world reached record highs while the US converted a record 20% of its corn crop to ethanol 2. Methods [7]. With an increasing global population and increasing demand for high agricultural intensity foods such as meat it seems prudent 2.1. Goal and scope to reserve arable land and crop production for food. The methodology of this study follows the ISO 14040 methods for conducting an attributional LCA [24–26]. The goal of this study

⇑ Corresponding author. Address: Keble College, Oxford University, Oxford OX1 is to assess the life cycle energy balance and GHG emissions associ- 3PG, UK. Tel.: +44 909414570. ated with biodiesel derived from camelina in several different sce- E-mail address: [email protected] (B.J. Krohn). narios. The scope of the study includes the agricultural production

0306-2619/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2011.10.025 B.J. Krohn, M. Fripp / Applied Energy 92 (2012) 92–98 93 of the fuel crop, extraction of the oil, conversion of the oil to biodie- sel, and transportation of biodiesel to market. To quantify and compare the energy and emissions in an adapt- able and transparent manner we developed Krohn’s Alternative Biodiesel Analysis Model (KABAM). KABAM uses a similar structure as the attributional LCA models BESS, EBAMM, and GBAMM, which utilize a fixed life cycle energy or emission factor for each input. The life cycle factors were derived using the GREET model and the current LCA literature [27–29]. The life cycle energy and emis- sions factors for each input can then be multiplied by their usage and then summed together to determine the LCA value for the bio- diesel system, as shown in Eq. (1). The benefit of the life cycle fac- tor method is that the assumptions for each input can be easily compared across scenarios and against other models; thus making the model more transparent and allowing for easier review and cri- tique of the models assumptions [30]. X

LCA value ¼ ðEmission factorÞx ðUsage rateÞx x ¼ Input into the biofuel system ð1Þ

To draw further conclusions from the KABAM model, we also conducted a sensitivity analysis. A sensitivity analysis is a helpful tool because it identifies and ranks the inputs that have the great- est influence on the model’s outcomes. Specifically, a sensitivity Fig. 1. The system boundaries for the life cycle assessment of biodiesel fuel. analysis aids in drawing conclusions from an LCA model by high- lighting the inputs of greatest concern. Sensitivity is evaluated by the sensitivity coefficient, which is defined in finite terms as the change in output from two model runs over the change in a single 2.3. Emission factors variable, see Eq. (2) [31]. The following section describes the data, data sources, and C2 C1 methods used to determine the life cycle factors for each input used S ¼ ð2Þ k2 k1 in the KABAM model. The life cycle factors describe the upstream energy or emissions of the inputs, such as fuels (e.g. gasoline) where S is the sensitivity, C the model output, and k is the model and chemicals (e.g. methanol). We utilized GREET’s life cycle path- input. ways to calculate most of the upstream energy and emissions for Finally, a significant issue in all LCAs is how to distribute the en- each input for the year 2010, unless otherwise noted [37]. In some ergy and emissions between the primary product (biodiesel) and instances GREET was insufficient or out of date, in which case we the co-products (glycerin and seed meal) [32]. Allocation methods utilized existing industry data or previous LCA studies to deter- distribute life cycle emissions and energy by numerical properties, mine the life cycle factors, for greater details see the supplemen- such as mass, energy content, or economic value [33]. Another tary material. The greenhouse warming equivalence factors for a method, called displacement, addresses the co-product issue by 100-year period for CO2,CH4, and N2O are 1, 25, 298 respectively, taking account of the energy or emissions that are avoided when were taken from the IPCC 2007 AR4 report. Table 1 lists the fossil the co-products replace other products in the market and thus gen- energy life cycle factors and Table 2 lists the emission life cycle fac- erating an offset credit [33]. The displacement approach is recom- tors for each input used in KABAM. mended by the LCA guidelines issued by ISO 14040-14049, however, it significantly increases the scope of the study [26,34]. Biofuels LCAs have shown considerable sensitivity to the choice of allocation method [35,36]. We address this issue in KABAM by Table 1 Fossil energy life cycle factors for KABAM’s inputs. using the energy and economic value allocation methods as well as the displacement method and comparing the three results. Input Fossil energy per Ref. unit of input Nitrogen MJ/kg 47.70 GREET 1.8c [37] 2.2. System boundary and functional unit Phosphorus MJ/kg 13.35 GREET 1.8c [37] Potassium MJ/kg 8.09 GREET 1.8c [37] The system boundary is defined by the direct inputs into each Lime MJ/kg 0.42 GREET 1.8c [37] and data from [38] Herbicide MJ/kg 274.63 GREET 1.8c [37] stage of biodiesel production. Fig. 1, shows the system boundaries Insecticide MJ/kg 313.46 GREET 1.8c [37] and the general type of life cycle inputs considered in this study. Seed MJ/kg 2.35 Calculated using method from [38] The functional unit of KABAM is one unit of energy of biodiesel Gasoline MJ/L 39.52 GREET 1.8c [37] produced from the system. This is reported in terms of the MJ fossil Diesel MJ/L 45.30 GREET 1.8c [37] energy used per GJ of biodiesel produced (MJ/GJ) for the fossil en- LPG MJ/L 26.62 GREET 1.8c [37] MJ/m3 39.24 GREET 1.8c [37] ergy consumption and in gCO2 equivalence per MJ of biodiesel pro- Electricity MJ/kWh 7.98 GREET 1.8c [37] duced (gCO2e/MJ) for the GHG emissions. All energy values fuels N-hexane MJ/kg 44.41 GREET 1.8c [39] are reported in lower heating values. The focus of this study is Methanol MJ/kg 33.67 GREET 1.8c [39] the agricultural stage of biodiesel production and is discussed sep- Sodium hydroxide MJ/kg 19.87 [40] Sodium methoxide MJ/kg 39.00 [40] arately. As a result, the agricultural stage of the system has its own Hydrochloric acid MJ/kg 20.98 [40] functional unit of one hectare of land. 94 B.J. Krohn, M. Fripp / Applied Energy 92 (2012) 92–98

Table 2 GHG emission life cycle factors for KABAM’s inputs.

Input GHG emissions per unit of input Ref. Agricultural emissions

Nitrogen gCO2e/g 3.08 GREET 1.8c [37]

Phosphorus gCO2e/g 1.12 GREET 1.8c [37]

Potassium gCO2e/g 0.78 GREET 1.8c [37]

Lime gCO2e/g 0.04 GREET 1.8c [37]

Herbicide gCO2e/g 23.30 GREET 1.8c [37]

Insecticide gCO2e/g 27.15 GREET 1.8c [37]

Seed gCO2e/g 0.39 Calculated in KABAM using method from [38] Field emissions

Field N2O emission % N emitted as N2O 1.33% [41]

Field CO2 (lime) kg CO2/kg lime 0.4400 Calculated Urea fraction of N % of applied N 21.10% [42,43]

Field CO2 (urea) kg CO2/kg N fertilizer 0.3316 Calculated Fuel emissions

Gasoline gCO2e/MJ 92.60 GREET 1.8c [37]

Diesel gCO2e/MJ 93.10 GREET 1.8c [37]

LPG gCO2e/MJ 76.90 GREET 1.8c [37]

Natural gas gCO2e/MJ 66.30 GREET 1.8c [37]

Electricity gCO2e/kWh 780.00 GREET 1.8c [37] Chemical emissions

N-hexane gCO2e/g 3.56 GREET 1.8c [39]+calculated emission from lost hexane

Methanol gCO2e/g 0.61 GREET 1.8c [37]

Sodium hydroxide gCO2e/g 2.84 [40]

Sodium methoxide gCO2e/g 2.43 [40]

Hydrochloric acid gCO2e/g 2.70 [40]

2.4. Land use change 27 years old. For KABAM we used the energy and material usage rates from the USB study because it provides the most recent To include the emissions from land use change (LUC) in KABAM and comprehensive data available. we treated LUC as a life cycle emissions factor. The EPA has con- ducted a series of LCAs on biofuels as part of the RFS2 program 2.7. Biodiesel conversion and has spent considerable effort in modeling the emissions gener- ated as a result of international land use change (LUC) [44]. The After extraction the oil is converted to biodiesel in a biodiesel assumptions and spreadsheet models are well described and avail- processing , which can be assumed to be co-located with the able to the public [5]. The EPA LUC emissions for canola and soy- extraction facility. The most common conversion process uses bean biodiesel were added to the final emissions calculated in methanol and sodium hydroxide. Methanol is not a renewable KABAM respectively. In the camelina scenarios we assumed that product and therefore when biodiesel is combusted 3% of the car- camelina biodiesel does not result in LUC except in the Double bon emitted is non-renewable. This 3% assumes that the biodiesel Cropped System (DCS) where there is partial LUC because of the re- has an average carbon composition of soybean FAME and equally duced yields of soybeans. splits the methanol carbon between the FAME and glycerol. Con- cerning the entire conversion process, the National Biodiesel Board 2.5. Life cycle inventory of camelina (NBB) conducted a survey of the energy and material consumption of 230 biodiesel across the US [62]. This data was released in The life cycle inventory of camelina is based on camelina’s agro- 2009 for the specific purpose of aiding researchers conducting LCAs nomic practices and data from specific field sites at Carrington of biodiesel. The transportation estimates from the field to the North Dakota, Prosper North Dakota, and Morris Minnesota as well extraction and conversion facilities and then to market were taken as surveying existing literature. The inventory was then used to from GREET 1.8c and adapted in KABAM. 2.8 Co-product Allocation. construct six camelina scenarios summarized in Table 3 along with Seed meal is a significant co-product in biodiesel production the key references used in each scenario. The data used in the KA- and is used as an animal feed. Camelina meal is very similar to soy- BAM is shown in Table 4. A detailed discussion of the data and bean meal in quality and protein content and has already shown assumptions used to arrive at each value is available in the in the value as an animal feed, especially for poultry [63–65]. Thus, the supplementary material. two are treated the same in KABAM. We obtained the energy of soybean meal and the energy of glycerin from the Hou et al. [66]. 2.6. Life cycle inventory of extraction We utilized Hass 2006’s estimates of the market value of glycerin and biodiesel and Ash and Dohlman 2006’s estimates for the value Once harvested the oilseeds are transported to an extraction of soy meal [67]. All prices are reported in 2005 dollars and are facility where the seeds are processed and the oil extracted using listed in Table 5 along with the energy content. To allocate energy a petroleum solvent, typically hexane. The life cycle inventory for and emissions to biodiesel the ratio of biodiesel to total output is the extraction stage was taken from the National Oilseed Proces- multiplied by the total energy or emissions of the system (i.e. the sors Association’s recent survey of 50 soybean extraction plants total energy/emissions are allocated among all of the outputs in for an LCA study of soy products conducted for the United Soybean proportion to the energy content or value of each output). In the Board (USB) [61]. The GREET model does provide its own life cycle displacement method the life cycle energy/emissions from the dis- inventory of oilseed extraction facilities but bases its assumptions placed co-products are subtracted from the system total and the on Sheehan et al. 1998 and Sheehan et al.’s data is now more than remaining net energy/emissions are assigned to the biodiesel [32]. B.J. Krohn, M. Fripp / Applied Energy 92 (2012) 92–98 95

Table 3 The nine scenarios that were considered in the KABAM model.

Scenario Abbr. Description References Spring SC The spring camelina scenario represents the current agricultural practices of growing camelina Yield: [45], general: [12,46], chemicals: camelina with sufficient nutrients and water. This scenario assumes high productivity but also high [47,48], lime: [49], direct energy: [50,51] inputs Dryland DC Current data indicates that dryland camelina has lower yields than camelina grown in areas General: [18,19,52,53], PK fertilizer: [10], camelina with higher rainfall; however, because rain is the limiting factor, fertilizer inputs will also be lime wheat: [49], direct energy: [50,51] lower Winter WC Winter camelina can be grown as an individual crop. Do to the increased risk of overwintering, General: [54], fertilizer: [47]. direct energy: camelina yields from WC are generally lower than SC but agricultural inputs are similar [50,51] Short season SSS Short season soybeans show potential to be the second crop in a double cropping system with General: [55], yield: [54], fertilizer: [47], soybeans winter camelina. The agricultural inputs of SSS are similar to SOY but the yields are lower direct energy: [50,51] Double DCS In the double cropping scenario camelina and short season soybeans are grown in a single year. Summation of WC and SSS Cropping The scenario also assumes that all the oil produced from the system is converted into biodiesel System Future FC The future production scenario estimates higher yields from camelina but with similar inputs General: [10] camelina as SC Diesel fuel DF Production emissions calculated using GREET 1.8c. Combustion: [56], production LCA: [39,37] Soybean SOY Soybeans (Glycine max) currently provide 90% of the feedstock for biodiesel in the US General: [55], yield: [57], lime: [49,58] biodiesel Canola CAN Canola (Brassica campestris) is the predominant oilseed crop produced in the EU and is also the General: [60], yield: [57] biodiesel major biodiesel crop [59]

Table 4 The life cycle inventory of the nine scenarios studied in KABAM.

Agriculture SC DC WC SSS DCS FC SOY CAN Seed yield kg/ha 2000 1185 1300 1870 3170 3000 2811 1685 Nitrogen kg/ha 75.0 45.0 75.0 4.8 79.8 75.0 4.8 112.1 Phosphorus kg/ha 0 17.0 0 14.2 14.2 17.0 14.2 25.8 Potassium kg/ha 0 11.0 0 28.6 28.6 11.0 28.6 67.2 Lime kg/ha 0 7.0 0 358.0 358.0 7.0 401.0 7.0 Herbicide kg/ha 1.1 1.1 0 1.4 1.4 1.1 1.4 1.1 Insecticide kg/ha 0 0 0 0.02 0.02 0 0.02 0 Seed kg/ha 8.0 8.0 8.0 76.1 84.1 8.0 76.1 8.0 Gasoline L/ha 8.7 8.7 8.7 11.8 20.5 8.7 11.8 8.7 Diesel L/ha 18.5 18.5 18.5 24.1 42.6 18.5 38.0 40.2 LPG L/ha 2.9 2.9 2.9 6.8 9.7 2.9 6.8 2.9 Natural gas m3/ha 0 0 0 4.1 4.1 0 4.1 0 Electricity kW h/ha 7.3 7.3 7.3 61.9 69.2 7.3 61.9 7.3 N kg N/ha 14.7 8.7 9.6 13.8 23.3 22.1 20.7 12.4 Oil in seed (by wt) 35% 35% 35% 19% 26% 35% 19% 40%

Table 5 1400 The energy, market, and displacement values used in the allocation procedures in KABAM. 1200

Allocation Displacement 1000 800 Energy (MJ/kg) $ 2005/kg Energy (MJ/kg) gCO2e/kg Biodiesel 37.25 1.08 – 600 Soy meal 9.87 0.60 2.54 312 400 Glycerin 18.54 0.33 91.69 6100

Fossil Energy (MJ/GJ) 200

0 FC SC DC 3. Results and discussion WC SSS DCS CAN SOY Diesel Energy Market Displacement 3.1. Life cycle energy of camelina biodiesel Fig. 2. The allocated life cycle fossil energy for eight different biodiesel scenarios The life cycle fossil energy consumed in the production of came- compared to diesel fuel. lina biodiesel is considerably lower than the fossil energy con- sumed in combusting petroleum diesel, as shown in Fig. 2. Fig. 2 shows that the various biodiesel scenarios result in a reduction of fossil fuel energy use, which is comparable to the findings pre- fossil energy consumption of 50–80%, with the energy allocation sented by Huo et al. 2008 using the GREET 1.8c model and the dis- method assigning the most emissions to biodiesel and the displace- placement allocation method. As expected, the low yielding and ment method the least. Fig. 2 also shows that the choice of alloca- high input winter camelina has the highest energy consumption tion method can change life cycle energy by approximately 5%. but surprisingly there is only a small improvement in the future Camelina demonstrates higher fossil energy use than soybeans camelina (FC) by increasing camelina’s yield to 3000 kg/ha. Also, but less than canola. Soybeans demonstrate 70–80% reduction in as expected the Double Cropped System (DCS) has one of highest 96 B.J. Krohn, M. Fripp / Applied Energy 92 (2012) 92–98 energy profiles because it is a combination of the lower yielding 1600 winter camelina and short season soybeans. Field CO2 (Urea) 1400 Field CO2 (lime) Field N2O emission 1200 3.2. Life cycle emissions from camelina biodiesel Electricity (kWh/ha) 1000 Natural gas The life cycle emissions of biodiesel follow a similar pattern as LPG e/ha the life cycle energy findings, as shown in Fig. 3. Without consider- 2 800 Diesel ing land-use change the camelina scenarios emit more GHG than Gasoline

kgCO 600 soybeans but less than canola and considerably less than petro- Seed Insecticide leum diesel. As exhibited in Fig. 3, the camelina biodiesel scenarios 400 Herbicide reduce GHG emissions by 37–73% when compared to diesel fuel 200 Lime and soybean biodiesel reduces emissions by 63–85% (depending Potassium on the allocation method chosen). Spring camelina (SC) has reduc- 0 Phosphorus tions of 57–73%, which is slightly greater than the future camelina Nitrogen FC SC DC WC SSS SOY (FC) scenario with 55–71% reductions. The SC scenario most likely DCS CAN has greater reductions than FC because even though the yield of FC Fig. 4. The emissions contribution for each input in the agricultural phase. is substantially higher the estimated fertilizer inputs are higher as well. Also, the variability in results is due to the choice in allocation method is slightly higher for the life cycle emissions than the life 3.5. Sensitivity coefficients and input impact cycle energy, varying from the mean by approximately 8%, which is most likely due to the additional variables of field emissions that In Table 6, we report the five inputs with the highest sensitivity are not included in the energy analysis. and the highest impact on KABAM’s estimated GHG emissions. We differentiate between high sensitivity and high impact because a lower sensitivity input may have a large impact on the model re- 3.3. Life cycle emissions in the agricultural phase sults due to large variability in the possible input values (variabil- ity is the minimum to maximum values reported in the literature). Fig. 4 shows the contribution to total emissions of each input For example, yield has a low sensitivity coefficient meaning that a during the agricultural phase of biodiesel production. Most evident marginal change in yield will result in a small change in the mod- is the large contribution from field emissions, specifically N O. This 2 el’s results. However, yield can reasonably vary between 1000 kg/ highlights the importance of examining the multiple environmen- ha and 3000 kg/ha and as a result cause large changes in the mod- tal metrics such as energy and emissions because the environmen- el’s results (in this case by 77%). The reverse is also true that the tal impact of nitrogen after it is added to the field is ignored when highly sensitive inputs may not vary greatly and thus will only only life cycle energy is studied as in the case with Pradhan et al. have a small effect on the final model results, e.g. herbicide appli- and Sheehan et al. The Double Cropped (DC) scenario is particularly cation rate will not vary more than 1–2 kg/ha. The detailed results affected by field emissions because it includes the high N O emis- 2 from the sensitivity analysis are reported in the supplementary sions from camelina cultivation as well as the high CO emissions 2 material. from the application of lime for soybeans. Notably, three of the top five most sensitive and most influen- tial inputs are related to nitrogen fertilizer. The percent of applied

3.4. GHG emissions including land use change nitrogen fertilizer that is converted into N2O emissions is extre- mely sensitive that even minor changes can greatly affect the re- After evaluating the direct emissions using KABAM, soybean sults. In fact, the input is so sensitive and the uncertainty biodiesel has the lowest fossil energy consumption and GHG emis- reported by the IPCC high enough that this single factor could sions due to the very low input of nitrogen fertilizer. However, the determine the biodiesel is environmentally favorable or not. An- main drawback to soybean biodiesel is the issue of land use other, noteworthy result is that the affect of yield on the output change, which is not addressed by analyzing the direct input emis- is non-linear unlike the other inputs. Instead, as yield increases sions. Fig. 5 indicates that when LUC is factored into the model, the marginal reduction to energy and emissions decreases, as show camelina biodiesel emits fewer GHGs than soybean biodiesel and canola is only marginally more beneficial than diesel fuel. 180 160 140 100 120 90 80 100 /MJ fuel 70 2 80 60

gCO 60 e / MJ

2 50 40 40 gCO 30 20 20 0 10 SOY SC DC WC SSS DCS FC CAN Diesel 0 Production Emissions Indirect Land use change FC SC DC WC SSS DCS CAN SOY

Diesel Fossil Combustion Emissions Renewable Combustion Emissions

Energy Market Displacement Fig. 5. The total production andcombustion emissions for the eight biodiesel scenarios and diesel fuel using the displacement method. The non-renewable combustion Fig. 3. The allocated GHG emissions for eight biodiesel scenarios compared to emissions in biodiesel are due to the use of methanol in the conversion process. diesel fuel. B.J. Krohn, M. Fripp / Applied Energy 92 (2012) 92–98 97

Table 6 the GHG emissions from farming is to reduce the application rate The sensitivity analysis results for the top five most sensitive and influential inputs to of N-fertilizer to the field. Therefore, farmers, researchers, and pol- the KABAM model. icy makers may want to explore low N-fertilizer crops such as le- Emissions gumes or low N-fertilizer cropping systems such as mixed % Change in output from low Sensitivity cropping with legumes [8]. Compared to other non-legume crops input to high input coefficient camelina does have lower N-fertilizer requirements but future Inputs with the highest breeding and agronomic studies could focus on further reducing sensitivity coefficients the N-fertilizer requirements. The greatest impact from N-fertil- %N emitted as N O field 169% 1610.56 2 izer, however, comes from the field emissions of N2O and there is emissions still significant uncertainty in the percent N-fertilizer that is emit- Oil content 9%a 37.28 N fertilizer life cycle factor 0.23 2.89 ted as N2O. As discussed in the sensitivity analysis the high end of Herbicide application rate 3% 0.90 N2O emissions estimated by the IPCC is sufficient to negate any N-fertilizer application rate 8% 0.37 GHG reductions generated by biodiesel from offsetting diesel fuel.

Inputs with largest influence Most of the literature expresses confidence that the N2O emissions on outputs are on the lower end of the IPCC estimates but the added uncer- %N emitted as N2O field 169% 1610.56 tainty is further reason to focus on reducing N-fertilizer inputs. emissions N-fertilizer application rate 8% 0.37 Yield 77% 0.04 4. Conclusions N fertilizer life cycle factor 0.23 2.89 Lime rate 20% 0.002 Using KABAM, we modeled three different camelina scenarios a Negative coefficients indicate an inverse relationship, e.g. as yield increases the that represent three potential cropping systems that camelina emissions per MJ of biodiesel decrease. might be grown: spring camelina, dryland camelina, and camelina in a dual cropping system. The dryland and dual cropping system in Fig. 6. This effect explains why the future scenario has limited had the higher energy and emissions per MJ of biodiesel than the benefits over current spring camelina biodiesel despite a dramatic summer camelina due to lower yields but still result in significant increase in yield. The analysis also shows that there is a yield reduction in energy and emissions compared to diesel fuel. On a threshold of 800 kg/ha where camelina biodiesel is no longer an whole, camelina appears to be an environmentally viable option environmentally viable option over diesel fuel. as a biodiesel crop. Camelina biodiesel in all scenarios had lower The results from the KABAM model and the sensitivity analysis life cycle energy and emissions than diesel fuel and when land show that yield and fertilizer application are the two most impor- use change emissions were considered it also had lower life cycle tant inputs for the future development of camelina biodiesel. Yield energy and emissions than the traditional biodiesel crops soybeans is critically important in the environmental impact of camelina and canola. Finally, a sensitivity analysis was conducted that con- biodiesel. Fig. 6 shows that when yield falls below 800 kg/ha came- cluded that to maintain and increase the environmental viability of lina biodiesel emits more GHGs than diesel fuel. Also, yield has a camelina and other niche filling biofuel crops researchers and pol- non-linear relationship with GHG emissions, which means dramat- icy makers should focus their efforts on achieving satisfactory ically increasing the yield does not dramatically reduce GHG emis- yields while reducing nitrogen fertilizer inputs. sions. Thus, from an environmental standpoint, it would be better to produce 2000 kg/ha with low agricultural inputs than produce Acknowledgements 3000 kg/ha with high agricultural inputs (of course high yields with low inputs would be ideal). Policy makers and farmers will The authors would like to thank Dr. Burton Johnson, Dr. Russel need to closely watch the yields and fertilizer rates of camelina Gesch, and the researchers at the Carrington Extension Center for or any other biofuel crop to ensure the lowest environmental providing me with their expert opinion on camelina and access impact. to their data and years of work. We would also like to acknowledge Furthermore, from the KABAM model we can conclude that NextEra Energy Resources, the Keble Association and the Environ- nitrogen fertilizer may be the most important input when consid- mental Change Institute for their financial support. ering emissions. Thus, one of the most effective ways of reducing References 140 [1] EIA, US Energy Information Agency. Annual energy outlook 2010: with 120 projections to 2035. DOE/EIA-0383; 2010. p. 56. [2] Searchinger T, Heimlich R, Houghton R, Dong F, Elobeid A, Fabiosa J, et al. Use 100 of US croplands for biofuels increases greenhouse gases through emissions from land-use change. Science 2008;319:1238. 80 [3] Fargione J, Hill J, Tilman D, Polasky S, Hawthorne P. Land clearing and the biofuel carbon debt. Science 2008;319:1235–8. 60 [4] Kim H, Kim S, Dale BE. Biofuels, land use change, and greenhouse gas /MJ biodiesel

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