Environmental Implications of Jatropha Biofuel from a Silvi-Pastoral

Article pubs.acs.org/est

Environmental Implications of Jatropha Biofuel from a Silvi-Pastoral Production System in Central-West Brazil Rob Bailis* and Goksin Kavlak Yale School of Forestry and Environmental Studies, 195 Prospect Street, New Haven, Connecticut 06517, United States S Supporting Information *

ABSTRACT: We present a life cycle assessment of synthetic paraffinic kerosene produced from Jatropha curcas. The feedstock is grown in an intercropping arrangement with pasture grasses so that Jatropha is coproduced with cattle. Additional innovations are introduced including hybrid seeds, detoxification of jatropha seedcake, and cogeneration. Two fuel pathways are examined including a newly developed catalytic decarboxylation process. Sensitivities are examined including higher planting density at the expense of cattle production as well as 50% lower yields. Intercropping with pasture and detoxifying seedcake yield coproducts that are expected to relieve pressure on Brazil’s forests and indirectly reduce environmental impacts of biofuel production. Other innovations also reduce impacts. Results of the baseline assessment indicate that innovations would reduce impacts relative to the fossil fuel reference scenario in most categories including 62−75% reduction in greenhouse gas emissions, 64−82% reduction in release of ozone depleting chemicals, 33−52% reduction in smog-forming pollutants, 6−25% reduction in acidification, and 60−72% reduction in use of nonrenewable energy. System expansion, which explicitly accounts for avoided deforestation, results in larger improvements. Results are robust across allocation methodologies, improve with higher planting density, and persist if yield is reduced by half.

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house gas (GHG) emissions.12 However, it is among the fastest growing segments of the transport sector, particularly in developing countries. Various measures to cut aviation emissions have been introduced including biofuels. The most common pathway used to produce jet fuel with biomass is through hydro-processed esters and fatty acids (HEFA), which yield a synthetic paraffinic kerosene (SPK) that closely resembles conventional jet fuel (CJF).11 Test flights were conducted and several airlines have carried out commercial flights using blends of HEFA-based SPK.13,14 Several HEFA pathways are being explored including “catalytic-treating” (HEFA-CHT) and “catalytic decarboxylation” (HEFACDC).15,16 The end products are very similar, but the processes and coproducts are quite different. As we discuss in more detail below, HEFA-CHT requires more hydrogen and more raw materials than HEFA-CDC and also produces more coproducts. As a result, the life cycle impacts of the two pathways are different, but the magnitude and, in some cases, direction of the difference is sensitive to allocation methodologies. Several life cycle assessments (LCAs) have been conducted of SPK produced via the HEFA-CHT pathway including SPK derived from jatropha.17−19 However, no assessments have yet been conducted of the HEFA-CDC pathway, although a few

INTRODUCTION Questions about environmental sustainability of biofuels have been raised repeatedly by academics, civil society groups, and governments.1−3 Food security and land use change (LUC) are topics of particular concern.4,5 To address these concerns, policies have been developed that favor cultivation on marginal land.6 Jatropha curcas (hereafter jatropha) seemed to be an ideal crop for this application.7 However, early experiences with jatropha showed that, although it can survive in marginal conditions, it is not likely to be commercially viable unless cultivated on more favorable land.8 Independent of debates over biofuels, agricultural intensification, particularly cattle production in the tropics, has been identified as a way to reduce negative LUC.9,10 This study examines the environmental impacts of a biofuel production system currently being implemented in the Central-Western Brazilian state of Mato Grosso do Sul, in which jatropha is intercropped with cattle pasture. The project has also introduced a number of other innovations including hybrid seeds, detoxification of jatropha seedcake (JSC), and cogeneration and is exploring an alternative refining process. Collectively, these innovations significantly lower the environmental impacts associated with biofuel production relative to the reference scenario of fossilbased jet fuel. Biofuels and Aviation. Biofuels are used primarily in ground transport; however, there is substantial interest in developing biofuels for aviation.11 The aviation sector is currently responsible for approximately 2% of global green© XXXX American Chemical Society

Received: October 9, 2012 Revised: May 10, 2013 Accepted: May 28, 2013

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dx.doi.org/10.1021/es303954g | Environ. Sci. Technol. XXXX, XXX, XXX−XXX

Environmental Science & Technology

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studies have examined its viability.15,20 Additionally, most jatropha LCAs are based on generic crop production, rather than site-specific data, and they do not consider emerging innovations.21−23 In this study, we develop a life cycle inventory and impact assessment that includes novel processes at each stage of production. Innovations in Biofuel Production. A number of innovations are introduced in this production system (see the Supporting Information for a schematic diagram of the full process). In addition to intercropping, hybrid seeds are utilized. Hybrid plants are developed to intentionally bring desirable traits into crops such as higher yields or uniform plant morphology. Several research groups have developed jatropha hybrids with different characteristics than open-pollinated varieties. This assessment examines feedstock and fuel produced through a partnership between Bio Ventures Brasil (BVB), a bioenergy company, SG Biofuels (a hybrid seed producer), and Rio Pardo Bioenergia (RPB), which is one of several large-scale field tests of new hybrid varieties.24 A third innovation involves the detoxification of seedcake coproduced with jatropha oil. The process, which has attracted investment in a 300 ton per day plant that is expected to begin operations in the first quarter of 2013, uses locally produced bioethanol as a solvent rather than hexane. The extraction facility utilizes the outer husk and inner shell of the jatropha fruit as fuel to supply heat and power. The electricity produced through cogeneration exceeds what is needed to run the facility so the surplus is exported to the grid. Last, the HEFA-CDC pathway was examined alongside HEFA-CHT. The processes differ in that HEFA-CHT requires more hydrogen than HEFA-CDC. The additional hydrogen enables a slightly higher output of hydrocarbon fuels per unit vegetable oil input but also requires more energy inputs and results in higher GHG emissions per unit output.

Figure 1. Map showing position of Jatropha-Cattle field trials.

Both cropping systems are examined with different yields and fuel production pathways; each scenario is described in Table 1. On-site trials in Mato Grosso do Sul began in late 2011 so that the plantation’s yield at maturity is not yet certain. However, based on a linear extrapolation of actual yields from test plots with similar agro-ecological conditions over two years, annual yields are expected to reach 2.4 kg dry seed per tree when the trees reach maturity (see the Supporting Information for details). This a considerable improvement over openpollinated varieties.28,29 Other analyses show that a linear projection of yield from the first two years of production provides a reasonable estimate of actual yields by the fifth year, at which time growth plateaus and the plantations reach maturity.30 This is the first attempt to plant hybrid jatropha in a commercial plantation, and there is some uncertainty about performance. To accommodate this uncertainty, we assess the effect of yields that are 50% lower than expected. The analysis also accounts for land use change. On the basis of prior studies, which included direct weighing of destructively sampled trees in Brazil, jatropha trees grown on degraded pasture with 8 × 1 m spacing add approximately 10 tons of carbon per ha to the landscape relative to degraded pasture without Jatropha [see refs 17 and 31 and the Supporting Information]. Under 4 × 1 m spacing, Jatropha adds nearly 20 tC/ha. Changes in soil carbon are not accounted for in the analysis (see the Supporting Information for additional discussion). The goal of this LCA is to analyze the environmental impacts of the innovations introduced above against a reference scenario of CJF. CJF is assessed using an existing life cycle inventory (LCI) 32 and combustion emissions data.33 We define the functional unit (FU) as 1 GJ of fuel. To assess environmental impacts, LCIs were developed in SimaPro34 using primary data obtained by surveying the feedstock producer and processor (RPB) as well as fuel refiners.35,36 Some materials and processes lacked Brazil-specific data and generic data were used.32 However, in those cases, inputs were modified by altering transport distances and the electricity mix to reflect Brazilian conditions. Impact assessment was conducted with categories defined by the Swedish Environmental Management Council (SEMC), including GHG emissions, ozone-depleting gases, acidifying compounds, photo-

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MATERIALS AND METHODS Site Description and Study Design. This analysis is based on data collected from BVB and RPB. RPB was one of several large Brazilian firms that invested in jatropha between 2006 and 2008. Their experiences were similar to many early investors; inappropriate planting material and uncertain market conditions contributed to the under-performance of the crop.25 They ceased production on much of the original planted area but, in late 2011, replanted a test plot with hybrid seeds and introduced the other innovations described above. RPB is located in Mato Grosso do Sul, roughly 1000 km northwest of São Paulo and 1000 km southeast of Brasilia (Figure 1). Average precipitation is 1500 mm/y, falling mainly between October and March.26 Ranching is a major economic activity in the state.27 Much of RPB’s property is degraded but is still used to graze cattle. A portion has been rehabilitated and intercropped with jatropha planted in 8 × 1 m spacing. Exotic pasture grass (Brachiaria spp) is planted in the space between trees. In this arrangement, inputs benefit both trees and pasture. Monoculture production is a common approach to jatropha cultivation. We compare the intercropping system described above to a monoculture systems planted with a density of 4 × 1 m. This spacing supports mechanized harvesting, although the analysis does not include mechanization because suitable machines have not been developed. This system produces twice as much jatropha but yields no cattle. It requires additional inputs, though not in direct proportion to the number of trees per hectare (see the Supporting Information). B



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Table 1. Scenarios Examined in This Analysis scenario

cropping system

spacing

yield of dry seeds (kg/tree)

HEFA method

1a

intercropping

8×1

2.4

CHT

1b 1c 1d 2a

intercropping intercropping intercropping monoculture

8 8 8 4

× × × ×

1 1 1 1

2.4 1.2 1.2 2.4

CDC CHT CDC CHT

2b 2c 2d

monoculture monoculture monoculture

4×1 4×1 4×1

2.4 1.2 1.2

CDC CHT CDC

comment baseline intercropping scenario with yields set to 2.4 kg dry seed per tree (the expected level for hybrid seeds utilized at the test farm); CJO is refined via HEFA-CHT processing tests a variant of scenario 1a with HEFA-CDC refining tests a variant of scenario 1a with jatropha yields reduced by half tests a variant of scenario 1c with HEFA-CDC refining baseline monoculture scenario with yields equal to the expected level for hybrid seeds utilized at the test farm; CJO is refined via HEFA-CHT processing tests a variant of scenario 2a with HEFA-CDC refining tests a variant of scenario 2a with jatropha yields reduced by half tests a variant of scenario 2c with HEFA-CDC refining

that one-quarter of cattle production in the LAR was produced on land deforested between 1986 and 2005, when deforestation rates averaged 1.9 million ha per year and released ∼572 t CO2e per ha. This represented about 6% of total national cattle production. Accounting for increasing stocking levels over a 20y period, the authors average GHG emissions from the LAR across all Brazilian cattle and estimate nationwide cattle emissions are ∼44 kg CO2e per kg CW. We use this to estimate emissions avoided by coproducing cattle with jatropha. Oil Extraction and Seedcake Detoxification with Cogeneration. This stage yields crude jatropha oil (CJO), detoxified seedcake, and electricity. Most varieties of jatropha have a high concentration of toxic phorbol esters.40 Toxins are prevalent in all parts of the plant, rendering the oil and seedcake unfit for human or animal consumption.40 However, several processes have been developed to break down the toxic compounds, including treatment with ethanol, methanol, enzymes, and/or heat.40,41 One analysis found that the most promising process involves enzymatic hydrolysis followed by an ethanol wash under moderate heat.41 Industrial vegetable oil extraction is typically accomplished by using hexane, derived from petroleum refining. The process examined in this analysis uses ethanol produced from Brazilian sugar cane in place of hexane. There are several benefits that arise as a result of this substitution. In addition to higher embodied energy and carbon than ethanol, hexane is a neurotoxin and is considered a hazardous air pollutant by the USEPA.42 Trials have shown that the seedcake detoxified in this manner can be safely used as feed for both fish and mammals.40,43 Under mass, energy, or economic allocation, the seedcake is simply allocated impacts from plantation and extraction based on the allocation factor, which varies from 20 to 41% of the total impacts from the extraction stage. Under system expansion, we assume JSC displaces Brazilian soymeal. Soy production in Brazil has grown by a factor of 3 since 199044 and is implicated as a major driver of deforestation in the Amazon.9,38,45 Thus, like cattle, displacing Brazilian soymeal carries potentially large benefits in the form of avoided deforestation. We estimate these benefits by assuming that JSC displaces a protein-equivalent quantity of soymeal. JSC contains 60% protein while soymeal contains 40%,28 making a displacement ratio of 1.3:1. Impacts potentially avoided by the displacement were calculated using existing LCI data for Brazilian conditions, which estimate the fraction of recent soy cultivation that occurred on newly deforested land and attributing the resulting emissions to the soymeal that will be displaced [see ref 32 and the Supporting Information for a more detailed discussion].

chemical ozone creation, release of eutrophying compounds, and nonrenewable energy consumption.37 The project time frame is 20 years, and the assessment of each scenario is based on total impacts divided by the total output of functional units in that time period. Coproducts form a significant part of the output stream for SPK. The SPK life cycle has distinct phases of production, which each provide coproducts described briefly below. Allocation of impacts is an essential component of this LCA. We compare results of different allocation methods assigning impacts by economic value, energy, as well as mass (all allocation factors are given in the Supporting Information). We also incorporate coproducts into the assessment through “system expansion”, which explicitly accounts for the reduction in impacts that occur when coproducts displace other products. Jatropha Cultivation Intercropped with Pasture. In the cultivation stage, Jatropha fruit are produced with (scenarios 1a−d) or without (scenarios 2a−d) cattle. In Brazil, over half of the country’s 152 million ha of pasture is held in parcels of 500 ha or more, much of which is considered degraded.27 Cattle production in Brazil is highly extensive with little or no inputs utilized. Stocking levels average just one animal unit (450 kg liveweight) per hectare nationwide.27 Together with soy production (discussed below), Brazil’s cattle industry is closely associated with deforestation in the Amazon.9,38 The project analyzed in this study intensifies land use by integrating cattle and biofuel production. Agricultural inputs are utilized by both pasture grass and jatropha. As a result, in this project, cattle stocks are 2 animal units per ha, which is double the national average. Cattle intensification can reduce deforestation pressure, potentially avoiding future deforestation because cattle production is the most common use of cleared forestland. Currently, one-fourth of Brazil’s beef production comes from the “Legal Amazon” region [(LAR) see ref 39 for an explanation]. Under mass, energy, or economic allocation, life-cycle impacts are allocated based on the proportional factors between jatropha fruit and cattle. These methods allocate 4−36% of the impacts associated with Jatropha fruit production to cattle, but they do not account for the displacement of cattle produced in other areas of Brazil and the potential to avoid deforestation by reducing production in the LAR. Under a system expansion methodology, avoided deforestation is explicitly included in the assessment. To quantify this, we estimate the contribution of cattle to deforestation in Brazil using Cederberg and colleagues’ analysis.39 In 2006, Brazil’s national cattle production was ∼8.6 million tons carcass weight (CW), 26% of which originated from the LAR. Cederberg and colleagues estimate C



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Figure 2. Impacts of jatropha fruit production with and without intercropping. Impact assessment methodology is EPD V1.03.37 Impact categories are GHG greenhouse gases (defined in kg CO2 equivalent units using 100-y global warming potentials); ODP ozone depletion potential (defined in kg CFC-11 equivalent units); PCO photochemical oxidation (defined in kg C2H4 equivalent units); ACID acidification potential (defined in kg SO2 equivalent units); EUT eutrophication potential (defined in PO43− equivalent units); and NRE nonrenewable energy consumption (defined in MJ).

scenario than with 4 × 1 monoculture production. Other impact categories follow similar patterns across allocation methodologies, with the exception of system expansion. Figure 2 compares the impacts of seed production under 4 × 1 monoculture (solid bars), 8 × 1 spacing without intercropping (white bars), and 8 × 1 m spacing with intercropping (shaded bars). Hybrid Seeds. One explanation given for the lack of success in early jatropha projects was their reliance on open-pollinated plant varieties,25 which produced offspring with variable and unpredictable characteristics. The breeding of hybrid species can avoid this uncertainty. Improvements rely on heterosis,46 a process by which the offspring of diverse inbred varieties exhibit more vigor (greater biomass, faster development, and greater seed production) than either of the parental lines.47 This is one factor that enabled yields of staple grains like maize to increase dramatically over the course of the 20th century.48 Recent studies note that yields in commercial jatropha projects have been well below expectations.8,49 Hybrid seeds are expected to provide higher, more uniform yields. Early evidence from this project indicates that yields may indeed meet expectations (Supporting Information). However, actual results will only be available when the trees reach maturity. If we assume yields would be half the expected value of 2.4 kg dry

Oil Refining via Two Pathways. This stage yields SPK with other biobased hydrocarbons. HEFA-CHT processing yields biobased naphtha, diesel, and a mix of lighter hydrocarbons. HEFA-CDC yields biobased petrol and glycerol. Each coproduct can be used as fuel or as an input in other industrial processes.17,36

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RESULTS In this section, we discuss the influence of each innovation in reducing the overall impacts of SPK production in our case study. We present the results of each scenario and allocation method. Then we examine the aggregate results of all innovations across each scenario. Impacts of Innovations. Intercropping. First we compare the results of intercropping on seed production. Impacts from intercropping vary with allocation methodology. For example, GHG emissions from intercropped jatropha production with 8 × 1 spacing would be 4−36% lower than without intercropping. However, if we double the planting density, this would add carbon to the landscape and increase output, which together lower GHG emissions to near zero. Indeed, intercropping would have larger impacts in all categories under most allocation methodologies. Only system expansion indicates that GHG emissions would be lower in the intercropping D



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Figure 3. Net impacts of 1 GJ J-SPK assessed with economic, energy, mass-based allocation methods as well as no allocation assuming 8 × 1 spacing with intercropping and expected annual yields of 2.4 kg dry seed per tree (categories are defined in Figure 2; percentages show changes relative to the CJF reference scenario for each impact category). Results of system expansion are shown in the Supporting Information.

seed per tree in the absence of hybrid seeds, then we find the use of hybrid seeds would reduce GHG emissions by 15−38% depending on allocation methods and by even larger margins for other impact categories. This is discussed in more detail below as well as in the Supporting Information. Oil Extraction and Seedcake Detoxification. Seedcake detoxification involves two innovations: ethanol used in place of hexane and use of JSC for livestock feed. Ethanol substitution reduces transportation distances and lowers some environmental impacts. For example, LCI data from EcoInvent 32 indicates that hexane requires more nonrenewable energy than ethanol and emits over 50% more GHGs (Supporting Information). However, ethanol is associated with higher photochemical oxidation and eutrophication. Thus, the shift from hexane to ethanol introduces trade-offs, although these impacts are small in comparison to changes associated with the other innovations examined in this assessment. Previous studies of jatropha biofuel assume JSC will be used as either fertilizer or fuel;17 others consider anaerobic digestion, which yields products suitable for both applications.21,29 In this system, JSC is detoxified and used as supplemental feed in place of soymeal. As fertilizer, JSC would displace a nutrientequivalent quantity of commercial fertilizer. JSC is relatively low in nitrogen, phosphor, and potassium so 1 kg can only substitute a few dozen grams of fertilizers. If JSC is used as a fuel, it could displace an energetically equivalent quantity of a common industrial fuel like heavy fuel oil (HFO). LCA of each displacement scenario shows that the displacement of soymeal by JSC would reduce impacts more than displacement of fuel or fertilizer in most impact categories (see the Supporting Information for additional details).

Cogeneration. Dried Jatropha fruits consist of 56% husks and shells by mass, which contain 44% of the fruit’s calorific value. In this study, husks and shells are burned to generate steam, which provides both heat and power to the extraction facility. The extraction facility processes 13.8 tons of dried fruits per hour, producing 3.6 tons of CJO, 7.7 tons of husks and shells, and 2.5 tons of JSC. Husks and shells have a calorific value comparable to wood. Converting them to electricity at 18% efficiency, which is typical for small-scale solid fuel cogeneration,50 each ton of fruit processed yields 526 kWh of electricity. The facility’s internal electrical demand is 62 kWh per ton of dried fruit, which leaves 464 kWh for export to the grid (or 83 kWh per FU of SPK produced). This electricity may be accounted for in the LCA by energy or economic allocation, or captured via system expansion that accounts for displacement of an equivalent amount of electricity from the grid. For the latter, we follow the USEPA’s assessment of Brazilian biofuels by assuming that output would displace a marginal unit of production from the national grid [see ref 51 and the Supporting Information for more detail]. Under energy and economic allocation, coproduction of electricity reduces impacts of the extraction phase by 9−11%. With system expansion, the electricity displaced by cogeneration reduces emissions from the grid by ∼44 kg CO2 eq, which is larger than the GHG emissions caused by the extraction process itself. Fuel Processing. HEFA-CHT production relies on deoxygenation of fatty acids, followed by selective catalytic cracking and partial isomerization to yield paraffinic products in the range of jet fuel with similar chemical characteristics and a slightly higher calorific value.11,52 The process also yields coproducts including diesel, naphtha and lighter hydrocarbons E



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Table 2. Differences in Impacts between 8 × 1 Intercropping and 4 × 1 Monoculturea allocation methodology economic impact category

b

GHG ODP PCO ACID EUT NRE

energy

mass

no allocation

system expansion

CHT

CDC

CHT

CDC

CHT

CDC

CHT

CDC

CHT

CDC

−24% 8% 6% 8% 12% 5%

−34% 5% 6% 9% 12% 7%

−33% −19% −19% −14% −16% −13%

−45% −14% −20% −16% −16% −17%

−30% −15% −17% −13% −14% −11%

−42% −12% −18% −14% −14% −15%

−41% −23% −22% −17% −19% −17%

−51% −18% −23% −18% −19% −21%

82% −12% −8% −161% −19% −22%

78% −38% −7% −192% −14% −51%

Negative entries (shaded) indicate the 4 × 1 monoculture system performs better than the 8 × 1 intercropping system. bImpact categories are defined in Figure 2.

a

Table 3. Relative Increase in Each Category of Impacts Resulting if Yield Is 50% Lower than Expected with Inputs Held Constant in the 8 × 1 Intercropping Scenario econ

a

energy

mass

no alloc

syst exp

impacta

CHT

CDC

CHT

CDC

CHT

CDC

CHT

CDC

CHT

CDC

GHG ODP PCO ACID EUT NRE

15% 30% 27% 22% 31% 19%

21% 21% 28% 25% 32% 27%

35% 63% 59% 51% 65% 43%

48% 46% 60% 56% 66% 57%

31% 59% 54% 45% 59% 37%

42% 40% 54% 51% 61% 50%

47% 75% 68% 59% 73% 57%

59% 59% 69% 63% 74% 70%

9% 37% 23% 554% 75% 71%

9% 122% 21% 659% 56% 168%

Impact categories are defined in Figure 2.

[described in ref 17]. The deoxygenation phase requires hydrogen, which we assume would be obtained via steam methane reformation (SMR). SMR is both energy and carbon intensive. HEFA-CDC has been proposed as an alternative to HEFA-CHT. HEFA-CDC starts by converting crude vegetable oil, consisting primarily of triglycerides, into free fatty acids (FFA) in a process that is similar to biodiesel production, yielding glycerin as a coproduct. In the next step, the HEFACDC process converts the FFA into straight-chain alkanes by removing the carboxyl group and releasing carbon dioxide,15 yielding jet fuel and high-octane biogasoline. Schematic diagrams of both HEFA-CHT and -CDC pathways are shown in the Supporting Information along with mass, energy, and market-based allocation factors for coproducts of both processes. Aggregate Results. In the baseline scenarios (1a and b) nearly all of the environmental impacts are reduced when CJF is replaced by J-SPK. Figure 3 shows the results for economic, energy, and mass allocation. In each case, impacts from CJF are shown as black bars, the HEFA-CHT pathways are shaded, and -CDC pathways are white. GHG emissions would be reduced by 62−75%, ozone depletion potential (ODP) would be reduced by 64−82%, nonrenewable energy (NRE) utilization is reduced by 60−72%. Ozone depletion potential (ODP) would improve by a similar magnitude. Photochemical oxidation (PCO) and acidification potential (ACID) would also improve, although by smaller margins than other categories. The only category that would not improve when CJF is substituted by JSPK is eutrophication potential (EUT), which would increase by 80−159%, largely from fertilizer applications. If no allocation is carried out and all impacts are attributed to SPK, most categories of environmental impacts would still improve relative to CJF. GHG emissions would decrease 17% in the HEFA-CHT pathway and 51% with HEFA-CDC. ODP

and NRE also decline; however, ACID, PCO, and EUT increase relative to CJF, again as a result of fertilizer use. With system expansion, the potential benefits of avoided deforestation from cattle and soy production are explicit, dramatically reducing impacts in all categories. The reductions are sufficient to completely offset the impact from other stages of production. Thus, with system expansion, SPK production would decrease impacts in absolute terms independent of CJF substitution (not shown in Figure 3; see the Supporting Information). Sensitivities. Monoculture. Under the monoculture scenarios (2a−d), spacing would be decreased to 4 × 1 m. Inputs would increase, but not in direct proportion to planting density (see the Supporting Information). Using energy and mass-based allocation, 4 × 1 monoculture would have lower impacts than 8 × 1 intercropping in all categories. The same is true if no allocation is utilized. Monoculture production appears more favorable under these methodologies because the system has higher output per unit input. However, if economic allocation is utilized, the intercropping scenario would have a slight advantage in most categories. This occurs because cattle have an economic value that is proportionally larger than their mass or energy content, which shifts impacts towards cattle and away from Jatropha. With system expansion, the 4 × 1 monoculture would also perform better in most categories. GHG emissions are an exception because the monoculture lacks the benefits of avoided deforestation from cattle. Table 2 shows differences between 8 × 1 intercropping and 4 × 1 monoculture for all impact categories and assessment methodologies using both HEFA-CDC and HEFA-CHT pathways. Lower Yields. To assess the implications of low yield, we repeated the LCA with yields cut by half, but inputs unchanged (both c and d scenarios). Results for scenario 1c and d are shown in Table 3, which shows increases in potential impacts resulting from the yield reduction relative to scenarios 1a and b. F



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intensification, the main drivers of our results, are poorly characterized in current models.53 Thus, additional analyses are required to estimate the degree to which cattle intensification and increased supply of animal feed derived from detoxified JSC reduces pressure on the LAR. However, independent of that discussion, this assessment demonstrates that both HEFA-CHT and CDC-fuel pathways reduce GHG emissions along with most other categories of environmental impacts in both intercropping and monoculture plantations without relying on large benefits derived by displacing Brazilian cattle and soymeal. We also demonstrate that one impact category, eutrophication potential, is expected to increase relative to CJF in all scenarios. Nutrient runoff should be monitored closely, with steps taken to reduce or eliminate it, particularly if the locality is subject to large amounts of runoff from other agricultural operations and/or bounded by surface water that is prone to eutrophication. Importantly, results in all impact categories are robust across all allocation methodologies and persist even if yields are reduced to half of their expected value. This level of productivity has been achieved in hybrid Jatropha plantations in their second year (Supporting Information) and is very likely to be exceeded when the plantations reach maturity.

All impacts would worsen with lower yields. However, all indicators with the exception of EUT show improvements relative to CJF (shown in the Supporting Information).

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DISCUSSION Many of the innovations that are introduced in the silvi-pastoral biofuel system would reduce environmental impacts of SPK production. Of course, the magnitude of each improvement depends on the allocation methodology. For example, comparing the impacts of seed production via intercropping with 8 × 1 m spacing to monoculture with 4 × 1 m spacing, energy, and mass-based allocation indicate that impacts are lower under the monoculture system. Economic allocation yields nearly identical impacts, while system expansion shows that intercropping would reduce more GHG emissions, but monoculture leads in other impact categories (see Figure 2 for details). Outcomes are also contingent on alternate uses of the seedcake, husks, and shells. Displacing soymeal with JSC would reduce GHG, ODP, PCO, and EUT more than other possible uses of seedcake like fertilizer and boiler fuel. However, the reductions are only explicit when assessed with system expansion. Economic, energy, and mass-based allocation are insensitive to end-uses outside the system boundary. Considering the alternative fuel pathways, under economic, energy, and mass-based allocation, the HEFA-CDC pathway is associated with lower GHG and NRE impacts but higher ODP impacts. Outcomes are mixed in other impact categories depending on the allocation methodology. However, with system expansion, the HEFA-CHT pathway appears better across all impact categories (see the Supporting Information). This shift in results arises under system expansion because the HEFA-CHT pathway requires more CJO per FU of SPK produced. Larger quantities of CJO result in higher output of cattle and JSC from the plantation, resulting in more displacement of destructive cattle and soy than the HEFACDC pathway. However, the large disparity between system expansion and other methods raises questions about the validity of system expansion. The coproduction of biofuel feedstock and livestock yields coproducts that would, in theory, avoid deforestation by displacing soymeal and cattle. But we should question the degree to which deforestation is actually avoided. There is some evidence in support of this claim. For example, Macedo and colleagues report that the declining rate of deforestation in the Amazon region observed between 2006 and 2010 was due, in part, to intensified production of soy and cattle9 and claim that both forest conservation and increased agricultural output is possible if “there is a sufficient supply of previously cleared land”, provided that policies exist encouraging productive use of that land (p 1344). Indeed, the silvi-pastoral system under consideration is attempting to make “productive use” of “previously cleared land”. However, the relationship between intensification in one location and deforestation in another remains poorly understood. To what extent does an additional unit of cattle or feed produced through intensification in Central-West Brazil reduce cattle or soy-induced deforestation in the LAR? This question must be explored further before placing any confidence in the system expansion results of this assessment. Analysts typically rely on macro-economic models to estimate how crop and/or livestock production in one area responds to changing production in other areas. However, impacts of cattle

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ASSOCIATED CONTENT

S Supporting Information *

Further information, figures, and tables as mentioned in the text. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +1 203 432 5412 Fax: +1 203 436 9158. Notes

The authors declare the following competing financial interest(s): One author (R.B.) received a consulting fee from AliphaJet and Brasil Bioventures to pay for the time required to include AliphaJets refining process in the analysis. Inclusion of the process was not part of the research agreement with Airbus.

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ACKNOWLEDGMENTS This research was supported by a grant from Airbus and funding from AliphaJet. Data collection was assisted by Bio Ventures Brasil, SG Biofuels, and Rio Pardo Bioenergia. We are also grateful for constructive input from three anonymous reviewers. The authors are solely responsible for any errors and omissions.

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REFERENCES

(1) Carbon and Sustainability Reporting Within the Renewable Transport Fuel Obligation, Technical Guidance Part 1, version 2.0; Renewable Fuels Agency: East Sussex, 2009. (2) FOOD, FARMERS AND FUEL: Balancing Global Grain and Energy Policies with Sustainable Land Use; ActionAid International: Johannesburg, South Africa, November, 2008; p 20. (3) Naylor, R. L.; Liska, A. J.; Burke, M. B.; Falcon, W. P.; Gaskell, J. C.; Rozelle, S. D.; Cassman, K. G. The Ripple Effect: Biofuels, Food Security, and The Environment. Environment 2007, 49 (9), 30−43. (4) Fischer, G.; Hizsnyik, E.; Prieler, S.; Shah, M.; Velthuizen, H. v. Biofuels and Food Security; IIASA: Laxenburg, Austria, May 2009; p 223.

G



Article

(26) INMET Gráficos Climatológicos. http://www.inmet.gov.br/ html/clima/graficos/index4.html (accessed May 2013). (27) IBGE. Censo Agropecuário 2006: resultados preliminares; Instituto ́ Brasileiro de Geografia e Estatistica (IBGE): Rio de Janeiro, 2007; p 141. (28) Jongschaap, R. E. E.; Corre, W. J.; Bindraban, P. S.; Brandenburg, W. A. Claims and Facts on Jatropha curcas L.: Global Jatropha curcas Evaluation, Breeding and Propagation Programme; Wageningen, Plant Research International B.V.: Wageningen, The Netherlands, 2007 (29) The Jatropha Handbook; FACT Foundation,: Eindhoven, 2009. (30) Achten, W. M. J.; Verchot, L.; Franken, Y. J.; Mathijs, E.; Singh, V. P.; Aerts, R.; Muys, B. Jatropha bio-diesel production and use. Biomass Bioenergy 2008, 32 (12), 1063−1084. (31) Bailis, R.; McCarthy, H. Carbon impacts of direct land use change in semiarid woodlands converted to biofuel plantations in India and Brazil. GCB Bioenergy 2011, 3 (6), 449−460. (32) Ecoinvent data v2.2; Ecoinvent: Zurich, 2010. (33) Skone, T. J.; Gerdes, K. Development of Baseline Data and Analysis of Life Cycle Greenhouse Gas Emissions of Petroleum-Based Fuels; National Energy Technology Laboratory: Morgantown, WV, Nov 26, 2008. (34) SimaPro 7; PRé Consultants: Amersfoort, The Netherlands, 2011. (35) AliphaJet. Personal communication, 2012. (36) Kalnes, T. Personal communication, 2009. (37) SEMCo Introduction, Intended Uses, and Key Programme Elements for Environmental Product Declarations. http://www.msr. se/en/EPD/ (accessed June 2012). (38) Barona, E.; et al. The role of pasture and soybean in deforestation of the Brazilian Amazon. Environ. Res. Lett. 2010, 5 (2), 024002. (39) Cederberg, C.; Persson, U. M.; Neovius, K.; Molander, S.; Clift, R. Including Carbon Emissions from Deforestation in the Carbon Footprint of Brazilian Beef. Environ. Sci. Technol. 2011, 45 (5), 1773− 1779. (40) Goel, G.; Makkar, H. P. S.; Francis, G.; Becker, K. Phorbol Esters: Structure, Biological Activity, and Toxicity in Animals. Int. J. Toxicol. 2007, 26 (4), 279−288. (41) Xiao, J.; Zhang, H.; Niu, L.; Wang, X.; Lu, X. Evaluation of Detoxification Methods on Toxic and Antinutritional Composition and Nutritional Quality of Proteins in Jatropha curcas Meal. J. Agric. Food Chem. 2011, 59 (8), 4040−4044. (42) USEPA. The Clean Air Act Amendments of 1990 List of Hazardous Air Pollutants. http://www.epa.gov/ttn/atw/orig189.html (accessed June 2012). (43) Berenchtein, B.; Abdalla, A. L.; Morsy, A. S.; Filho, A. L. A.; Castilho, L. A.; Schiavinatto, P. B. G.; Santos, P. P. d.; Peçanha, M. R. S. R.; Gomes, J. D. F.; Silva, J.; Shen, C. G.; Lucas, R. C.; Arieta, N. F. In Use of biodiesel co-product from Jatopha curcas as ingredient for animal feed; Athanasiadou, S., Ed.; British Society of Animal Science: Belfast, 2010; p 286. (44) FAOSTAT Agricultural Production Data. http://faostat.fao.org/ site/339/default.aspx (accessed Oct 2011). (45) Nepstad, D. C.; Stickler, C. M.; Almeida, O. T. Globalization of the Amazon Soy and Beef Industries: Opportunities for Conservation. Conserv. Biol. 2006, 20 (6), 1595−1603. (46) Mayo, O. The theory of plant breeding; Clarendon press: Gloucestershire, U.K., 1987. (47) Birchler, J. A.; Auger, D. L.; Riddle, N. C. In search of the molecular basis of heterosis. The Plant Cell Online 2003, 15 (10), 2236−2239. (48) Evenson, R. E.; Gollin, D. Assessing the Impact of the Green Revolution, 1960 to 2000. Science 2003, 300 (5620), 758−762. (49) Kant, P.; Wu, S. The Extraordinary Collapse of Jatropha as a Global Biofuel. Environ. Sci. Technol. 2011, 45 (17), 7114−7115. (50) Kautto, N. Analysis of Policy Options and Implementation Measures Promoting Electricity from Renewable Biomass in the European Union; EUR 21672 EN; 2005; p 271.

(5) Fargione, J.; Hill, J.; Tilman, D.; Polasky, S.; Hawthorne, P. Land Clearing and the Biofuel Carbon Debt. Science 2008, 319 (5867), 1235−1238. (6) Bailis, R.; Baka, J. Constructing sustainable biofuels: governance of the emerging biofuel economy. Ann. Assoc. Am. Geograph. 2011, 104 (4), 1−12. (7) Baka, J. Biofuels and Wasteland Grabbing: How India’s Biofuel Policy is Facilitating Land Grabs in Tamil Nadu, India. In International Conference on Global Land Grabbing, Sussex, UK, April 6−8; Institute of Development Studies, 2011. (8) Achten, W. M. J.; Maes, W. H.; Aerts, R.; Verchot, L.; Trabucco, A.; Mathijs, E.; Singh, V. P.; Muys, B. Jatropha: From global hype to local opportunity. J. Arid. Environ. 2010, 74 (1), 164−165. (9) Macedo, M. N.; DeFries, R. S.; Morton, D. C.; Stickler, C. M.; Galford, G. L.; Shimabukuro, Y. E. Decoupling of deforestation and soy production in the southern Amazon during the late 2000s. Proc. Natl. Acad. Sci. 2012, 109 (4), 1341−1346. (10) Angelsen, A. Policies for reduced deforestation and their impact on agricultural production. Proc. Natl. Acad. Sci. 2010, 107 (46), 19639−19644. (11) 2008 Report on Alternative Fuels; International Air Transport Association: Geneva, December 2008; p 78. (12) IPCC. Climate Change 2007: Mitigation Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change; Metz, B., Davidson, O.R., Bosch, P.R., Dave, R., Meyer, L. A., Eds.; Cambridge University Press: United Kingdom and New York, 2007; p 851. (13) GreenAir Online Finnair’s scheduled commercial biofuel flight marks a step towards more sustainable flying, says airline. http://www. greenaironline.com/news.php?viewStory=1 (accessed Nov 2011). (14) Reals, K. Lufthansa buoyed by biofuel testing. Flight Int. 2012, 181 (5324), 10−10. (15) Wang, W.-C.; Thapaliya, N.; Campos, A.; Stikeleather, L. F.; Roberts, W. L. Hydrocarbon fuels from vegetable oils via hydrolysis and thermo-catalytic decarboxylation. Fuel 2012, 95 (0), 622−629. (16) AliphaJet. AliphaJet BoxCar Technology. http://www.aliphajet. com/technology.html (accessed Aug 2012). (17) Bailis, R.; Baka, J. Greenhouse Gas Emissions And Land Use Change From Jatropha Curcas-Based Jet Fuel In Brazil. Environ. Sci. Technol. 2010, 44, 8684−8691. (18) Warshay, B.; Pan, J.; Sgouridis, S. Aviation industry’s quest for a sustainable fuel: considerations of scale and modal opportunity carbon benefit. Biofuels 2011, 2 (1), 33−58. (19) GIACC. Review of aviation emissions-related activities within ICAO and internationally - U.S. Fuel Trends Analysis and Comparison to GIACC. Fourth Meeting of the Group on International Avaiation and Climate Change (GIACC/4), Montreal, CA, May 25−28; ICAO: Montréal, 2009; p 80. (20) Li, L.; Coppola, E.; Rine, J.; Miller, J. L.; Walker, D. Catalytic Hydrothermal Conversion of Triglycerides to Non-ester Biofuels. Energy Fuels 2010, 24 (2), 1305−1315. (21) Almeida, J.; Achten, W. M. J.; Duarte, M. P.; Mendes, B.; Muys, B. Benchmarking the Environmental Performance of the Jatropha Biodiesel System through a Generic Life Cycle Assessment. Environ. Sci. Technol. 2011, 45, 5447−5453. (22) Ndong, R.; Montrejaud-Vignoles, M.; Saint Girons, O.; Gabrielle, B.; Pirot, R.; Domergue, M.; Sablayrolles, C. Life cycle assessment of biofuels from Jatropha curcas in West Africa: a field study. GCB Bioenergy 2009, 1 (3), 197−210. (23) Whitaker, M.; Heath, G. Life Cycle Assessment Comparing the Use of Jatropha Biodiesel in the Indian Road and Rail Sectors; National Renewable Energy Laboratory: Golden, CO, May, 2010; p 118. (24) Lane, J. Moving from Jatropha 2.0 to Jatropha 2.$. http://www. biofuelsdigest.com/bdigest/2012/01/17/moving-from-jatropha-2-0to-jatropha-2/ (accessed June 2012). (25) Achten, W.; Nielsen, L.; Aerts, R.; Lengkeek, A. G.; Kjær, E. D.; Trabucco, A.; Hansen, J. K.; Maes, W. H.; Graudal, L.; Akinnifesi, F. K.; Muys, B. Towards domestication of Jatropha curcas. Biofuels 2010, 1 (1), 91−107. H



Article

(51) USEPA. Renewable Fuel Standard Program (RFS2) Regulatory Impact Analysis; OTAQ-USEPA: Washington DC, 2010; p 1120, EPA420-R-10-006. (52) Knothe, G. Biodiesel and renewable diesel: A comparison. Prog. Energy Combust. Sci. 2010, 36 (3), 364−373. (53) Nassar, A. M.; Harfuch, L.; Bachion, L. C.; Moreira, M. R. Biofuels and land-use changes: searching for the top model. Interface Focus 2011, 1 (2), 224−232.

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