Feedstock For Biofuel Production Research Articles

Multi-dimensional poverty effects around operational biofuel projects in Malawi, Mozambique and Swaziland

There is a long-term concern that the cultivation of biofuel feedstocks could have negative impacts on communities involved in, or adjacent to, such projects. In southern Africa, the acquisition and allocation of large blocks of land for biofuel feedstock production has been especially contentious. The present study investigates the local multi-dimensional poverty effects of growing biofuel crops using the Oxford Poverty & Human Development Initiative's Multidimensional Poverty Index. It investigates different modes of production (large-scale vs. smallholder-based) and different feedstocks (sugarcane vs. jatropha) in four study sites in Malawi, Swaziland and Mozambique. In the sugarcane growing areas, those who participated in its value chain as farmers or workers had lower poverty than those who were not involved. However, for jatropha growing areas, there were no clearly defined differences between the controls and the jatropha farmers in Mangochi, while in Mozambique the plantation workers had slightly lower poverty than the control groups. Although it was not possible to make direct comparisons between all projects, sugarcane areas seem to be better off than non-sugarcane areas. In all projects there was generally high incidence of deprivations in indicators related to living standards, particularly, access to electricity and cooking fuel.

Screening microalgae isolated from urban storm- and wastewater systems as feedstock for biofuel.

Exploiting microalgae as feedstock for biofuel production is a growing field of research and application, but there remain challenges related to industrial viability and economic sustainability. A solution to the water requirements of industrial-scale production is the use of wastewater as a growth medium. Considering the variable quality and contaminant loads of wastewater, algal feedstock would need to have broad tolerance and resilience to fluctuating wastewater conditions during growth. As a first step in targeting strains for growth in wastewater, our study isolated microalgae from wastewater habitats, including urban stormwater-ponds and a municipal wastewater-treatment system, to assess growth, fatty acids and metal tolerance under standardized conditions. Stormwater ponds in particular have widely fluctuating conditions and metal loads, so microalgae from this type of environment may have desirable traits for growth in wastewater. Forty-three algal strains were isolated in total, including several strains from natural habitats. All strains, with the exception of one cyanobacterial strain, are members of the Chlorophyta, including several taxa commonly targeted for biofuel production. Isolates were identified using taxonomic and 18S rRNA sequence methods, and the fastest growing strains with ideal fatty acid profiles for biodiesel production included Scenedesmus and Desmodesmus species (Growth rate (d−1) > 1). All isolates in a small, but diverse taxonomic group of test-strains were tolerant of copper at wastewater-relevant concentrations. Overall, more than half of the isolated strains, particularly those from stormwater ponds, show promise as candidates for biofuel feedstock.

Evaluation of filamentous green algae as feedstocks for biofuel production

Compared with unicellular microalgae, filamentous algae have high resistance to grazer-predation and low-cost recovery in large-scale production. Green algae, as the most diverse group of algae, included numerous filamentous genera and species. In this study, records of filamentous genera and species in green algae were firstly censused and classified. Then, seven filamentous strains subordinated in different genera were cultivated in bubbled-column to investigate their growth rate and energy molecular (lipid and starch) capacity. Four strains including Stigeoclonium sp., Oedogonium nodulosum, Hormidium sp. and Zygnema extenue were screened out due to their robust growth. And they all could accumulate triacylglycerols and starch in their biomass, but with different capacity. After nitrogen starvation, Hormidium sp. and Oedogonium nodulosum respectively exhibited high capacity of lipid (45.38% in dry weight) and starch (46.19% in dry weight) accumulation, which could be of high potential as feedstocks for biodiesel and bioethanol production.

Household food security and biofuel feedstock production in rural Mozambique and Tanzania

The ongoing debate over the impact of biofuels on food security makes it difficult for governments to develop clear policies for an industry that can enhance rural employment and help to alleviate rural poverty, but may also reduce food availability and raise food prices. Whilst there have been many studies reporting a wide range of global commodity price impacts arising from the sharp rise in biofuel use over the past decade, there has been less evidence on food security impacts at a local level in developing countries. Where evidence does exist the impact is difficult to assess, often due to different types of production models and feedstocks, but also due to weaknesses in the methodologies and measures of food security used. This paper aims to help address this evidence gap by analysing household survey data from sites close to different types of biofuel operations in Mozambique and Tanzania, using an index that measures key macronutrient and micronutrient deficits at the household level. The results show that those households with employees in medium to large-scale biofuel feedstock operations achieved significantly higher food security outcomes than other households in the same locations. Furthermore, most of the households with better food security outcomes reported an improvement in food security since the biofuel operations had been established and attributed this mainly to increased and more regular income from salaried employment.

Alternative Energy Resources: Brassica Napus for Biofuel Production

Submit Manuscript | http://medcraveonline.com could be able to partly decrease the depth by using oil crops as base for biodiesel production. Brassica napus, widely known as rapeseed, is the most productive oil crops Europe mainly uses for biodiesel production in fact almost 65% of biodiesel production in Europe comes from rapeseed feedstock. Feed stocks for biofuel production can result from plants cultivated directly for this use or from crops parts. In this case plants are being cultivated for feed or any other use, while their wastes are being used for biofuel production. Furthermore, oil crops can be use as alternatives to petroleum-based substances in order to reduce the fossil fuel use, nevertheless, chemical composition of these fuels is highly leveled. Brassica napus, B. rapa, B. juncea Brassica’s commercial supply is dominated by two species, Brassica napus L. and B. rapa L. Both contain spring and winter forms that are distinguished by vernalization requirement. Seeds of these species contain 40 % or more oil. In 2013/2014 rape seed holds ca. 14 % of the world production of major oil crops [1,2]. According to FAO statistics (2014), rapeseed ranked number 14 in agricultural commodity production in Europe in 2012. Although many farmers still have doubts about cultivating crops for biodiesel production thinking of it as a risky action, agriculturists assure that oil crops cultivation is similar to any other one they may be used to. Brassica for example grows excellent in temperature not beyond 30 degrees while some species resist under -20 degrees. The plant does not have any specific need as for the soil structure, it grows well in any type of soil from 5, 5 up to 8,3 Ph levels, as soon as there is not poor natural internal drainage so as for the crop root to be adequate aerationed. Crop’s yield is 120-210 kg per acre while from this amount 4070 kg oil could be extracted (almost 50 % oil production). Oil can be extracted by crushing the seed and sqeezing the oil out. This oil tranfesterified to make biodiesel. The prices are usually specified under contracts between the farmer and the oil production company, however according to farmer prices range between 4045 Euros per kilo. In addition to Brassica napus, many other plants produce oil which could be used as biodiesel. Soybean, canola, mustard, camelina, safflower, and tropical oilseed trees like palm tree and coconut are already being used for this purpose. Yet, researches are being held about three more oilseed crops that could be used as biodiesel feedstock, lesquerella, pennycress and hazelnuts might help us increase our future biofuel production. References

Characterization of sugarcane (Saccharum spp.) leaf senescence: implications for biofuel production.

BackgroundSecond-generation ethanol (2G-bioethanol) uses lignocellulosic feedstocks for ethanol production. Sugarcane is one among the most suitable crops for biofuel production. Its juice is extracted for sugar production, while sugarcane bagasse, straw, and senescing leaves are considered industrial waste. Senescence is the age-dependent deterioration of plant cells, ultimately leading to cell death and completion of the plant life cycle. Because senescing leaves may also be used for biofuel production, understanding the process of natural senescence, including remobilization of nutrients and its effect on cell walls can provide useful information for 2G-bioethanol production from sugarcane leaves.ResultsThe natural senescence process in leaves of the commercial sugarcane cultivar RB867515 was investigated. Senescence was characterized by strong reduction in photosynthetic pigments content, remobilization of the nutrients N, P, K, B, Cu, Fe, and Zn, and accumulation of Ca, S, Mg, B, Mn, and Al. No significant changes in the cell-wall composition occurred, and only small changes in the expression of cell wall-related genes were observed, suggesting that cell walls are preserved during senescence. Senescence-marker genes, such as SAG12-like and XET-like genes, were also identified in sugarcane and found to be highly expressed.ConclusionsOur study on nutrient remobilization under senescence in a vigorous sugarcane cultivar can contribute to the understanding on how nutrient balance in a high-yielding crop is achieved. In general, neutral monosaccharide profile did not change significantly with leaf senescence, suggesting that senescing leaves of sugarcane can be as a feedstock for biofuel production using pretreatments established for non-senescing leaves without additional efforts. Based on our findings, the potential biotechnological applications for the improvement of sugarcane cultivars are discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0568-0) contains supplementary material, which is available to authorized users.

Belowground impacts of perennial grass cultivation for sustainable biofuel feedstock production in the tropics

AbstractPerennial grasses can sequester soil organic carbon (SOC) in sustainably managed biofuel systems, directly mitigating atmospheric CO2 concentrations while simultaneously generating biomass for renewable energy. The objective of this study was to quantify SOC accumulation and identify the primary drivers of belowground C dynamics in a zero‐tillage production system of tropical perennial C4 grasses grown for biofuel feedstock in Hawaii. Specifically, the quantity, quality, and fate of soil C inputs were determined for eight grass accessions – four varieties each of napier grass and guinea grass. Carbon fluxes (soil CO2 efflux, aboveground net primary productivity, litterfall, total belowground carbon flux, root decay constant), C pools (SOC pool and root biomass), and C quality (root chemistry, C and nitrogen concentrations, and ratios) were measured through three harvest cycles following conversion of a fallow field to cultivated perennial grasses. A wide range of SOC accumulation occurred, with both significant species and accession effects. Aboveground biomass yield was greater, and root lignin concentration was lower for napier grass than guinea grass. Structural equation modeling revealed that root lignin concentration was the most important driver of SOC pool: varieties with low root lignin concentration, which was significantly related to rapid root decomposition, accumulated the greatest amount of SOC. Roots with low lignin concentration decomposed rapidly, but the residue and associated microbial biomass/by‐products accumulated as SOC. In general, napier grass was better suited for promoting soil C sequestration in this system. Further, high‐yielding varieties with low root lignin concentration provided the greatest climate change mitigation potential in a ratoon system. Understanding the factors affecting SOC accumulation and the net greenhouse gas trade‐offs within a biofuel production system will aid in crop selection to meet multiple goals toward environmental and economic sustainability.

Energy analysis of extractive-transesterification of algal lipids for biocrude production

ABSTRACTAlgae biomass is the most promising feedstock for biofuel production since it can provide a sustainable route to achieve independence from fossil fuel sources. Energy-positive biofuel production from algal biomass has been the major goal for many researchers in recent years. The search for efficient extraction and chemical conversion methods that produce high energy ratios has become an important endeavor in this field. In this regard, microwaves and ultrasound have been utilized as convenient mechanisms in algal biodiesel production. However, none of the studies reported on the energy analysis of the extraction and transesterification methods. Energy analysis of the extractive-transesterification processes using microwave (with ethanol and with ethanol and hexane as co-solvent) and ultrasound irradiations to produce biocrude from microalgae (Chlorella sp.) is presented in this paper. Power input and reaction volumes were varied to study the effects of power density and intensity on the biocrude yields. Results from this analysis show that a biocrude yield higher than 90% could be obtained with an energy input to output ratio of less than one when microwave irradiation is used as the heating mechanism.

Cost – Benefit of water resource use in biofuel feedstock production

An increase in the output of crops such as cassava, sugarcane, and oil palm, is necessary for biofuels development. To increase the crop yield, a large amount of water is required which can have an impact on the net social welfare. This study aims to assess the benefit and cost of water resource use in biofuel crops production to support the cost-benefit analysis of biofuels development. Benefit of water is presented through the value of its marginal product estimated by using economic valuation methods. The loss due to water consumption is assessed and monetized based on life cycle impact assessment. To show how the approach is applied to the regional level, Thailand is considered as a case study. The results show that the economic gains from using a cubic meter of water in cassava, sugarcane, and oil palm production are 1.6–6.9, 1.0–5.0, and 0.8–2.9 Thai baht, respectively. However, using this amount of water can also bring about the external cost around 0.2 Thai baht, leading to the net benefits of using a cubic meter of water in cassava, sugarcane, and oil palm production between 1.5 and 6.7, 0.9–4.8, and 0.6–2.6 Thai baht, respectively. Gain and loss of the water used in cassava, sugarcane, and oil palm cultivation are expressed in monetary units for the first time by this study. Besides, this paper could be a guideline for future research towards an integration of life cycle impact assessment and the economic analysis tool, cost-benefit analysis.

Bioremediation of wastewater from edible oil refinery factory using oleaginous microalga Desmodesmus sp. S1

ABSTRACTEdible oil industry produced massive wastewater, which requires extensive treatment to remove pungent smell, high phosphate, carbon oxygen demand (COD), and metal ions prior to discharge. Traditional anaerobic and aerobic digestion could mainly reduce COD of the wastewater from oil refinery factories (WEORF). In this study, a robust oleaginous microalga Desmodesmus sp. S1 was adapted to grow in WEORF. The biomass and lipid content of Desmodesmus sp. S1 cultivated in the WEORF supplemented with sodium nitrate were 5.62 g·L−1 and 14.49%, whereas those in the WEORF without adding nitrate were 2.98 g·L−1 and 21.95%. More than 82% of the COD and 53% of total phosphorous were removed by Desmodesmus sp. S1. In addition, metal ions, including ferric, aluminum, manganese and zinc were also diminished significantly in the WEORF after microalgal growth, and pungent smell vanished as well. In comparison with the cells grown in BG-11 medium, the cilia-like bulges and wrinkles on the cell surface of Desmodesmus sp. S1 grown in WEORF became out of order, and more polyunsaturated fatty acids were detected due to stress derived from the wastewater. The study suggests that growing microalgae in WEORF can be applied for the dual roles of nutrient removal and biofuel feedstock production.

Development of Dryland Oilseed Production Systems in Northwestern Region of the USA

This report addresses the development of dryland oilseed crops to provide feedstock for production of biofuels in semi-arid portions of the northwestern USA. Bioenergy feedstocks derived from Brassica oilseed crops have been considered for production of hydrotreated renewable jet fuel, but crop growth and yields in the northwestern region are limited by a lack of plant available water. Based on a review of the scientific literature, several areas were identified where research could be directed to provide improvements. The current agronomic limitations for oilseed production are mainly due to seedling establishment under extreme heat, dry seedbeds at optimum planting times, survival under extreme cold, and interspecific competition with weeds. To improve emergence and stand establishment, future work should focus on developing soil management and seeding techniques that optimize plant available water, reduce heat stress, and provide a competitive advantage against weeds that are customized for specific crops, soil types, and soil and environmental conditions. Spring and winter cultivars are needed that offer increased seedling vigor, drought resistance, and cold tolerance.

The Origin of the USDA Regional Biomass Research Centers

The U.S. Department of Agriculture (USDA) Regional Biomass Research Centers (RBRC) were created to contribute to the planning, research, and development of entire long-term sustainable biofuel production supply chains based on agricultural and forest-based feedstocks. The intent of the centers is to provide a catalyst that links feedstock genetic development, sustainable production and management, logistics, conversion, co-product production, distribution, and market demand suited to the available economic, social, and natural resources within different regions. The centers provide a coordinated, region-based research focus designed with relatively short-term deliverables to help accelerate the commercial production of biomass and other biofuel feedstocks. The centers provide a leadership structure for coordinating biomass research across the country, providing a national perspective that complements other USDA agency efforts designed to help US rural communities participate in the emerging biofuels and biobased products economy. Through coordination with the RBRC, USDA research and service agency programs and resources have been leveraged with the U.S. Department of Energy (DOE) and other federal department, university, and private industry efforts to help accelerate commercial advancement of advanced biofuel production to promote rural economic opportunities and achieve transportation biofuel policy goals.

A Watershed Level Economic Analysis of Cellulosic Biofuel Feedstock Production with Consideration of Water Quality

<p>National policy supports the production of renewable energy from cellulosic feedstocks such as corn stover and switchgrass. These feedstocks have contrasting impacts on water quality. In this study, the regional supply response for cellulosic biofuel from these two feedstocks is estimated for the Le Sueur Watershed in South-Central Minnesota. The impacts of the resulting agricultural production activities on water quality in this northern corn belt watershed are also estimated. The Le Sueur River is a tributary of the Minnesota River, which in turn feeds into the Mississippi. The analysis is conducted with a multi-region, endogenous supply, mathematical programming model of the agriculture sector in the watershed. A unique aspect of the analysis is the spatial detail used in the production model. Results from a previous simulation analysis conducted with the Soil Water Assessment Tool (SWAT) model are used in the economic model to simulate the effects of the feedstock supply response on water quality in the Le Sueur. Sediment and nutrient losses from corn stover production make switchgrass more promising on environmental grounds, but the relatively high cost of production causes switchgrass to cover only a small part of crop land if farmers have unrestricted choice about how to supply cellulosic feedstocks.</p>

KdgF, the missing link in the microbial metabolism of uronate sugars from pectin and alginate

Uronates are charged sugars that form the basis of two abundant sources of biomass-pectin and alginate-found in the cell walls of terrestrial plants and marine algae, respectively. These polysaccharides represent an important source of carbon to those organisms with the machinery to degrade them. The microbial pathways of pectin and alginate metabolism are well studied and essentially parallel; in both cases, unsaturated monouronates are produced and processed into the key metabolite 2-keto-3-deoxygluconate (KDG). The enzymes required to catalyze each step have been identified within pectinolytic and alginolytic microbes; yet the function of a small ORF, kdgF, which cooccurs with the genes for these enzymes, is unknown. Here we show that KdgF catalyzes the conversion of pectin- and alginate-derived 4,5-unsaturated monouronates to linear ketonized forms, a step in uronate metabolism that was previously thought to occur spontaneously. Using enzyme assays, NMR, mutagenesis, and deletion of kdgF, we show that KdgF proteins from both pectinolytic and alginolytic bacteria catalyze the ketonization of unsaturated monouronates and contribute to efficient production of KDG. We also report the X-ray crystal structures of two KdgF proteins and propose a mechanism for catalysis. The discovery of the function of KdgF fills a 50-y-old gap in the knowledge of uronate metabolism. Our findings have implications not only for the understanding of an important metabolic pathway, but also the role of pectinolysis in plant-pathogen virulence and the growing interest in the use of pectin and alginate as feedstocks for biofuel production.

Municipal Solid Waste Management in a Low Income Economy Through Biogas and Bioethanol Production

The biodegradable fraction of municipal solid wastes generated from households in Ghana has favourable characteristics worth considering for bioenergy production. The suitability of this biodegradable portion for biogas and bioethanol production was assessed in this study. The assessment was performed on both untreated and hydrothermally treated unsorted and sorted fractions of the waste using standard methods for biomass conversion to bioenergy. Compositional analysis of the waste indicated that unsorted biodegradable municipal solid wastes (BMSW) consisted of 38.7 % dry matter (DM) glucan, 8.3 % DM hemicellulose, 10.1 % DM lignin and 7.6 % DM ash. The sorted fractions with the highest glucan but least lignin and hemicellulose were the pool of cassava, yam and plantain peeling wastes (CYPPW) with 84 % DM glucan much of which was starch, 5.6 % DM lignin and 0.5 % DM hemicellulose. The highest ethanol yield of 0.29 l/kg DM was measured from this same CYPPW while fruit wastes (FW) had the highest biomethane potential of 408 ml CH4/g VS. The BMSW had ethanol yield of 0.17 l/kg DM and biogas 369 ml CH4/g VS. The hydrothermally pretreated wastes had marginal increases in glucose and ethanol yield except the treated yard waste which significantly increased by 54 % in glucose over the untreated waste. The most promising waste fractions were FW, CYPPW and mixed paper wastes. Careful selection of these fractions in feedstock for biofuel production would reduce generation of the waste, improve the quality and effectively lead to higher yield of biofuel over the unsorted form.

Innovative technological paradigm-based approach towards biofuel feedstock

Biofuels produced from renewable energy biomass are playing a more significant role because of the environmental problems resulting from the use of fossil fuels. However, a major problem with biofuel production is that despite the range of feedstock that can be used, raw material availability varies considerably. By combining a series of theories and methods, the research objective of this study is to determine the current developments and the future trends in biofuel feedstock. By combining technological paradigm theory with literature mining, it was found that biofuel feedstock production development followed a three-stage trajectory, which was in accordance with the traditional technological paradigm – the S-curve. This new curve can be divided into BFDP (biofuel feedstock development paradigm) competition, BFDP diffusion, and BFDP shift. The biofuel production diffusion velocity model showed that there has been constant growth from 2000, with the growth rate reaching a peak in 2008, after which time it began to drop. Biofuel production worldwide is expected to remain unchanged until 2030 when a paradigm shift is expected. This study also illustrates the results of our innovative procedure – a combination of the data analysis system and the technological paradigm theory – for the present biofuel feedstock soft path that will lead to this paradigm shift, with integrated biofuel production feedstock systems expected to be a significant new trend.

Cellulosic feedstock production on Conservation Reserve Program land: potential yields and environmental effects

AbstractProducing biofuel feedstocks on current agricultural land raises questions of a ‘food‐vs.‐fuel’ trade‐off. The use of current or former Conservation Reserve Program (CRP) land offers an alternative; yet the volumes of ethanol that could be produced and the potential environmental impacts of such a policy are unclear. Here, we applied the Environmental Policy Integrated Climate model to a US Department of Agriculture database of over 200 000 CRP polygons in Iowa, USA, as a case study. We simulated yields and environmental impacts of growing three cellulosic biofuel feedstocks on CRP land: (i) an Alamo‐variety switchgrass (Panicum virgatum L.); (ii) a generalized mixture of C4 and C3 grasses; (iii) and no‐till corn (Zea mays L.) with residue removal. We simulated yields, soil erosion, and soil carbon (C) and nitrogen (N) stocks and fluxes. We found that although no‐till corn with residue removal produced approximately 2.6–4.4 times more ethanol per area compared to switchgrass and the grass mixture, it also led to 3.9–4.5 times more erosion, 4.4–5.2 times more cumulative N loss, and a 10% reduction in total soil carbon as opposed to a 6–11% increase. Switchgrass resulted in the best environmental outcomes even when expressed on a per liter ethanol basis. Our results suggest planting no‐till corn with residue removal should only be done on low slope soils to minimize environmental concerns. Overall, this analysis provides additional information to policy makers on the potential outcome and effects of producing biofuel feedstocks on current or former conservation lands.

Recovery of Sugars and Lipids from Spent Coffee Grounds: A New Approach

Spent coffee grounds (SCG) is an agro-industrial waste which could potentially be tapped as feedstock for biofuel production. The direct hydrolysis of non-delipidated SCG was investigated in this study. Hydrolysis of SCG was carried out with the use of sulfuric acid (3–5 %v/v) as hydrolyzing medium, over a period of 30–180 min at a solvent to solid ratio of 10 mL/g at 95 °C. The optimum yield (26 and 31 g/g) and recovery (86 and 78 %) of the available reducing sugar was achieved at a local optimum employing an acid concentration of 4 % and a hydrolysis time of 120 min. Lipids were recoverable from the hydrolyzed biomass residue and bound lipids were also released through the hydrolysis process resulting in a recovery of over 100 %. This approach may potentially reduce production steps, avoiding energy intensive process for removal of water content in SCG.

Growth and fatty acid characterization of microalgae isolated from municipal waste-treatment systems and the potential role of algal-associated bacteria in feedstock production.

Much research has focused on growing microalgae for biofuel feedstock, yet there remain concerns about the feasibility of freshwater feedstock systems. To reduce cost and improve environmental sustainability, an ideal microalgal feedstock system would be fed by municipal, agricultural or industrial wastewater as a main source of water and nutrients. Nonetheless, the microalgae must also be tolerant of fluctuating wastewater quality, while still producing adequate biomass and lipid yields. To address this problem, our study focused on isolating and characterizing microalgal strains from three municipal wastewater treatment systems (two activated sludge and one aerated-stabilization basin systems) for their potential use in biofuel feedstock production. Most of the 19 isolates from wastewater grew faster than two culture collection strains under mixotrophic conditions, particularly with glucose. The fastest growing wastewater strains included the genera Chlorella and Dictyochloris. The fastest growing microalgal strains were not necessarily the best lipid producers. Under photoautotrophic and mixotrophic growth conditions, single strains of Chlorella and Scenedesmus each produced the highest lipid yields, including those most relevant to biodiesel production. A comparison of axenic and non-axenic versions of wastewater strains showed a notable effect of commensal bacteria on fatty acid composition. Strains grown with bacteria tended to produce relatively equal proportions of saturated and unsaturated fatty acids, which is an ideal lipid blend for biodiesel production. These results not only show the potential for using microalgae isolated from wastewater for growth in wastewater-fed feedstock systems, but also the important role that commensal bacteria may have in impacting the fatty acid profiles of microalgal feedstock.

Influence of spatially dependent, modeled soil carbon emission factors on life‐cycle greenhouse gas emissions of corn and cellulosic ethanol

AbstractConverting land to biofuel feedstock production incurs changes in soil organic carbon (SOC) that can influence biofuel life‐cycle greenhouse gas (GHG) emissions. Estimates of these land use change (LUC) and life‐cycle GHG emissions affect biofuels' attractiveness and eligibility under a number of renewable fuel policies in the USA and abroad. Modeling was used to refine the spatial resolution and depth extent of domestic estimates of SOC change for land (cropland, cropland pasture, grassland, and forest) conversion scenarios to biofuel crops (corn, corn stover, switchgrass, Miscanthus, poplar, and willow) at the county level in the USA. Results show that in most regions, conversions from cropland and cropland pasture to biofuel crops led to neutral or small levels of SOC sequestration, while conversion of grassland and forest generally caused net SOC loss. SOC change results were incorporated into the Greenhouse Gases, Regulated Emissions, and Energy use in Transportation (GREET) model to assess their influence on life‐cycle GHG emissions of corn and cellulosic ethanol. Total LUC GHG emissions (g CO2eq MJ−1) were 2.1–9.3 for corn‐, −0.7 for corn stover‐, −3.4 to 12.9 for switchgrass‐, and −20.1 to −6.2 for Miscanthus ethanol; these varied with SOC modeling assumptions applied. Extending the soil depth from 30 to 100 cm affected spatially explicit SOC change and overall LUC GHG emissions; however, the influence on LUC GHG emission estimates was less significant in corn and corn stover than cellulosic feedstocks. Total life‐cycle GHG emissions (g CO2eq MJ−1, 100 cm) were estimated to be 59–66 for corn ethanol, 14 for stover ethanol, 18–26 for switchgrass ethanol, and −7 to −0.6 for Miscanthus ethanol. The LUC GHG emissions associated with poplar‐ and willow‐derived ethanol may be higher than that for switchgrass ethanol due to lower biomass yield.