A monthly roundup of journal articles on bioenergy and the environment by Amy Elvidge.
Spatially robust estimates of biological nitrogen (N) fixation imply substantial human alteration of the tropical N cycle
Sullivan, et al. | Proceedings of National Academy of Science, June 3 (Vol. 111, No. 22)
Introduce a spatial sampling method to assess biological nitrogen fixation (BFN) and present evidence that tropical forest BNF is much lower than previously assumed–humans have doubled N inputs to the tropical forest biome relative to N inputs through BNF. Biofuels make up part of anthropogenic N inputs in tropical regions due to the nature of high-N-input agriculture.
Life cycle GHG emissions from microalgal biodiesel – A CA-GREET Model
Woertz, et al. | Environmental Science and Technology, June 3 2014 (Vol. 48, Issue 11, p.6055-6522)
LCA shows that GHG emissions from algal biodiesel system to be 70% lower than those of conventional diesel fuel, meeting the minimum 50% GHG reduction requirements under the EPA RFS2 and 60% for the European Union Renewable Energy Directive. Study provides a guide to the research and development objectives that must be achieved to meet both economic and environmental goals for microalgae biodiesel production.
Best practices for biofuels
Youngs and Somerville | Science, June 6 (Vol. 344, No. 6188, p.1057-1196)
In light of the food vs. fuel debate, comments in reports from Working Groups 2 and 3 of the IPCC have special weight in the public discourse. Data-based standards should guide biofuel production.
Humanity’s unsustainable environmental footprint
Hoekstra and Wiedmann | Science, June 6 (Vol. 344, No. 6188, p.1057-1196)
Major transformative changes in global economy needed to reduce humanity’s environmental footprint to sustainable levels. Biofuels contributes as a water-intensive commodity and a necessary import for countries to meet set targets (contributing to land and water footprints).
Global evaluation of biofuel potential from microalgae
Moody, McGinty and Quinn | Proceedings of National Academy of Science, June 10 (Vol. 111, No. 23)
Research into microalgae continues due to inherent potential advantage over traditional terrestrial feedstocks, however large-scale productivity is uncertain. Study integrates a large-scale, outdoor growth model with historical data to estimate current near-term lipid and biomass productivity potential from microalgae cultivated in a photobioreactor architecture.
Carbon payback period and carbon offset parity point of wood pellet production in the South-Eastern United States
Jonker, et al. | Proceedings of National Academy of Science, June 10 (Vol. 111, No. 23)
Examines effect of methodological choices to determine the carbon payback time and the offset parity point for wood pellet production from softwood plantations in the Southeastern US. Conclude that issue of carbon payback is basically nonexistent. If comparison against a protection scenario is realistic and policy relevant, and assuming that wood pellets directly replace coal, the carbon offset parity point is in the range of 12-46 years. Switching to intensely managed plantations yields most drastic reduction in the time to parity points (less than 17 years).
Meeting the global demand for biofuels in 2021 through sustainable land use change policy
Goldemberg, et al. | Energy Policy, June 2014 (Vol. 69, p.1-648)
2014 renewable energy policy mandates adopted in 27 countries will increase the need for liquid biofuels–ethanol from corn and sugarcane will increase from 80 to ~200 billion l in 2021. Conservationist policy programs with scientific basis needed to drive expansion of biofuel production.
The role of biomass in US industrial interfuel substitution
Jones, C. | Energy Policy, June 2014 (Vol. 69, p.1-648)
Biomass exceeds coal usage in US industrial sector. Model used to examine role of biomass in interfuel substitution, which lowers estimated price elasticities for traditional fuels. Biomass found to be a substitute for natural gas for industrial users.
Ethical and legal challenges in bioenergy governance: Coping with value disagreement and regulatory complexity
Gamborg, et al. | Energy Policy, June 2014 (Vol. 69, p.1-648)
Interplay between value disagreements (e.g. prioritizing carbon concerns over non-carbon related concerns) and regulatory complexity (regulatory measures and options). Illustrate two cases in EU: liquid biofuels for transport and solid biomass-based bioenergy. Failure to deal explicitly with underlying value disagreements, or to make apparent the regulatory complexity, impedes forward motion of governance of bioenergy.
Achieving reductions in GHG in the US road transportation sector
Kay, Noland and Rodier | Energy Policy, June 2014 (Vol. 69, p.1-648)
Travel elasticities calculated for policy scenarios and then used to estimate changes in total lifecycle GHG emissions. Current technology and fuel policy and the strongest behavioral policy will not meet targets, need for more aggressive technology and fuel options for heavy and medium-duty trucks.
The regional effects of a biomass fuel industry on US agriculture
Gallagher | Energy Policy, June 2014 (Vol. 69, p.1-648)
Potential competitiveness of mature biomass fuel (BF) industry in the US. Model a land policy that allows BF-cattle competition for forage, crop residues, and pasture. Estimate cost reductions and welfare gains associated with modifying the land use policy. A broader definition of agriculture land suitable for biomass inputs would reduce biofuel processing costs, relieve the food vs fuel conflict, and increase net gain to fuel consumers, food consumers, and producers of food and fuel.
Will energy crop yields meet expectations?
Searle and Malins | Biomass & Bioenergy, June 2014 (Vol. 65, p.1-182)
Review covers Miscanthus, switchgrass, poplar, willow and Eucalyptus. Field scale yields (compared to small experimental plots) lower due to real world harvesting losses and edge effects. Potential for yield improvement relatively limited and expectations must be realistic for successful policies and commercial production.
Climate mitigation comparison of woody biomass systems with the inclusion of land-use in the reference fossil system
Haus, Gustavsson and Sathre | Biomass & Bioenergy, June 2014 (Vol. 65, p.1-182)
Dynamics of GHG emissions from woody biomass and fossil systems, accounting for forest land-use. Replacing fossil fuels and increasing intensity of forest management both give greater climate benefit. Methodological choices in defining temporal system boundaries important.
Atmospheric chemistry: ethanol and ozone
Madronich, S. | Nature – GeoScience, June 2014 (Issue 6, p.389-475)
Analysis of air quality data suggests that a switch from ethanol to gasoline use in Sao Paulo in response to changing prices led to lower local levels of ozone pollution.
Reduction in local ozone levels in urban Sao Paulo due to a shift from ethanol to gasoline use
Salvo and Geiger | Nature – GeoScience, June 2014 (Issue 6, p.389-475)
Predicted effect of various ethanol/gasoline blends on the concentration of atmospheric pollutants such as ozone varies between model and lab studies. Real-world shift in fuel use show that ambient ozone concentrations fell by ~20% as the share of bi-fuel vehicles burning gasoline rose from 14 to 74%; however, nitric oxide and carbon monoxide concentrations increased.
Health co-benefits of climate change mitigation policies in the transport sector
Shaw, et al. | Nature – Climate Change, June 2014
Some interventions to mitigate carbon emissions in the transport sector can also have substantial short-term benefits for population health. For example, an increase in diesel vehicles or a change to ethanol-blended fuel could increase urban air pollution and have associated health consequences.
Study on modelling microalgae growth in nitrogen-limited culture system for estimating biomass productivity
Yuan, et al. | Renewable & Sustainable Energy Reviews, June 2014 (Vol. 34, p. 1-670)
Microalgae promising future biofuel resource to fix CO2. Models of microalgae growth in nitrogen-limited and light-limited culture system for estimating biomass productivity; results show differences due to different expressions and coefficients used in models.
A monthly roundup of journal articles on bioenergy and the environment by Amy Elvidge.
Greater sensitivity to drought accompanies maize yield increase in the US Midwest
Lobell, Roberts, et al. | Science, May 2 (Vol. 344, Issue 6183, p.441-548)
Selective breeding focused on increasing corn and soybean yields has left a weakness in corn drought tolerance. Results suggest that agronomic changes tend to translate improved drought tolerance of plants to higher average yields but not to decreasing drought sensitivity of yields at the field scale.
Response of farmland biodiversity to the introduction of bioenergy crops: effects of local factors and surrounding landscape context
Bourke, et al. | Global Change Biology- Bioenergy, May 2014 (Vol. 6, Issue 3, p.169-304)
Assess impact of replacing conventional agricultural crops with two model bioenergy crops on vascular plant, bumblebee, solitary bee, hoverfly and carabid beetle richness, diversity and abundance in 50 sites in Ireland. Found that local- and landscape-scale variables correlated with biodiversity. Bioenergy crops compare favorably with conventional crops in terms of biodiversity of taxa studied, but effects of large-scale planting could result in very different impacts.
Bioenergy: Challenge or support for the conservation of biodiversity?
Dauber and Bolte | Global Change Biology- Bioenergy, May 2014 (Vol. 6, Issue 3, p.169-304)
Major direct and/or indirect land-use change from bioenergy needs drive loss of biodiversity.
Concern that extensive commercial production of bioenergy feedstock could further aggravate biodiversity loss. Report shows that bioenergy crops shouldn’t be viewed as phenomenon outside the scope of conventional agriculture and farming diversity strongly depends on the proportion of the area the crop is covering within a landscape. There is a potential to either increased or decrease the diversity, complementarity, and quality of habitats provided within a landscape.
GHG emissions of forest-biomass supply chains to commercial-scale liquid-biofuel production plants in Finland
Jappinen, et al. | Global Change Biology- Bioenergy, May 2014 (Vol. 6, Issue 3, p. 169-304)
Assess GHG emissions from feedstock supply and transportation chain to three possible commercial-scale biodiesel plant locations in Finland at site-specific level. Results show that GHG emissions of supply chains reduced through use of railway transportation from distant supply areas and GHG emissions are relatively low (2–4%) when compared with the GHG emissions of fossil diesel.
Increased energy maize production reduces farmland bird diversity
Sauerbrei, et al. | Global Change Biology- Bioenergy, May 2014 (Vol. 6, Issue 3, p. 169-304)
Quantify potential impact of an increase in maize fields on the diversity of farmland birds in Germany; predict that total number of breeding pairs of indicator species to decline by about 0.4 million pairs in the most intensive scenario.
Securing a bioenergy future without imports
Welfle, Gilbert and Thornley | Energy Policy, May 2014 (Vol. 68, p. 1-608)
Biomass Resource Model applied to the UK that reflects key biomass supply-chain dynamics and interactions determining resource availability, taking into account climate, food, land and other constraints.
US biofuels subsidies and CO2 emissions: An empirical test for a weak and a strong green paradox
Grafton, et al. | Energy Policy, May 2014 (Vol. 68, p. 1-608)
US biofuel subsidies increased fossil fuel extraction and CO2 emissions from 1981-2011; governments must consider effects of biofuel subsidies on fossil fuel extraction.
The impact of energy prices on the volatility of ethanol prices and the role of gasoline emissions
Zafeiriou, et al. | Renewable & Sustainable Energy Reviews, May 2014 (Vol. 33, p. 1-782)
Surveys role of alternative energy prices and gas emissions in the formation of ethanol prices and confirms existence of a sole relationship. An increase in volume of emissions or in gasoline prices results in an increase in ethanol prices while the opposite is confirmed with crude oil. Elasticity of ethanol prices to the increase of the emissions shows significant role of emissions in formation of ethanol prices.
Integrating mitigation and adaptation into development: the case of Jatropha curcas in sub-Saharan Africa
Muys, et al. | Global Change Biology- Bioenergy, May 2014 (Vol. 6, Issue 3, p.169-304)
Jatropha research to find biofuel crops that can grow on marginal land in SSA. Recent study conclude that jatropha only competitive with fossil fuels when produced in a family farm labor setting, however much uncertainty regarding yield information from Africa and elsewhere–this paper shows that jatropha has potential to contribute to sustainable rural development in Africa but at present isn’t sufficiently productive and profitable to play that role.
Biodiversity impacts of bioenergy crop production: a state-of-the-art review
Immerzeel, et al. | Global Change Biology- Bioenergy, May 2014 (Vol. 6, Issue 3, p.169-304)
The article confirms that concerns about the expansion of bioenergy crop production not only relate to the direct effects on biodiversity by replacing natural vegetation, but increasingly to indirect effects as well (albeit difficult to quantify). The land sparing vs. land sharing debate continues to grow, but little evidence exists in the literature on the impacts of large-scale application of these strategies on (agro)biodiversity.
A monthly roundup of journal articles on bioenergy and the environment by Amy Elvidge.
Life Cycle Water Footprints of Nonfood Biomass Fuels in China
Zhang, Cie and Huang | Environmental Science and Technology, April 1 2014 (Vol. 48. Issue 7, p. 3601- 4216)
Life cycle water footprints (WFs) of biofuels from biomass in China based on resource distribution, climate conditions, soil conditions and crop growing characteristics. The crop growing stage was main contributor to the whole life cycle of each pathway; find certain crop in certain region more suitable for promotion.
Monolignol Ferulate Transferase Introduces Chemically Labile Linkages into the Lignin Backbone
Wilkerson, et al. | Science Magazine, April 4 2014 (Vol. 344, Issue 6179, p. 1-116)
Engineered poplar to produce lignin that is more amenable to degradation and therefore has a greater capacity for biofuel.
Mitigating Nitrous Oxide Emissions from Corn Cropping Systems in the Midwestern U.S.: Potential and Data Gaps
Decock | Environmental Science and Technology, April 15 (Vol. 48, Issue 8, p.4217-4634)
Potential of alternative agronomic management practices to mitigate N2O emissions from corn cropping.
Climate policy decisions require policy-based Lifecycle Analysis
Bento and Klotz | http://pubs.acs.org/doi/full/10.1021/es405164g
Environmental Science and Technology, April 15 (Vol. 48, Issue 8, p.4217-4634)
LCAs evaluate emissions not impacts of policies; policy-based consequential LCA shows that emissions impacts of four US biofuel policies range from a reduction of 16.1 gCO2e to an increase of 24.0 gCO2e per MJ corn ethanol added by the policy.
More sophisticated forecasts yield glimmer of hope in climate gloom
Kintisch | Science, April 18 (Vol. 344, Issue 6181, p.225-332)
Evaluate how political and economic issues could affect various strategies to reduce emissions. Finds that opposition to biofuels and carbon capture strategies could drive up costs of stabilizing atmospheric CO2, and that these technologies can offer significant co-benefits.
Renewable energy: Biofuels heat up
Krieger | Nature, April 24 (Vol. 508, No. 7497, p.432-560)
New generation of industrial plants can make liquid fuels from almost any organic scraps (corn stalks, wood chips, urban rubbish, etc.).
Inhibitor analysis and adaptive evolution of S. cerevisiae for simultaneous saccharification and ethanol fermentation from industrial waste corncob resides
Gu, Zhang and Bao | Bioresource Technology, April 2014 (Vol. 157)
Industrial waste corncob residues (CCR) rich in cellulose and can be hydrolyzed directly without pretreatment; study finds a practical method for improving performance of simultaneous saccharification and ethanol production from CCR.
Temperature and drought effects on maize yield
Basso and Ritchie | Nature – Climate Change, April 2014
Critique of Lobell paper. Argue that excessive temperature above 30 Celsius during June-August contributed did not contribute more significantly to lowering maize yields in US corn belt than did total rainfall; major and consistent cause of rain fed maize yield reductions in US corn belt is prolonged absence of significant rainfall and resulting soil-water deficit.
Reply to ‘Temperature and drought effects on maize yield’
Lobell, et al. | Nature – Climate Change, April 2014
Argue why comments by Basso are unconvincing.
Focus on bioenergy industry development and energy security in China
Zhao and Liu | Renewable & Sustainable Energy Reviews, April 2014 (Vol. 32 p. 1-994)
Conclusions: The bioenergy industry s an effective way to achieve China’s energy security, China already has ability to sub bioenergy for fossil fuels, but China’s technologies aren’t mature so biomass and fossil energy will jointly develop in a mutually beneficial way.
The effect of bioenergy expansion: Food, energy, and environment
Popp, Lakner, Rakos and Fari | Renewable & Sustainable Energy Reviews, April 2014 (Vol. 32 p. 1-994)
Risk to food and energy security, estimates of bioenergy potential with regard to biofuel production, and the challenges of the environmental impact.
Analysis of the policies of biomass power generation in China
Zhang, Zhou and Fang | Renewable & Sustainable Energy Reviews, April 2014 (Vol. 32 p. 1-994)
Policies of biomass power generation from 2006-2012 based on actual demand of biomass power generation project. Conclusion that biomass power generation should be developed steadily in China and fiscal supporting shouldn’t be introduced anymore.
Life cycle assessment of corn stover torrefaction plant integrated with a corn ethanol plant and a coal fired power plant
Kaliyan, et al. | Biomass & Bioenergy, April 2014 (Vol. 63, p. 1-344)
Findings: Life cycle GHG emissions for corn stover biocoal is 11.35 g MJ-1. Using torrefaction gas for steam production reduced GHG emissions for corn ethanol. Co-firing biocoal with coal reduced GHG emissions for coal-fired electricity.
Pretreatment of corn stover with diluted acetic acid for enhancement of acidogenic fermentation
Zhao, et al. | Bioresource Technology, April 2014 (Volume 158, p.1-400)
Results show pretreatment with 0.25% acetic acid at 191 Celsius for 7.74 min most optimal condition for corn stover for production of acids to reach highest level. Acidogenic fermentation with hydrolyzate of pretreatment at the optimal condition at initial pH of 5 was butyric acid type fermentation.
A monthly roundup of journal articles on bioenergy and the environment compiled by Amy Elvidge.
Regional Allocation of Biomass to U.S. Energy Demands under a Portfolio of Policy Scenarios
Mullins K, et al. | Environmental Science and Technology, March 4 (Vol. 48, Issue 5, p. 2517-3094)
A spatially explicit, best-use framework to optimally allocate cellulosic biomass feedstocks to energy demands in transportation, electricity, and residential heating sectors, while minimizing total system costs and tracking GHG emissions. Comparing biomass usage across 3 climate policy scenarios shows that biomass used for space heating is a low cost emissions reduction option, while biomass for liquid fuel or electricity is less so. Study makes strong case for national and regional coordination in policy design and compliance pathways.
Tradeoffs and Synergies between Biofuel Production and Large Solar Infrastructure in Deserts
Ravi, Lobell and Field | Environmental Science and Technology, March 4 (Volume 48, Issue 5, p. 2517-3094)
Water use and GHG emissions associated with solar installations in North American deserts compared to agave-based biofuel production (a widely promoted potential energy source from arid systems). Life-cycle analyses show that energy outputs and GHG offsets from solar PV systems are much larger than agave; however, water inputs for cleaning solar panels and dust suspension are similar to those for agave growth, suggesting integrating the two systems to maximize land and water use efficiency to produce electricity and liquid fuel.
Siting Algae Cultivation Facilities for Biofuel Production in the United States: Trade-Offs between Growth Rate, Site Constructability, Water Availability, and Infrastructure
Venteris, et al. | Environmental Science and Technology, March 18 (Vol. 48, Issue 6, p. 3095-3600)
Use of a spatiotemporal Biomass Assessment tool (BAT) to select promising locations based on open pond cultivation of algae. Strains demonstrated maximum productivity along Gulf of Mexico coast, with highest values on the Florida peninsula; however, sites meeting selection criteria were located along southern coast of Texas or Louisiana and southern Arkansas. Results were driven by lack of oil pipeline access in Florida and elevated groundwater salinity in southern Texas.
Effects of compositional changes of AFEX-treated and H-AFEX-treated corn stover on enzymatic digestibility
Zhao, et al. | Bioresource Technology, March 2014 (Vol. 155)
Evaluation of the effectiveness of AFEX pretreatment for converting corn stover to fermentable sugars, both with and without pre-soaking in hydrogen peroxide. Results show that H-AFEX is a feasible pretreatment to improve the enzymatic saccharification of corn stover for bioethanol producetion.
Ethanol fermentation of energy beets by self-flocculating and non-flocculating yeasts
Zhang, Green, Ge, Savary and Xu | http://www.sciencedirect.com/science/article/pii/S0960852413019214
Bioresource Technology, March 2014 (Vol. 155)
Study shows that self-flocculating yeast is suitable for developing efficient bioprocesses to ferment industrial sugar from Energy Beets (specialized variety of sugar beets).
Comparison of gaseous and particulate matter emissions from the combustion of agricultural and forest biomasses
Brassard, et al. | Bioresource Technology, March 2014 (Vol. 155)
Comparison of gaseous and particulate matter (PM) emissions from the combustion of agricultural (switchgrass, fast-growing willow and dried solid fraction of pig manure) and forest (wood mixture of Black Spruce and Jack Pine) biomasses in a small-scale unit. Results show higher emissions of SO2, NO2 and PM for agricultural biomass compared to forest.
Correspondence: Palm oil wastewater methane emissions and bioenergy potential
Taylor, et al. | Nature – Climate Change, March 2014 (p. 151-152)
Methane emissions from palm oil wastewater effluent represent a significant rising source of atmospheric warming. The emissions are well suited for bioenergy production, and present a potential win-win for climate mitigation and renewable energy production.
Process effect of microalgal-carbon dioxide fixation and biomass production: A review
Zhao and Su | Renewable & Sustainable Energy Reviews, March 2014 (Vol. 31, p.121-132)
Microalgae-based CO2 biological fixation is a potential way to reduce CO2 emissions and achieve energy energy utilization of microalgal biomass. This review looks at the process effect, especially on the effects of photobiochemical process, microalgal species, physiochemical process and hydrodynamic process on the performance of microalgal-CO2 fixation and biomass production.
Storage dynamics and fuel quality of poplar chips
Barontini, et al. | Biomass and Bioenergy, March 2014 (Vol. 62, p. 17-25)
Investigation of possibility to use byproducts (considered waste material) in wood industry as energy source and evaluating their value as a fuel. Evaluation of storage effects on chipped biomass deriving from crown and stem wood of poplar and how they affect fuel quality and dry matter losses. Results show that chips from crown material had better storage properties and exhibited lower decay than chips from stem wood.
Generating renewable energy from palm oil biomass in Malaysia: The Feed-in Tariff policy framework
Umar, Jennings and Urmee | Biomass and Bioenergy, March 2014 (Vol. 62, p.37-46)
Examination of the sustainability of the new policy framework in steering the future expansion of small-scale biomass renewable energy businesses in Malaysia. Outline of strategies for enhancing the scheme and suggestions for future studies aimed at improving flaws in present system.
Indirect land use change (iLUC) – Help beyond the hype?
Finkbeiner | Biomass and Bioenergy, March 2014 (Vol. 62, p. 218-221)
Science and policy should focus on proactive real world mitigation of iLUC rather than reactive and theoretical iLUC factors.
Woody biomass energy potential in 2050
Lauri, et al. | Energy Policy, March 2014 (Volume 66, p. 19-31)
Woody biomass resources are large enough to cover a substantial share of the world’s primary energy consumption in 2050 but these resources have alternative uses and their accessibility is limited. This study considers the question of the price of woody biomass from the perspectives of energy wood supply curves.
Sustainable energy transitions in emerging economies: The formation of a palm oil biomass waste-to-energy niche in Malaysia 1990-2011
Hansen and Nygaard | Energy Policy, March 2014 (Volume 66, p. 666-676)
This paper identifies reluctant implementation of energy policy, rise in biomass resource prices, limited network formation and negative results at the niche level as the main factors hindering niche development of palm biomass waste into energy.
Fresh water green microalga Scenedesmus abundans: A potential feedstock for high quality biodiesel production
Mandotra, et al. | Bioresource Technology, March 2014 (Vol. 156, p. 42-47)
Various biodiesel properties such as cetane number, iodine value and saponification value were found to be in accordance with international biodiesel standards (Brazilian National Petroleum Agency and European Biodiesel standard), which makes S. abundans a potential feedstock for biodiesel production.
High quality fuel gas from biomass pyrolysis with calcium oxide
Zhao, et al. | Bioresource Technology, March 2014 (Vol. 156, p. 78-83)
Study on high quality fuel gas production from sawdust pyrolysis with CaO; results slow that this technology may be a promising route to achieve high quality fuel gas for biomass utilization.
A monthly roundup of journal articles on bioenergy and the environment by Amy Elvidge.
Worldview: China must protect high quality arable land
Xiangbin Kong | Nature News, February 6 2014 (Vol. 506, No. 7486)
China needs 120 million hectares of arable land to feed its people; officials pledge to protect this amount of land for food security. Surplus amount of land in cropland but quality and suitability have decreased (pollution, urban sprawl, mountainous). Argues to stop agricultural development in northern marginal lands.
Detection of greenhouse gas precursors from ethanol powered vehicles in Brazil
Juliana R Tavares, et al. | Biomass and Bioenergy, February 2014 (Vol. 61, p. 46-52)
Study finds the presence of ethylene in the exhaust of ethanol vehicles for the first time, as well as CO and NOx in the vehicles in the ppmV range.
The power of biomass: Experts disclose the potential for success of bioenergy technologies
Giulia Fiorese, Michaela Valentina Bosetti, Elena Verdolini | Energy Policy, February 2014 (p. 94-114)
Researchers find that without climate policy, by 2030 bioenergy will unlikely be cost-competitive and that a high contribution of biomass to the production of electricity is very unlikely.
Emergence of green business models: The case of algae biofuel for aviation
Sujith Nair, Hanna Paulose | Energy Policy, February 2014 (p. 175 – 184)
Case study on algae based biofuel system for airline industry using a framework developed for green energy business models that are global in nature. Innovation, flexibility and sustainability are the basic enablers of the framework.
Nonconformity of policy ambitions with biomass potential in regional bioenergy transition: A Dutch example
Ozcan and Arentsen | Energy Policy, February 2014 (p. 212-222)
Biomass resource potential assessment with Dutch province case study; five policy measures identified to cope with nonconformity between the province’s policy ambition and technical biomass potential.
Estimating maximum land use change potential from a regional biofuel industry
Sharp and Miller | Energy Policy, February 2014 (p. 261-269)
The potential for switchgrass is assessed for a region of the southeastern US. Switchgrass breaks even on half of marginal and pastureland at $55 MG^-1, while row crops and hay require more than $90 Mg^-1 to break even on half the land area, suggesting the extent for land use change impacts.
A consistency mapping for the effects on enzymatic hydrolysis sugar yield using two sugar yield definitions in cellulosic biofuel manufacturing
Zhang, Song, et al. | Renewable Energy, February 2014, (Vol. 62, p. 243 – 248)
Consistency mapping developed to show relationship between biomass particle size and enzymatic hydrolysis sugar yield. This mapping is applicable to investigate relationships between other factors and sugar yield.
Policy Analysis: Impact of Air Pollution Control Costs on the Cost and Spatial Arrangement of Cellulosic Biofuel Production in the U.S.
Colin W Murphy and Nathan C Parker | Environmental Science and Technology, February 18, 2014 (Vol. 48, Issue 4, p. 2157-2164)
Researchers use Geospatial Bioenergy Systems Model (GBSM) to evaluate the effect of air pollution control costs on the availability, cost, and distribution of U.S. biofuel production. Findings show that while air quality regulation may substantially affect local decisions regarding siting or technology choices, their effect on the system as a whole is small. Most biofuel facilities are expected to be sited near to feedstock supplies, which are seldom in nonattainment areas (according to Clean Air Act). The average cost per unit of produced energy is less than 1% higher in the scenarios with air quality compliance costs than in scenarios without such costs. When facility construction is prohibited in nonattainment areas, the costs increase by slightly over 1%, due to increases in the distance feedstock is transported to facilities in attainment areas.
Article: Chovau S., Degrauwe D., Van der Bruggen B. (2013). Critical analysis of techno-economic estimates for the production cost of lignocellulosic bio-ethanol. Renewable and Sustainable Energy Reviews, 26, 307-321.
First generation (G1) biofuels are produced using starchy biomass such as corn and sugarcane. Because G1 biofuel is typically produced from edible feedstocks grown on prime farmland, it can compete with food production and contribute to increased food prices. Life cycle analysis (LCA) have also shown limited greenhouse gas (GHG) savings for these G1 biofuels. Second generation (G2) biofuels, which are made from lignocellulosic biomass (including plant wastes such as corn stover), are more promising due to their potential to reduce transportation emissions while avoiding adverse impacts on food prices. These G2 biofuels are technically feasible, but the economic feasibility of commercial scale production remains uncertain. Dozens of techno-economic models have attempted to project the future cost of G2 biofuels, with varied results.
In this study, Chovau et al. compare techno-economic models of lignocellulosic ethanol production to better understand discrepancies among the models, and then calculate the minimal ethanol selling price (MESP) for cellulosic ethanol in order to compare it with production costs of G1 biofuel and gasoline. Techno-economic models attempt to evaluate the costs of all stages of the production process to assess the cost impacts of research and industrial developments and may be used to create an MESP that can be compared to other fuel options.
The lignocellulosic bio-ethanol production differs from G1 bio-ethanol production in two key respects. First, it is more difficult to break down lignocellulosic biomass and therefore the pre-treatment stage is more involved. Secondly, the pre-treatment process leaves a residual that can be used to produce heat and electricity, which provides the facility’s energy and reduces waste disposal costs.
By comparing prior techno-economic studies, Chovau et al. identify major factors that influence the production cost of lignocellulosic ethanol and discuss discrepancies in feedstock cost, pre-treatment cost, enzyme cost, ethanol yield, and capital investment.
- Feedstock – The feedstock cost is 30-40% of the total production cost and has a large impact on MESP. Chovau et al. found large variability in the assumed cost of feedstocks even when the same feedstock is used (most studies used corn stover). A supply chain analysis found the cost of corn stover to be $71.30 per dry metric ton, yet the reviewed studies used prices that ranged from $33 – $83.
- Pre-treatment – Pre-treatment costs were found to be less variable with most researchers assuming dilute sulfuric acid as the most viable option.
- Enzyme cost – The enzyme needed to produce ethanol, cellulase, is currently only used for a few high value products and costs $132 per m3 ethanol. Studies typically assumed that enzyme cost will decrease as production increases, and some studies use values below the current cost. Assumed costs varied from $13 – $174 per m3 ethanol. A general trend of higher MESP with higher enzyme cost was observed.
- Ethanol yield – The percent conversion of lignocellulosic biomass varied, which led to a wide range of assumed ethanol yield (197 to 385 liters per dry metric ton). Higher ethanol yield correlates with lower MESP.
- Capital investment – The studies reviewed by Chovau et al. assumed that fixed capital investment costs for a facility with a 2000-tonne loading capacity (dry matter) ranged from $218,600,000 – $398,000,000. A general trend of higher capital investment with higher MESP was observed. Chovau et al. postulate that if the same processing methods, plant capacity and construction costs are assumed, a similar plant would be designed and therefore capital costs would be similar.
After identifying these major discrepancies within previous techno-economic models, Chovau et al. complete a cash flow analysis, calculating a current and future MESP for lignocellulosic ethanol. To determine the current MESP, Chovau et al. assume a feedstock price of $70 per dry metric ton, pre-treatment using dilute sulfuric acid, an enzyme cost of $132 per m3 ethanol, an ethanol yield of 300 liters per dry metric ton, and fixed capital investment costs of $316,000,000. Feedstock was found to have the highest relative contribution of 38% of the MESP, while enzyme cost was 21% and pre-treatment 19%.
Projecting forward 5 years, the authors calculate future MESP using most of the same assumptions. Feedstock price are kept the same because fertilizer prices are expected to increase, while ethanol yield increases slightly to 347 liters per dry metric ton. Enzyme price has the highest uncertainty: many studies assume enzymes will fall to 25% of the current cost, however Chovau et al. chose a more conservative 50% price reduction ($66/m3 ethanol). Using these assumptions Chovau et al. calculate the current MESP to be $651/m3 ethanol ($2.46 per gallon) and a future MESP of $495/m3 ($1.87 per gallon), which is 12.5% lower than the current estimate.
Comparing the current and future MESP of lignocellulosic ethanol to the production cost of gasoline and corn ethanol, Chovau et al. propose that G2 biofuels can be economically competitive in the near future. After adjusting for the higher heating capacity of gasoline, they calculate the production cost to be $458/m3 ($1.73 per gallon) ethanol equivalent. This is much lower than the current MESP for lignocellulosic ethanol, but the near future scenario is only slightly higher. Chovau et al. write that because gasoline prices are expected to rise it is possible that the production cost of G2 ethanol could be less than gasoline. Using current research, Chovau et al. estimate the production cost of corn ethanol to be $799/m3, which is 18% higher than their calculated cost of lignocellulosic ethanol. Because gasoline and corn prices are closely correlated, they expect that corn prices will rise. Chovau et al. conclude that corn stover-based ethanol will be economically attractive over other transportation fuel options in the near future.
Unlike most G1 biofuels, lignocellulosic biofuel can be produced in ways that do not compete with food crops, which in turn contributes to lower GHG emissions on average. However, G2 biofuels have yet to reach large-scale commercial production and the economic picture is currently uncertain. By conducting a comparative study of techno-economic models of G2 ethanol production, Chovau et al. attempt to provide more clarity around the economic feasibility of G2 biofuels now and in the near future. Their analysis indicates that cellulosic fuels will quickly become increasingly competitive – in fact, the authors expect that the cost of ethanol made from corn stover will come within 10% of the cost of gasoline by 2018,
The study may prove too much, though. Chovau et al.’s calculation that the cost of corn ethanol production is currently 18% higher than the cost of cellulosic ethanol production is not supported by real-world production data, and suggests a possible flaw in their methodology. Moreover, numerous studies over the past couple of decades have predicted that cellulosic biofuels are “five years away.” Chovau et al. believe that cellulosic fuels have truly turned the corner but their conclusions do not fully dispel the substantial uncertainty that continues to surround the cellulosic industry.
Article: Menten, F., Chèze, B., Patouillard, L., & Bouvart, F. (2013). A review of LCA greenhouse gas emissions results for advanced biofuels: The use of meta-regression analysis. Renewable and Sustainable Energy Reviews, 26, 108-134.
Background: The European Union and the United States have set aggressive renewable transportation fuel targets that require significant use of advanced biofuels. These policies are leading to further research assessing the environmental impacts of first generation (G1) and advanced (G2 and G3) biofuels. The European Union’s Renewable Energy Directive requires that 10% of all transportation fuel in the EU is renewable fuel and of this half should be advanced biofuels. The US Energy Independence and Security Act 2007 (EISA) sets a target of 136 billion liters of fuel from biofuels by 2022, of which 79.3 billion liters should be advanced biofuels. (Note: US policy makers have begun to acknowledge that these targets will not be reached, mainly because the commercialization of cellulosic ethanol is happening more slowly than the drafters of EISA anticipated.) To assess the impacts of these policies on the environment, many Life Cycle Assessments (LCAs) are being completed on advanced biofuels. Significant variations currently exist in these LCA analyses, making it difficult to assess the impacts these policies will have.
Summary: The great variability in LCA GHG emissions estimates for advanced biofuels is preventing policy makers and investors from assessing which technologies are most beneficial to the environment. The purpose of the Menten et. al. study is two-fold. First, this study aims to identify factors that influence variability in LCA GHG emissions estimates for advanced biofuels. To do this they created a database of 47 LCA studies, using Meta Regression Analysis (MRA) to determine the statistical significance of different variables within the categories of technical data, methodological choices and typology of the study. Second, the study aims to create a mean global warming indicator and standard deviation for advanced biofuels to help policy makers and investors understand which types of advanced biofuels are most beneficial.
Menten et al. focus on advanced biofuels because of the controversy over the environmental benefits of first generation biofuels and the resulting political push for development of advanced biofuels. First generation biofuels (G1) are created from potential food products such as wheat, corn, sugar cane, or sugar beets. These G1 biofuels are economically viable and produced at industrial scale, but since they use food products as the feedstock they can increase food prices and use arable land necessary for food production. Advanced biofuels use non-food stock biomass or algal oil to create fuel. Cellulosic ethanol, which is created from a biochemical conversion of lignocellulosic biomass, and Biomass to liquid (BtL), created by a thermochemical conversion of lignocellulosic biomass, are both second generation (G2) biofuels. Third generation (G3) biofuels use algal oil created by microalgae as the feedstock. Variability among the LCA GHG emissions estimates for both G2 and G3 biofuels was the focus of this study.
To begin, Menten et. al. gathered studies that used LCA to determine GHG emissions estimates for advanced biofuels. They located 47 studies with a total of 593 observations, an average of 13 observations per study. They used peer reviewed studies (61% of the studies), as well as “grey” literature such as dissertations and white papers. These studies dated from 2002 to 2011, simply because no advanced biofuel LCA studies were found before that date. The number of studies found after 2007 increased sharply, possibly due to the creation of EU and US biofuel policies. Of the studies included in the database 87% focused on G2, with the rest on G3 biofuels. The 593 observations in these studies were used to create the database.
Due to the many factors influencing LCAs, the GHG emissions estimates varied significantly. LCAs evaluate environmental impact of a product through all steps of its life cycle, from extraction through to its end of life use or destruction. LCAs establish a functional unit (for example consumption of one MJ of fuel in a motor) and a reference system (usually fossil fuels) to make these environmental impact comparisons possible. There are many variables within an LCA that can lead to inconsistency of results between studies. There are two main approaches, attributional LCA (A LCA), which considers all flows physically linked to the product, or consequential LCA (C LCA), which considers impacts occurring beyond direct physical connections. Other factors include methods for addressing uncertainties, choices of system boundaries, methods to account for co-products, incorporation of direct or indirect Land Use Changes (LUC), methods for accounting for N2O impacts, and inclusion of carbon neutrality theory. The choices researchers make with regards to each of these issues can impact the final outcome of the study. The primary purpose of this study was to determine which factors had statistically significant impact on the results.
To determine which LCA factors had a significant impact on the results, a Meta Regression Analysis (MRA) was used. Meta analysis can be considered a quantitative literature review, and MRA is a statistical methodology within this discipline for comparing observations. Each report result is viewed as a scientific observation. Once it is placed in the data set it can be compared objectively against other observations. The variable of interest or the dependent variable for the MRA conducted by Menten et al. was the GHG emissions per MJ of advanced biofuels calculated using LCA approach. The factors of influence or the independent variables were broken into three categories: technical data (type of biofuel, type of feedstock, type of co-products, type of technology), methodological choices (LCA approach, system boundaries, carbon neutral, methods of N2O assessment, land use change, uncertainties, number of environmental impacts assessed) and typology of study (type of study, year of publication, location of authors). Once placed in the database, the 597 observations were compared to determine which factors influenced outcomes.
Menten et al.’s findings from this quantitative literature review are meant to complement narrative literature reviews by giving solid evidence to interpretations. Their study finds a statistically significant hierarchy between fuel types, with G3 biofuels having higher GHG emissions than G2 fuels. Among G2 fuels, cellulosic ethanol was found to have higher GHG emissions than BtL. Another significant, although surprising, finding is that North American authors reported higher GHG emissions than authors from the European Union. While the reasons for this discrepancy are unclear, Menten et al. identify inaccuracies in the statistical model or author bias as possible explanations.
Menten et al. also find that methodological choices such as type of LCA approach, co-production accounting method, and inclusion of indirect LUC influence the results, all of which are discussed as important factors in previous literature reviews. In contrast, their finding that results are influenced by the type of uncertainty analysis utilized and number of environmental indicators assessed is less intuitive and previously unreported. The authors speculate that a shadow variable could be present and more research should be done in this area. In terms of technical variables, they found statistical significance for the mass yield, type of process and type of biomass feedstock for the G2 biofuels and algal productivity and oil content for the G3 biofuels.
The second objective of this study was to use MRA to harmonize the data and report GHG emissions for each type of advanced biofuel. Harmonization is identifying and quantifying factors that influence GHG emissions in order to be conclusive in regards to the environmental performance of the product, in this case advanced biofuels. Harmonized data would be useful to policy makers and investors looking for more conclusive evidence to aid their decision-making. Menten et al. use the MRA to calculate Life Cycle GHG emissions for each type of biofuel, and find that G3 biofuels have the highest emissions (60 g CO2eq/MJ). Both G2 biofuels are significantly lower, with cellulosic ethanol at 19.7g CO2eq/MJ and BtL at 19.5 g CO2eq/MJ. All advanced biofuels have lower GHG emissions than fossil fuel, which the authors determine to be 83.8g CO2eq/MJ. Only G2 biofuels comply with emissions reduction thresholds set by both the EU and US for advanced biofuels.
It is not uncommon for even relatively well-designed LCAs to produce some highly anomalous results. Consequently, the ability of meta analyses such the study by Menten et al. to “smooth out” LCA outputs can be highly useful when assessing the GHG emissions associated with different biofuels and the policies that promote them. CATF has supported the development of meta analyses by Witzke et al. and Plevin et al., and will continue to look for opportunities to incorporate the results of meta analyses into the assessment and development of bioenergy policies.
Article: Hartmut Michel. The Nonsense of Biofuels. Angew. Chem. Int. Ed. 51: 2516-2518. (2012)
Background: Hartmut Michel, the director of the Max Planck Institute of Biophysics and the recipient of a Nobel Prize for his research on photosynthesis, considers whether biofuel production is an efficient use of land when compared to other energy options.
Summary: Michel shared the 1988 Nobel Prize in Chemistry for isolating the crystalline membrane proteins that some bacteria use to initiate photosynthesis. Michel and his colleagues also showed that the protein complex, called the photosynthetic reaction center, was similar in bacteria and plants; in doing so, says the Nobel Foundation, they enabled “a giant leap in the general understanding of the mechanism of plant photosynthesis,” and allowed “researchers to finally access and explore a raft of other important proteins housed in the cell’s living frontier.”
Drawing on this expertise, Michel begins his 2012 paper by describing the efficiency at which plants’ photosynthetic reaction centers convert sunlight to energy. Taking the average energy of the photons and the energy that plants store as a coenzyme called NADPH, Michel writes that “it is easy to calculate that only 11.8% of the energy of sunlight is stored in the form NADPH.” But because plants prevent photodamage by converting only portion of the available light energy, “4.5% is considered the upper limit of photosynthetic efficiency of C3 plants.” (C3 carbon fixation is the photosynthetic process used by many of the plants that thrive in temperate climates.) In reality, writes Michel, “values of only around 1% are observed, even for rapidly growing trees like poplars.”
Applying that analysis to data on the energy density of biofuels and the volume of biofuels produced per hectare, Michel writes:
[O]ne can easily calculate how much of the energy of the sunlight is stored in the biofuels. For German “biodiesel” which is based on rapeseed, it is less than 0.1%, for bioethanol less than 0.2%, and for biogas around 0.3%. However, these values even do not take into account that more than 50% of the energy stored in the biofuel had to be invested in order to obtain the biomass (for producing fertilizers and pesticides, for ploughing the fields, for transport) and the chemical conversion into the respective biofuel.
Michel’s conclusion is hardly a surprise, given the title of his paper. The production of biofuels, he writes, “constitutes an extremely inefficient land use.”
Because of the low photosynthetic efficiency and the competition of energy plants with food plants for agricultural land, we should not grow plants for biofuel production. The growth of such energy plants will undoubtedly lead to an increase in food prices, which will predominantly hit poorer people.
In Michel’s view, PV-powered electrification offers a far better method for converting light into useful energy. “[T]he combination photovoltaic cells/electric battery/electric engine uses the available land 600 times better than the combination biomass/biofuels/combustion engine,” he writes. Biofuels made from algae “could be better than land plants because of the absence of non photosynthetic cells and the continuous availability of water,” but “the existence of photoinhibition and a poor RuBisCO [the enzyme used in carbon fixation] will limit the advantages of microalgae together with the demands for growing and harvesting them.”
Michel also suggests that using available biomass for heat production or electricity generation would be “preferable over biofuel production.” Saving fossil fuel that would otherwise be used for heat and power and redirecting it to the transportation sector could help prevent tropical forests from being converted into biofuel plantations, he writes. “With respect to the carbon footprint, it would be even much better to reforest the land used to grow energy plants[.]”
CATF Analysis: While Michel’s assessment that “we should not grow plants for biofuel production” is based on an engineering-type analysis that draws on his specific area of expertise, his paper is also animated by more general concerns about biofuels’ net impact on global climate change and their effect on global food security. The points are related, of course: if energy crops could capture more of the energy made available by sunlight, the amount of energy yielded per acre of cultivation would improve, as would biofuels’ impact on climate change and food security. The point that unifies Michel’s photosynthesis analysis and other broader critiques is his conclusion that “the production of biofuels constitutes an extremely inefficient land use.”
Michel’s condemnation of biofuels echoes the criticisms leveled by other highly regarded scientists who are not otherwise directly engaged in the controversy around bioenergy. See, for example, Jesse Ausubel’s characterization of biofuels as an “ecological disaster,” quoted in an earlier post, or the 2007 study by Paul Crutzen (another Nobel laureate in chemistry) on the nitrous oxide emitted during energy crop cultivation.
Post-script: Michel expresses doubt that the photosynthetic efficiency of plants can be improved enough to make biofuels worthwhile, in part because plants have evolved photoinhibition mechanisms to defend themselves against overexposure to sunlight. But if photodamage was not a concern, could humans use photosynthesis to make fuel? Nate Lewis is tackling that challenge at Caltech, with his fascinating effort to produce cheap, mass-producible artificial leaves.
Article: Jesse H. Ausubel, et al. Peak Farmland and the Prospect for Land Sparing. Population and Development Review 38 (Supplement): 217-238 (2012)
Background: Even as the world grows more populous and more affluent, other countervailing trends like dematerialization and the intensification of land use “encourage a rational hope that humanity’s pressure will not overwhelm Nature.” Biofuel production and other “wild cards” could slow the progress toward a peak in demand for cropland, however.
Summary: Over the next fifty years, will a larger, more affluent global population be able to grow and consume enough food? According to Jesse H. Ausubel, Iddo K. Wernick, and Paul E. Waggoner, trends that have been developing over the last half-century suggest that the answer is yes. Their optimism is tempered by several big caveats, though, and of those caveats the uncertainty around future demand for biofuels looms particularly large.
Ausubel et al. use an analytic approach they call the “ImPACT identity” to organize their examination of the effect that changes in population, affluence, diet, and agricultural performance have on the use of land for crop production. The ImPACT identity determines the amount of cropland used [Im] by multiplying assumptions about future population [P] and affluence [A]; the number of food calories consumed per GDP [C1]; crop production per calorie [C2], which tracks the relationship between planting choices and the supply of food calories; and land required per unit of production [T], which tracks the application of yield-improving technologies:
Im = P · A · C1 · C2 · T
Reviewing a recent 50-year period (1961-2010) through the lens of the ImPACT identity, the authors find a set of “diverse, durable patterns,” including a deceleration in population growth, annual increases in GDP per capita that hover between one and two percent, and the decoupling of calorie consumption from GDP (to the extent that caloric intake in developed countries plateaus even as incomes continue to rise). Looking forward across the subsequent 50-year period (2010-2060), Ausubel et al. contend that these trends and a few others will produce a steady decline in the number of total hectares under cultivation:
Allowing for wild cards, we believe that projecting conservative values for population, affluence, consumers, and technology shows humanity peaking the use of farmland. Over the next 50 years, the prospect is that humanity is likely to release at least 146 MHa, one and a half times the size of Egypt, two and a half times that of France, or ten Iowas, and possibly multiples of this amount.
Notwithstanding the biofuels case, the trends of the past 15 years largely resemble those for the past 50 and 150. We see no evidence of exhaustion of the factors that allow the peaking of cropland and the subsequent restoration of Nature.
“Nothwithstanding the biofuels case ….” The authors identify a handful of “wild cards” that could slow or reverse the predicted trend toward land sparing. Shifting consumer preferences in diet (how much meat will increasingly affluent societies eat, and what kind of meat will it be?) and fabric (how much farmland will be used to grow cotton, linen, and hemp?) are two of the wild cards, along with the possibility of radical innovations in food production technology.
The most confounding wild card might be biofuels. But for “the sharp rise in C2” over the past 15 years, the authors contend the ImPACT analysis would look even more promising. (Recall that higher C2 values mean that a larger percentage of harvested biomass is being used for non-food purposes.) According to Ausubel et al., biofuels lie behind this trend:
Starting with a baseline of less than 4MHa in 1995, by 2007 according to the USDA and FAO, nearly 25MHa were devoted to crops used for fuel.* This number exceeds the additions to arable land globally from 1995 to 2010, suggesting that much of the addition to cropland over this period was used to grow fuels … The entry of biofuels as major crops in the mid-1990s helps explain the fourfold increase in C2 from 0.24 percent in the 1961-2010 period to 1.04 in the last 15 years of that period.
[*internal citation: Ronald Trostle. 2008. Global Agricultural Supply and Demand: Factors Contributing to the Recent Increase in Food Commodity Prices. WRS-0801. USDA Economic Research Service.]
CATF Analysis: The core assertion by Ausubel et al. – that humanity will use less and less cropland even as population and income increase – assumes a fairly dramatic reversal on biofuels. “As the shortcomings of biofuels become evident to governments and champions of the environment alike,” the authors write, “we conservatively project C2 as slowing to 0.4 percent annually, slightly less than half of the 1995-2010 level.”
Just how conservative is that projection, though? It’s clear from Ausubel et al.’s analysis that even relatively low biofuel production levels can confound the trend toward peak farmland. “Absent the 3.4 percent of arable land devoted to energy crops,” they write, “absolute declines [in hectares of cropland] would have begun during the last decade.” But biofuel production in the United States and elsewhere was still fairly modest during the 1995-2010 period when “the entry of biofuels as major crops” contributed to a “fourfold increase in C2.” The United States did not begin mandating biofuel consumption until after the Renewable Fuel Standard was enacted in 2005, and by 2010 – when the RFS required Americans to use 13 billion gallons of biofuel – the policy-driven ramp-up in consumption was just getting underway. The RFS volumetric mandate is set to double by 2018 (expanding to 26 billion gallons per year) and almost triple by 2022 (to 36 billion gallons). The scheduled increase in biofuel production in the United States and other countries makes it likely that more harvested biomass will be used for non-food purposes and, for the purposes of the ImPACT identity, that C2 will rise faster in 2010-2025 than it did in 1995-2010. Taking that trajectory into account, the authors’ projection that C2 will slow to less than half what it was in 1995-2010 looks more hopeful than conservative.
Hopeful, but also doable – given that biofuel production is largely a function of policy, not economic demand. In a December 2012 interview following the release of his paper, lead author Jesse Ausubel urged environmental organizations to tackle those policies. “Conservation groups,” he told the The New York Times, “ought to attend more to the ecological disaster called biofuels.”
Article: Mehaffey, M. et al. (2012). Midwest U.S. landscape change to 2020 driven by biofuel mandates. Ecological Application 22: 8-19.
Background: As a result of current energy policy stipulated by the Energy Independence and Security Act of 2007 (EISA), the U.S. has established the target of producing 136 billion liters (36 billion gallons) of domestic ethanol by 2022. Since the U.S. Midwest has the highest overall crop production capacity, there is concern for how such a large increase in ethanol production will affect land-use change and the composition of agriculture in the region.
Summary: Mehaffey et al. developed a possible future scenario to predict how the U.S. biofuel demand for corn will alter the Midwest landscape. They combined an economic model output with a gridded land cover data to spatially determine the land use change in the 12 most-productive states between 2001 (BY, Base Year) and 2020 (BT, Biofuel Target). They adopted the Center for Agricultural and Rural Development (CARD) econometric model, which is structured around the requirements of EISA, the 2008 Farm Bill, and economic forcing factors. This economic model produced 2001 agriculture acreages by state, and yields by region necessary to meet the ethanol demand in the year 2020. The group used these economic predictions of future acreages, crop rotation, and soil productivity to spatially allocate shifts in cropping practices in the Midwest to create their final product: a hypothetical BT 2020 land cover map, which mapped 18 classes of agriculture, 155 natural cover types, 3 urban, 1 barren, and water. In making the BT 2020 they assumed that (1) most of the initial biofuel production will be provided by planting more corn, (2) land conversion to continuous corn growing would occur first on the most fertile soils, and (3) shifting crop rotational practices on currently farmed fields would occur before farming land that is currently pasture and conservation land. The overall expected Midwest corn acreage only differed by 1% between the CARD econometric model and the BT 2020 land cover map; the two did vary in the distribution of acreage between states, with the BT 2020 land cover having greater acreage allocation in the Corn Belt states.
Mehaffey et al. predict that by 2020, several states will have watersheds that see more than a 50% increase in continuous corn planting. Iowa and Illinois will have the greatest amount of corn planting. In their scenario, they expect that a total of 40 million acres of farmland will be converted to continuous corn cultivation, with 25 million of these acres coming from land that was originally used for rotational cropping. The study highlights the fact that, already, between 2001 and 2010, the area of planted corn has increased by 13.8 million acres, which has been accompanied by an equivalent decrease in wheat, sorghum, and cotton. The group also predicts that by 2020, urbanization will result in the loss of over 7 million acres of productive farmland. The above trends have implications for high increases in fertilizer use, irrigation in areas where corn has not been traditionally grown, and loss of topsoil and organic matter from corn stover removal. Mehaffey et al. expect that the dominant problem with the Midwest’s extensive corn planting will be declining soil productivity.
CATF take-away message: The study by Mehaffey et al. contributes to an already swelling body of research that ties the expansion in corn production being driven by biofuel policies to a variety of environmental challenges (e.g., soil degradation, water pollution). Interestingly, the US Environmental Protection Agency — the agency charged with overseeing the world’s largest corn ethanol subsidy, the Renewable Fuel Standard — is behind some of the most critical analyses of corn’s impact on the environment. The lead author of this study, Megan Mehaffey, works at EPA’s Environmental Sciences Division; her study’s analysis of environmental impacts echoes findings that are detailed in EPA’s Biofuels and the Environment: First Triennial Report to Congress (2012).
Additionally, the litany of environmental challenges that Mehaffey et al. connect to the policy-driven expansion in corn production could — and should — include greenhouse gas emissions from indirect land use change. The authors note that corn displaced millions of acres of wheat, sorghum, and cotton over the previous decade. Inevitably, other farmers around the world responded to the unmet demand for displaced crops by cultivating additional farmland, resulting in the release of plant- and soil-carbon.