Biofuels

by

Barry D. Solomon

• LAST REVIEWED: 26 May 2021
• LAST MODIFIED: 26 May 2021
• DOI: 10.1093/obo/9780199830060-0212

Introduction

Biofuels were humanity’s earliest energy carrier in the form of firewood. Forest biomass energy was the dominant energy form used in the United Kingdom, United States, and other industrialized countries before the Industrial Revolution when coal took over. Traditional biomass energy resources such as firewood and straw still dominate energy consumption today in sub-Saharan Africa, Myanmar, Nepal, Pakistan, Cambodia, Guatemala, and Haiti, and it is the largest renewable energy source used worldwide. However, biomass energy sources are not always used sustainably. Since these energy sources are used for heating and cooking, they can be considered biofuel, though most 21st-century analysts more commonly think of biofuel as alternative transportation fuels such as ethanol, biodiesel, methanol, and biobutanol. These modern, “advanced” forms of biofuel are divided into “first generation”—based on food sources such as starch, sugar, animal fats, and vegetable oils (especially corn oil, soy oil, and sugarcane); “second generation”—based on non-food feedstocks such as lignocellulosic biomass (e.g., agricultural and forestry residues, short rotation woody crops, Miscanthus and switchgrass); and “third generation”—based on algae and synthetic biology. This bibliography will address the considerable scholarship and special concerns raised by ecologists over biofuel feedstock production and use. To accurately analyze the ecological effects of biofuel crop growth, baseline land use, and indirect land-use change caused by their production must be considered. It should also be noted that biofuel crops produce multiple products that are used in multiple markets, including human food, animal feed, specialty chemicals, electricity, among others. Since biofuels and ecology is a somewhat interdisciplinary and transdisciplinary subject, however, not all works listed herein have been authored by ecologists. Readers may also want to see the separate Oxford Bibliographies article “Geography of Biofuels.” The next section of this article will cover some broad overviews written by ecologists on the topic. Following that, we will list some of the major journals that have published much of the leading scholarship on biofuels and ecology. The rest of this review is divided into four main sections, though these are not mutually exclusive: Land Use and Land-Use Change, Ecosystem Services, Biodiversity, and Alternative Ecologies. In each section, relevant subthemes of importance to ecologists will be identified and discussed.

General Overviews

While no single publication covers all of the issues and concerns with biofuels that have been raised by ecologists, a few articles come close. For example, Fargione, et al. 2010 reviewed the negative ecological impacts associated with first-generation biofuels from food crops, such as increased greenhouse gas emissions, excessive water use, and adverse effects on biodiversity, though the authors also offer useful suggestions for mitigation. Most of the chapters contained in Pimentel 2012 are even more critical. This volume discusses biofuels in the context of global problems such as food shortages, malnutrition, overpopulation, resource depletion, and climate change. In contrast, Robertson, et al. 2017, and Tilman, et al. 2009 address the opportunity to ameliorate these impacts through careful, policy-driven deployment of second-generation biofuels, which are argued to be superior and more sustainable on almost all grounds. Correa, et al. 2019 extend these arguments in a comprehensive review of biofuel alternatives based on the classic sustainability dimensions at local, regional and global scales. Finally, Shurin, et al. 2013, Newby, et al. 2016, and Maeda, et al. 2018 promote third-generation biofuels from algae in particular in an aquatic environment, which have yet to prove commercially viable. These authors review the evidence for tradeoffs, challenges, and opportunities in the cultivation of algal biofuel.

• Correa, Diego F., Hawthorne L. Beyer, Joseph E. Fargione, et al. 2019. Towards the implementation of sustainable biofuel production systems. Renewable and Sustainable Energy Reviews 107: 250-263.

  DOI: 10.1016/j.rser.2019.03.005

  The environmental impacts of multiple generations of biofuel production are reviewed, with a focus on biodiversity and ecosystem services. Total cultivation areas for biofuels by country and the main feedstock are presented. The authors develop criteria and strategies that can be used to move toward truly sustainable biofuel production systems.

• Fargione, Joseph E., Richard J. Plevin, and Jason D. Hill. 2010. The ecological impact of biofuels. Annual Review of Ecology, Evolution, and Systematics 41.1: 351–377.

  DOI: 10.1146/annurev-ecolsys-102209-144720

  A review of the effects of biofuels on land, air, and water, with projections to 2020. Significant losses in biodiversity are identified from corn, soy oil, and oil palm crops and plantations in particular. The study notes that the largest impact of biofuels may come from land-use changes though market responses to shifts in crop and livestock production patterns, with several suggestions offered to improve the impacts.

• Maeda, Yoshiaki, Tomoko Yoshino, Tadashi Matsunaga, et al. 2018. Marine microalgae for production of biofuels and chemicals. Current Opinion in Biotechnology 50: 111-120.

  DOI: 10.1016/j.copbio.2017.11.018

  This piece summarizes the production of biofuels and chemical coproducts by marine microalgae, their advantages and market potential. The water footprint and land use advantages are also considered. Genome editing techniques are reviewed that can further exploit the vast potential of this third generation biofuel.

• Newby, Deborah T., Teresa J. Mathews, Ron C. Pate, et al. 2016. Assessing the potential of polyculture to accelerate algal biofuel production. Algal Research 19: 264-277.

  DOI: 10.1016/j.algal.2016.09.004

  Argues that algal polyculture cultivation can result in greater biofuel production than conventional algal monocultures. Algal assemblies with species that have complementary traits are especially promising to increase crop productivity and stability by using natural resources more efficiently through tighter niche packaging.

• Pimentel, David, ed. 2012. Global economic and environmental aspects of biofuels. Boca Raton, FL: CRC Press.

  An overview of some of the main debates regarding biofuel crops from a global perspective, including effect on food supplies, soils, water, greenhouse gas emissions, use of marginal croplands, net energy balance, and the promises and pitfalls of second and third generation feedstocks. Most of the contributors to this volume are biofuel critics, and the book is well worth a read.

• Robertson, G. Philip, Stephen K. Hamilton, Bradford L. Barham, et al. 2017. Cellulosic biofuel contributes to a sustainable energy future: Choices and outcomes. Science 356.6345: eaal2324.

  DOI: 10.1126/science.aal2324

  This piece, along with Correa, et al. 2019, and Solomon 2010 in the Ecosystem Services subsection on Supporting Services, is a good place to start for researchers interested in a comprehensive overview of the environmental sustainability issues associated with second generation biofuels. Empirical research from the Upper Midwest region of the U.S. is presented. Notes the common pitfalls that can hamper a cellulosic biofuel industry. Six research priorities are also identified.

• Shurin, Jonathan B., Rachel L. Abbott, Michael S. Deal, et al. 2013. Industrial-strength ecology: Trade-offs and opportunities in algal biofuel production. Ecology Letters 16.11.

  DOI: 10.1111/ele.12176

  Provides a fine overview of the great potential and unique challenges for producing third generation biofuels from microalgae in a large, industrial-scale aquaculture environment. Argues for a community engineering approach that manages microalgae diversity, species composition, and environmental conditions based on principles of community and ecosystem ecology.

• Tilman, David, Robert Socolow, Jonathan A. Foley, et al. 2009. Beneficial biofuels—The food, energy, and environment trilemma. Science 325.5938: 270–271.

  DOI: 10.1126/science.1177970

  Compares and contrasts the environmental effects, social impacts, and greenhouse gas emissions of first-generation versus second-generation biofuels. The latter fuels are shown to be superior and are categorized into five types of feedstocks, which can be produced in substantial quantities.