Environmental and Sustainability Factors Associated With Next-Generation Biofuels in the U.S.: What Do We Really Know?

Abstract

In this paper, we assess what is known or anticipated about environmental and sustainability factors associated with next-generation biofuels relative to the primary conventional biofuels (i.e., corn grain-based ethanol and soybean-based diesel) in the United States during feedstock production and conversion processes. Factors considered include greenhouse (GHG) emissions, air pollutant emissions, soil health and quality, water use and water quality, wastewater and solid waste streams, and biodiversity and land-use changes. Based on our review of the available literature, we find that the production of next-generation feedstocks in the U.S. (e.g., municipal solid waste, forest residues, dedicated energy crops, microalgae) are expected to fare better than corn-grain or soybean production on most of these factors, although the magnitude of these differences may vary significantly among feedstocks. Ethanol produced using a biochemical or thermochemical conversion platform is expected to result in fewer GHG and air pollutant emissions, but to have similar or potentially greater water demands and solid waste streams than conventional ethanol biorefineries in the U.S. However, these conversion-related differences are likely to be small, particularly relative to those associated with feedstock production. Modeling performed for illustrative purposes and to allow for standardized quantitative comparisons across feedstocks and conversion technologies generally confirms the findings from the literature. Despite current expectations, significant uncertainty remains regarding how well next-generation biofuels will fare on different environmental and sustainability factors when produced on a commercial scale in the U.S. Additional research is needed in several broad areas including quantifying impacts, designing standardized metrics and approaches, and developing decision-support tools to identify and quantify environmental trade-offs and ensure sustainable biofuels production.

Genetic and biotechnological approaches for biofuel crop improvement

“…This knowledge will be used to produce the next generation of biofuel crops by increasing fatty acid content and by optimizing the hydrolysis of plant cell walls to release fermentable sugars. Introduction Biofuels are commonly defined as fuels derived from renewable biological products and are often regarded as an attractive, 'green' alternative to fossil sources of energy due to their potential contribution to lowering carbon dioxide emissions [1]. Globally, plants produce an estimated 200 billion tones of biomass per year [2] in the form of sugars, polysaccharides, oils and other biopolymers, representing an unprecedented resource for biofuel production.…”

Biobased Economy – Sustainable Use of Agricultural Resources

“…Growing grain crops probably has the greatest detrimental impact on biodiversity if these crops are managed more intensively, with increased inputs and fewer rotations (Dyer et al, 2011). Growing perennial herbaceous crops on marginal land can often reduce biodiversity loss compared to using the land for row crops such as corn (Williams et al, 2009). However, Dyer et al (2011) found that if the marginal land is natural grassland, such as much of the rangeland in Western Canada, rather than the result of land degradation, even a perennial feedstock crop (such as switchgrass) could result in the loss of extensive areas of natural habitat.…”

“…The balance between the residue removal rate and long-term soil health is a challenge (Williams et al, 2009). Soil erosion is affected by crop type and its production practices.…”

“…Consequently, bioenergy can increase eutrophication compared to fossil fuels even in highly optimized production systems (Cherubini & Jungmeier, 2010). The use of perennial biomass crops for bioenergy feedstocks can decrease contamination of water with nutrients compared to annual crops (Williams et al, 2009). Similarly, removal of crop residue can increase nutrient contamination from surface runoff (Blanco-Canqui et al, 2009).…”

A Review of Life Cycle Assessment (LCA) of Bioethanol from Lignocellulosic Biomass

“…Although several researchers have compiled LCA studies of lignocellulosic ethanol to discuss some of the key issues: energy pathways, system boundaries, functional units, allocation methods, utilization of coproducts etc. 14,23,24,42,63,77,81,88,111,132 , some recent advances in LCAs of lignocellulosic bioethanol remain to be reported. Therefore, this study aims to compile recent LCA studies of lignocellulosic bioethanol, and discuss the energetic, environment and socioeconomic aspects of the bioethanol industry.…”