Biomass Production a Stronger Driver of Cellulosic Ethanol Yield than Biomass Quality

1 Corn grain produced on fertile cropland is used for both human and livestock consumption. However, co-production of distiller’s grains notwithstanding, the use of corn grain and fertile cropland to produce fuel remains controversial, driving interest in cellulosic fuels generated from vegetative (non-grain) plant biomass (Biello, 2011; Wetzstein and Wetzstein, 2011; Bonin and Lal, 2012). Bioethanol is important strategically if we are to meet the goals of the U.S. Energy Independence and Security Act of 2007 (Skolrud et al., 2016). While the price of nonrenewable fuel sources are currently low, it is likely that countries will continue to pursue greater energy independence, and reductions in greenhouse gas emissions, by adopting long-term strategies that include cellulosic fuels (Reboredo et al., 2016). Perennial crops in particular, some of which have historically been used for livestock feed, have the potential to promote more sustainable social, environmental, and economic outcomes by reducing dependence on fossil fuels and conserving soils, nutrients, and biodiversity (Gelfand et al., 2013; Landis et al., 2017). Another advantage is these outcomes can be achieved while avoiding both real and perceived competition with food security (Tilman et al., 2006; Dale et al., 2014). Nevertheless, because of its ubiquity on the landscape, agronomic efficiencies, and mature markets (James et al., 2010; Barham et al., 2016), corn stover is currently the main feedstock used for cellulosic ethanol in both the United States and the European Union (Janssen et al., 2013). The importance of corn stover to the emerging cellulosic ethanol industry makes it an important benchmark crop for comparison against biofuel produced from other candidate biomass crops. However, comparisons are complicated because cropping system inputs (e.g., pesticides and fertilizer) typically are greater for corn than other candidate bioenergy crops, and stover comprises just half of the aboveground corn biomass, whereas all harvestable biomass is collected and used from perennial Biomass Production a Stronger Driver of Cellulosic Ethanol Yield than Biomass Quality