Biofuel’s carbon balance: doubts, certainties and implications

Abstract

Liquid fuels will remain valued energy carriers well into any upcoming period when CO 2 reductions are sought. Biofuels are the presumed replacement for the petroleum-based transportation fuels that dominate liquid fuel use. Lifecycle analysis embeds a closed-loop model of biofuel-related carbon flows, making net CO 2 uptake an assumption to be refuted. However, evaluating net CO 2 uptake through dynamic industrial and agriforestry supply chains at real-world commercial scales is extremely difficult. All such estimates carry a great deal of doubt and cannot be verified empirically. A different perspective follows by anchoring analysis in the certainty that end-use CO 2 emissions from biofuels are essentially the same as those of the petroleum fuels they replace. A first-order model of the globally coupled bio-and fossil-fuel system reveals conditions for biofuel use to provide an atmospheric benefit. No benefit occurs in the energy sectors where biofuels are used, but rather must be found elsewhere in locations of carbon absorption or retention. The implication is that climate mitigation efforts should focus on such locations and include any mechanisms through which net uptake (an enhanced sink or verifiable offset) can be achieved by biological, chemical, geological or other means. Although biofuels can play a mitigation role when certain conditions are met, deemphasizing biofuel production in favor of terrestrial carbon management may offer more immediate and effective ways to counterbalance the CO 2 emitted when using carbon-based liquid fuels of any origin. Climate policies for transportation fuels should be reconsidered accordingly.

Why landscape ecologists should contribute to life cycle sustainability approaches

“…Minimal emissions from other stages likely reflect the originally-intended potential of palm oil as a sustainable energy source when cultivated in appropriate environments. Incorporation of emissions from land use change into sustainability assessments for biofuels is clearly needed (Cherubini and Strømman 2011;DeCicco 2013) as emissions from other stages were low by comparison. However, of the few Indonesian palm oil LCA studies that address land cover change, various land use assumptions over the drivers and proportions of primary forest loss have led to widely divergent conclusions (Schmidt 2007;Harsono et al 2012).…”

“…Questions surrounding the sustainability of landscape change are numerous and varied (West et al 2010;DeCicco 2013); however the loss of forest, especially tropical primary forests, is of great concern worldwide. Forest loss exceeded 2,000 km 2 /year between 2000 and 2012 (Hansen et al 2013).…”

Implications of sustainability for the United States light-duty transportation sector

“…53 However, there have been some questions posed in the literature as to whether or not this analysis correctly accounts for the carbon fi xing. 54 For a given CI of biofuels (CI b ), the fraction of biofuel ( f b ) needed to meet a CI target (CI T ) is given by:…”

Author’s response to commentary on “Carbon balance effects of U.S. biofuel production and use”

“…Our decision to eschew LCA and its conventions is deliberate and follows from the recent literature that highlights the uncertainties, limitations, and risks of applying the method to biofuels. Key papers include: McCarl (2008); Cherubini et al (2009);Johnson (2009);Melillo et al (2009);DeCicco (2012DeCicco ( , 2013DeCicco ( , 2015; Delucchi (2010Delucchi ( , 2011Delucchi ( , 2013; Mullins et al (2011);Plevin et al (2014Plevin et al ( , 2017and McManus and Taylor (2015). The error due to the bioenergy carbon neutrality assumption was highlighted by Searchinger et al (2009) andHaberl et al (2012).…”

“…LCA's major limitation is that it is a static method of analysis that by construction treats biogenic carbon flows as if they are in balance over the defined Blifecycle.^However, that is an incorrect depiction of the situation because biofuel production engages the dynamic flows of the terrestrial carbon cycle (DeCicco 2013;Haberl 2013). Correct analysis must capture the system dynamics and reflect both the time-varying nature of key flows and the initial conditions of the system.…”