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Title: Time effects of climate change mitigation strategies for second generation biofuels and co-products with temporary carbon storage

item POURHASHEM, GHASIDEH - Drexel University
item Adler, Paul
item SPATARI, SABRINA - Drexel University

Submitted to: Journal of Cleaner Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2015
Publication Date: 10/17/2015
Citation: Pourhashem, G., Adler, P.R., Spatari, S. 2015. Time effects of climate change mitigation strategies for second generation biofuels and co-products with temporary carbon storage. Journal of Cleaner Production. 112:2642-2653. doi:10.1016/j.jclepro.2015.09.135.

Interpretive Summary: The carbon footprint of biofuels is usually estimated as an average emission over multiple years of crop production, however, these emissions can be highly variable over time and then this can lead to a poor estimate. To understand the risk of ignoring year to year variability, we used a mathematical procedure to predict the carbon footprint of biofuels that incorporate sustainable soil carbon management practices. The mathematical procedure confirmed that averaging emissions could under-estimate the carbon footprint of biofuels that do not protect soil carbon. This finding could help policy makers ensure that biofuel policies ensure steps for farmers to protect soil carbon when growing bioenergy crops through capturing this in their methods to estimate the carbon footprint.

Technical Abstract: Second generation biofuels that are under development to address the climate change impacts of transportation offer different means of reducing greenhouse gas emissions and storing or delaying carbon emissions relative to petroleum-based fuels depending upon the strategy used to synthesize the biofuel and coproducts from biomass. When agricultural residues such as corn stover or wheat straw are used as biofuel feedstock, highi soil carbon (SOC) loss may cause greenhouse gas (GHG) policy non-compliance risk. Strategies to mitigate SOC loss have been proposed, including using carbon-rich and stable land amendments to compensate for SOC loss. Whether a strategy to mitigate SOC loss is or is not employed, changes in SOC will be variable in time due to the effects of climate and soil characteristics at a growing site. Moreover, soil and climate conditions also result in variable nitrous oxide emissions. Few LCA studies have examined the impact of variable biogeochemical emissions of SOC in time using tier 3 models, and, recent studies have argued for using time-dependent rather than time-averaged radiative forcing GHG accounting approaches. We applied a time-dependent radiative forcing approach to a 100-year time-series data set for bio-ethanol life cycle GHG emissions that includes temporally variable soil biogeochemical emissions to evaluate the effects of SOC loss and conclude that early mitigation of SOC loss (or employing strategies to maintain SOC stock early within a biofuel program) supports climate change mitigation. Time-dependent approaches underscore the need for early measures of GHG curtailment to support sustainable transportation policy.