|Spatari, Sabrina - Drexel University|
|D'ottone, Federico - Instituto Nacional De Investigação Agrária E Veterinária|
|Vazquez, Daniel - Instituto Nacional De Investigação Agrária E Veterinária|
|Peterson, Lisa - Drexel University|
|Del Grosso, Stephen - Steve|
|Baethgen, Walter E - Columbia University - New York|
|Parton, William J - Colorado State University|
Submitted to: Global Change Biology Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2017
Publication Date: 6/1/2017
Citation: Adler, P.R., Spatari, S., D'Ottone, F., Vazquez, D., Peterson, L., Del Grosso, S.J., Baethgen, W., Parton, W. 2017. Legacy effects of individual crops affect N2O emissions accounting within crop rotations. Global Change Biology Bioenergy.10:123-136.doi: 10.1111/gcbb.12462.
DOI: https://doi.org/10.1111/gcbb.12462 Interpretive Summary: Both grain and sweet sorghum are feedstocks for new ethanol production facilities in Uruguay and are seen as important to their strategy for independence from foreign oil and mitigation of climate change. However, it isn’t known how much it can reduce greenhouse gas emissions compared with petroleum or what the cost is of this mitigation relative to other renewable energy alternatives. We conducted a life cycle assessment and cost analysis and found that both grain and sweet sorghum were able to reduce greenhouse gas emission by greater than 50%, and grain sorghum could do this at a cost savings. These results demonstrate the potential of both grain and sweet sorghum to reduce GHG emissions to meet both climate mitigation and energy security goals of Uruguay.
Technical Abstract: Uruguay is pursuing renewable energy production pathways using feedstocks from its agricultural sector to supply transportation fuels, among them ethanol produced from commercial technologies that use sweet and grain sorghum. We investigate the life cycle environmental and cost performance of these two major agricultural crops used to produce ethanol that have begun commercial production and are poised to grow to meet national energy targets for replacing gasoline. Using a life cycle assessment (LCA) framework that contrasts consequential and attributional system boundaries, results show that ethanol fuels significantly reduce greenhouse gas (GHG) emissions relative to gasoline; however, depending upon the boundary applied, the absolute value of the global warming intensity (GWI) for the two crop-to-ethanol pathways differ significantly and underscore three critical boundary conditions for biofuels; 1) legacy effects from specific crops in rotations can have significant effects on N2O emissions which may not be captured in IPCC Tier 1 N2O estimates in contrast to Tier 3 within an attributional LCA framework; 2) both grain and sweet sorghum have a high probability of meeting advanced fuel GWI targets for renewable transportation fuels in the US market, and 3) attributional and consequential LCA frameworks lead to significantly different soil GHG emissions in the multi-crop rotations in Uruguay. Unless accompanied by a carbon tax or subsidy, our estimates show that sweet sorghum ethanol production leads to slightly positive GHG abatement costs; grain sorghum-to-ethanol pathways are estimated to lead to some cost savings with the abatement of GHGs relative to gasoline using consequential LCA framework.