Life cycle analysis of ethanol obtained from lignocellulosic biomass: A case study of a native perennial grass from Argentina

Abstract

The increasing concentrations of greenhouse gases (GHG) are the main cause of climate change. The scientific community agree that transition to renewable energies will play a key role as a mitigation strategy for this problem. In this work, an abundant biomass resource of central-eastern zone of Argentina is evaluated: rangelands of the Submeridional Lowlands dominated by Spartina argentinensis (espartillo). Bioethanol production from this species would not change the current land use; it has been assessed using a consequential Life Cycle Analysis (LCA) methodology. LCA was carried out with comparative objectives with the fuel to replace (gasoline). The functional unit was defined as “The production and use of 1 MJ of liquid fuel”. Two impact categories were considered: (i) Climate Change and (ii) Energy Use through global warming potential and energy return on investment (EROI), respectively. Gasoline's GHG emissions were 96.9 g of CO_2eq per MJ while the bioethanol obtained from espartillo was carbon negative in most scenarios. The EROI of gasoline had a value of 0.7 while bioethanol presented a range of 0.7 to 1.8. This LCA was realized with a consequential approach except for the by-products of fermentation at the biorefinery which were not considered to be used for any activity due to not having real data of such by-product; hence the obtained figures could be improved if these by-products were able to replace another product. The energy self-sufficiency of the plant and the avoided fires in rangelands are key factors to improve the environmental performance of bioethanol.