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Abstract

The Renewable Energy Directive (RED) specifies that biomass feedstocks must be sustainable and are not directly implicated with conversion of areas of high carbon stock and biodiversity. There are concerns that first generation biofuels from food-based crops will lead to negative indirect impacts on food prices and place pressure on agricultural land. The RED incentivises the use of non-food and land biomass resources by awarding them with financial credits and assigning them a zero greenhouse gas (GHG) 'cost'. This paper questions whether there are any GHG implications with straw removal from soil that should be accounted for in the life cycle assessment (LCA) of straw-based bioethanol. Emission savings of 21-58% are calculated for straw-bioethanol compared to conventional fossil fuels. The direct GHG implications of straw removal from soil are highly dependent on assumptions on the changes in soil organic carbon (SOC) experienced during straw removal, as well as replacing nutrients removed in straw. The results show that these impacts have the potential to reduce the GHG emission savings to -133%. If straw was alternatively incorporated into the soil, this could sequester between 0.58 and 2.24tonnes CO2 eq./ha, whereas substitution of fossil fuels would avoid 0.46 and 1.16tonnes CO2 eq./ha, although the full accountable benefit of straw removal is questionable as it is easily reversible. Understanding the full implications of straw removal on GHG emissions relies on further research on residue removal limitations, the impact that losses of SOC has on soil quality, as well as determining whether straw will be acquired from increased removal from soil or displacement from existing markets.
Original languageEnglish
Pages (from-to)207-215
Number of pages9
JournalApplied Energy
Volume122
Early online date1 Jun 2014
DOIs
Publication statusPublished - Jun 2014

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