Environmental impacts of ethanol depend on the biomass feedstocks used
Bio-based products are often perceived as sustainable because they are made from renewable biomass. However, a genuine environmental assessment requires a life cycle perspective to reveal the full picture of benefits and trade-offs. This study presents a comprehensive life cycle assessment (LCA) of bio-based ethanol, one of the world’s most important bio-based commodities, produced from different feedstocks and geographical origins. Our goal is to identify the main environmental drivers in ethanol production — from farming practices to processing — and to compare its performance against fossil-based ethanol.
Methods: Comparing Six Bio-Based Ethanol Feedstocks
We assessed ethanol production from cradle to gate, including end-of-life emissions to enable a full comparison of greenhouse gas (GHG) emissions. These end-of-life emissions account for the degradation of ethanol released to air from household and personal care products.
The functional unit is 1 kg of ethanol, produced from:
- Maize grain and maize stover (USA)
- Sugarcane (North-East and Centre-South Brazil)
- Sugar beet and wheat (France)
As a fossil reference, we used ethanol produced from fossil ethylene in Western Europe. Six impact categories from the ReCiPe LCA method were evaluated, together with seven novel impact categories covering biodiversity and ecosystem services (BES).
Results: Carbon Footprint of Bio-Based vs. Fossil-Based Ethanol
GHG emissions of bio-based ethanol range from 0.7 to 1.5 kg CO₂ eq per kg, rising to 1.3–2.0 kg CO₂ eq per kg when end-of-life emissions are included. By comparison, fossil-based ethanol emits 1.3 kg CO₂ eq per kg cradle-to-gate, and 3.7 kg CO₂ eq per kg including end-of-life.
Maize stover (USA) and sugar beet (France) deliver the lowest carbon footprint. However, trade-offs emerge in other impact categories, and the BES indicators clearly favour fossil-based ethanol.
Our sensitivity analyses show how methodological choices — allocation rules, land use change accounting, and land use biomes — as well as scenario choices such as sugarcane harvest method and maize drying, strongly affect the environmental results. The uncertainty assessment further reveals that the results for the bio-based alternatives often overlap, meaning they are rarely statistically distinguishable from one another.
Conclusions: Is Bio-Based Ethanol More Sustainable Than Fossil Ethanol?
Bio-based ethanol is the better option in terms of carbon footprint, but once other impacts — especially those related to land use — are considered, fossil-based ethanol performs better. A key unresolved methodological issue is the quantification of land use change (LUC), which strongly influences the results, particularly GHG emissions. Harmonizing LUC accounting across studies is essential for reliable sustainability comparisons of bio-based fuels and chemicals
Publications
Muñoz I., Flury K., Jungbluth N., Rigarlsford R., Milà i Canals L. and King H. (2013) Life Cycle Assessment of bio-based ethanol produced from different agricultural feedstocks. In: Int J LCA, Online First, pp., DOI 10.1007/s11367-013-0613-1.
Flury K. and Jungbluth N. (2012) Greenhouse Gas Emissions and Water Footprint of Ethanol from Maize, Sugarcane, Wheat and Sugar Beet. ESU-services, Zürich. (Data-on-Demand Report)
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