Energy and greenhouse gas assessment of European glucose production from corn – a multiple allocation approach for a key ingredient of the bio-based economy

Bio-based products are considered to be a sustainable alternative to conventional fossil fuel-based materials. This paper studies the production of glucose from corn starch, an important feedstock for a wide range of bio-based products (e.g. ethanol, bio-based monomers), in a European corn wet mill (CWM). Following the Life Cycle Assessment (LCA) principles, non-renewable energy use (NREU) and greenhouse gas (GHG) emissions are assessed for the system cradle-to-factory gate. The allocation problem that the analysis is faced with is addressed by applying seven different approaches: namely sub-division (two variants), partitioning based on physical causalities and on economic relationships and the principles of system expansion (three variants). Depending on the approach, the NREU for glucose production ranges from 6.8 to 9.3 MJ/kg glucose dry solids (ds) and the GHG emissions from 0.7 to 1.1 kg CO2 eq./kg glucose ds. The results for NREU per tonne of glucose are robust while for GHG, large deviation from the average is found for system expansion and for the approach main process. The influence of each calculation should be kept in mind when assessing bio-based products from glucose produced in a CWM. The results provide a good basis for future analyses of bio-based products, as they are also similar to values published by other authors for the US, bearing in mind the different impacts of corn production in the two regions.