Assessing the environmental sustainability of glucose from wheat as a fermentation feedstock

In recent years, the need to substitute fossil fuels with renewable biomass has been a key driver in the development of the biorefinery concept. One of the possible routes towards the development of bioproducts under this scheme is through a sugar intermediate. Sugars, such as glucose, can be produced through starch crops, for instance wheat. While there are many environmental assessment studies that consider sugar as a platform for biofuel production, the main focus is on the end product of the value chain (typically bioethanol), but not on sugars as the basic feedstock. Taking the bottom-up perspective as a roadmap, the assessment of technological, economic and environmental barriers in the biorefinery scheme must take into account the sustainability of sugar production with the aim of improving its current framework or finding novel technologies. This study investigates the environmental sustainability of wheat cultivation and grain processing in different European countries by applying the life cycle assessment (LCA) methodology with a cradle to gate approach. Moreover, 1 kg of glucose at the factory gate has been considered as a functional unit for reporting the environmental results. The chosen impact categories are climate change (CC), particular matter (PM), human toxicity (HT), freshwater eutrophication (FE), terrestrial eutrophication (TE), acidification (AC) and abiotic depletion (AD). Mass and economic allocations are evaluated as the processing of grain wheat generates different valuable by-products, namely wheat bran, gluten meal and gluten feed. The results show that agricultural activities play an important role in the environmental impacts, predominantly due to the production of agrochemicals and field emissions derived from fertilisation. In addition, the choice of allocation has a greater environmental influence (both positive or negative) on the by-products than the main product under investigation.