Development of plant concepts for ethanol production from wheat and wheat straw

Fuel ethanol produced from sugar and starch is to be complemented and eventually even replaced by ethanol produced from lignocellulose, in order to mitigate possible competition with the food sector. A first step towards this goal may be a combination of both feedstocks in one plant. This is topic of the presented study, whether synergies in lowering the production costs and greenhouse gas (GHG) emissions can be reached through combined processing was topic of the presented study. A greenfield straw ethanol plant, a wheat ethanol plant and an integrated plant, processing both wheat grain and straw were developed and compared regarding the resulting GHG emissions and production costs. Despite showing the best results with regard to greenhouse gas emissions, greenfield straw ethanol production is related to relatively high production costs. The wheat based ethanol plant again is associated with higher GHG emissions, but low production costs. By combining straw and wheat processing, resulting production costs of EUR651/m(3) ethanol are at a level close to market prices, but the same mitigation potential as separate straw based ethanol cannot be reached. The low level of 16.1 g CO2-eq/MJ of straw based ethanol results mainly from the use of the agricultural residue as feedstock and the use of the internally produced lignin to ensure the steam supply. In the assessment of the production costs, feedstock costs are one of the most relevant parameters. Since straw prices are not available from market statistics, an assessment of Germany's sustainable straw potential in a high spatial resolution has served to calculate straw supply costs. Depending on the exact location of the plant, a range of EUR50/t to EUR90/t (fresh matter) was found to be the cost for straw provision.