Postponing of the intracellular disintegration step improves efficiency of phytomass processing

In the last two decades, subsidised purchase prices for electricity produced from biogas generated from purpose-grown crops has seen the construction of hundreds of biogas plants across Central Europe in response. The resulting intensive cultivation of monocultures has had a negative impact on the environment and has been a waste of taxpayers' money. In addition, this policy has made the processing of other biowaste uncompetitive, resulting in further public funds being spent on their disposal in landfill sites, thereby raising more environmental concerns. Given that the conditions under which the subsidies are provided cannot be changed retroactively, proposals are being sought to increase the efficiency of biogas generation in order to reduce the volume of purpose-grown feedstock required, thereby mitigating the negative impacts on the environment and public funds alike. A new proposal, as outlined in this article, sees the incorporation of a steam explosion device at a later stage of the fermentation process, rather than at the beginning (pre-treatment of feedstock) as conventional wisdom would have it. This proposed process change was applied on a commercial scale and techno-economically assessed. The process change generated significant savings in feedstock (29% reduction due to the intensification of the process parameters ceasing to be limited by the formation of inhibitors) whilst maintaining the same level of electricity production. As a result, the payback period was reduced by 9%, which is a good prerequisite for commercial expansion. However, this comes at a cost, namely in the form of a doubling of water demands. Intensive work is now being conducted to determine how this issue can be overcome. (C) 2018 Elsevier Ltd. All rights reserved.