Ecological evaluation of biogas from catch crops with Sustainable Process Index (SPI)

Background: Ever increasing global population requires to find additional options or increase the efficiency of food and feed supply to fulfil its dietary needs. In agricultural sector, competing situations with energy supply occur and ask for more sustainable solutions in an ethically correct manner. Methods: The Sustainable Process Index (SPI) provides a powerful method for an ecological evaluation of various processes. The comparison of partial ecological pressures allows to identify main spots of ecological pressure and provides a base for an integrated discussion about ecological improvement. Results: The results show scenarios about different options to change typical agricultural business as usual (BAU) successions. Mulching and fermentation of catch crops show high grades of reduction potential of the ecological footprint evaluated with the SPI method. A comparison to natural gas equivalent shows the direct potential to improve agricultural farming towards higher sustainability. The highest reduction of the ecological footprint can be between 56% in case of summer catch crops with wheat as a main crop and 59% in case of winter catch crops with maize as a main crop in comparison to the BAU scenario without catch crops. Conclusions: Besides energy generation, the use of catch crops instead of main crops in biogas plants has several additional ecological benefits. Leaving main crops untouched for food and feed purposes, the additional seeding of catch crops after the harvest of main crops reduces the risk of erosion and nitrate leaching as well reduce the application of mineral fertiliser. Additionally, soil humus content improves due to the application of fermentation residues to the fields. Background In many places, agricultural energy generation from biomass can result in competing situations between food, feed and energy. Cropping systems focussing on one or two main crops in order to achieve maximum yields can lead to heavy pressures on soil and environment and as a consequence endanger future food and feed supply. Current challenges in bio-resource management are to: Sustain intact arable land and food production [1] Guarantee economic feasibility Further develop farming processes so that they can bring increased economic and ecological benefits [2] Agriculture is limited in providing comparably small amounts of renewable resources to cover total energy needs. However, the local availability and the variety of options to provide food and energy resources can be better organised. Flexible solutions, in some cases decentralised systems, can contribute to both, food and energy security. Hence, agriculture finds itself in the middle of a competition to provide biomass for materials and energy purposes and food. A confrontation with this challenge is needed followed by actions to handle this concurrency situation. Alternative options must be found by all actors involved in farming processes. Fields do not have to be necessarily harnessed for the purpose of energy generation only. Agricultural areas can also be used more efficiently. Soil cultivation in a temperate climate where usually only one catch crop per year is harvested does not necessarily mean that additional biomass cultivation must be supplemented * Correspondence: [email protected] Institute of Process and Particle Engineering, Petersgasse 116-118, 8010 Graz, Austria Full list of author information is available at the end of the article Energy, Sustainability and Society © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Maier et al. Energy, Sustainability and Society (2017) 7:4 DOI 10.1186/s13705-017-0106-3