Site-specific economic and ecological analysis of enhanced production, upgrade and feed-in of biomethane from organic wastes J. Lindorfer and M. M. Schwarz ABSTRACT The present study analyses the cost structure and ecological performance of biomethane production and feed-in from organic wastes and manure in a site-specific approach for Upper Austria. The theoretically available quantities of biowaste and manure can feed representative biogas plant capacities resulting in relatively high biomethane full costs in the natural gas grid of at least 9.0 €-cents/kWh, which shows strong economies of scale when feed-in flows of methane from 30 to 120 Nm 3 /h are considered. From the ecological point of view small plant capacities are to be preferred since the environmental effect, i.e. the global warming potential (up to –22% of CO 2eq ), is lower in comparison to higher capacities as a consequence of reduced transport in the evaluated scenarios. To enforce the combined energetic use of the biowaste fraction, co-operation between compost facility, gas grid and biogas plant operators is necessary to use existing infrastructure, logistics and knowledge to promote the production, upgrade and feed-in of biomethane from biowastes at attractive locations in Upper Austria and in the whole of Europe. J. Lindorfer (corresponding author) M. M. Schwarz Energy Institute at the Johannes Kepler University Linz, Altenberger Strasse 69, 4040 Linz, Austria E-mail: lindorfer@energieinstitut-linz.at Key words | biomethane, economic analysis, feed-in, organic waste INTRODUCTION In addition to the disposal of residual waste, the treatment of organic household and garden waste is a substantial part of the waste management structure in Austria. The mobilisation of improvements in the field of eco-efficiency in dealing with bio-waste is therefore an important component of sustainable development in this field. In the present study of the Upper Austrian province, 48% of the households are provided with a pick-up system for biowastes whereby approx. 82 kg per capita per year are collected. A share of 5% of the households are connected to a bring system of composting facilities or col- lection points, which results in an average amount of 16 kg per capita per year. Consequently around 47% of the households are not connected to a collection system for biowastes. The declared target of the regional authorities is to increase the share of households connected to a collection system up to 60%. The combined use of organic waste in composting, biogas and biomass heating plants is the future goal. (Amt der oö. Landesregierung ). The aim of the paper is to ana- lyse key economic and ecological determinants for the viability of alternative organic waste management concepts in a regional context. The present study analyses the theoretically available quantities of biogenic waste from households and companies as well as agricultural manure for more than 30 geo- graphical locations and regions with a diameter of around 10 km in the province of Upper Austria. The site-specific impacts of the utilisation of wastes in biogas plants of different capacity and the subsequent upgrading and feed-in of bio- methane into the existing natural gas grid is evaluated in an economic and ecological comparison with respect to disposal of solid fermentation residues to nearby compost facilities. Liquid digestate is considered as fertiliser in agricultural appli- cations. In digestate management, dewatering without drying was assumed to enhance transportation efficiency and not to deteriorate energy performance as no surplus heat is available in the proposed process configuration. As a consequence, regional biomethane production costs are calculated for attractive disposal sites. On the one hand, the combined economic and ecological assess- ment is of systemic importance as growing plant capacities result in higher transport distances for substrate provision and induced emissions, and, on the other hand, growing plant capacities lead to stronger economies of scale. 682 © IWA Publishing 2013 Water Science & Technology | 67.3 | 2013 doi: 10.2166/wst.2012.617 Downloaded from https://iwaponline.com/wst/article-pdf/67/3/682/441553/682.pdf by guest on 24 November 2018