Impacts of biogas plant performance factors on total substrate costs

Substrate costs in biogas production can be reduced by up to 30% by adjusting logistic capacity to chopper performance. The aim of this article is to analyze the impacts of biogas plant performance factors on total substrate costs for two common biogas plant sizes in Austria. A nonlinear optimization model is built to analyze the impact of alternative substrates, machinery chains, and field distances on total substrate costs of a 250 kW(el) and a 500 kW(el) biogas plant. The model minimizes total substrate costs subject to land which is available in different distant land circles around the plant. It optimizes machinery chains from planting to silo storage and considers nitrogen balances at field scales. Scenarios are constructed to investigate the impact of crop rotational constraints and alternative land availabilities on total substrate costs. Model results indicate that maize silage provides the least substrate costs. However, avoiding monoculture maize cropping can increase these costs by up to 29%. We also show that least biogas productions costs are not covered by current electricity prices in Austria. (C) 2011 Elsevier Ltd. All rights reserved.