Comparative evaluation of biogas valorization into electricity/heat and polyhydroxyalkanoates in waste treatment plants: Assessing the influence of local commodity prices and current biotechnological limitations

Abstract

The transformation of CH4-rich biogas into poly(hydroxyalkanoates) (PHAs) using methanotrophic bacteria has recently emerged as an attractive and worldwide applicable alternative to its current use as an energy source. The influence of the geographical location on the economic performance of combined heat and electricity production (CHP) and/or PHA production from biogas generated in waste treatment plants was evaluated in 13 representative regions of the world. In addition, the sensitivity of PHA production costs toward current biotechnological limitations and commodity prices was evaluated. The geographical analysis showed a high net present value (NPV20) variability around the world (from −7.17 to +16.27 M€). Countries with the lowest NPV20 also exhibited the lowest PHA production costs (4.1 €·kg–1 PHA), which suggested that biopolymer production represents an alternative biogas valorization pathway in regions where CHP is not economically viable. In countries with high energy prices, the use of biogas surplus from anaerobic waste treatment for PHA production enhanced the economic performance and mitigated the electric market dependence of current CHP plants. CH4 elimination capacity in bioreactors and PHA accumulation yield in bacterial cells were identified as the main biotechnological bottlenecks toward production of biopolymers competitive in price (0.2–1.7 €·kg–1 PHA) with their oil-based counterparts.