Development of a decision support tool, for the design of sewage biogas energy production/recovery plants based on experimental data

Abstract

Within the context of sustainable development, today burning sewage biogas via a flare cannot be considered a long-term solution, and although conventional cogeneration systems have been widely developed, other emerging and promising biogas end-use routes must be taken into account. For this reason, and under the R+i Alliance© framework, an excel-based decision-support tool has been developed, with the objective of providing a first approach to the design of sewage biogas energy production/recovery plants, based on previous literature research and experimental data. In this document, six different case studies using this tool have been presented, covering many of the available biogas end-use technologies (internal combustion engines, fuel cells, and gas-grid injection), as well as other variables such as plant size and biogas cleaning processes. Results have shown that internal combustion engines are a mature and deployed technology, offering a good technical and economical performance in most of the situations. On the contrary, even though fuel cells have proved to be a promising technology in terms of technical and environmental performance, investment costs are still too high, and incoming biogas valorisation projects may only consider fuel cell facilities, if investment subsidies are provided. According to the results, gas-grid injection is the midpoint option, showing good mid-term prospects and playing an important role in replacing natural gas fossil fuel with renewable biomethane. However, it is only a competitive technology at large scale environments.