High Flux Membranes to Upgrade Biogas from Anaerobic Digesters

Despite the general decrease in total methane emissions since 1990, methane emissions from manure management increased by 33% from 1.5 Tg in 1990 to 2.0 Tg in 2006. The majority of this increase was due to general changes in methods of manure management. It is reasonable to expect that methane emissions from manure management will increase if there is no effective way to collect and utilize this gas. Anaerobic digestion with biogas utilization is starting to be adopted as a means to reduce methane emissions, as well as to reduce odor and protect water quality. Biogas produced in an anaerobic digester contains methane (60-70%), carbon dioxide (30-40%), water (1-2%), and various toxic gases, such as hydrogen sulfide. This biogas needs to be upgraded. The utilization of biogas methane on or near the recovery site can help meet rural demands for heat and electricity, and provides product credits that help offset the costs associated with more environmentally responsible waste management. A key objective of this project is to reduce biogas decontamination cost to the lowest value possible to make broad implementation of the technology feasible. In the Phase I project, the feasibility of using a membrane-based process for biogas decontamination will be determined. We have discovered a new family of polymeric membranes with exceptionally high carbon dioxide and water permeance, and moderate carbon dioxide/ methane selectivity. These membranes will be further optimized for better separation performance and reproducibility. Bench-scale spiral wound modules will be fabricated and tested to provide enough data for preliminary technical and economic analysis. If the Phase I project demonstrates feasibility at the bench scale, a small demonstration system will be constructed in the Phase II project. This unit will be operated in the laboratory and at field sites. Also, a commercialization plan will be developed to bring this membrane technology to the market.