Renewable Natural Gas Production from Woody Biomass via Gasification and Fluidized-Bed Methanation

Converting forest waste to renewable natural gas for pipeline injection has the potential to reduce the carbon footprint of the natural gas system and provide a beneficial use for abundant forest waste in California. However, there are significant cost and technological barriers to enabling the conversion pathway. One barrier is the cleanup and methanation processes to convert gas derived from woody biomass into pipeline-quality renewable natural gas since there are no successfully demonstrated methods for performing this difficult chemical conversion. Through laboratory and pilot-scale testing, this study developed novel gas cleanup and methanation methods to convert woody biomass to renewable natural gas. In particular, this study focused on fluidized bed methanation, a highly efficient form of methanation that can reduce the operating costs of the methanation process. The research team tested two different feedstocks, seven adsorbents, and two methanation catalysts. Researchers developed and tested new methods to measure trace contaminants in the product gas, new gas cleanup methods, and production of renewable natural gas from fluidized bed methanation. Finally, the researchers performed technical and economic analysis for a full-scale, 60 megawatt renewable natural gas facility. Researchers found the fluidized bed methanation technology could deliver a levelized cost of renewable natural gas of $26 per million British thermal units a fully commercialized, full-scale scenario. Further improvements, outlined in the recommendations section, could further reduce this cost. Overall, this study found fluidized bed methanation to be a viable technology to produce renewable natural gas from woody biomass.