As incentivization increases in the waste-to-energy sector, the limitations with cellulosic ethanol or anaerobic digestion biogas as a conversion pathway for carbonaceous waste streams is becoming more apparent. There is a growing need to expand the technology portfolio beyond these technologies due to limitations in feedstock selectivity, volume reduction, and conversion speed with enzymatic-based processes. An often-overlooked technology in the waste-to-energy sector is a thermochemical pathway, commonly known as pyrolysis/gasification which overcomes these issues. This presentation will describe the advantages of pyrolysis/gasification, its current commercial limitations, and the opportunity that pyrolysis/gasification can provide in the waste management sector.
Fundamentally, pyrolysis/gasification takes a feedstock, and using heat, converts the feedstock into char + volatiles. The feedstock limitations of enzymatic hydrolysis are not an issue for pyrolysis/gasification. Carbonaceous waste biomass consists of 3 major structural components: cellulose, hemicellulose, and lignin. Lignin constitutes a large fraction of biomass (15%-30%). Although cellulose and hemicellulose are quite easily broken down for energy recovery in a multitude of ways, the recalcitrant nature of lignin requires significant pretreatment steps which would render the capital expenditures for an enzymatic process similar to pyrolysis/gasification. Pyrolysis/gasification can be much more robust with its feedstock, processing various other input materials. These feedstocks range from pharmaceuticals, PFAS laden organic wastes, industrial pulp/paper, municipal waste solids even extending to various end-of-life products like plastics, photovoltaic solar panels, and lithium ion batteries, an ever growing waste stream of concern especially with market incentivization for electrification.
The volatile fraction, also known as syngas, has a large number of opportunities for high value product generation. The current incentivization with sustainable aviation fuel (SAF) from California’s Low Carbon Fuel Credit (LCFS) program and U.S. EPA Renewable Fuels Standard RINS Credits has made gas-to-liquid (GTL) technologies economically feasible despite intensive capital costs of catalytic conversion technologies for syngas processing. The discussion will expand on the limitations in syngas clean up, gas phase selectivity, and existing syngas conversion technologies lack of operational longevity.
.jpg)
