Distributed Biomass Waste-to-Energy Technology for a Sustainable Future
The majority of electricity in the U.S. is produced at large, centralized coal, gas or nuclear power plants. Only Hawaii still maintains significant oil-fired power generation. For the past several years, however, federal and state rules, incentives, and energy portfolio standards have led to significant new power generation from sustainable sources of distributed energy, such as locally available biomass.
Distributed biomass power generation systems can range in size from less than 1 MW to 50 MW, depending on the amount of opportunistic, residual, or waste biomass fuel available. Oftentimes, landfill restrictions or higher costs stimulate interest in smaller biomass power systems. These opportunity biomass fuels and feedstocks can include forestry byproducts, used railroad ties, high-moisture animal waste, or liquid effluents generated in ethanol distilleries and food-processing plants. In utilizing these waste materials, not only can power be generated sustainably, but the amount of material that needs treatment or processing prior to landfilling is reduced, thereby reducing costs for producers.
Gasification is one option for well-contained conversion of biomass to power, using the resulting syngas in boilers or an internal combustion engine generator. The Energy & Environmental Research Center’s experience in the technology goes back six decades in the coal industry and at least a decade with respect to distributed-scale biomass gasification. From a research standpoint, gasification is a good option for biomass-to-energy and value-added byproduct recovery. Through integration of a biomass-to-energy recovery technology with manufacturing or waste sources, both economic and environmental sustainability can be achieved.
An examination of commercially available distributed-scale power systems, however, reveals a lack of turnkey options. Some of the key technical challenges responsible for the limited development include: the difficulties in maintaining consistent gasifier performance with variations in the physical and chemical composition, as well as moisture content of a biomass feedstock; the resultant presence of contaminants in the syngas requiring extensive syngas cleaning; and the lack of available efficient and reliable syngas-to-energy technologies, such as engine generators, microgas turbines, or fuel cells.
In ongoing efforts to develop a reliable distributed waste biomass-to-energy technology, the EERC has partnered with Cummins Inc., an industry leader in internal combustion engine generator technology and manufacturing. The partnership has three goals: develop an integrated gasifier and electrical generator technology with improved syngas-to-power efficiency; design a system that is tolerant of varying syngas compositions; and design a system with exhaust emissions that are well within environmental limits and has lower maintenance costs. Engine manufacturers provide warranties on traditional fuels such as diesel or natural gas, but varied compositions of biomass gasification syngas are currently difficult to certify for warranties.
The EERC and Cummins plan to couple expertise in gasification processes and engine technology to find solutions suitable for commercial industry. A follow-up Energy Review column will highlight achievements toward producing a reliable biomass fuel distributed power plant.
Author: Nikhil M. Patel
Research Scientist, EERC