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Currently, the majority of power generation in the United States is produced at large centralized coal-, gas-, or nuclear-fueled power plants. Only Hawaii still maintains significant oil-fired power generation. However, for the past several years, federal and state rules, incentives, and energy portfolio standards have led to significant new power generation from sustainable sources of energy that are distributed in their nature, such as locally available biomass.

Distributed biomass power generation systems can range in size from less than 1 to 50 MW, with the size determined by the amount of opportunistic, residual, or “waste” biomass fuel that is available. Oftentimes, landfill restrictions or higher costs stimulate interest in smaller biomass power systems. These opportunity biomass fuels and feedstocks can comprise forestry by-products, 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 it effects a significant reduction in material that requires either treatment or processing prior to landfilling, thereby reducing costs for producers.

One option for well-contained conversion of biomass to energy is to use gasification. The Energy & Environmental Research Center’s (EERC’s) experience in gasification 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 by-product recovery. With the innovative integration of a biomass-to-energy recovery technology with manufacturing or waste sources, both economic and environmental sustainability can be achieved.

A small biomass gasifier can produce clean combustible gases or syngas that can be utilized on-site in an existing boiler by offsetting natural gas use or can be utilized in a small internal combustion engine generator; both approaches produce renewable electricity.

A quick examination of commercially available distributed-scale power systems, however, reveals a lack of turnkey systems. Some of the key technical challenges responsible for the limited development are the difficulties in maintaining consistent gasifier performance with variations in the physical and chemical composition and 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 EERC–Cummins partnership has three goals: 1) to develop an integrated gasifier–electrical generator technology with improved syngas-to-electricity efficiency, 2) to design a system that is tolerant of varying syngas compositions, and 3) to design a system with exhaust emissions that are well within environmental limits and with 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.

Together, the EERC and Cummins plan to couple expertise in gasification processes and engine technology to find solutions suitable for commercial industry. A follow-on column will highlight incredible achievements toward producing a reliable biomass fuel distributed power plant.

By Nikhil M. Patel, Research Manager, Energy & Environmental Research Center (EERC)