U.S. Department of Energy - Energy Efficiency and Renewable Energy

Biomass Program

Small-Modular Gasification

Gasification-based small modular biomass systems are emerging as a promising technology to supply electricity and heat to rural areas, businesses, and the billions of people who live without power worldwide. Biomass Program support through subcontracted efforts with private sector companies over the past several years, has advanced several versions of the technology to the point where they are now approaching commercialization. By adopting a standardized modular design, these 5 kW-to-5 MW systems are expected to lend themselves to high volume manufacturing techniques to bring them on a competitive level with large stand-alone plants. Using locally available biomass fuels such as wood, crop waste, animal manures, and landfill gas, small modular systems can be brought to the source of the fuel rather than incurring transportation costs to bring biomass fuels to a large centrally located plant. Small modular biomass systems also fulfill the great market potential for distributed, on-site, electric power and heat generation throughout the world.

Small modular biomass systems typically convert a solid biomass fuel into a gaseous fuel through a process called gasification. The resulting gas, comprised primarily of carbon monoxide and hydrogen, is then cleaned before use in gas turbine or internal combustion engine connected to an electrical generator. Waste heat from the turbine or engine can also be captured and directed to useful applications. Small modular systems lend themselves to such combined heat and power operations much better than large central facilities.

Benefits of Small Modular Systems

Small Modular biomass systems offer many benefits to potential customers. They have minimal environmental impact when compared to other existing technologies using coal or biomass as the fuel. On the one hand, economics can be attractive when owners connect the unit to a power grid that will buy unused power. On the other, small modular systems can electrify isolated areas for which the cost of connection to the grid is prohibitive. Another economic benefit may be realized if the customer has a biomass waste stream that can be converted into a source of energy rather than being an economic burden.

The flexibility to use more than one fuel also appeals to many users. Modern microprocessor control has been coupled to gasification technology to result in systems requiring minimal operator attention. And, in off-grid locations small modular biomass systems offer the potential for lights, refrigeration, heat and power to enable small cottage industries to become economically viable.

The Program and Collaborations

The U.S. Department of Energy's Small Modular Biomass Initiative worked with industry to develop small modular biomass systems capable of producing combined heat and power at scales ranging from 5kW to 5 MW. In 1998 the National Renewable Energy Laboratory in Golden, Colorado, and Sandia National Laboratories in Albuquerque, New Mexico, began work on the Small Modular Biomass Initiative. This two-phase project included feasibility studies followed by prototype demonstrations, and finally complete system integration based on a business strategy for commercialization. In the first phase of the Small Modular Biomass Initiative, ten projects were selected to determine the feasibility of developing systems for selected markets using each private subcontractor's conceptual design. In Phase 2 the initial ten projects were reduced to four with the objective of completing the system design and then fabricating and testing of integrated prototypes.

• Carbona Corp. is using fluidized bed gasification incorporating a novel tar reforming catalyst to produce clean producer gas. The gas will be used in large internal combustion engines to produce both heat and power at the 5-MW scale. Plant fabrication is expected to begin in summer of 2004.

• FlexEnergy is developing a novel catalytic combustion technology coupled to microturbines at the 30 kW to 60 kW scale. This technology promises to enable the utilization of very low heating value gases from sources such as landfills and anaerobic digesters. Its use of low combustion temperatures results in almost no NO_x emissions.

• Community Power Corporation is using a fixed bed downdraft gasifier design that converts solid biomass to producer gas for consumption in an internal combustion engine coupled to a generator. Key features of this technology are a dry gas cleanup system and use of microprocessor control for complete turnkey operation.

• External Power LLC was the fourth small modular biomass technology, using heat from combustion flue gases to drive a Stirling engine. Their effort was focused in two areas: (1) re-design of Stirling engine components for high volume mass production and (2) interfacing the burner to the Stirling engine heater head. In late 2002 External Power lost the license to the original Stirling engine design and were forced to discontinue this development effort.

During phase II the U. S. Department of Agriculture Forest Service became keenly interested in the Community Power Corporation technology as a potential solution to managing the enormous volumes of biomass that will need to be removed from the nations forests for fire mitigation. They have collaborated with DOE to provide support to build additional systems that are deployed to private sector host sites for technology validation and demonstration. These demonstrations are intended to identify any remaining design flaws in the system prior to locking in the design for commercial production. The host sites in this scenario are essentially pseudo customers and will play an important role in speeding the development of this technology to the marketplace.

For Further Reading

• Search the Biomass Topical Search
• Search the Biomass Document Database