In the path of pitches from technology manufacturers and project developers looking to drum up business in certain states, members of the Clean Energy States Alliance realized they were unaware of the commercial status of biomass combustion and gasification technologies. A request to the U.S. DOE’s Technical Assistance Program resulted in a study by the National Renewable Energy Laboratory titled “Market Assessment of Biomass Gasification and Combustion Technology for Small- and Medium-Scale Applications.”
Free of charge to CESA, the 2009 report focused on conversion technologies with capacities of less than 5 megawatts (MW) or 50 million Btu per hour. Primary applications considered were thermal, combined-heat-and-power (CHP), and district heating. The report analyzed biomass availability, strengths and weaknesses of both technologies, system economics, and included an assessment of their commercial statuses, as well as inventories of suppliers of both technologies.
“[CESA] wasn’t quite familiar with the status of the technologies and the commercial viability, so they wanted some type of overview,” says study co-author Scott Haase.
Not surprisingly, the study found that direct combustion systems for heat, power or CHP are available commercially from a number of manufacturers. Gasification systems, however, showed different and more diverse results. Close-coupled gasification systems, where the syngas is burned directly for space heat, drying or to produce steam, were already commercially available from manufacturers. But what Haase calls two-stage gasification, where the syngas is conditioned for tar and particulate matter removal before use in a genset or gas turbine, were largely still in development with a number of technologies in the demonstration phase.
In light of those findings and others, NREL concluded its study with three important recommendations: entities wishing to support the development of gasification applications and technologies should consider funding demonstration projects of near-commercial technologies in their states; a central clearinghouse of the market potential for small- and community-scale biomass direct combustion and gasification systems should be commissioned; and a national assessment of the market potential for small- and medium-scale systems that is searchable online should be created and maintained.
Two years later, the study may not have spurred rapid development of either technology in CESA member states, but it certainly proved useful in more than one aspect.
“For many states, biomass has been a challenge for our members to figure out a strategy and program approach that really evaluates the efficiency of biomass conversion,” says Mark Sinclair, executive director of CESA, which is made up of major state-level programs that invest public dollars in renewable energy. He added that the study confirmed what CESA already knew: state clean energy programs have an important role in supporting research and development to move forward with biomass gasification and more efficient direct combustion technologies.
Thus, NREL’s recommendation that entities supportive of gasification technologies fund demonstration projects was taken seriously by a number of CESA members. “Several of our states relied on that recommendation for demonstration projects to direct some funding into supporting biomass conversion technology acceleration,” Sinclair says. The Alaska Renewable Energy Fund invested $2 million in a 400-kilowatt biomass-fired Organic Rankine Cycle combined-heat-and-power plant that is scheduled for start-up this fall, he says. Massachusetts and Wisconsin have referenced the report in funding considerations, he adds, and the California Energy Commission took it as confirmation that the money it had already invested in biomass conversion technologies through its Public Interest Energy Research program over the past decade was crucial to development. “They say while the NREL report didn’t spur new activity, it basically confirmed the need for their continued research in support of future gasification advancement activity,” Sinclair says, adding that California has two demonstration-scale two-stage gasifiers currently operating. Both were developed, however, before NREL released its report.
Not only did the report confirm the need for state support in research and development, but it proved useful in understanding where manufacturers of the technologies are located, and therefore how important demonstration projects could be in certain states. “When there’s a number of manufacturers in your state that are focusing on this technology, that’s another good reason to put clean energy dollars into the technology,” Sinclair explains. “That’s becoming even more important in this economic climate. That inventory provided by NREL was extremely useful in finding out how valuable this technology is in terms of manufacturing for each of the states.” A state industrial development aspect can carry weight in determining whether to make investments in clean energy projects, he adds.
It can be hard to find objective, detailed information about biomass conversion technologies for use by agencies wishing to support them, Sinclair laments. “This NREL report really helped our members confirm that if you’re going to increase efficiency, there really needs to be some public-funded demonstration projects for gasification. The study gave new impetus to focusing on biomass gasification and combined heat and power.”
NREL’s report is one example of a promising and necessary partnership between the DOE and states investing public dollars in clean energy development, Sinclair stresses. “One of the strong beliefs of our organization is that there is a real need for DOE and the national laboratories to work closely with individual states in advancing clean energy investment and technology,” he says. “There can be a lot more of this activity between the state and federal government going forward.”
And while the states move forward in supporting technology development, NREL will continually update the report to reflect the current environment. The lab is reworking its equipment supplier inventory and adding a few manufacturers, Haase says, but beyond that, not much else has changed. The demonstration-phase status of two-stage gasification, the finding that may allow the most room for growth and updates, has remained unchanged with the rest.
But while two-stage biomass gasification, categorized by gas conditioning before use in an engine, lingers in its precommercial-scale classification, progress is certainly being made. Gasification system developer and manufacturer Nexterra is partnering with General Electric Co. for two identical, demonstration-scale, two-stage gasification systems, having sold a number of commercial close-coupled systems. The first two-stage system, scheduled to commence operation in the first quarter of 2012, has been widely publicized and will be at the University of British Columbia in Vancouver. The CHP plant, dubbed the Bioenergy Research Demonstration project, will produce 2 MW of power and 10,000 pounds per hour of steam, supplying up to 25 percent of the campus’s heating demand. Prepared for woody biomass feedstock, the project has received millions in provincial funding and will also provide learning opportunities for the university’s students and faculty.
The gasification system’s twin will be installed at a landfill in Catawba County, N.C., and will run on wood diverted from the landfill, according to Nexterra CEO Jonathan Rhone. Both systems will be paired with a GE Jenbacher engine, a technology to which the landfill is no stranger. “They were a real pioneering site for GE,” he says, adding that the landfill served as somewhat of a test site when the Jenbacher technology was brought to North America. The systems will be standard module designs and will include a single gasifier, single gas conditioning system and Jenbacher engine.
Nexterra’s gas conditioning system is not like others that take approaches such as tar scrubbing or chemical conversion, Rhone says. “Our approach is quite different,” he explains. “We take the syngas after it comes out of the gasifier … and we thermally crack the tars.” That process is given sufficient residence time, he says, converting the tars into more syngas. In addition, the heat used to reach the high temperatures for tar cracking is recovered and recirculated into the process. Downstream of the tar cracking, inorganics are removed through a filter system and the syngas is then fed into the Jenbacher engine.
“We looked at about half a dozen different approaches,” Rhone says. “We didn’t like any of them because they were either too expensive, unproven with a fair amount of technology risk, or they produced another environmental problem such as tarry water that needs to be treated before disposal.”
Perhaps the most famous example of two-stage gasification demonstration is in Gussing, Austria, where a wood-fired 2 MW CHP plant with the capacity to cover the entire town’s electricity demand has turned the former poor region into a prospering center of renewable energy. The system also generates 4.5 MW of thermal energy for district heat and has helped the small community of 4,000 completely change its energy supply to renewable sources.
Such a shining example is nonexistent thus far in the U.S., but Rhone says demand for and interest in gasification systems is enormous. “We’ve got a huge demand for this type of technology,” he says, citing three main reasons. First, it represents a step change in overall system efficiency compared with combustion CHP. Second, it doesn’t require steam plant operators, who are expensive and hard to find; and last, it provides a favorable power-to-heat ratio. “There’s a lot more electricity-to-thermal energy produced from the engine system versus a steam CHP system,” he says.
While demand grows and Nexterra and other technology providers move forward with development, maybe an upgrade for two-stage gasification to commercial-scale status will be the first major update to Haase’s report. With already apparent progress in convincing state-level renewable energy agencies that financially supporting advancements in gasification technology is necessary, it seems such a sizable and meaningful advancement could be just over the horizon.
Author: Lisa Gibson
Associate Editor, Biomass Power & Thermal