NETL Researchers Focus on Combining Coal and Biomass in
Co-Gasification

	Todd Gardner is one of the NETL researchers studying co-gasification of various types of coal and biomass.  He’s holding pelletized corn stover. Two other types of biomass are in the containers: poplar dust and switchgrass.

Researchers at the Department of Energy’s National Energy Technology Laboratory are looking at ways to combine the natural resources of coal and biomass – biomass including such growing things as wheat straw, corn stover, switchgrass, mixed hardwood and distillers’ dried grains with corn fiber, and even algae – but avoid the emission of carbon dioxide.

NETL researchers are studying a process called co-gasification, in which various types of coal and biomass are put together and converted into a gaseous product stream that can be used to produce electricity, hydrogen, chemicals and liquid transportation fuels.

What about the carbon that resides in coal and biomass? Doesn’t it manage to escape into the atmosphere?

“No,” explains researcher Bryan Morreale in the Chemistry and Surface Science Division of NETL’s Office of Research and Development. “With the blending of biomass and coal in the co-gasification process, you decrease the environmental impact because biomass is carbon neutral. If you apply carbon sequestration technologies, you actually have a process that’s carbon negative – it consumes the carbon.”

The process produces a product stream called synthesis gas, which has great flexibility to be used in several ways. That flexibility is one of the advantages of the co-gasification process; another advantage is the contribution to our national security through utilization of an abundant natural resource without environmental consequences.

“Coal is one of the most abundant resources we have. With extensive use of co-gasification, we would reduce our dependence on foreign oil,” Morreale notes.

NETL’s research focuses on energy crops, not food crops. Because co-gasification can use any biomass to produce the synthesis gas, there is no need to develop a particular energy crop. Existing mixed prairie grass, forest residues, waste-wood, and even various waste streams can be converted to synthesis gas. The advantage with co-gasification using coal is that the steady supply of coal supplies a baseline that can be supplemented by biomass whenever available.

	Dr. Bryan Morreale stands next to the test rig used for studying the effects of coal and biomass mixtures on gasification products.

“Energy and food are two of our most important national needs,” Morreale says to explain the focus on non-food crops. “If we don’t have food we can’t live.”

The energy crops – wheat straw, switchgrass – grow quickly. Some of the other biomass that would be used is waste product today, such things as corn stover (the leaves and stalks left in a field after harvest), mixed hardwood left over from lumber operations or even limbs left in the forest by timber cutters. The coals being evaluated include Illinois #6, Wyodak, Pittsburgh River Basin, North Dakota Lignite and Texas Sub-bituminous.

Other types of biomass used in the NETL research are distillers’ dried grains with corn fiber, and algae produced for biomass in algae farms.

Even though there’s no question that co-gasification can produce a very flexible product stream, there are uncertainties that are being addressed by the NETL research.

“There are technologies to gasify coal and to gasify biomass, but there are uncertainties on how to mix them,” Morreale explains. For instance, how does the quality of the feedstock affect the quality of the product? What are the optimum percentages of various blends of coal and biomass?

There also are geographic implications that must be addressed. NETL research is looking at how best to couple the coals and biomasses that make sense geographically. An example might be that there’s a specific type of coal that’s abundant in a particular location and a particular type of biomass. It makes sense to use the abundant materials at the location if they work well together instead of having to transport other materials from elsewhere.

As is true with most emerging technologies, one of the drivers to commercial utilization is the economic driver. As energy prices increase, some alternative approaches such as co-gasification become more attractive.

NETL’s co-gasification research program for DOE’s Office of Fossil Energy has been going on for about a year. NETL researchers are using a small-scale gasification system to evaluate various products.

“The co-gasification technology is drawing lots of attention,” Morreale says. “NETL is the right place to be doing this type of research because of our expertise and many years of experience in doing research and developing technologies to address national energy needs. With this research, we’re trying to address industry’s concerns about co-gasification.