Roasting biomass could be key to bioenergy economics
BY GREENING OF OIL STAFF
A process similar to roasting coffee beans could be the key to making biorefining economically feasible.
A new collaborative study between Idaho National Laboratory and Pacific Northwest National Laboratory will investigate whether such roasting can create a more valuable product for the budding biofuels industry.
(Start the conversation. See comments section at bottom of page.)
Initial studies, the two laboratories said in a Feb. 23 press release, show that driving moisture and volatile compounds from wood or straw could make the biomass more stable, compactable and, most important, more energy dense.
Roasting biomass could “cut a lot of costs by providing a less expensive and higher-value product,” Idaho National Laboratory biofuels researcher Christopher Wright said in the press release. “This technology has the ability to overcome biomass's moisture, mass and energy density problems, which make up a huge proportion of the cost barriers.”
Heating biomass above 250 degrees Celsius
The technology Wright is referring to is called ‘torrefaction’, which means heating biomass above 250 degrees Celsius in an oxygen-free environment.
“It's not very different from roasting coffee beans," Wright said. But while coffee beans are roasted for flavor, biomass would be ‘torrefied’ to improve its physical characteristics.
Dealing with moisture and density
Two characteristics that heavily influence the logistics and economics of today's biomass industry are moisture and density, the laboratories said, explaining that most biomass is wet, which complicates long-term storage. Plus, biomass is not very dense, which negatively impacts the cost efficiency of mass transportation.
Driving out moisture and volatile compounds through the torrefaction process could address both issues, they said.
Biomass that has been roasted has almost no water and actually becomes water resistant, which could improve storage in humid climates. The torrefied product also breaks down more easily so it's more uniform after grinding, the laboratories said.
With research funding from the U.S. Department of Energy's biomass program researchers from Idaho National Laboratory, or INL, are now torrefying biomass to further study the physical characteristics of the dried product, its production cost and how much energy it can generate.
For example, they want to know whether the deeply dried biomass is easier to compact into pellets or briquettes.
The energy used in the torrefaction process and the resulting energy content of the torrefied biomass needs to be measured to determine production costs, they said.
PNNL looking at overall conversion into fuels
Collaborators at Pacific Northwest National Laboratory, or PNNL, led by researcher Doug Elliott's team, will study whether the torrefaction process improves the quality of the resulting biorefinery product.
“We want to understand if the properties of the torrefied biomass can improve the overall conversion of biomass into fuels,” Elliott said.
INL recently shipped 30 kilograms of both raw and torrefied white oak to the PNNL team. Future shipments will include torrefied corn stover, wheat straw, switchgrass and two types of woody biomass.
Creating a homogeneous commodity product
Both research teams said they are eager to determine whether torrefaction can economically deliver a more stable, energy-dense feedstock that can be effectively converted into higher quality products at biorefineries. If so, the process could help cellulosic biomass compete as a nationally traded energy commodity.
This may open access to more material,” Wright said. “INL is looking at whether it's possible to create a homogeneous commodity product from biomass.
INL and Washington-based PNNL are two of DOE's 10 multi-program national laboratories. The laboratories perform work in each of DOE's strategic goal areas: energy, national security, science and environment.
INL is the nation's leading center for nuclear energy research and development, the press release said.
Day-to-day management and operation of both laboratories is the responsibility of Battelle Energy Alliance.
Links of interest
Office of Energy Efficiency and Renewable Energy's Biomass Program
Idaho National Laboratory
Pacific Northwest National Laboratory
Contact Greening of Oil at publisher@greeningofoil.com
The following are comments from our readers. They do not represent the view of Greening of Oil or its owner.