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Biobutanol: Ethanol's Energy-Dense Cousin

Salem, Ore.-based Diesel Brewing is working to implement a unique business model for the gasification of waste biomass into biobutanol and other valuable energy products.
By Anna Austin
Biobutanol has an energy density only 10 percent to 20 percent lower than gasoline, and its energy content is higher than ethanol, according to the U.S. DOE Alternative Fuels and Advanced Vehicles Data Center. It's compatible with the current gasoline distribution infrastructure and would not require new or modified pipelines, blending facilities, storage tanks or retail station pumps. Biobutanol can be efficiently blended with ethanol to improve the blending of ethanol with gasoline, and can also be produced using existing ethanol production facilities with relatively minor modifications.

Under current U.S. EPA regulations, biobutanol can be blended as an oxygenate with gasoline in concentrations up to 11.5 percent by volume.

While possessing these attractive qualities, like many other renewable fuels, the commercial-scale production of biobutanol has been hampered by challenges. Production costs have typically amounted to nearly double those of ethanol, since traditional fermentation processes have proven too inefficient to make biobutanol in large amounts.

By virtue of innovation in process technologies, however, more players are entering the game. With a slightly different approach than others, Salem, Ore.-based Diesel Brewing is moving full-steam ahead with plans to build multiple stand-alone biobutanol production facilities in the Northwest U.S.

Tweaking Technologies
Don't let the name throw you off-Diesel Brewing doesn't manufacture or plan to manufacture diesel fuel. Rather, the company will produce biobutanol for use within local fuel markets as a renewable diesel blending agent.

Uniquely, Diesel Brewing will use a gasification process that converts biomass into a synthesis gas that is cleaned, fed into a catalytic reactor, and purified to generate biobutanol, ethanol and methanol. The individual alcohol components and the ash from the post-combustion process are then separated and stored.

The plan to focus on biobutanol was developed as a result of thorough investigation and comparative analyses, according to Diesel Brewing CEO Mark Stapleton.

"We originally looked at a variety of fuels such as cellulosic alcohols and synthetic diesel," he says. "We were drawn to biobutanol after several months of investigating various existing technologies."

Stapleton says other fuels the company looked at simply were not providing satisfactory percentage yields. "There were too many other products as a result of that process, so we were looking for an alternative where we could get higher yields for our primary product-which is going to be biobutanol," he says.

By changing the conversion chemistry, the company could produce other fuels such as biodiesel and dimethyl ether (propane) or anhydrous ammonia for the production of fertilizer. "For now, we'll focus on the production of biobutanol," Stapleton says.

He could not disclose the company's preliminary yield estimates, but Stapleton says they will soon be validated at Diesel Brewing's first pilot plant, construction of which is slated to begin in September. "It will be a small plant, located right here in our backyard, that'll process roughly a ton of biomass per day," he says. "It's due to be commissioned in December, and we're on track for that."

Using the prototype, Diesel Brewing will develop baseline data on feedstocks, synthesis gas production, emissions composition and relative thermal efficiencies-employing a technology that consists of multiple previously existing platforms that have been redesigned and integrated. "We're not purchasing any machines," says Diesel Brewing Chief
Operations Officer Kevin Caldwell. "Rather, we're buying many different parts from different people."

Unitel Technologies Inc., an engineering company based in Chicago, Ill., has designed the basic system for Diesel Brewing. "We used other people's platforms that are already in the public arena, and basically had Unitel redesign them," Caldwell says. "For instance, the gasifier itself, to do the thermal conversion, is a designed working system that sits at the University of Utah in Salt Lake City, but they use it for an application that's a little bit different," he explains. "We took that public domain gasifier, gave it to Unitel and told them what we wanted it to do, and then they redesigned it for us. [The technology is] the result of the collaboration of many bright people and their work over the past 50 years, refined one more time to fit our specific feedstock."

Caldwell says the same is true for the development of the company's synthesis gas cleanup, which was developed through the selection and redesign of existing systems in order to suit the company's catalyst.

Pressure vessel and refractory specialist CH Murphy Clark-Ullman Inc., based in Portland, Ore., will work with Diesel Brewing for the fabrication and installation of multiple specialized pressurized vessels.

All design engineering and technology rights will be held by Pacific BioPower, an associated company to Diesel Brewing.

Community Sustainability
Aside from the distinctive advantages that biobutanol has when compared to other fuels, Stapleton says the real thrust that adds to what Diesel Brewing has planned is its focus on small-sized biorefineries. "Most of the biorefineries across the world are very large in nature," he points out. "Every day they consume 500 to 1,000 plus tons of biomass. We're unique because we're focusing on a much smaller amount of biomass so we won't over-consume."

Stapleton expects a typical facility to process 120 to 125 tons of biomass per day. "We can go to a fairly small, rural community and not have such a huge impact on the biomass availability-consuming more than is there-and be forced to ship biomass from other places," he said.

Although the feedstock processing capability of Diesel Brewing's technology is relatively flexible, Caldwell says the company will utilize a narrowed group of materials. "It won't be a biomass recycling center," he says. "We've pretty much relegated ourselves to agriculture waste and woody biomass. There are a couple of reasons for that. Everything has a little bit different chemical make-up, and by narrowing that just a little bit, it gives us a narrower range of chemistry that we have to deal with in the gasifier and the catalyst unit."

Oregon currently has an estimated 9.8 million bone-dry tons of woody biomass resources and 1.5 million bone-dry tons of agricultural residues available for energy use each year.

The state also has many renewable energy incentives, such as a business tax credit of 50 percent of eligible project costs (up to $10 million in credits) for facilities that use renewable energy resources and plants that manufacture equipment used for renewable energy projects.

In addition to fuel, electricity will be generated at the site of Diesel Brewing's biobutanol plants. "We'll have our own internal electrical needs, so we'll use what we need and sell the balance of it," Caldwell says. Out of the estimated 5 megawatts (MW) generated, Diesel Brewing facilities will require 1 to 1.5 MW.

"Oregon's a unique state in that we can either wheel it to the grid as a small producer under the PURPA (Public Utility Regulatory Policies Act) or, if we have a neighbor or a local co-op or public utility district, we can actually execute private power contracts," Caldwell says. "Our preference will be to sell it to a local co-op to distribute it locally, but there are a lot of options in Oregon for what we can do with the balance of the electricity."

Under state regulations, Oregon utilities must meet a percentage of their retail electricity loads with renewable resources. For the three largest utilities-Portland General Electric, Pacific Power and Eugene Water and Electric Board-the targets are 5 percent in 2011 and 25 percent by 2025. For the other utilities in the state, the targets are 5 percent or 10 percent by 2025, depending on the size of the utility. If any of these utilities builds or signs a new contract with a coal-fired plant, the targets for the large utilities apply.

A Map of the Future
Diesel Brewing intends to roll out its plans quickly. After the start-up of its pilot facility in December, work will begin on a 10-ton per day production unit in Boardman, Ore., which will demonstrate production yields, fuel ratios, gas cleanup procedures, and will allow the company to further fine-tune and balance the processes. Completion of that project is slated for October 2010. Based on the findings of the two preliminary test plants, a commercial-scale plant that would use at least 100 dry tons of biomass per day will be constructed; more will be built across the state when all the kinks are worked out.

"The bottom line is we're not transporting biomass into our communities and transporting liquid fuels out," Stapleton says. "Our whole business philosophy is to establish small, rural plants near where we get our feedstock, and then produce and consume the biofuels within that same community."

Anna Austin is a Biomass Magazine associate editor. Reach her at aaustin@bbiinternational.com or (701) 738-4968.
 

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