The Elusive Biorefinery
Replacing fossil fuel-based products such as plastics and solvents with biomass-based equivalents has long been a goal of the biobased industry. The vision is a biorefinery-the equivalent of an oil refinery-producing many chemicals with hundreds of end uses. So, why aren't such facilities being built?
The ultimate biomass facility would in many ways resemble an oil refinery. A largely homogenous product goes in one end and many different products come out of the other. Substitute biomass for petroleum, and you have a biorefinery. The National Renewable Energy Laboratory (NREL) in Golden, Colo., and other research institutions have identified a range of interesting and potentially valuable chemicals that could form the product base of a viable biorefinery.
The idea of a biorefinery has some influential supporters. Among them is Vinod Khosla, a venture capitalist and former head of the computer company Sun Microsystems. He believes that biomass-derived chemical intermediates could displace a major portion of petroleum used for plastics. As an example, he uses bottled water, which he describes as water wrapped in oil. "There is no reason that this product should not be renewable and hopefully biodegradable," he said.
There are operating facilities that are being called biorefineries. Some notable examples are DuPont's plant that produces 1,3 propanediol in Loudon, Tenn., and Archer Daniels Midland Co.'s polyhydroxybutyric acid (PHA) plant in Clinton, Iowa. But these plants are focused on single products, albeit products with a range of uses. However, these plants do show that the concept of producing intermediates for the chemical industry is a solid concept. They are also closer to the ideal of a diversified biorefinery than one might think. "Maybe we should call this [concept] the elusive next-generation biorefinery, because there are some very significant existing facilities," says Jim McMillan, an acting research supervisor for NREL. "They just aren't cellulosic [facilities] yet."
Fueling a Revolution
The idea that a biorefinery needs to start with a wide range of products is flawed, according to Preston Schutt. Schutt worked with the state of Wisconsin on its Biorefining Development Initiative and his company, CleanTech Partners Inc., provides management services for the Biorefinery Deployment Collaborative (BDC).
The road to a biorefinery will likely be more evolutionary than revolutionary, Schutt says. After all, the first oil refineries didn't start out to supply the chemical industry. They started as fuel suppliers, first for oil lamps and then for transportation and heating. Even today, the vast majority of oil is used for fuels. So when the biorefinery becomes a reality, it will likely be a natural outgrowth from an established, profitable industry. "Is there a biorefinery operating in Wisconsin? That depends," Schutt says. "I would argue an ethanol plant is an early stage biorefinery. They do sell multiple products-ethanol, distillers grains, carbon dioxide. Those types of plants haven't gone so far [into biorefining]. Why, because ethanol is so valuable. Why would they be looking to sell other products when ethanol is so incredibly valuable? That will change in the future. Then I think we will see them saying, ‘I'm not making as much money as I used to in ethanol what else can I make?'" Schutt says.
McMillan agrees that at the present time, economics favor the side of fuel production rather than chemicals. "The challenge in the scale disparity is huge between fuels and nonfuel products," he says. "If you go to nonfuel products, even if it is a large [market], it is an order of magnitude smaller and for a typical chemical it's a couple of orders of magnitude smaller. So the flywheel is the fuel. But if they can get it to cash flow on that basis, then they will be in the position as they go forward to keep increasing their revenues by being able to diversify out into additional products."
The DuPont and ADM plants represent this first stage of the biorefinery development concept. The DuPont plant is collocated with an ethanol plant operated by Tate and Lyle PLC. ADM's PHA facility is next to one of the company's wet mills.
Breaking It Up
A problem for biorefining, McMillan says, is that there is a critical difference "between a mixture of valuable chemicals and valuable mixture of chemicals. The latter is where you're trying to end up. Biomass has everything in it. It is a mixture of valuable chemicals that isn't very valuable when they are all together like that." Part of the challenge of biorefining is finding ways to economically capture the high-value fractions of biomass.
Biorefining advocates may be better off looking at different industries for inspiration. McMillan says one such model would be the corn wet milling industry. Starch is the product that pays the bills for these companies, but they also produce a host of other products including dextrose, high-fructose corn syrup, dextrans, corn oil, corn gluten and corn fiber. As market conditions change, the wet mill can shift production to its most profitable mix of products. "Another example is the sugar industry in Brazil," McMillan says. "There you are taking a product-sugar-that can be made into ethanol. Then you ask which is more valuable, ethanol or sugar? You are taking the same starting material and asking, which way should I go, how do I break this down or fractionate to maximize my return and minimize my risk?"
The pulp and paper industry is another player well-positioned for biorefining. It has a history of efficiently harvesting and transporting large quantities of biomass and separating it into its components. The BDC is a paid membership group of pulp and paper companies and their suppliers working to advance biorefining in the forestry industry in Wisconsin. "We are doing our investigation of the multiple pathways of transitioning paper mills into biorefineries," Schutt says. "A paper mill is a little like a cow. You put the wood chips in a digester much like a cow's stomach. Out of it comes cellulose that the paper companies want, but you can also pull out the hemicellulose."
Paper plants using the sulfite process for making pulp can also extract the hemicellulose, which can be broken down for ethanol and acetic acid production. However, there are only a few sulfite mills left because they are more costly to operate than kraft mills, Schutt says. If biorefining becomes more profitable sulfite mills could make a come back.
The lignin content of wood is another potential feedstock stream for pulp and paper producers. Currently, most pulp mills burn the lignin for process heat and steam. Some pulp mills are installing gasifiers to make syngas out of the lignin, Schutt says. At worst, these mills are guaranteeing themselves a reliable source of energy, but using a gasifier opens up other avenues for biorefining as well. "The technologies for scrubbing the syngas are becoming more practical," Schutt says. "Suddenly, you can start looking at what else you can make out of the syngas. Well, we know once the syngas is scrubbed there are a number of things you can start working on."
The U.S. DOE has refocused its attention on the production of biofuels, McMillan says. However, the USDA, along with the DOE, recently called for proposals for $18 million into biomass research. Thirty percent of that money will be targeted to product diversification.
McMillan also believes the recent DOE grants totaling $385 million awarded to six companies for cellulosic ethanol pilot projects will be very important to the eventual development of biorefineries. Each company is using different technologies to make sugars or syngas from biomass, which will be the necessary first step in any biorefining process. "You will see in two to four years all of these plants starting up and testing the technology at that scale," he says.
Schutt thinks the biorefinery concept may be inevitable. Eventually, ethanol supply will begin to catch up with demand and, like the pulp and paper industry, the ethanol industry will start looking for ways to diversify its income stream. Although that may be years down the road, he thinks forward looking companies are already thinking about that. "They're asking, ‘What should I be doing five years from now when the price of ethanol is 70 percent of what it is today?'" Schutt says. "We're trying to help them develop strategies and know what new technologies are out there. We want to introduce them to these new processes and technologies so they are ready. These things take time."
Jerry W. Kram is a Biomass Magazine staff writer. Reach him at email@example.com or (701) 746-8385.