Sustainable Energy
Gasoline from Vinegar
A process that converts acids from garbage into fuel gets a boost.
A company that has developed a process for converting organic waste and other biomass into gasoline–Terrabon, based in Houston–recently announced a partnership with Waste Management, the giant garbage-collection and -disposal company based in Houston. The partnership could help Terrabon bring its technology to market.
Amid a profusion of new biofuels technologies, this one stands out because it will be relatively easy to scale up for producing millions of gallons of fuel, says James McMillan, the biochemical process R&D group manager at the National Renewable Energy Laboratory in Golden, CO, who is not connected to the company.
Most biofuels companies fall into one of two categories. Some use enzymes to break down biomass into simple sugars and a single organism to convert sugars into fuel, such as yeast. Others use high temperatures and pressure to break biomass down into basic chemical building blocks–carbon monoxide and hydrogen–which are then chemically processed into fuels. Terrabon has developed a process that combines the two. It uses a naturally occurring mixture of organisms to convert biomass, not into fuels, but into carboxylic acids. These can be converted into fuel and other chemicals using well-known chemical processes. Gary Luce, the company’s CEO, says Terrabon’s fuels can compete with petroleum-based fuels if prices are above $75 a barrel. (The price of oil is currently about $70 a barrel.)
The approach has an advantage over single-organism-based methods because the mixture of organisms used, collected from salt marshes, are adapted to survive in the wild. They don’t require the special sterile environments needed to prevent single-organism cultures from being contaminated, which brings down the cost of equipment.
These organisms naturally break down biomass into carboxylic acids, such as acetic acid, the key component of vinegar. These acids can serve as chemical precursors for a wide variety of chemicals and fuels, including gasoline and diesel, via processing steps that convert the acids into ketones and alcohols. The acids can be made without the expensive equipment required for high-pressure and -temperature processes. They can also then be processed into fuels using equipment at existing refineries, helping keep costs down.
Because the organisms don’t require special treatment and because the acids they produce can be converted to fuels at existing refineries, it should be relatively easy to ramp up production, McMillan says. Terrabon’s partnership with Waste Management should help, he says, since one of the biggest challenges with advanced biofuels is collecting the large amounts of biomass needed. Waste Management already has trucks and other equipment for collecting garbage and separating the organic waste.
Terrabon’s composting centers, where biomass is converted into acids, can be located near sources of biomass–such as municipal landfills or farms. The acids–or solid salts made from these acids–would then be shipped to a refinery for conversion to biofuels. Terrabon also has a partnership with Valero, the major oil refiner based in San Antonio, which will help in this stage of the process.
One potential disadvantage of Terrabon’s method is that it would be extremely difficult, if not impossible, to improve the organisms via the powerful genetic engineering tools other biofuels companies are using. That’s because it uses a complex mix of organisms, rather than a single organism, each of which plays a role in breaking biomass down into sugar and converting the sugar to acids. Cesar Granda, Terrabon’s chief technology officer, calls the mix a “black box,” because the company doesn’t understand exactly how it works, at the level of the individual microbes and their genetic make-up.
McMillan says the success of the company will depend in part on the costs and energy required for transporting raw materials and converting acids into fuels. He also says the carbon-dioxide emissions from the chemical process could be higher than with other advanced biofuels. One step in particular, hydrogenation, requires hydrogen, which is typically derived from fossil fuels. Depending on the source of the hydrogen, and the energy required in other steps, it may be difficult for Terrabon’s fuels to qualify as advanced biofuels and so qualify for key federal incentives.
Terrabon, which has been operating a pilot-scale plant in Bryan, TX, plans to begin building a 55-ton-per-day facility in Port Arthur, TX, starting early next year. With the help of Valero’s Port Arthur refinery, that facility is expected to produce about 1.3 million gallons of biofuel a year when finished in 2011.
