In the spring of 2013, KiOR, a start-up backed by venture capital, began shipping cellulosic diesel made from pine wood chips from its facility in Columbus, Miss. And in Vero Beach, Fla., the Indian River County Bioenergy Center became the first large-scale plant in the United States to produce electricity and fuel from waste (non-food plant and yard trimmings). Owned by INEOS Bio, the plant is using bacteria and a patented gasification and fermentation process to break down vegetative and wood waste. In August 2013 it began producing cellulosic ethanol on a commercial scale.
Meanwhile, across the country at its demonstration refinery near Boardman, Ore., Zeachem Inc., is producing ethanol from wood. ZeaChem uses a combination of enzymes and heat to break down the cellulose from poplar trees grown on a nearby plantation as well as waste from local wheat fields. The sugars are then fermented in a process that releases no carbon dioxide. The company is currently building a new full-scale refinery with the potential to process 10 tons of biomass every day and produce 25 million gallons of ethanol every year.
ZeaChem’s demonstration refinery could get by largely on poplar left-overs from a sawmill, but the new refinery will also need whole trees that are grown specifically for biofuel, says company spokesperson Carrie Atiyeh. “One of the advantages of wood is that it’s so dense,” compared to some other next-generation biofuel crops such as tall grasses, she says. “We can get 10 to 15 tons of biomass per acre, which means that we can have a relatively small (carbon) footprint” by using less land.”
Scientists around the world are also looking for new enzymes that could streamline the production of ethanol by breaking down wood more efficiently. Norwegian researchers, for example, have discovered an enzyme that could potentially shrink the days-long process for turning wood chips to biofuel to a matter of hours; the enzyme functions by “shooting holes into the wood surface with the help of oxygen bullets” so that other enzymes can gain access, according to Science Daily. In another example, researchers at the University of York in England announced that an enzyme produced by tiny ocean-dwelling crustaceans, or “gribbles,” could help speed up the transformation from wood waste to ethanol.
Such work is definitely intriguing, but it doesn’t necessarily point to the future of the industry, says forest specialist Steve Kelley of North Carolina State University. “There’s a lot of enzyme prospecting going on,” he says. “But I don’t think we need better enzymes. We need cheaper ways to produce the enzymes that we have.”
There are still other ways to unleash the energy of wood. Companies such as Canada-based Nexterra use gasification to extract usable fuel from wood chips and other sources of biomass. This involves heating the material to 815-980 degrees Celsius with limited amounts of oxygen. This produces a combustible fuel called syngas that’s mainly composed of hydrogen and carbon monoxide. Syngas can be used in internal combustion engines, or it can be converted to diesel, jet fuel, or gasoline by chemical catalysis.
Another approach, called pyrolysis, heats wood waste to 550 degrees Celsius or above without any oxygen. This releases a vapor that can be condensed into bio-oil, a thick, energy-dense fuel that’s notoriously difficult to work with. It’s watery, for one thing, and it has large molecules of lignins left over from the cellulose in the wood. “Making bio-oil is easy,” says Naoko Ellis, Ph.D., associate professor of chemical and biological engineering at the University of British Columbia. “Finding the best way to utilize this is the challenge.” Ellis and colleagues are currently looking at cost-efficient ways to emulsify bio-oil with biodiesel. When the two are combined, water and lignins from the bio-oil separate from the more combustible elements, leaving behind a clean-burning fuel.