Biofuels produced from plant and animal feedstocks are growing by 10 percent per year. Nevertheless, if biofuels are ever to supply more than a small percentage of transportation fuels, the technology will need new, more efficient production methods. The most recent sign of such investment in new methods of production is Royal Dutch Shell’s partnership with German biodiesel innovator Choren Industries.
Choren’s technology addresses a key limitation with today’s biofuels: most start as feedstocks such as corn syrup or vegetable oil, which are already in demand as foods. So competition for these feedstocks props up the price of conventional biofuels and, ultimately, even limits their production volumes. A study commissioned recently by the Canadian government, for example, concluded that diverting half of that country’s hefty exports of canola to domestic biodiesel production would yield only enough biodiesel to meet 2.7 percent of current diesel demand in Canada.
Choren and other biofuel innovators such as Canadian ethanol developer Iogen (also partnered with Shell) work instead with biomass – organic leftovers such as sawdust – which are as abundant as they are cheap. The same Canadian study, for instance, revealed that the biodiesel produced from just 10 percent of the country’s agricultural wastes would satisfy 16.7 percent of its appetite for diesel.
Choren breaks down biomass into a gaseous mix of carbon monoxide and hydrogen, then uses catalysts to reassemble this synthesis gas, or “syngas,” into diesel fuel. Historically, Nazi Germany developed this so-called Fischer-Tropsch process to produce synthetic fuels from coal. Shell uses it to produce diesel from natural gas.
Compared with coal and natural gas, however, biomass makes a troublesome feedstock. That’s because it contains lots of large, complex molecules, and the same equipment that easily breaks down the mineralized carbon in coal chokes on the tar-like hydrocarbons in biomass.
According to Matthias Rudloff, head of business development for Choren, the result is an impure synthesis gas that is unsuitable for processing. The tar “sticks everywhere, on every heat exchanger. Tubes become clogged in just a few hours,” says Rudloff.
But Choren founder Bodo Wolf turned the tar into an advantage. Wolf comes from former East Germany’s combustion research institute, where he helped develop equipment to turn coal into chemicals, motor fuels, and electricity. He found that the type of high-temperature processes favored in East Germany were suited to tackling biomass. His key innovation, though, was to add a processing step at the front end.