Pyrolysis: the third way to biofuels
Imagine a giant pile of biomass - lets say wood chips for simplicity sake. And next to the wood chips is a big pile of money (likely from investors, whose patience for payback may vary). In a third pile is a group of job candidates: engineers, chemists & microbiologists.
To get useful energy from the first pile of feedstocks requires careful consideration of all your piles. The wood chips can be burned, fermented, or - bear with me now - squeezed. Each approach requires different amounts of feedstock, cash up front, and expertise to get a particular type and amount of fuel or energy.
C&EN's own Craig Bettenhausen has taken a look at the benefits - and potential downsides - of squeezing the wood chips to make liquid fuels, specifically hydrocarbons that can be made into drop-in biofuels (the best kind!). Of course he doesn't say "squeezing" - experts call it pyrolysis. Bettenhausen explains that the biomass is subjected to high temperature and pressure in an oxygen-free environment (imagining this is making me feel a little breathless and claustrophobic). Check out the free story to learn what happens next.
Meanwhile a press release from our friends at Battelle in Columbus, Ohio, nicely illustrates one way pyrolysis might pull ahead of other technologies (i.e., fermentation into ethanol or gasification into syngas). A group of Battelle engineers and scientists have built a mobile factory that can travel to the site of your big pile of wood chips and convert it into up to 130 gal of oily hydrocarbons per ton of chips per day. The little factory is installed on the flatbed trailer of an 18 wheeler.
"This feature makes it ideal to access the woody biomass that is often left stranded in agricultural regions, far away from industrial facilities," the press release notes. "It’s potentially a significant cost advantage over competing processes represented by large facilities that require shipment of the biomass from its home site."
Still, as Bettenhausen explains, pyrolysis - as it is being scaled up today - has not yet proven itself at scale or made profits for anyone. Stay tuned.