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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.

Learning to Like Natural Gas

This week’s cover story – Seeking Biomass Feedstocks That Can Compete – discusses the competition that natural gas might bring to the young renewable fuels and chemicals industry. [You can also check out the YouTube video about Energy Cane]

The story discusses one positive that the rise of natural gas brings to biobased chemical makers – at least those that produce C4 chemicals (i.e. butanediol, butadiene). As the chemical industry swaps petroleum feedstocks for natural gas, their processes will generate a much smaller ratio of C4 chemicals. Firms that rely on those intermediates will seek other sources of C4s.

gas well

Green companies are looking at natural gas. Credit: Chesapeake Energy

But there are a few other ways that the natural gas story intersects with the renewable industries – some obvious, and some not so obvious. One obvious way – cheaper energy from natural gas may help decrease operating costs at all chemical producers, including ones that use biomass feedstocks.

Less obvious – there is a group of renewable companies that use syngas as a feedstock. You know what makes an excellent syngas? Why, that’d be natural gas. Sure, you could gasify plant matter, old tires, construction debris, municipal waste (anything carbon based). Any of those feedstocks will make a flow of carbon monoxide and hydrogen. With chemical or biological catalysts, that syngas can be made into chemicals and fuels.

At least two firms that started out with plans to make syngas from biomass or waste sources now say they will ramp up on natural gas – Coskata, and Primus Green Energy. Coskata’s end product is ethanol, while Primus is targeting drop-in hydrocarbons. Presumably, with a working gasifier and catalysts, they could switch feedstocks whenever the cost basis dictates.

Newlight Technologies wants to make polymers from waste gases like methane from water treatment plants. But methane from under the ground would work well, too. The company says it can also make polymers from CO2 (with a helping hand from a hydrogen generator). Which brings us to…

BASF, which is not really a renewable company, but has got some irons in the fire. The chemical giant has a research project going to rip the hydrogen off of natural gas, and mix that with waste CO2 to make a custom-blended syngas. The firm says getting hydrogen this way is cheaper than other ways (tearing up water molecules, etc). Waste CO2 is something many industries – especially in Europe – would like to do something with. LanzaTech is also in the waste CO2 business. Not sure what its natural gas plans are.

Lastly, two stalwarts of the biobased chemicals industry, Genomatica and OPX Bio are getting a handle on natural gas. Genomatica is working with Waste Management to make C4s from syngas (derived from municipal waste). The syngas project came up in my interview with Genomatica’s CEO Christophe Schilling about natural gas.

More directly, OPX Bio, which is working to make acrylic acid from sugar,  has a lab-scale project for its second product – fatty acids. The company says its process can use syngas made from all the usual suspects including natural gas. There is already a significant market for chemicals based on fatty acids; they can also be converted into nice things like jet fuel.

Natural gas is not a renewable resource, so one might wonder why these green tech firms would bother using it at all. I can think of three reasons: one – as a first feedstock to prove one’s catalyst technology, two, as an alternate feedstock to balance price and availability of biomass or waste, and three, as a way to fix the mass-balance of hydrogens and carbons in your syngas. If adding 10% of syngas increases yields by 20%, that might be tempting.

There is one way that natural gas as a feedstock might be considered “green.” This comes via Alan Shaw of Calysta. The company uses methane munching bacteria to capture natural gas, then enzymes in the cells can make desired products. Shaw suggests a good use of the technology would be to install small-scale units where there is so-called “stranded” natural gas. That would include oil wells that flare the natural gas that comes up with the crude oil in places like North Dakota.