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Home » Farming/Growing, Feedstock, Feedstocks, Forestry/Wood, Infrastructure, New Zealand, Opinions, Process, R & D Focus, Sustainability

Lumber’s Lure: Thanks to Physics, Viable Biofuel May Grow in the Woods

Submitted by on April 6, 2018 – 5:49 pmNo Comment

by Chris Lee (Ars Technica)  Future biofuel production requires new catalysts—or better training for stubborn enzymes.  … I thought New Zealand would offer some chemistry-minded contrast. The country makes a lot of money on timber exports, but this profit is generally not from primary forest. Rather, New Zealand moves a lot of fast growing exotic species. There is a lot of waste wood in this processing, and, at the moment, much of it is left to rot, contributing to overall carbon dioxide emissions from the country’s forest industry.

The institute I was to visit, Scion, has a long-standing research program to convert the waste wood into biofuels. …

I eventually discovered my whole premise was misguided—biofuels in New Zealand aren’t really about biochemistry, either. Or, at least they’re not just about biochemistry. During my afternoon at Scion’s sprawl-y innovation park, I found myself listening to a lot of economics and… physics?

And this tension has already produced some regulatory action, with the EU restricting the growth of biofuels on land that would otherwise be used for food production.

This initiative is actually all about economics.

 In a modern forestry operation, there is plenty of waste wood. Although modern sawmills and pulp and paper mills are designed to turn every bit of useable wood into product, a lot of waste is unavoidable. Sawmills do burn sawdust for energy, but burning wet and muddy sawdust efficiently is not as simple as lighting a match. It could be more efficient to turn this into liquid fuel first.

“One of the big costs around biofuels is always the feedstock cost,” (Dr. Paul) Bennett says. “You don’t want to haul that feedstock long distance, because you’re basically taking a lot of water. So, if you can do [the processing] close to where you grow the material to densify it in energy terms, that could be better.”

Clearly, waste wood from forestry is not going to go far, but plantations of faster growing, shrubbery trees may well provide an advantage, since they can be grown at high density with cycle times of less than 10 years. And because they would be harvested using something more like traditional forestry equipment, they are still appropriate for growing on reasonably steep landscapes, thus avoiding competition with food crops.

What seems to be clear, however, is that biofuels, if done right, can supply local energy needs. In the US, using waste agricultural and forestry biomass could meet more than 30 percent of US transport fuel needs. Now, I know that batteries are the current favorite, but liquid fuels still have a higher energy density and are still better suited to powering long-haul trucks, ships, and airplanes.

Trees have two types of cellulose, called cellulose and hemicellulose, neither of which can be broken down by the same enzyme. And lignin is like the Roman concrete of the organic world: nothing seems to break it down. Complicating things further, the structure and quantity of lignin vary with species (softwoods have more lignin than hardwoods, for instance).

Instead of a relatively simple industrial process, the raw material has to be broken down enough to be sorted and the lignin removed (it can be used in other products). Then, instead of getting a single type of alcohol out, the two cellulose types produce two different alcohols. If you want to process the alcohols into other fuel products, it is likely that you’ll have to separate the alcohols and treat them individually. All of this represents a challenge that has kept wood-based biofuels from being economical.

The process of removing the water and breaking up the cellulose and lignin, called pyrolysis, is the best way to get fuel from trees at the moment.

The trick to creating liquid fuels is to hit that happy medium where the cellulose and lignin polymers fall apart enough to form short chain hydrocarbons, but not so much that the hydrogen falls off the carbon, or you break things up so much that you end up with methane, carbon dioxide, or carbon monoxide.

This is what a catalyst does. Somehow, and often not in a way that we understand, a catalyst lowers the energy barrier so that two chemicals can react at a lower temperature and pressure than they otherwise would.

So, the search is now on to find the right mixture of catalysts to maximize the production of useful hydrocarbons.

For (Dr. Katharine) Challis, the ultimate goal is to reverse the enzyme design process. Instead of asking how to improve an existing enzyme or modify an existing enzyme for a new task, you first figure out the energy landscape that the enzyme must operate in. From there, you design the enzyme to operate within that landscape. It’s an ambitious goal. READ MORE

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