ROTORUA, New Zealand—My pitches to Ars’ editors are, in contrast to my articles, short and to the point. “I’m going to New Zealand soon. They have a big forestry industry and there is a local research institute trying to turn waste wood into biofuels. I think that would make an excellent story.
In my mind, its acceptance was equally brief: “Sweet as. Enjoy your trip to biochemistry land.”
Today, biofuels may conjure images of ears of corn or Priuses for US readers, but the domestic industry has been as much about politics lately as it has been about scientific innovation. While researchers and scientific organizations have looked into finding green energy sources in everything from human waste to humble algae, state and federal governments continue to tangle over how much of a priority this area should be.
I 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. While that doesn’t mitigate the emissions entirely, at least you get something useful out of the process. And with wood versus crops specifically grown for biofuels, you can’t choose your materials and match a process to make it efficient. Instead, Scion faces a unique challenge: find a process that works for New Zealand timber, and then come up with an efficient processing chain. Compared to the grasses and corn of the States, this seemed to be a biofuels battle taking place primarily in the lab.
I eventually discovered my whole premise was misguided—biofuels in New Zealand aren’t really about biochemistry, either. Or, at least they’re not about biochemistry. During my afternoon at Scion’s sprawl-y innovation park, I found myself listening to a lot of economics and… physics? Sometimes you just can’t escape your day job, I suppose. But it turns out that physics may offer some insight into how, long-term, the biochemistry of biofuels might be improved.
Wait, why do we care about corn again?
I’m getting ahead of myself, of course. Why do people anywhere care about biofuels, again?
The biggest problem with fossil fuels isn’t that burning fuel releases CO2. No, the problem is that the loop is not closed. Rather, the fuel cycle is closed, but the time between CO2 being released by your Ford F150 and that CO2 turning up as an oil deposit is millions of years. In the intervening years, the equilibrium amount of free CO2 is far too high for our own good.
An ideal fuel cycle would turn CO2 back into fuel within just a few years—or, at least, fuel and other things. Reliance on long-dead trees for hydrocarbons doesn’t stop at gasoline, after all. Lubricants and plastics are another two uses that spring to mind, and there are others—more loops that need to be closed in the near future.
So, what are the alternatives? Deriving oils and fuels directly from plants is an ancient tradition among humans. Can a high-tech version play a role in supplying our future energy needs?
The US already devotes a lot of corn to making fuel. Of course, corn is also food, so that raises a second issue: land used for fuel cannot be used to grow food. As the world’s population does like their daily nutrition, this creates some tension. 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.
You can, of course, separate the edible parts of the plant from the inedible and use the latter to make fuel—that way you don’t lose as much arable land to fuel production. Unfortunately, that doesn’t help much because the plant that gives us corn is actually a pretty low-quality biofuel feedstock. There are other crops, like switch grasses, that offer a much larger fuel yield per land area. But there are distinct environmental costs associated with those, too. Grasses may need a lot more water than can be sustainably supplied, for instance.
All this means that the hunt for good biofuel crops and processing techniques is far from over. And all that brought me to Scion.
Welcome to Scion
As befitting a research institute devoted to all things wood, Scion has a large and beautiful campus, set on the edges of a recreational forest and an active geothermal field. The main building is a lovely affair of wood paneling, wood art, and Maori wood carving. The receptionist greeted my arrival in typical kiwi-friendly fashion and quickly worked out that I was early. (Not an hour early, I was early—the joys of jet lag and a relaxed attitude toward my agenda.) I took advantage of my host’s surprise to sleep through a safety video and leach some Wi-Fi to catch up on email.
In an aged office piled high with paper, my host, Dr. Paul Bennet, took me through the ins and outs of a very practical approach to biofuels. Bennett was the first to disabuse me of the notion that I would be getting a story of biochemical research. This initiative is actually all about economics. Biofuels and forestry are not, I discovered, exactly a match made in heaven.
Now, on the surface, they could be. Plantation forests for timber and paper usually use fast-growing trees, and often they are grown on land that is unsuitable for other forms of farming: hill country, for example. At face value, this removes the problem of competing with food crops, and you gain a viable source of fuel from forestry waste.
Dig a bit deeper and it still looks OK. 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.
But Bennett also pointed out the big problem: trees harvested for timber grow for a long time before they are harvested. Fuel, ideally, comes from a fast growth-and-harvest cycle. And that’s before even considering the transport issue.
Oil comes out of wells and can be transported in pipelines. It’s easy to get a lot of crude from a single location and deliver it to a single location, so you can build an enormous refinery that distills, cracks, polymerizes, and otherwise cooks the crude oil into a huge range of organic chemicals that can be shipped off for use or further processing. Scale is built in.
Biofuel feedstocks don’t transport easily, and they’re hard to scale.
“One of the big costs around biofuels is always the feedstock cost,” 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.”
Plant matter is spread out over a wide area and has to be harvested. After harvesting it needs to be brought to a central location for processing. What scale is most economical for that? One huge refinery gives you economies of scale on the processing end but increased losses due to transportation; smaller plants might meet somewhere in the middle.
That balance point where the scale makes sense really depends on the nature of the crop and the land that you are going to harvest from. And both of those can change depending on historical land use.
In the US biofuel market, for instance, corn is king, and the economics of turning it into biofuel are well established. But it is probably not going to stay that way. It competes with food production on two counts: it grows on the same land as food crops, and every kernel of corn that goes into a biofuel reactor is a kernel removed from a potential mouth. For the next generations of biofuel crops, it is not yet clear what the future looks like—small and distributed, large and centralized, or somewhere in between.
That economic reality is what drives current research. 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.
But even assuming the basic economics of harvesting and transport eventually work out, this trip to Scion reminded me there remain problems with the chemistry.