3 things you need to know about biofuels

Why care about liquid fuel?

There's a reason we use different forms of energy to do different jobs, and it's not because we're all just that fickle. Instead, we've made these decisions based on some combination of what has (historically, anyway) given us the best results, what is safest, what is most efficient, and what costs us the least money.

In a nutshell, that's why liquid fuel is so valuable. So far, it's the clear winner when we need energy for transportation—especially air transportation and heavy, long-distance shipping—because it allows you to stuff a lot of energy into relatively small amount of storage space, and easily refill on the go. There are other options, of course, like electricity. And that can work quite well, depending on what you're trying to do. Eventually, we may find ourselves in a world where liquid fuel is no longer the best option. But we aren't there yet. And for those forms of transport that take us into the air or move our belongings very long distances, we aren't likely to get there for a good long time.

That's why I care about liquid fuel, and why I'm interested in the future of biofuels. Yes, biofuels do have a future. But what that future will be depends on whether we can control for some very messy variables. Here, in three points, are the big things you need to know about biofuel.

1. Corn ethanol really is flawed. But maybe not as much as you think.

Biofuel is a nice, round word encompassing a lot of tricky, little, oddly shaped dots. You can make biofuel from lots of different things, in lots of different ways. Corn ethanol, cellulosic ethanol, bio-oil, bio-diesel, algae oil—they all have some benefits and some detriments, which means they all have some big backers and some big haters. Right now, any biofuel produced at a big, commercially useful scale is bound to be ethanol, and in the United Sates, that means corn ethanol. But, from what I see, the evidence favors using options that aren't dependent on a dedicated corn crop. That's not to say that corn ethanol is the devil—its bad reputation comes, at least in part, from backlash against some pretty heinous overselling—but it does have some big drawbacks and we might have an easier time making truly Green biofuels another way.

Part of this stems from corn's big appetite for inputs, like fertilizer. Those inputs represent energy spent, and energy spent is (in today's world) greenhouse gas emissions produced. The more energy you have to spend on producing a biofuel—from making fertilizer and running the tractor for annual replanting, to powering the fuel production process and shipping fuel to the gas station—the less benefit you actually end up with at the end. There are lots of different ways to tally those numbers up, but Argonne National Laboratory has one of the best calculators around. Called GREET—a perky, welcoming acronym for The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model—it's a software program that adds up all the different ways energy is used and greenhouse gases are emitted over the life of a fuel, and runs simulations based on variables like geographic location, types of farming methods, and types of fuel production methods.

GREET figures that corn ethanol really can be better than gasoline. You can get more energy out of a gallon of corn ethanol than you used to make it. And a gallon of corn ethanol can reduce greenhouse gas emissions by somewhere between 18% and 28%, compared to a gallon of gasoline.

But here comes our friend, the yesbut. Yes, you can get an emissions benefit from corn ethanol. But, this only works if the ethanol plant is powered by natural gas. If it runs on coal, you're not reducing emissions at all.

Also: The picture only looks this rosy when you compare corn ethanol to gasoline, but not to any of the other competing biofuels. A 28% reduction in greenhouse gas emissions sounds fabulous, until you look at cellulosic biofuels—made from things like grass, stems, wood chips, and trash paper. There's lots of different ways to make cellulosic biofuels, including a cellulosic version of ethanol, and they reduce emissions by a whopping 82%-to-87%. Nobody is producing them at scale yet, but in a world of limited time and resources, cellulosic biofuels look like a better bang for our buck. Plus, you get some ancillary benefits from the plants that make cellulosics that corn can't match, including improvements to soil quality, and reduction of erosion.

2. We can screw up cellulosic biofuel, too.

It's important that I don't give cellulosic biofuels the used-car lot megaphone treatment that corn ethanol received. They're better, not perfect, and a lot of the research being done on cellulosic biofuels is focused on figuring out how to not screw them up. They could still backfire spectacularly—driving up food prices, dumping more fertilizer into the Mississippi, or even increasing the amount of carbon dioxide in the atmosphere. To keep that from happening, scientists say we have to pay a lot of attention to what's being grown, and where.

For instance, in the Midwest, it's likely the best biofuel crop won't be a single crop at all. David Tilman, an ecologist at the University of Minnesota and winner of the 2008 International Prize for Biology, has been studying prairie plant biofuels for more than a decade.

Out on the prairie, Tilman and his team found significant problems with growing a field of nothing but switch grass. By its lonesome, the grass grows in the sickly, patchy style of a 15-year-old's goatee—creating a temptation to douse it in fertilizer. After seven years, Tilman said, it usually needs to be plowed under and planted again. But when the team planted a mix of four native grasses and four native legumes—think alfalfa or clover—the results were very different. Together, the plants grew in a thick mass and didn't need to be re-seeded or fertilized. After 10 years, Tilman found these mixtures were producing 238 percent more energy, every year, than any one plant grown alone. They also made the soil more fertile, naturally increasing levels of nitrogen and phosphorous. "It makes sense," Tilman said. "It's a mixture of prairie plants that made that soil to begin with."

But even the most well-meaning, soil-enriching mix of plants has to deal with the problem of land-use change.

3. Land use matters. But there's still a lot we don't know about that.

Direct land-use change is easy to wrap one's head around. Say you own an acre of timber and you decide to clear it, because you can get a good price for growing biofuel crops there, instead. That timber was locking in a lot of carbon in the form of trees, and plants, and virgin soil. Depending on what happens to the trees, and how you treat that soil, you can end up inadvertently releasing a lot of carbon dioxide into the atmosphere. Enough to affect the net emissions of the biofuel crop you grow there later.

Indirect land-use change is a little more thorny. The world, as they say, is flat. An acre of corn or wheat grown in the United States isn't merely used to fatten American cattle or bake American bread. We participate in a global food market and what we do here has consequences abroad. So, if a farmer in the Midwest decides that she's going to take an acre of corn and replant it with a prairie grass and legume mix for biofuel, what happens?

Some experts are worried it would lead to an decrease in availability of corn, which would lead to a rise in the price of corn, and a farmer in some other part of the world, or even just another part of the U.S., deciding that he's going to capture that cash benefit by taking an acre of timber and turning it into an acre of corn. Or, just as bad, that the price increase would lead someone, somewhere, to go hungry.

At first glance, that logic sounds foolproof. And most researchers agree that it has to be taken into account and studied as we plan the future of energy. But, when you ask how big an impact land—use change might have—that's when the experts start to disagree.

There are some researchers who think land-use change basically negates the usefulness of all but a tiny portion of biofuels that come from certain farm, industrial, and municipal wastes. There are others who think that it won't really be a problem. Based on the majority of scientists I've spoken with and the research I've read, I think the reality lies somewhere in between, and that there's a good chance cellulosic fuels can skirt the issue if they're done the way people like David Tilman have proposed.

At the heart of this debate: How well the computer models used to predict land-use change reflect reality. A model is only as accurate as the assumptions that go into it, and critics say that the worst-case-scenarios are based on some pretty faulty assumptions. First, there's the assumption that increased demand for a crop like corn will inevitably lead to deforestation, or plowing under previously wild land. But in the United States, as well as overseas, there's a surprising amount of previously cleared land that isn't being used to grow much of anything, either because farmers have been paid a subsidy to leave it fallow, or because the land turned out to be no good for annual row crops, or, as is common in developing countries like Brazil, because cleared land is owned land—even if you're just keeping one cow on it.

"We're only using between half and a fourth of all previously cleared forest land on Earth for crop production in any given year," says Keith Kline, a global change and developing countries analyst with the Oak Ridge National Laboratory.

Kline, who worked in developing countries for 22 years studying and promoting biodiversity, is one of several scientists I spoke with who said that—contrary to some land-use change models—deforestation is not about crop prices. At least, not solely. Social and cultural factors—like the desire to own land you can get for free just by clearing it—are equally important. You can't assume that a rise in global crop prices will naturally lead to an increase in deforestation, or that deforestation would stop if crop prices stayed the same or went down. In fact, according to Kline, the highest rates of deforestation worldwide happened in the 1990s, before the ethanol boom in the U.S. and at a time when food commodity prices were consistently low. And deforestation rates have been falling ever since.

The second bad assumption the worst-case models make is that the same amount of land can't grow more crops. Perennial mixes for cellulosic biofuels could actually be grown alongside row crops, or on the same land, between the harvest and next planting, Tilman told me. At the same time, crop yields—the amount of useable stuff you can grow without increasing the square footage—have consistently gone up, every year, in the United States. That happens in small increments today, but there's plenty of room for yields to improve dramatically overseas. The productivity of what you do with the crops can also increase. For instance, most corn is actually used for feeding livestock, not people. But less corn being available doesn't necessarily mean people eat less meat. Instead, they might just switch the kind of meat they eat. It takes about 10x as much corn to grow a pound of beef as it takes to grow a pound of chicken.

Finally, some predictions in the worst-case models don't match up with what we've seen in the real-world. They assume corn exports will go down, as U.S. ethanol production rises, leading to those higher global prices that theoretically inspire deforestation to begin with. But that's not what happened. Instead, in 2007, as corn ethanol production in America hit 6 billion gallons, corn exports rose by 14 percent, compared to the previous year. In fact, they've been, generally, trending on the rise since 2003.

Image: Cornfield, a Creative Commons Attribution No-Derivative-Works (2.0) image from der_bauer's photostream