In the world of biofuels, the pattern is familiar: Concerns grow over one crop's impacts or overhyped potential, and another then appears to take its place with promises of planet-saving prowess.
The latest savior is jatropha, a drought-resistant and hardy plant that supposedly can deliver high energy yields on marginal land and eliminate concerns about food competing with fuel for farmland.
Only a few large-scale jatropha projects have begun around the world, but their potential is drawing investors' attention. U.S. automaker General Motors just announced a five-year partnership with the U.S. Department of Energy and India's Central Salt and Marine Chemicals Research Institute to demonstrate the commercial viability of jatropha as a biofuel feedstock.
That commercial viability GM is looking for will depend on the yields of a crop that up until recently was considered simply a weed.
Yield Hopes and Hype
Native to South America, jatropha has been transplanted as a biofuel crop to tropical areas around the world, with momentum growing in India and Africa.
As of 2008, 242 jatropha biofuel projects covered 2.2 million acres; those numbers are likely much higher now, and they will continue to grow as more companies vie to get in on the ground floor of the next miracle energy crop and countries like India and China expand their biofuel demand. The Global Exchange for Social Investment predicted in its 2008 report that 32 million acres would be in production by 2015.
"I think there is good reason to have hopes for it," said Alice McKeown, a research associate at environmental group Worldwatch Institute.
"That being said, whenever you try and take a plant like that that has typically been a pest or a weed, and then you try and cultivate it intentionally, that's where the problems come in.
"A lot of the testing for jatropha has been under controlled circumstances, and it has had very high yields, and then when you move it out of the controlled environments and on to the marginal lands, of course the yields go down. So there is a question about the actual scale that you could do it at."
Estimates of jatropha's biofuel production potential vary. Several estimates put the oil yield at about 200 gallons per acre per year, or even higher; this would place it second only to palm oil — environmental scourge of forests in Indonesia and Malaysia — on the productivity list among common agricultural biofuel crops.
Achieving those yields on a large scale, though, will most likely require better than "marginal" lands and better than primitive farming practices.
"It is highly uncertain, because no one has really gone in there and done a comparative study to actually examine what the yields are across various landscapes," said Jennifer Baka, a researcher at Yale University who will soon head to India and Brazil to study some of those unknown details of the jatropha plant.
"But most of the academic literature is casting doubt; the initial hype was that you can get 15 kilograms of seeds per tree per year. That's unrealistic, most of the stuff in India now is at about 1.5 kg of seeds per year, and that's with applying fertilizer and irrigating."
What is Marginal?
In Central America, the United Biofuels of America industry group is supporting a project known as the Million Gallon Challenge. It aims to eventually produce 2 million gallons of jatropha-based biodiesel per day, from about 605,000 acres of land.
Notably, one of the project's development areas is "intense farming for propagation" along with irrigation and fertilization. Clearly, growing jatropha on large scales does not mean simply finding a rocky hillside, throwing down some seeds and waiting for a gas tank to fill up.
"There is no such thing as marginal land, not really, not when you're trying to make money with a crop," said K. Shaine Tyson, of Rocky Mountain Biodiesel Consulting.
"When you start looking at crops on an international scale, then you're going to put in some resources, and eventually take up some relatively good quality land. To get that yield, you have to be on pretty good quality land, with sufficient water and fertilization, and you have to manage it."
Small-scale jatropha farming may have more potential than scaling up to meet international fuel demands. McKeown said that small, rural communities in Asia that don't have access to the electricity grid could benefit from the crop's energy potential.
"You can bring in a biodiesel generator and then grow jatropha, that can significantly improve the quality of lives for these communities," she said.
"It lets them have lights and all sorts of other advantages. So in that sense, I think jatropha will have a role to play in the biofuels future, I just don't know that it is going to be the next sugarcane or the next corn. We just really don't know about scale."
A 2008 policy brief from USAID agreed on the plant's local potential, especially given that when kept to the marginal lands it won't compete with much-needed food crops in those areas.
Ecosystems and GHG Emissions
The other issue that often goes unmentioned is that even marginal lands aren't complete wastes of space.
"They're often providing habitats, they provide filtration services, they provide a lot of benefits," McKeown said. "And if you put them under cultivation, some of those benefits are taken away. So it is not exactly free lands without any negatives."
Also, research into jatropha's potential as a greenhouse gas emissions saver has yet to be fully explored. The major sticking point that arose with corn ethanol, sugarcane and other feedstocks is the concept of indirect land use changes and other elements of total lifecycle emissions that reduce the overall benefits, with corn-based ethanol in particular.
"What are the material and energy needs to move into these marginal lands, and how would that compare to putting it on arable land?" Baka asked.
"Marginal lands are usually marginal for a reason: they're off the main transportation routes, maybe they're on rocky hillsides – what does it take to actually get out there? How are you going to get your water out there?"
It has only been a few years since jatropha burst on to the biofuels scene, but already that familiar refrain of too much hype and not enough benefit has gained volume. Whether or not projects like GM's India partnership — which is starting with about 200 acres in India devoted to jatropha farming — or the Million Gallon Challenge in Central America herald a new major player in the alternative fuels world or just a flash in the pan remains to be seen.
"I think its going to be a bridge crop, trying to get us from the food grain-based feedstocks, the corn and the soybeans, into algae and cellulosic," Baka said. "In the long term, it does require land, and I predict that there will be some competition with arable land. There is a still a high degree of uncertainty. Nobody really knows how to grow this thing properly yet."