There's money to be made in the barren corners of the world.
From the California desert to the badlands around Chernobyl, Ukraine, bioenergy is taking root in the form of moss and algae. In Ireland and Denmark, farmers are planting switchgrass and miscanthus in low-grade soil, hoping to turn a profit on biofuels markets.
Surplus land, or land unused in either conservation or agricultural production, offers an elegant solution to the food versus fuel arguments that have plagued bioenergy since its inception. If you can't grow food on it, the logic runs, why not plant fuel?
The problem, according to a new study in the journal BioRisk, is that the productive capacity of known surplus lands may be greatly overestimated. A number of caveats need to be taken into consideration when assessing land, particularly degraded, marginal or abandoned land, as a potential site for biofuels, the study finds.
"When we looked at the different estimates of [the size] of existing surplus land, we saw a huge variability of assessments," said Jens Dauber, a researcher at the Johann Heinrich von Thunen Institute of Biodiversity and lead author of the study. "The different groups of researchers were comparing different types of land, and there was no consensus over what is or isn't surplus land."
"If you want to make a better map of our land use -- who's living on the land, who's working on the land, what ecosystems services you're dealing with -- we might find out there's a whole lot of land we just can't convert into anything else," he added.
Putting the brakes on bioenergy
Many countries, particularly in Europe, include ambitious biofuel quotas as part of their short- and long-term renewable energy goals. This has catalyzed an aggressive top-down approach that often fails to properly assess the specific characteristics of a particular landscape, and sometimes leads to lower-than-expected yields, wasted investment and dissolution among farmers.
"Pressure is going to increase because many countries have set their bioenergy targets very high," Dauber said. "To meet our 2050 targets, we still don't know where we're going to plants the crops we need."
A collaborative work by 11 scientists in Europe and the United States, the BioRisk study identifies a series of caveats that must be taken into consideration when assessing the viability of surplus land for biofuel cultivation.
The study finds that availability of water resources, soil quality, conservation requirements, greenhouse gas emissions from disturbed soils and existing habitation or other human use are all factors that need to be taken into consideration -- and have sometimes been ignored -- when designating marginal land for the production of biofuel.
Even hearty species like switchgrass and miscanthus, perennial species that grow in regions unsuitable for agriculture, tend to yield less biomass when planted in nutrient-poor or degraded soil, Dauber said.
Coming at the problem from both sides
Rather than the top-down approach to bioenergy taken in the past, the study advocates a stronger role for local players, like farmers and regional governments, in assessing the viability of new projects.
These parties tend to better understand the complex interplay of water, soil and human use that accompanies any given landscape, Dauber said.
At the same time, action from the top -- from national governments or intergovernmental bodies -- is necessary to ensure long-term stability in bioenergy markets, he said.
"You have to create demand for crops," he added. "Perennial crops will be on the land for 10 to 20 years, and farmers need to know that in that time, there will still be customers to take their products."