Which is the better use for a plot of land: growing crops to feed nations or growing crops to power them with biofuel? The answer to this question is, perhaps not surprisingly, complex and turns on the definition of “surplus” land, or idle, marginal spaces. Now, an interdisciplinary group of researchers from Europe and the US has decided to nail these concepts.

Despite the heated “food versus fuel” debates, researchers noted that there is no common language or guidelines that brings together this emerging field. Moreover, no one seemed to agree on what, exactly, defines surplus land.

For example, does the region already have more than enough food to feed its population? Do people living around the area support nuclear energy, or prefer wind or solar? How much gas will farmers have to use driving to and from those new plots? Are there any endangered or endemic species living there? What’s the soil type and the annual rainfall?

“This is exactly what we stumbled over when reading the international literature about land availability for producing bioenergy crops – there is no clear-cut definition of surplus land,” says Jens Dauber, a landscape ecologist at the Thunen Institute in Germany and one authors of the paper in the journal BioRisk discussing the concept. “We thought it was worthwhile to have a look at what people understand when talking about surplus land.”

Combing through all of the published literature on the topic, Dauber and his colleagues encountered a plethora of terminology that seemingly all referred to different versions of the same thing, including marginal land, reclaimed land and degraded land.

This confusion “might not be very helpful” when it comes to making proper assessments of bioenergy potential for land plots, Dauber says, so he and his colleagues created detailed definitions of various types of surplus land; these are areas not currently used for agriculture due to unfavorable soil, climate or other factors.

Definition in hand, governments or individuals can identify the ideal places to grow biofuel plants and, from there, figure out which crops are best suited for plots of surplus land.

Most food crops, like corn and cereals, require pesticides, fertilizers and fossil fuels during steps in their production, making them ill suited for the surplus plots. Perennial crops like oilseed rape and switch grass, however, require fewer inputs necessary for them to thrive, and thus stand out as energy crops. Cultivated trees like poplars and willows could work as biofuel staples, too.

Once biofuel producers identify which crop or group of plants are the best match for the local landscape, they can brainstorm ways to creatively utilize surplus land to benefit not just energy production, but the environment, too.

Biofuel crops can be planted along the edges of farmers’ fields, for example, where they’ll make use of formerly wasted space and also trap crop runoff – a common pollutant – and prevent it from emptying into nearby streams and lakes. Mosaics of biofuel crops planted together would create better habitat for wildlife than the typical crop monocultures. And amidst the broader agricultural landscape, diverse biofuel plants may help create microclimates that mitigate climate change.

“We might get socioeconomic benefits and at the same time preserve biodiversity in these areas,” Dauber says.

Dauber and his colleagues point out that biofuels can couple with other green energy options and contribute to overall regional sustainability.

All told, a country, region or even company’s decision to convert a plot of land to biofuel crop production depends on individual tradeoffs between food availability, other alternative energy options, the environmental friendliness of an energy crop design and the project’s economic viability.

“We have to openly discuss all of these issues, but in the end this should be a decision by the people about what kind of energy they want for the future,” Dauber says. “Though, if we run out of fossil fuels, there’s not much of a choice anymore.”

Reprinted from Ecomagination, October 21, 2012.