Web exclusive posted June 27, 2008 at 1:26 p.m. CST

The global biomass community continues to be in search of sustainable and cost-effective sources of biomass materials for producing cellulosic and other advanced biofuels. To that end, scientists from the Carnegie Institution at Stanford University released a report indicating that current abandoned or degraded agricultural lands are a viable option for growing energy crops that could be converted into biofuels.

According to Elliot Campbell, a post-doctoral fellow at Carnegie Institute who led the research effort, there are approximately 470 hectares (1.8 million square-miles) of abandoned lands globally that could be available for growing energy crops. However, the potential yield of this land area, equivalent to nearly half of the land area of the United States (including Alaska), depends on local soils and climate, as well as the specific energy crops cultivation practices in each region. "Recently, there has been criticism of biofuels if you implement them by using cropland or current forestland," Campbell said. "So, one alternative would be to use abandoned agricultural lands, and that was our motivation. I think we might be the first group to actually get a data-driven estimate of the global potential of these lands."

Campbell and his team determined that the global harvestable biomass that could be utilized would be between 1.6 billion and 2.1 billion dry tons per year, which would satisfy approximately 8 percent of worldwide energy demand. "If you think about [1.6 billion to 2.1 billion dry tons per year] in terms of energy content, that's about 32 to 41 exajoules per year or about 7 [percent] to 8 percent of primary energy demand," Campbell said. One exajoule is a billion billion joules, equivalent to approximately 170 million barrels of oil.

Additionally, the research team factored in historical land-use data, satellite imaging and ecosystem models into their assessment to make their conclusions. "The main data we used was historical maps of crops and pastures," Campbell said. "The maps we used were about a decade time-scale, where every decade you have another new map. We were able to identify abandoned agricultural regions in areas where the crop or pasture decreased over time."

At a regional scale, the study revealed larger opportunities for other parts of the world such as African regions where grassland ecosystems are productive and fossil fuel demand is low. In regions like this, biomass could provide up to 37 times the energy currently used, Campbell noted. "If you look at the regional scale, there are some places where within a given country the amount of biofuel potential from this abandoned agricultural land could be actually much larger than the total primary energy demand," he said.
Campbell said the United States, Brazil and Australia possess bioenergy potential from abandoned agricultural lands, but even if the lands were used exclusively for bioenergy, they would still only yield enough for approximately 6 percent of national energy needs. "I think there are a lot of efforts right now to figure out how much biomass we can get from marginally productive lands, and I think our paper gives these current efforts a global context for how much they might be able to scale up to," he said.