Advanced biofuel technologies could provide significant benefits in countering climate change, a study project led by scientists at Colorado State University (CSU) in the US has found. Couple these technologies with carbon capture and storage (CCS) and the result could be the achievement of negative carbon emissions. Their research, which was funded by US and Brazilian agencies, has been published in the Proceedings of the National Academy of Sciences.
Biofuels have been controversial in some circles over fears regarding changes in land use and the possibility that other land uses would ‘sequestrate’ carbon more efficiently. Plants, of course, absorb carbon to grow and build their tissues, and some have suggested that planting grasslands and/or forests would be a more efficient method of sequestrating carbon than growing and using biofuels.
The CSU-led team, which included plant scientists, engineers and ecologists, accounted for all the carbon flows in biofuel systems and then compared them with those for grasslands and forests. This was one of the first such studies undertaken and the results indicated that there were certain clear strategies that would have a net carbon benefit.
The focus was on cellulosic biofuels, which are created from the non-edible parts of plants. As the research was conducted in the US, the plant that was examined was switchgrass, a native grass found in many areas of North America. In that continent, it is a major contender for sustainable biofuel production.
The research team used modelling to simulate the cultivation of switchgrass, its use to make cellulosic biofuels and subsequent CCS. Throughout, ecosystem and carbon flows were tracked. “What we found is that around half of the carbon in the switchgrass that comes into the refinery becomes a byproduct that would be available for carbon capture and storage,” reported CSU Natural Resource Ecology Lab research scientist John Field. (In CCS, the carbon dioxide byproduct of biofuel production is pumped into depleted oil wells or other suitable geological formations.)
It should be noted that at least one biofuel refinery, in the US state of Illinois, which is producing ethanol from corn (maize), is already using CCS technology. However, this is still not common practice.
The researchers also compared the results of their modelling with alternative carbon sequestration methods, including planting forests or grasslands. Analysing three differing case studies in the US, the team concluded that growing switchgrass for biofuels had a carbon benefit per hectare equivalent to reforestation but significantly greater than what could be achieved by planting grasslands.
“In the Great Plains, prairie is the more natural cover,” he pointed out. “Those systems don’t suck up as much carbon as a forest system does. If you start putting biofuels in the mix, they have two-and-a-half times the carbon benefits over grasslands. If you’re in an area where grassland would be the native cover, there’s a clear advantage to using biofuels.”