While ethanol produced from corn and cellulosic feedstocks offers a viable renewable energy alternative, it also comes with some limitations — primarily the fact that the majority of America’s transportation fuel infrastructure (pipelines and distribution networks, storage facilities, and engines) have been designed for petroleum products, not ethanol.

Because of this, researchers at SDSU and around the country are pushing ahead to develop third generation biofuels that could be used as direct replacements for gasoline, diesel or jet fuel. “Because these third generation biofuels are similar or identical to their petroleum-derived counterparts, they are called direct ‘drop in’ replacements. They will seamlessly fit into the existing fuel transportation, storage, and utilization infrastructure,” explains Gibbons.

Research at SDSU to create these third generation biofuels is focusing on two approaches. One approach uses photosynthetic cyanobacteria — a bacterial version of algae — which can be reengineered to convert sunlight, carbon dioxide and water directly into third generation biofuels. “They are like little factories that spit out biofuel molecules without the need for starch or cellulose,” explains Gibbons.

A second process, called thermochemical pyrolysis, uses high temperatures and pressures to convert cellulosic biomass into long hydrocarbon chains that are similar to gas, diesel or jet fuel.

Gibbons acknowledges that the challenges with these third generation processes is obtaining high yields at fast rates, but the research is promising. He anticipates seeing these third generation fuels in pilot scale, pre-commercial testing by 2015.

Gibbons sees all three generations of biofuels being utilized in the future. “Our new research is not intended to replace corn-based ethanol. We have the infrastructure for corn-ethanol plants in place, corn ethanol has benefits, and distillers’ grains are a valuable feed coproduct. So, those plants will remain,” he says, and anticipates that as corn yields continue to increase over the next decade there will likely also be similar continuous growth in corn ethanol production.

“The incentive with second and third generation biofuel research is to add to the portfolio and diversity of how liquid transportation fuels can be produced and where they can be used,” he explains, noting that the military is increasingly interested in using renewable fuels.

As these new production processes emerge, Gibbons foresees ethanol production facilities with greenhouses constructed alongside, using engineered cyanobacteria to produce additional ethanol or drop-in biofuels from the unused carbon dioxide and low grade heat. “There are a lot of synergies between these systems to add value and efficiency to existing plants,” says Gibbons.

The first round of cellulosic ethanol facilities are primarily being constructed as “bolt-ons” to existing corn ethanol biorefineries, to also take advantage of these synergies. Gibbons anticipates that as stand-alone cellulosic facilities are built in the future, they will likely be smaller plants (20 to 30 million gallons), and will be strategically located near the feedstock (grass, cornstover or timber) that they use. He explains this is because transporting these lower density feedstocks over long distances can be challenging and expensive. He adds that these new facilities could easily include secondary biofuel production via a facility for cyanobacteria as well.

Gibbons believes these formats will lead to a total biorefinery concept in the U.S. in the future. “Instead of producing one product, a cluster of facilities could produce ethanol, green gasoline or diesel, jet fuel, and industrial chemicals such as isoprene,” he explains.

On that note, Gibbons believes the sky is the limit for where biofuel research and development is headed – and he says that spells opportunity for young people looking ahead to future careers. “The growth in biomass ethanol and third generation fuels is just beginning. We are going to need many more students in science and engineering to make this a reality. For individuals who want to stay in the Midwest and rural communities this is a great career field,” Gibbons concludes.