Researchers are envisioning a day when we could replace fossil fuels with biofuels from algae grown on large platforms in the ocean.
The strategy could enable us to produce algae-based fuels without using up land that supports food production, and could also reduce some of the costly inputs now required for algae production.
In theory, algae can produce far more oil than other common biofuel crops. Compared to the average annual yield of 50 gallons per acre for soybeans, for example, some types of algae can produce as much as 6,000 gallons per acre. However, many hurdles still stand in the way of large-scale and economically viable production. Half of the cost of growing algae is in providing a steady supply of food and water, the growth medium. And harvesting the algae, which floats around suspended in water, is energy intensive.
Even with these best technologies today, algae-based biodiesel costs about $56 a gallon to produce.
However, two engineers at Kansas State University — Wenqiao “Wayne” Yuan and Zhijian “Z.J.” Pei — believe that cost could be significantly reduced by growing algae in the ocean on very large, supporting platforms. In fact, with more research effort, Yuan says he believes it could be possible to lower the cost of algae-based fuels to about $5 a gallon within five to 10 years.
“It will take that much time to really understand the fundamentals of large-scale algae production and to establish pilot projects,” he said.
One of the areas that Pei and Yuan are working on is to identify oil-rich algae species that are inclined to settle down and grow en masse on a solid surface, a characteristic that would make algae production manageable and harvesting much simpler.
“We think there is tremendous potential for algae oil production if we grow it on big platforms and incorporate the ocean into the system,” Yuan said. The ocean would provide a steady supply of both food and water, eliminating much of the costly input that goest into algae-based fuel production today.
The researchers are currently addressing several broad questions: By what mechanisms do algae attach to various surfaces, what materials do algae prefer, and what surface textures, if any, encourage the algae to bloom and grow?
Pei says the research team has achieved some exciting results. In studies of two species of algae characteristically high in oil content and fast growing, both species attached very well to a stainless steel, thin-film surface that was slightly dimpled. Furthermore, once the algae attach, they grow very well, producing a green clump several millimeters thick.
“Just like geckoes cannot walk on a perfectly smooth surface, our results indicate that the algae attach better on a slightly textured surface,” Yuan said.
Stainless steel was chosen because it is easy to machine or texture, durable and reasonably cheap.
“We are doing very fundamental research now,” Yuan said. “We need to understand the algae attachment mechanism before we can select species more likely to attach to a solid support.”
Pei and Yuan think large-scale algae production done on very large support surfaces in ocean water is quite feasible. They are imagining a long, continuously rolling surface like a conveyer belt.
“Right now, we really are thinking in terms of a large-scale biological and mechanical production system,” Yuan said.
As Yuan describes the system, the algae would grow on the thin-film surface submerged under the ocean. At some point, the growth surface would roll up into the sunlight and the algae dries. A harvesting knife at the end of the conveyer system would then scrape off the dried algae, at which point the surface would submerge again to become home to the next growth of oil-rich algal material.