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The ultimate biofuel? Researchers turn algae into oil

Is petrol going to literally be the green fuel of the future? A paper published by a team from Pacific Northwest National Laboratory (PNNL) in Utah, United States suggests that it might be. Researchers from the lab have developed a method to turn a thick “pea soup”-like paste of algae into a crude oil substitute in minutes. With additional refining, the PNNL team says, it’s possible to turn the crude into regular gasoline, aviation fuel or diesel.

Other useful byproducts of the process include clean water and a nitrogen, potassium and phosphorus, all of which can be recycled and used to grow more algae.

According to the lead author of the paper, Douglas Elliot, the technique developed by the Utah team marks a significant breakthrough over previous methods explored as it doesn’t require the algae to be dried first, thus making it cheaper, nor does the plant matter feedstock have to be pretreated with costly and dangerous solvent. The team adapted the design of an existing catalytic hydrothermal gasification (CHG) reactor and stripped out the chemical cleaners, leaving them with a high pressure system capable of separating out the mineral parts of the algae slurry using water, temperatures of up to 350 degrees Celsius and pressures of 3 000PSI.

“It’s a bit like using a pressure cooker, only the pressures and temperatures we use are much higher,” Elliot writes, “In a sense, we are duplicating the process in the Earth that converted algae into oil over the course of millions of years. We’re just doing it much, much faster.”

The three stages of algae fuel: slurry feedstock, crude oil and gasoline at the end. Isn't science amazing?
The three stages of algae fuel: slurry feedstock, crude oil and gasoline at the end. Isn’t science amazing?

The paper, Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor, was published in Algal Research back in September but the breakthrough went undetected until PNNL put out a press release last night.

Algae-based fuels have an advantage over other forms of biofuel, in that large areas of arable land aren’t required to cultivate algae in the same way that they are for ethanol derived from corn, for example. Therefore they wouldn’t have the same effect on food prices, yet retain the same carbon neutral benefits as a renewable resource. Research into algae also includes using the fast-growing plant matter to generate hydrogen, but if this process can be developed to an industrial scale it would get around the problem of having to build out a new fuel distribution system to handle hydrogen fuel. The existing supply network could be used globally.

The PNNL reactor can currently convert 1.5l of algae to about half its weight in crude and the other half into nutrients, with less than 10% wastage, in an hour. A key part of the process, however, is that the reactor can be run continuously rather than in batches – which has proved a stumbling point for other researchers  in the field. While building a suitable reactor would be costly, Elliot says, “We believe that the process we’ve created will help make algae biofuels much more economical.”

There’s no information in the report as to how energy efficient the process is at this stage, but work on commercialising the process is being undertaken by PNNL and Genifuel Corp.

One problem that it yet to be overcome, of course, is the smell of burning algae. If you thought gasoline fumes were unpleasant, try “a mix of dirty socks, rotten eggs and wood smoke”. Nice.

Want to see the reactor in action? Non smell-o-vision clip below.

(Images: PNNL)

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