Scientists Convert Algae Into Crude Oil In One Minute -- A Process That Takes Nature Millions Of Years
Scientists at the U.S. Department of Energy's Pacific Northwest National Laboratory have created a quick and cheap way to change algae into crude oil. The algae fuel conversion process, called hydrothermal liquefaction, has been around in various forms since the 1970s, but it has always been prohibitively expensive and time-consuming. This new process condenses several parts of the liquefaction process into one step, allowing PNNL scientists to cheaply convert algae into oil in just a minute--something that takes nature millions of years to do.
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"It's a bit like using a pressure cooker, only the pressures and temperatures we use are much higher," said Douglas Elliott, the laboratory fellow who led PNNL's research. "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 process starts with a wet algae slurry that resembles pea soup. Scientists pour the algae soup, which is about 20 percent algae and 80 percent water, into a tube that churns around the algae while subjecting it to 660 degree temperatures and a pressure of 3,000 psi. This pressure cooker process breaks down the algae into a light, crude oil in a matter of minutes. "We can clean up that bio-crude and make it into liquid hydrocarbons that could well serve to displace the gas, diesel, and jet (fuel) that we make from petroleum now," said Elliott. The refining part of the process can even be performed in existing petroleum facilities.
One of the things that has made previous hydrothermal liquefaction efforts so expensive is that they've required algae which has been dried, a process that is not only expensive but time consuming. But the PNNL process works with wet algae, which cuts costs "a great deal," according to Elliott. And there are ancillary benefits to using wet algae over dry: the water from the processed algae yields usable gas, and the water can be recycled to grow more algae, further lowering costs.
Another issue with making a viable algae fuel has been that growing large quantities of algae is difficult. Open-pond systems are cheap to run but can yield contaminated algae; indoor systems yield better algae, but are expensive to run. With the PNNL process, though, pretty much any type of algae can be throw in with good results.
"People have this slightly inaccurate idea that you can grow algae anywhere just because they'll find it growing in places like their swimming pool, but harvesting fuel-grade algae on a massive scale is actually very challenging," says Elliott. "The beauty of our system is you can put in just about any kind of algae into it, even mixed strains. You can grow as much as you can, any strain, even lower lipid types and we can turn it into crude."
The Department of Energy has estimated that it would take 15,000 square miles of land--a few thousand miles larger than Maryland--to grow enough algae to replace all petroleum fuel in the U.S.
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