Algae to crude oil: Million-year natural process takes minutes in the lab
Process simplifies transformation of algae to oil, water and usable byproducts
(L-R): Algae slurry; biocrude oil; and, with further processing, refined biocrude which contains mostly the makings of gasoline and diesel fuel.
Engineers at PNNL have created a continuous chemical process that produces useful crude oil minutes after they pour in harvested algae — a verdant green paste with the consistency of pea soup. The research was reported recently in the journal Algal Research. A biofuels company, Utah-based Genifuel Corp., has licensed the technology and is working with an industrial partner to build a pilot plant using the technology.
Why it matters:
While algae has long been considered a potential source of biofuel, and several companies have produced algae-based fuels on a research scale, the fuel is projected to be expensive. The PNNL technology harnesses algae's energy potential efficiently and incorporates a number of methods to reduce the cost of producing algae fuel. "Cost is the big roadblock for algae-based fuel," said Douglas Elliott, the laboratory fellow who led the PNNL team's research. "We believe that the process we've created will help make algae biofuels much more economical."
In the PNNL process, a slurry of wet algae is pumped into the front end of a chemical reactor. Once the system is up and running, out comes crude oil in less than an hour, along with water and a byproduct stream of material containing phosphorus that can be recycled to grow more algae. With additional conventional refining, the crude algae oil is converted into aviation fuel, gasoline or diesel fuel. And the waste water is processed further, yielding burnable gas and substances like potassium and nitrogen, which, along with the cleansed water, can also be recycled to grow more algae.
PNNL scientists and engineers simplified the production of crude oil from algae by combining several chemical steps into one continuous process. The most important cost-saving step is that the process works with wet algae. Most current processes require the algae to be dried — a process that takes a lot of energy and is expensive. The new process works with an algae slurry that contains as much as 80 to 90 percent water. Researchers have been able to extract usable gas from the water and then recycle the remaining water and nutrients to help grow more algae, which further reduces costs.
Laboratory manager Todd Hart pours algae into a bucket as he begins an experiment to convert the substance into biocrude oil.
The PNNL system runs continuously, processing about 1.5 liters of algae slurry in the research reactor per hour, an amount that's much closer to the type of continuous system required for large-scale commercial production than systems that run a batch at a time.
In addition to Doug C. Elliott, authors include PNNL staff Todd R. Hart, Andrew J. Schmidt, Gary G. Neuenschwander, Leslie J. Rotness, Mariefel V. Olarte, Alan H. Zacher, Karl O. Albrecht, Richard T. Hallen and Johnathan E. Holladay.
The recent work is part of DOE's National Alliance for Advanced Biofuels & Bioproducts, or NAABB. This project was funded with American Recovery and Reinvestment Act funds by DOE's Office of Energy Efficiency and Renewable Energy. Both PNNL and Genifuel Corp. have been partners in the NAABB program.
Genifuel has worked closely with Elliott's team since 2008, licensing the technology and working initially with PNNL through DOE's Technology Assistance Program to assess the technology.
Elliott, Doug C., TR Hart, AJ Schmidt, GG Neuenschwander, LJ Rotness, MV Olarte, AH Zacher, KO Albrecht, RT Hallen, JE Holladay. 2013. "Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor." Algal Research 2:4: 445-454.
For more information, see the PNNL news release.