Engineers have designed a continuous chemical process that produces useful crude oil in under an hour. All from a verdant green algae paste with the consistency of pea soup…
The crude oil produced at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) can be refined into gasoline, heating oil, diesel fractions, and with a bit more expense and effort, aviation grade kerosene. The PNNL research was reported recently in the journal Algal Research. A bio-energy company, Utah-based Genifuel Corp., has licensed the technology and is working with an industrial partner to build a pilot plant using the technology.
Nature’s Million-Year Old Process in Minutes
“It’s a bit like using a pressure cooker, only the processes and temperatures we use are much higher,” says Douglas Elliott, the research leader. “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 faster.”
A previous incarnation of this technology, called hydrothermal liquefaction, was pioneered in the 1970s, a time of heightened worries about fuel shortages. But the method involved drying the algae and adding chemicals to extract lipids: a process that was difficult, energy-intensive and expensive.
The experiment, part of the US Department of Energy’s National Alliance for Advanced Biofuels and Bio-products, eliminates two stages in the laborious laboratory process of converting algae to oil.
Scientists don’t have to expend fuel to dry the algae before sticking it in the reactor. Instead, the mix goes into the reactor as a well-stirred slurry with the consistency of pea soup: as much as 90% is water and the rest is algae, rich in lipids – these are molecules which can store energy.
And they don’t have to process the mix with solvents to get the oil out of what’s left of the algae: gravity does that for them.
Eliminating those steps will reduce the costs.
The fact that the team can also recover something that could be turned into natural gas, and therefore energy, is one bonus. Another is that they can reclaim water and nutrients to sustain the process.
Third Generation Biofuel
The innovative chemical process begins with an algae slurry, and efficiently produces crude oil in less than an hour. The biocrude oil can then be refined conventionally into gasoline, diesel and aviation fuel. Pacific Northwest National Laboratory (PNNL) engineers say their method is a continuous process that beats previous attempts to harness algae as fuel.
The largest problem they solved was to get the system to start with wet algae instead of dry, a previous requirement to create crude oil that meant significant energy inputs. Instead, they can convert slurries that are up to 90 % water into black crude.
They say their work has led to a cheaper and less energy intensive technique. It also results in a wastewater stream from which flammable gas can be recovered and nutrients that can grow more algae.
“Cost is the big roadblock for algae-based fuel,” said lead researcher Douglas Elliott in a statement. “We believe that the process we’ve created will help make algae biofuels much more economical. Not having to dry the algae is a big win in this process; that cuts the cost a great deal. Then there are bonuses, like being 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.”
The system runs at around 350 degrees Celsius (662 degrees Fahrenheit) at a pressure of around 3,000 PSI (pounds per square inch), combining processes known as hydrothermal liquefaction and catalytic hydrothermal gasification. Elliott says such a high-pressure system is not easy or cheap to build, which is one drawback to the technology, though the cost savings on the back end more than makes up for the investment.
The products of the process are: • Crude oil, which can be converted to aviation fuel, gasoline or diesel fuel. In the team’s experiments, generally more than 50 percent of the algae’s carbon is converted to energy in crude oil – sometimes as much as 70 percent. • Clean water, which can be re-used to grow more algae. • Fuel gas, which can be burned to make electricity or cleaned to make natural gas for vehicle fuel in the form of compressed natural gas. • Nutrients such as nitrogen, phosphorus, and potassium — the key nutrients for growing algae.
The products of the process are:
• Crude oil, which can be converted to aviation fuel, gasoline or diesel fuel. In the team’s experiments, generally more than 50 percent of the algae’s carbon is converted to energy in crude oil – sometimes as much as 70 percent.
• Clean water, which can be re-used to grow more algae.
• Fuel gas, which can be burned to make electricity or cleaned to make natural gas for vehicle fuel in the form of compressed natural gas.
• Nutrients such as nitrogen, phosphorus, and potassium — the key nutrients for growing algae.
Scalability Underlines Cost-Competitiveness
Their research-sized reactor can process 1.6 quarts of algae per hour, a major improvement over previous batch-by-batch processing that opens the door to scaling production up to industrial levels. To convert the wet soup of simple organisms into crude, the system subjects them to water heated to 662 degrees Fahrenheit and pressure of around 3,000 pounds per square inch.
These extreme conditions trigger hydrothermal liquefaction and catalytic hydrothermal gasification, which are the same processes that organic matter undergoes in the natural conversion to crude oil underground.
“It’s a formidable challenge to make a biofuel that is cost-competitive with established petroleum-based fuels,” James Oyler, president of Genifuel, a biofuel company that licensed the PNNL technology and is building a pilot plant to try it out. “This is a huge step in the right direction.”
Exciting stuff that sounds promising…