“Revolutionary Biofuel System Converts Waste Carbon into Valuable Chemicals and Hydrogen”

In a significant breakthrough for the biofuel industry, researchers at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) have developed a system that converts waste carbon into high-grade biofuels and generates hydrogen, a valuable fuel that can be captured, reducing the cost of the entire operation. This patent-pending process removes biofuel contaminants from wastewater using an additive-free process that generates hydrogen to fuel its own operation.

The PNNL electrocatalytic oxidation fuel recovery system converts what was previously thought to be unrecoverable, diluted “waste” carbon into valuable chemicals while also producing useful hydrogen. Because renewable energy is used, the process is carbon-neutral or even possibly carbon-negative.

The key to making it all work is an elegantly designed catalyst that combines billions of infinitesimally small metal particles and an electric current to speed up the energy conversion at room temperature and pressure.

Juan A. Lopez-Ruiz, a PNNL chemical engineer and project lead, said, “Our system can generate that hydrogen itself while simultaneously treating the wastewater at near atmospheric conditions using excess renewable electricity, making it inexpensive to operate and potentially carbon neutral.”

The research group tested the system in the laboratory using a sample of wastewater from an industrial-scale biomass conversion process for over 200 hours of continuous operation without losing any efficiency in the process. The sole constraint was that the research team’s wastewater sample had run out.

“It’s a hungry system,” Lopez-Ruiz said. “The reaction rate of the process is proportional to how much waste carbon you are trying to convert. It could run indefinitely if you had wastewater to keep cycling through it.”

The patent-pending system solves several problems that have plagued efforts to make biomass an economically viable source of renewable energy, according to Lopez-Ruiz.

“We know how to turn biomass into fuel,” Lopez-Ruiz said. “But we still struggle to make the process energy-efficient, economical, and environmentally sustainable—especially for small, distributed scales. This system runs on electricity, which can come from renewable sources. And it generates its own heat and fuel to keep it running. It has the potential to complete the energy recovery cycle.”

The PNNL process consists of a flow cell where the wastewater and biocrude flows through the cell and encounters a charged environment created by an electric current. The cell itself is divided in half by a membrane. The positively charged half, called an anode, contains a thin titanium foil coated with nanoparticles of ruthenium oxide. Here, the waste stream undergoes a catalytic conversion, with biocrude being converted to useful oils and paraffin. Simultaneously, water-soluble contaminants, such as oxygen and nitrogen-containing compounds, undergo a chemical conversion that turns them into nitrogen and oxygen gasses—normal components of the atmosphere. The wastewater that emerges from the system, with contaminants removed, can then be fed back into the HTL process.

On the negatively charged half of the flow cell, called a cathode, a different reaction takes place that can either hydrogenate organic molecules (such as the ones in treated biocrude) or generate hydrogen gas—an emerging energy source that the flow cell developers see as a potential source of fuel.

“We see the hydrogen byproduct generated by the process as a net plus. When collected and fed into the system as a fuel, it could keep the system running with fewer energy inputs, potentially making it more economical and carbon-neutral than current biomass conversion operations,” said Lopez-Ruiz.

The system addresses the problem of dependency on rare Earth metals by incorporating a unique method of depositing nanoparticles of the metals responsible for the chemical conversion. These particles have a large surface area, which requires less metal to do its work. “We found that using metal nanoparticles as opposed to metal thin films and foils reduced the metal content and improved the electrochemical performance,” said Lopez-Ruiz. The novel catalyst requires 1,000 times less precious metal, in this case ruthenium, than is commonly needed for similar processes.

The research team has also shown that the PNNL process can handle the processing of small water-soluble carbon compounds—byproducts found in the water waste stream of current HTL processes—as well as many other industrial processes. These short-chain carbon compounds, like propanoic acid and butanoic acid, undergo transformation to fuels, such as ethane, propane, hexane, and hydrogen, during the newly developed process.

A preliminary cost analysis showed the electricity cost required to run the system can be fully offset by running the operation at low voltage, using the propane or butane to generate heat and selling the excess hydrogen generated.

Battelle, which manages and operates PNNL for the federal government, has applied for a United States patent for the electrochemical process. CogniTek Management Systems (CogniTek), a global company that brings energy products and technology solutions to market, has licensed the technology from PNNL. CogniTek will be integrating the PNNL wastewater treatment technology into patented biomass processing systems that CogniTek and its strategic partners are developing and commercializing. Their goal is the production of biofuels, such as biodiesel and bio jet fuels.

“We at CogniTek are excited by the opportunity to extend the PNNL technology, in combination with our core patents and patent pending decarbonization technology,” said CogniTek Chief Executive Officer Michael Gurin.

The technology, dubbed Clean Sustainable Electrochemical Treatment—or CleanSET, is available for license by other companies or municipalities interested in developing it for industry-specific uses in municipal wastewater treatment plants, dairy farms, breweries, chemical manufacturers and food and beverage producers. To learn more about how this technology works, or to schedule a meeting with a technology commercialization manager, visit PNNL’s Available Technologies site.