Home Science & Technology Patented technology converts “waste” carbon into valuable chemicals and nutrients

Patented technology converts “waste” carbon into valuable chemicals and nutrients

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Carbon wastes from farms, wastewater and other sources can be more easily recycled into high quality biofuels with a new flow cell developed by PNNL. In this animation, the flow cell receives bioresisting and wastewater from the hydrothermal liquefaction process. It then removes carbon from the wastewater, allowing clean water to be reused. The system even produces hydrogen, a valuable fuel that can be captured, reducing the cost of the entire operation. Credit: Sarah Levin | Pacific Northwest National Laboratory

The patented process removes contaminants of biofuels from wastewater through a process without additives, which produces hydrogen to feed its own work

The Holy Grail of biofuels researchers is to create a self-sustaining process that converts waste from wastewater, food crops, algae and other renewable carbon sources into fuel, while conserving carbon waste in the environment and water. Although much progress has been made in converting such waste into usable fuel, completing the cycle using clean energy has proved to be a tough nut to crack.

A team of researchers from the Pacific Northwest National Laboratory (PNNL) of the Department of Energy has now developed a system that allows just that. The PNNL electrocatalytic oxidation fuel recovery system converts what was previously considered unproductive, dilutes the “waste” of carbon into valuable chemicals, and produces useful hydrogen. Because renewable energy is used, the process is neutral or even possibly negative.

The key to making it all work is an elegant catalyst that combines billions of infinitesimal metal particles and electric current to accelerate energy conversion at room temperature and pressure.

Juan A. Lopez Ruiz PNNL

Juan A. Lopez-Ruiz, a PNNL chemical engineer, led a research team that recently developed a new flow-cell reactor that facilitates the path to renewable fuels. Credit: Andrea Starr Pacific Northwest National Laboratory

“Currently used bioprocessing techniques require high-pressure hydrogen, which is typically produced from natural gas,” said Juan A. Lopez-Ruiz, PNNL chemical engineer and project manager. “Our system can generate this hydrogen itself, while treating wastewater in atmospheric conditions, using excess renewable electricity, making it inexpensive to operate and potentially carbon-neutral.”

The Hunger System

The research team tested the system in the laboratory using a wastewater sample from an industrial-scale biomass conversion process for more than 200 hours of continuous operation without losing efficiency in the process. The only obstacle was that the research group’s wastewater tests were over.

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

According to Lopez-Ruiz, the patented system solves several problems that have hampered efforts to make biomass a cost-effective source of renewable energy.

“We know how to turn biomass into fuel,” Lopez-Ruiz said. “But we are still struggling to make the process energy efficient, cost-effective and environmentally sustainable, especially for small-scale distribution. This system runs on electricity that can come from renewable sources. And it generates its own heat and fuel to keep it running. It can complete the energy recovery cycle. ”

“As the electricity grid begins to move its energy sources towards integrating more renewable energy sources,” he added, “it is becoming more and more reasonable to rely on electricity for our energy needs. We have developed a process that uses electricity to convert carbon compounds in wastewater into useful products, while removing impurities such as nitrogen and sulfur compounds. ”

Close the energy gap

Hydrothermal liquefaction (HTL) is a very efficient method of converting wet carbon waste into fuel. This process essentially reduces the time required to produce natural fossil fuels by converting wet biomass to energy-rich biodisard oil in hours rather than millennia. However, the process is incomplete in the sense that the wastewater generated as part of the process requires additional treatment to gain added value from what would otherwise be a commitment.

“We realized that the same (electro) chemical reaction that removes organic molecules from wastewater can also be used to directly improve bio-raw materials at room temperature and atmospheric pressure,” Lopez-Ruiz said.

This is where the new PNNL process comes into play. Untreated bio-raw and wastewater can enter the system directly from the HTL or other wet waste effluent. The PNNL process consists of what is called a flow cell, where wastewater and biocheese flow through the cell and collide with a charged medium created by an electric current. The cell itself is divided in half by a membrane.

PNNL flow cell bioreactor

A new patented flow cell bioreactor, developed at the Pacific Northwest National Laboratory, can purify wastewater (seen here) and generate hydrogen to aid the process. Credit: Andrea Starr Pacific Northwest National Laboratory

The positively charged half, called the anode, contains a thin titanium foil coated with ruthenium oxide nanoparticles. Here, the waste stream undergoes catalytic conversion, with biocheese being converted into useful oils and paraffin. At the same time, water-soluble pollutants, such as oxygen and nitrogen-containing compounds, undergo chemical conversion that converts them into nitrogen and oxygen gases, normal components of the atmosphere. Sewage flowing from a system with removed contaminants can be returned to the HTL process.

The negatively charged half of the flow cell, called the cathode, undergoes another reaction that can either hydrogenate organic molecules (such as treated biosurf) or generate hydrogen gas, a new source of energy that flow cell developers see as a potential source of fuel.

“We view the by-product hydrogen formed in the process as a pure plus. By collecting and feeding the system as fuel, it can keep the system running at lower energy costs, potentially making it more economical and carbon-neutral than current biomass conversion operations, ”Lopez-Ruiz said.

The rate of chemical conversion provides additional benefits to the system.

“We compared the speed – that is, how fast we can remove oxygen from organic molecules with our system, as opposed to energy-intensive thermal removal,” Lopez-Ruiz said. “We have obtained more than 100 times higher conversion rates with an electrochemical system in atmospheric conditions than with a thermal system at intermediate pressures and hydrogen temperatures.” These findings were published in Journal of Applied Catalysis B: Environment in November 2020.

Reduce the use of rare earth metals

One of the major disadvantages of many commercial technologies is their dependence on rare earth metals, sometimes called platinum group metals. The global supply chain of these elements is largely dependent on outdated mining technologies that are energy-intensive, use huge amounts of water and generate hazardous waste. According to the Department of Energy, which has made domestic supplies a top priority, imports account for 100 percent of supplies in the United States 14 of the 35 most important materials and more than half of the 17 others.

The system solves this problem by incorporating a unique method of applying metal nanoparticles responsible for chemical conversion. These particles have a larger surface area that requires less metal to do its job. “We found that the use of metal nanoparticles as opposed to metal thin films and foils reduces the metal content and improves the electrochemical characteristics,” Lopez-Ruiz said. These findings were recently published in Journal of Applied Catalysis B: Environment. The new catalyst requires 1,000 times less precious metal, in this case ruthenium, than is usually required for similar processes. In particular, a laboratory-scale flow reactor uses an electrode with about 5 to 15 milligrams of ruthenium compared to about 10 grams of platinum for a comparative reactor.

About those useless carbon compounds

The research team also found that the PNNL process can handle the treatment of small water-soluble carbon compounds – by-products that are in the wastewater stream of current HTL processes – as well as many other industrial processes. In low-concentration wastewater streams, there are about a dozen such, damn difficult to handle, small carbon compounds. Until now, there were no cost-effective technologies for their processing. These short-chain carbon compounds are like propane[{” attribute=””>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. These findings were published in the July 2020 issue of the Journal of Applied Electrochemistry.

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. In addition to the commercialization agreement, PNNL and CogniTek will collaborate to scale up the wastewater treatment reactor from laboratory scale to demonstration scale.

“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.

In addition to Lopez-Ruiz, the PNNL research team included Yang Qiu, Evan Andrews, Oliver Gutiérrez and Jamie Holladay. The research was supported by the Department of Energy’s Advanced Manufacturing Office and the Chemical Transformation Initiative, a Laboratory Directed Research and Development Program at PNNL. Portions of the research were conducted as part of a Cooperative Research and Development Agreement with Southern California Gas Company.

References: “Anodic electrocatalytic conversion of carboxylic acids on thin films of RuO2, IrO2, and Pt” by Yang Qiu, Juan A. Lopez-Ruiz, Udishnu Sanyal, Evan Andrews, Oliver Y. Gutiérrez and Jamie D. Holladay, 25 June 2020, Applied Catalysis B: Environmental.
DOI: 10.1016/j.apcatb.2020.119277

“Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction” by Juan A. Lopez-Ruiz, Yang Qiu, Evan Andrews, Oliver Y. Gutiérrez and Jamie D. Holladay, 9 July 2020, Journal of Applied Electrochemistry.
DOI: 10.1007/s10800-020-01452-x

“Electrocatalytic decarboxylation of carboxylic acids over RuO2 and Pt nanoparticles” by Yang Qiu, Juan A. Lopez-Ruiza, Guomin Zhu, Mark H. Engelhard, Oliver Y. Gutiérrez and Jamie D. Holladay, 1 January 2022, Applied Catalysis B: Environmental.
DOI: 10.1016/j.apcatb.2021.121060

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