People have long known there is energy in wastewater; extracting it economically is the problem. Startup Cambrian Innovation claims its technology can do it and a brewery and a winery are now using it to clean their wastewater while producing energy.
The company's EcoVolt machine is a shipping container-size reactor that uses microbes to convert dissolved carbon in industrial wastewater into biogas, which can be burned on site for electricity or heat. Its first demonstration unit is running at the Clos du Bois winery in Sonoma county, and last month nearby Bear Republic Brewery in Cloverdale, Calif. flipped the switch on the second system.
Typically, food and beverage businesses remove the organic material in wastewater—measured as biological oxygen demand (BOD)—by aerating water with pumps. But that can be an energy-intensive process. The Bear Republic Brewery expects it will be able to eliminate 80 percent to 90 percent of the BOD of its wastewater with the EcoVolt and reuse 10 percent of its water. By burning the biogas, the brewery thinks it can cover 50 percent of its electricity needs.
The return on investment for the brewery is about four years in reduced energy costs, says Cambrian Innovation CEO Matthew Silver who I spoke to at the company’s headquarters in South Boston. Silver had planned to work in aerospace but became fascinated by advances in biotech and genetic engineering while a research scientist at MIT. Under a NASA grant, he led research into how bioelectric systems could be used to manage water in space. In doing that, he saw the potential for using electrochemically active microbes to clean water in industry. There's plenty of need: About three percent of the U.S. electricity is consumed treating wastewater, and producing one bottle of beer typically results in up to ten times as much in wastewater.
Making biogas from waste has been done for years and is not necessarily high tech. Industrial anaerobic digesters, which often look like farm silos, use naturally occurring bacteria to consume organic material to make biogas, which is siphoned off.
Cambrian Innovation's EcoVolt achieves a similar result but with a different anaerobic process. Its reactor has microbes that consume organic matter as food and deposit electrons directly on a metal electrode. Found in soil, these microbes, sometimes called exoelectrogens or anode-respiring bacteria, are the active component in some types of microbial fuel cells.
The EcoVolt system uses these microbes to produce a flow of electrons from a bacterial-film-covered anode to a cathode. They do this by breaking down organic molecules into hydrogen and carbon dioxide. At the cathode, another set of microbes, with the aid of the electric current, convert the CO2 and hydrogen from the first reaction to methane. A byproduct of that reaction is clean water.
The company is also working on a microbial fuel cell under a Department of Defense contract, which is part of US $8 million Cambrian Innovation has secured in DoD and National Science Foundation grants. The plan is to make a self-powered wastewater treatment facility for operating bases or for off-grid applications in the developing world.
CEO Silver has confidence that it can make an economic microbial fuel cell, but decided to target its first commercial product on the wastewater industry. By taking advantages of advances in other fields of engineering, the company was able to design a product that has compelling economics, he says. "We realized we needed to combine the advantages of biological systems with electrochemistry and information technology and really create a package," says Silver. It's now targeting companies in the food and beverage industry and seeking applications in other industries.
One of the advantages of the EcoVolt over traditional anaerobic processes is that it can be remotely monitored in real time. By viewing the rate and the health of reactions on the electrodes, Cambrian Innovation engineers can adjust flow rates and other bioreactor parameters. That’s much quicker control than a typical anaerobic reactor, which requires taking a sample and doing tests, says company chief technology officer Justin Buck. Company engineers have also developed techniques to adjust the reactor’s biology, which allows the EcoVolt to be robust and work with different types of waste streams, he adds. “We make sure that the proper community of microbes gets established on these electrodes,” he says. “If we don’t do that, incoming water will bring in new microbes, which is essentially a source of contamination.”
There are several reseachers and companies trying to take advantage of microbes to make electricity from wastewater. A group at Penn State, for example, combined a microbial fuel cell with reverse electrodialysis, a way to capture energy from a difference in water salinity, in an effort to increase electricity output.
Israeli company Emefcy (a play on the acronym for microbial fuel cell) has engineered a microbial fuel cell optimized for municipal wastewater. Another wastewater-to-energy startup is Arizona State University spin-off, Arbsource, an Arizona State University spin-off, uses anode-respiring bacteria to produce electricity, as Cambrian Innovation does, as well as hydrogen, ammonia, and other chemicals. And a number of municipalities produce biogas with digesters and use it to generate electricity and heat through fuel cells.
By contrast, the EcoVolt system is designed specifically for wastewater reuse. Cambrian Innovation hopes to appeal to businesses with high energy costs from wastewater treatment and, in general, bring more innovation to the slow-moving and conservative world of water treatment. "Up until now, compliance (with water treatment regulations) was viewed as a cost of doing business and a big part of the industry is designed around avoiding liability,” he says. “Now wastewater can be a source of revenue.”
Image credit: Cambrian Innovation