By George Harvey
Microbial fuel cells, in which microbes make electricity, were first demonstrated as early as 1911. A problem with all new technologies, however, is that in order to have effect in the real world, they have to be practical solutions for recognized problems. Like early photovoltaic systems, the microbial fuel cells languished as scientific curiosities.
In 1990s and 2000s, a number of developments not only showed promise, but spurred development. It became clear that there were processes that could use very small amounts of electricity to produce valuable chemicals. One of these, electrohydrogenesis could use a charge of one volt to produce hydrogen at an efficiency of 288%. The process has such a high level of efficiency because the electricity is not producing hydrogen directly, but is used to induce bacteria, which have access to other energy resources such as chemical energy, to make hydrogen.
Electromethanogenesis is a similar process, in which the hydrogen is reacted with carbon dioxide, and the output is methane. Methane is much more useful than hydrogen in some ways. It is easier to store. But more to the point, the methane produced through the process can be used as a high-quality substitute for natural gas with no alterations needed.
A company in Boston, Cambrian Innovation, was started up to use these reactions to treat wastewater while simultaneously generating fuel. One product of their research and development is a small modular system called the EcoVolt Reactor. Another is a membrane bioreactor called the EcoVolt MBR.
The EcoVolt systems are well suited to processing wastewater from the food and beverage industries. For example, brewing uses a lot of water, producing large quantities of waste that has to be treated. By using electrically active microbes to work on the waste, the whole process can be leveraged to convert the waste into much cleaner water that is easier to deal with than the unprocessed waste is, while producing high quality methane.
The methane in a small system is sufficient to drive the system, cleaning water in the process. In a larger system, there is excess methane, which can be used to generate electricity to put on the power grid, or for other purposes. Clean water can be reused across a variety of brewery applications.
An example of how the EcoVolt Reactor does in the field is provided by an installation at the Lagunitas Brewing Company brewery in Petaluma, California. The brewery was having 50,000 gallons of high-strength waste water trucked to a treatment plant each day, and more low-strength waste was sent to a local utility as sewage. This represented a drain on the systems and a large expense to the brewery. It also meant water was being used in large quantities while California suffered in a drought.
The combination of the EcoVolt Reactor and the EcoVolt MBR meant that close to 99% of the waste material in the water was removed, allowing 80,000 gallons of water to be recycled each day, eliminating 1,600 of carbon emissions each year, and reducing the brewery’s costs.
Cambrian Innovation’s website is cambrianinnovation.com.
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