The Microbial Energy Device (MED) was designed to solve a significant problem, universal with all anaerobic digesters. Anaerobic digesters generate Volatile Acids (VA’s) when the organic loading rate exceeds the threshold rate. VA’s lower the pH in the reactor killing the microorganisms responsible for producing Renewable Natural Gas (RNG). Once this happens, the digester fails. The condition is called digester souring. Souring limits the concentration of waste that can be processed in the digester which in turn limits the amount of RNG that can be produced. The current protocol is to only process dilute waste streams dictating the size of the digester and the economics of producing RNG. The threshold rate essentially governs the size, performance and economics of RNG production.
The MED uses an Electrogenic Bacteria (EB) with microbial electrochemistry to consume and control VA’s. The MED produces hydrogen which in turn is converted to methane (RNG) in an anaerobic digester. RNG production is then increased 5-fold by using electrochemistry to raise the threshold rate and the conversion of VA’s to methane. With the MED, we can increase the loading rate to increase VAs which increases RNG production. The MED removes the acid from the digester acting to buffer the reactor while it converts the acid to more methane thus producing more RNG. The MED enhances the economics of RNG production enabling smaller, less expensive digesters to produce more RNG, lowering both capital expenditures and increasing revenue. The MED is designed to retrofit existing anaerobic digesters and is applied as an exterior solution. It can also be incorporated inside new digesters, which we call “MED Inside”.