The treatment of high-strength wet wastes, like municipal wastewater sludges and food wastes
by Anaerobic Digestion (AD) can lead to digester failure. AD also has well known limitations that have inhibited it from living up to its energy potential. Key limitations include low efficiency, long retention times, and conditions that lead to AD souring. AD can generate useful biogas as an energy source. However, factors like digester acidification and long hydraulic retention times (HRT) can limit biogas production when processing food waste (FW). FW is key to achieve higher volumetric loading rates that are
needed to generate higher volumes of biogas, thus rendering AD derived electricity unfeasible
for large-scale water purification. Meanwhile, FW is the second largest component of municipal
solid waste, leading to major greenhouse gas (GHG) emissions in landfills. Many states like the State of California are working towards implementing statewide mandates like California's Senate Bill 1383, aimed at keeping organic waste out of landfills and reducing greenhouse gas emissions. GELF Energy will make it technically and economically feasible to co-digest FW with wastewater sludge so that the generation of useful biogas can be increased by up to 5-fold while the adverse conditions usually associated with increased volumetric loading rates are mitigated. Thus, allowing for renewable electricity generated from enhanced AD made possible through the MED to power water purification for large scale water purification projects. The MED technology is a cost-effective, retrofit capable advancement of AD that will help to meet the goals and objectives of large scale direct potable reuse projects and achieve renewable energy targets and make wastewater treatment and solid waste (SW) management economically favorable.
The MED uses Microbial Electrochemistry to control electroactive bacteria which consume volatile fatty acids achieving pH balance in the digester which allows for significant increases in volumetric loading rates that are needed to generate higher volumes of biogas, increase efficiency and lower retention times. The bacteria are ubiquitous in the natural environment and naturally consume volatile fatty acids (VFAs) that are produced by the rapid fermentation of FW. This rapid consumption of VFAs prevents their accumulation, preventing AD souring, a condition that can force an increase in the HRT or totally inactivate the digester. When the electroactive bacteria consume the VFAs, they generate an electrical current that leads hydrogen gas (H2) formation. The H2 is then converted to CH4 by H2-oxidizing methanogens. Thus, the MED stabilizes AD operation by accelerating the consumption of VFAs into CH4.