Anaerobic digestion of organic waste occurs as a result of the activity of microorganisms. Research and development of “high performance” bacteria has emerged as a means to increase biogas yield and raw material processing time to improve digester plant efficiency. Several approaches can be used to implement this practice.
- A computer assisted screening program can systematically select organisms optimized to different wastewater types. This is most useful in the design phase of a treatment plant
- A microbial stimulant in the form of an organic liquid biostimulant called BAE (Biological Activity Enhancer) can be added to digesters. BAE is added at a rate of several gallons per week to several gallons per day depending on the size of the treatment plant.
- A genetically engineered bacteria can be used in place of traditional bacteria. Genetically engineered bacteria can increase gas yield by up to 20 percent.
Cost and Energy Savings
Based on the limited case study results available in applications in the U.S., the addition of biogas performance microorganisms to an anaerobic digester has shown to increase biogas yields anywhere from 20-70%. Additionally, advanced micro-organisms can increase digester raw material processing by up to 100%.
Challenges facing the emergence and adoption of new biogas performance microorganisms include technology cost and customer acceptance. While no cost estimates are available, the process to create, test and validate performance microorganisms are likely significant. Digester material discharge is highly regulated, and the introduction of a new organism into a feedstock can be perceived as risky, from an environmental perspective. The time required to ensure that a new microorganism is safe and effective is, therefore, likely significant. The product can also appear to be risky from a customer’s perspective given the lack of familiarity with the concept.
With the funding from the California Energy Commission, the Dublin San Ramon Service District (DSRSD) wastewater treatment facility began a demonstration project. The project uses a 1,000-gallon digester at in hopes of demonstrating and improvement of digester efficiency by 30% and reduction of retention time by 50% with increased substrate utilization. The produced methane will be used by the onsite fuel cells to generate electricity for the facility.