Methanogenesis and Increased Bioavailability

A long-standing method to capture the energy value from biomass is methanogenesis, in which communities of anaerobic microorganisms generate methane gas (CH₄) as the final reduced product of fermentation and respiration. Methane is the same as natural gas and has a well-developed infrastructure in place for its use. The challenge today is to make methanogenesis more efficient for converting complex biomass to methane. The limiting step in most cases is making the complex biomass bioavailable for the microorganisms to begin fermentation and respiration. We are following two complementary paths for improved bioavailability and methanogenesis.

The first path is to treat the biomass with a novel form of pulsed-electric field (PEF) technology. A PEF device sends high voltage (above 20 kV) electrical pulses across the material being treated thousands of times per second. This pulsed electrical treatment lyses cell membranes, breaks down large aggregates, and may reduce complex organic molecules to simpler forms. These effects increase the dissolved organic material available for the anaerobic microorganisms to convert to methane. The PEF technique also makes the biomass bio-available for H₂ and electricity generation.

The second path is to combine complementary biomass forms to increase the total conversion to methane (or H₂) or electricity. A good example is mixing pig-farm waste with paper-mill waste. Pig-farm waste is very high in nitrogen content, but paper-mill waste is nitrogen deficient. Adding the two materials together overcomes limitations of each alone, and we see approximately twice the methane output from the two wastes combined over keeping them separate.