Enhancement of Methane Production by Codigestion of Dairy Manure with Aquatic Plant Biomass

Abstract

Codigestion of manures with plant wastes is a promising strategy to increasing methane production during anaerobic digestion. Aquatic plant biomass has the potential to serve as a common, plentiful, and free source of plant matter for anaerobic digestion of animal livestock wastes. In batch anaerobic digesters at 35C, addition of 2% to 3% duckweed significantly increased methane production. Enhancement of methane production was greater than that expected from an increase in feedstock carbon or change in C:N ratio. Analysis of macro- and micronutrient concentrations in duckweed tissues indicated that methane production in batch digesters with 2% duckweed was correlated to tissue concentrations of zinc, sodium, and sulfur and (to a lesser extent) calcium and potassium. Increases in methane production for codigestion of dairy manures with 2% duckweed were also observed at 15C, 25C, and 30C, with the greatest enhancement at 25C.