Co-digestion of dairy cow manure and food waste creates a more efficient biogas cycle
The AgSTAR project of the U.S. EPA analyzed the possibility of installing anaerobic digesters with energy generation and nutrient capture in all confined dairy operations in the US with 500+ cows, with a total potential capacity of more than 2,000 digesters nationwide. This study uses environmental life cycle assessment to identify the potential benefits of disposing locally accessible commercial food waste with manure at those digesters (via co-fermentation) in comparison to other disposal options. Anaerobic digesters show an advantage compared to compost or landfill for all impact indicators examined: human health, climate change, ecosystem quality and water withdrawal. For greenhouse gases, the installation of digesters could potentially reduce 20-25 million metric tons (MMT) CO2e of fugitive methane emissions from manure compared to current manure management practices, 10 MMT CO2e of fugitive methane emissions from landfilled food waste, and another 10 MMT of CO2e from avoided electricity, fertilizer production and peat moss production by harvesting energy, nutrients, and fibers from digesters, respectively.