The dairy industry is one of the main sources of methane in California, making up half of the state’s total, so reducing them is a goal of federal and state governments.
“This is a wonderful example of an untapped climate solution,” said Life and Environmental Sciences Professor Rebecca Ryals . “Biochar reduces pollutant emissions from open burning of biomass and methane emissions from decaying biomass.”
California dairies typically stockpile manure solids, then spread it on fields or burn it.
The study looked at composting the manure with biochar instead of stockpiling it. Biochar also improves the composted manure so that it makes a better fertilizer for farmers to use on other parts of their land, said Mechanical Engineering Professor Gerardo Diaz .
“Composting the solid manure isn’t the common practice, but if we go from stockpiling to composting, now we’ve gone from a carbon source to a carbon sink,” Ryals said.
“Composting in and of itself is a very climate-beneficial practice. And you can basically double your impact by adding a little bit of biochar into that compost,” he said.
So far only a small percentage of California’s dairy farms process manure through anaerobic digesters, but the federal and state governments plan to have that increase.