California has approved a law to reduce greenhouse-gas emissions, especially methane, from dairy farms and landfills. One of the main methane culprits is manure. Per the bill, dairy farmers have to cut methane emissions to 40 percent below 2013 levels by 2030. Under a cap-and-trade plan, farmers will receive aid from the $50 million or so raised via polluter fees, which they can then put toward machinery that uses methane to create energy they can in turn sell to electric companies. The state’s Air Resources Board can also now regulate bovine flatulence, as long as there are practical ways to reduce the cows’ belching and breaking wind.