A European start-up has started selling carbon credits for cattle raised on a feed supplement that reduces the amount of heat-trapping greenhouse gas they release. Mootral, based in Switzerland and the UK, says its garlic-and-citrus feed can cut methane emissions from livestock by an average of 30 percent. Under its offset program, a certified farmer that has produced milk using Mootral’s supplement can sell credits equal to 1 ton (0.9 metric tonnes) of carbon dioxide to customers that want to offset their pollution. Livestock farming accounts for about 15 percent of global greenhouse gas emissions, largely from cows, sheep and other ruminants