According to this report, voluntary demand for carbon offsetting grew 4% in 2012, when buyers committed more than $523 million to offset 101 million metric tonnes of greenhouse gas emissions (GHGs). Private sector buyers flocked to offsets earned by planting trees, saving tropical forests, and distributing clean cookstoves in the developing world, according to this report, released by Forest Trends" Ecosystem Marketplace. The European private sector, including regulated energy utilities, was the market"s biggest voluntary buyer. Demand grew 34% to 43.4 million tonnes of offsets even in the face of significant challenges to Europe"s mandatory carbon market.