Peat

Peat is an accumulation of partially decayed vegetation matter. Peat forms in wetlands or peatlands, variously called bogs, moors, muskegs, pocosins, mires, and peat swamp forests. The world's peatlands are thought to contain 180 to 455 petagrams of sequestered carbon, and they release into the atmosphere 20 to 45 teragrams of methane annually.