This chapter introduces the influence of biological processing of solid waste on greenhouse gas (GHG) emissions reduction. Landfill is one of the major sources of methane emissions. Landfills are a garbage disposal sites where all kinds of waste are deposited directly without prior any treatment. Composting is the ecofriendly mineralization and conversion of organic matter into a stable end product call humus by the action of microorganisms under aerobic or anaerobic conditions. Anaerobic fermentation of domestic waste is the process by which microorganisms decompose organic matter in anaerobic conditions. The complex organics are converted to volatile acids by rapid value-added and pH-sensitive acid bacteria through hydrolysis and fermentation. Landfill is the main method of solid waste disposal in China and in most countries of the world. Controlled and uncontrolled landfilling of untreated waste has become a primary source of GHGs.