Technical Bulletin No. 0872: Critical Review of Forest Products Decomposition in Municipal Solid Waste Landfills

This report reviews the published information on the factors that affect the decomposition of forest products in municipal solid waste (MSW) landfills and the data available for estimating the fate of carbon in these products.<br /><br />Estimates of carbon sequestration in, and greenhouse gas emissions from, municipal solid waste (MSW) landfills are usually derived from mathematical models. A variety of models have been developed for this purpose, but the most commonly used models apply first order decay kinetics to the degradable fraction of the carbon and assume that the nondegradable carbon remains in the landfill indefinitely. Two parameters, therefore, are needed to use the models: the nondegradable fraction of the waste, and the first order decay rate for the degradable fraction.<br /><br />Laboratory studies have been used to determine the ultimate degradability of a number of forest products in a landfill environment. The data can be used to develop carbon storage factors representing the fraction of the carbon in the original product that is nondegradable in the landfill. Carbon storage factors vary from approximately 0.1 to over 0.8 depending on the product. Higher carbon storage factors are associated with wood products and paper/paperboard products that are high in lignin content (e.g., lumber and newsprint) or are coated. Carbon storage factors for a variety of industry products are summarized in this report.<br /><br />The rate at which the degradable carbon municipal solid waste is converted to landfill gas is determined by a number of factors, most notably moisture content, pH, and nutrient availability. First order decay rates for municipal solid waste vary by more than an order of magnitude. The rates identified in this review range from 0.003 to 0.094 yr-1, although most of the values are in the range of 0.02 to 0.07 yr-1.