In the first order decay (FOD) model of landfill methane generation, the methane generation potential ( L) and methane generation rate constant ( k) for both bulk municipal solid waste (MSW) and individual waste components have been determined by a variety of approaches throughout various literature. Differences in the determination methods for L and k are related to differences in our understanding of the waste decomposition dynamics. A thorough understanding of the various available methods for determining L and k values is critical for comparative study and the drawing of valid conclusions. The aim of this paper is to review the literature on the available determining methods and the ranges for L and k values of both bulk MSW and individual waste components, while focusing on understanding the decomposition of waste, including the role of lignin. L estimates in the literature are highly variable and have been derived from theoretical stoichiometric calculations, laboratory experiments, or actual field measurements. The lignin concentration in waste is correlated with the fraction of total degradable organic carbon (DOC) that will actually anaerobically degrade in the landfill. The k value has been determined by precipitation rates, laboratory simulations, aged-defined waste sample, and model fitting or regression analysis using actual gas data. However, the lignin concentration does not correlate well with the k value, presumably due to the impact of lignin arrangement and structure on cellulose bioavailability and degradation rate. In sum, this review summarizes the literature on the measurement of L and k values, including the dynamics and decomposition of bulk MSW and individual waste components within landfills.

Landfill gas (LFG) emissions from a given amount of landfill waste depend on the carbon flows in the waste. The objective of this study was to more accurately estimate the first-order decay parameters through methane (CH4) and carbon flow balances based on the analysis of a full-scale landfill with long-term data and detailed field records on LFG and leachate. The carbon storage factor for the case-study landfill was 0.055 g-degradable organic carbon (DOC) stored per g-wet waste and the amounts of DOC lost with the leachate were less than 1.3%. The appropriate CH4 generation rate constant (k) for bulk waste was 0.24 y-1. The the CH4 generation potential (L0) values ranged 33.7-46.7 m3-CH4 Mg-1, based on the fraction of DOC that can decompose (DOCf) value of 0.40. Results show that CH4 and carbon flow balance methods can be used to estimate model parameters appropriately and to predict long-term carbon emissions from landfills.

No abstract

No abstract