Improvement and optimization for the first order decay model parameters at typical municipal solid waste landfills in China

Abstract

Landfill gas (LFG) generation is commonly modeled by using a first-order model. Methane generation potential (L0) and methane generation rate constant (k) are two key parameters in the first-order model. Coal-ash based default values or roughly analyzed values often used in China may not be appropriate for accurately estimating of LFG generation. In this study, seven groups of parameters were evaluated by comparing the theoretical predictions with real measurements from five Chinese landfills. The optimal approach for calculating L0 is the use of site-specific waste composition and the default values of degradable organic carbon (DOC) reported by the Chinese industry standard (CJJ133-2009), and the matching k can be adjusted by fitting and regression. The optimized average values were L0 = 67 m3 Mg−1, k = 0.06 per year for landfills in Beijing and Zhengzhou in cold–dry regions, L0 = 69 m3 Mg−1, k = 0.16 per year for landfill in Shanghai in cold–wet region, and L0 = 64 m3 Mg−1, k = 0.21 per year for landfills in Guangzhou and Shenzhen in hot–wet regions. Monte Carlo analysis showed that the uncertainty of LFG generation at closure year varied in −22.5% to 20.5%, −17.1% to 17.1% and −28.2% to 34.7% for three climatic regions, respectively. The k value is the key influencing factor, with a 95.6% contribution ratio in the hot–wet region landfill. The results provide references for future better waste management.