EVALUATION OF CONFINEMENT CONDITIONS AND CONTENT OF LIGNOCELLULOSIC COMPOUNDS ON URBAN SOLID WASTE BIODEGRADATION RATES

Abstract

The organic fraction (OF) is the main component of urban solid wastes (USW) generated in Mexico and other developing countries. The increasing generation of USW in combination with the long periods required for OF stabilization at confinement sites has exceeded the management capacity of environmental authorities. OF biodegradation has commonly been estimated using theoretical approaches and by characterizing fresh USW, while confinement scenarios have been ignored. This study evaluated the effects of composition, biodegradability and confined conditions on biodegradation of USW in a characteristic dumpsite. Biodegradability was evaluated by the characterization of lignocellulosic compounds, biodegradation by volatile solids (VS) and the confinement conditions by temperature, pH and humidity measurements. On average, the OF represented 56.1 % of the confined USW, and was primarily derived from vegetable wastes (~78 %). The results indicate heterogeneity in the confined USW composition and different degradation stages. Measurement of temperature, pH, moisture and VS suggests that confinement conditions do not promote the establishment of a microbial consortia that degrades the OF. Lignin (LI) and cellulose + hemicellulose (CE + HE) contents suggest low biodegradability of the USW, which was confirmed by inverse correlations between lignocellulosic content and VS. The common use of soil as cover material in dumpsites allows considerable variations in crucial physical and chemical parameters that, when combined with the high percentages of lignocellulosic compounds in the USW, lead to low biodegradation rates.