Methodology for the Assessment of Potential Waste Landfill Biogas Recovery

Although the majority of the EU countries explore controlled waste management landfill sites for alternative electrical and thermal energy resources it has been found that some of these infrastructures exhibit several instability situations and environmental problems due to lack of landfill maintenance or inadequate waste separation, which may result in post closure inefficient biogas exploration or in reduction of potential landfill mining [1; 2]. In Portugal, there are presently several landfills in exploitation and among them just a few have biogas production.
According to some authors [3] the optimum moisture content for enhancing microorganism’s degradation activity of organic matter varies between 50% and 60% being however that, in some cases high rates of waste decomposition with much lower humidity levels were observed.
To enhance the biogas recovery conditions of a municipal solid waste landfill (Amarsul Ecopark Municipal System) it is presented an approach that allowed the spatial zoning of the humidification conditions and organic matter content of the MSW landfill in order to enhance the biogas production by improving local optimum humidity conditions [4].
To meet the objectives a three step methodology was followed: Step 1 – MSW sampling and assessment of landfill saturation; Step 2 – MSW characterization; Step 3 – Modeling of the landfill biogas conditions.
Step 1, enclosed 3 field survey campaigns: a geophysical survey to assess the internal saturation condition of the landfill, which was validated with data from a biogas leachate monitoring campaign. In order to characterize and quantify the proportion and typology of the MSW, six drillings were performed, and MSW samples collected for all the crossed waste media. Waste materials were classified into 10 categories, depending on typology, composition and source.
Based on the proportion of the waste categories observed on each strata a new log design is proposed to represent the composition of the drilled boreholes.
Step 2, consisted on laboratorial tests to quantify the organic matter (OM) and moisture content of the MSW. Representative samples of each drilled core were collected based on the homogeneity/heterogeneity of the waste strata.
Step 3, corresponds to the statistical analysis of the biogas waste properties (MO, type of waste and moisture content) and spatial modeling of the landfill potential conditions for biogas production.