ECONOMIC FEASIBILITY AND PERFORMANCES OF TWO LFG COLLECTION SYSTEMS: OPTIMIZATION OF THE AMOUNT OF BIOGAS RECOVERED

摘要

The methane flow available for a landfill gas recovery unit is related to two types of parameters: (ⅰ) the natural parameters which depend on the characteristics of the waste itself, its composition, temperature and moisture content and (ⅱ) the operational parameters which relate to the gas collection system, such as its design and the vacuum pressure applied. To enhance the amount of biogas produced, it is feasible either to increase the production of methane (bioreactor landfill management) and/or to optimise the collection system. The performances of two biogas collection system configurations are studied by CREED, the Environmental Energy and Waste research center of Vivendi Environnement on a sanitary landfill The first configuration comprises a conventional system with vertical wells. The second is based on an innovative system with a drainage layer of gravel placed at the top of the cell just beneath the liner (geomembrane). This program seeks to evaluate the technical and economic feasibility of the two systems by comparing their relative efficiency and identifying their optimal operational parameters. In a first instance, data on the quality and on the flow of biogas recovered are collected in order to establish the optimal depression to apply to each system. A second phase consists in applying the optimal depression of functioning and evaluating the long-term performance of each collection system depending on the weather conditions (rainfall, atmospheric pressure, outside temperature). The flow and the quality of the biogas are measured at the flare for each collection system. Furthermore, in order to evaluate the range of influence of each depression, pressure is measured at several strategic locations: in the waste, in the wells and in the biogas subsurface drainage layer.