Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 22 Issue 1

Mt - mass of waste received in the year in each section (ton.); t i,j - corresponds to the year, in each section, of receipt of the mass of waste (time with decimal precision). The parameters L 0 and k are the most important, as they reflect variations according to location, climate and type of waste. Theoretically, the k factor varies from 0.003 to 0.21 (year -1 ). According to IPCC [20], the most rapid rates (k = 0.2) are associated with high humidity site conditions and rapidly degradable waste such as food waste. The slower rates of decomposition (k = 0.002) are associated with dry site conditions and slowly degradable residues such as wood or paper. The Land GEM model suggests a k value of 0.05 as a default value. On the other hand, the L 0 factor is proportional to the percentage of organic materials present in the waste, and it can range from 0 (lack of degradable material) to 300 m³/ton[21]. The default used by Land GEM is a Lo value of 170. Table 3 shows the values recommended by the EPA, the World Bank and the values adopted by the Land GEM model for k and L 0 . Table 3: K and L 0 values Parameters EPA LandGEM k (year -1 ) 0.04 0.06 0.05 L 0 ( m 3 CH 4 .t MSW -1 ) 100 170 170 In the model adopted by the Land GEM, the default CH 4 and CO 2 content of LFG is 50% for both. i) Calculation of power and energy Once the volume of CH 4 was determined through Land GEM it is possible to estimate the power and energy. According to [22], the most used technology for recovering energy from biogas is the internal combustion engines (MCI) due to its economic feasibility. The computer program developed by [23] uses the equations (6) and (7) to estimate the power and energy. The parameters used by this program are in Table 4. P = (Q CH4 * PCI CH4 / 31,536,000) * ɳ *Er * c (6) Where: P - available power per year (MW) Q CH4 - annual methane flow (m³/year) PCI CH4 - calorific value of methane (J/m³) 31,536,000 - Seconds in a year (s/year) ɳ - energy conversion efficiency according to the chosen technology (%) Er - landfill gas recovery efficiency (%) c = 10 -3 E = P * 8760 (7) Where: E - energy available per year (MWh) 8760 - hours in a year (h/year) Table 4: Parameters for calculating the energy use of biogas Parameters Value CH 4 percent by volume of biogas (%) 50 CH 4 recovery index (%) 75 Engine efficiency 0,2 Santos et al. [24] study determines as optimal power, for the dimensioning of a generator set at full load, the value of 45% of the maximum potential. j) Feasibility Analysis The economic viability analysis of installing a LFG plant from the landfill in the municipality of Jacareí will be carried out from the net present value (NPV). According to [25], NPV consists on determining the present value of a future values cash flow, discounted at an internal rate of return (IRR). If the present value is positive, the project is attractive and the higher is the positive value, the more attractive is the project. FC 0 + FC 1 /(1+j) 1 +...+ FC t (1+j) t Where: FC = cash flow of the n th year, in U$; j = discount rate (%); t = project lifetime, in years For the study a period of 20 years was considered, which corresponds to the lifetime of the installation. During this period it will be possible to observe the attractiveness of the project. An IRR of 8% per year was chosen to discount the annual cash flow and calculate the NPV. The estimed costs for implementation, operation and maintenance (O&M) based on [26] and the reference values in dollar are shown in the Table 5. Table 5: Installation and O&M costs [26]. Component Un. Value (U$) Preliminary studies un 12.500,00 Design un 10.000,00 LFG collection and flare system un 1.143.000,00 Purchase and installation of equipment kW 2.400,00 O&M (collection) annual un 191.000,00 O&M (installation) annual kW 160,00 It will be considered a financing of 75% of the value of the investment, with an interest of 2.50% per © 2022 Global Journals 1 Year 2022 60 Global Journal of Science Frontier Research Volume XXII Issue ersion I VI ( H ) Energetic Potential of the Biogas from Urban Solid Waste Generated in the Jacareí Municipal Landfill, Brazil NPV= World Bank