Estimates of methane emissions and comparison with gas mass burned in CDM action in a large landfill in Eastern...

This work studied the methane gas production of the Aura landfill, the official destination of all Municipal Solid Waste of the Metropolitan Region of Belem (Brazil), operational until 2015. In 2007, the Aura Landfill was equipped with a landfill gas burning system in a CDM/UNFCCC project, with reported measured volumes of burned methane gas. These volumes were used to retrieve the methane generation potential (L₀) and the decay rate (k) parameters of single-phase, first order landfill emission model, yielding L₀=(61.0±6.6)m_CH4³/Mg_MSW and k=(0.25±0.07)yr^-1. To model the Aura landfill, local gravimetric waste composition and local per capita waste production studies were collected, and the IPCC first order multiphase model was used. For the generation potential, observation and model are consistent, but for the decay rate, observations provide a 39% higher value, suggesting that the methane production from deposited MSW is occurring much faster than predicted by the IPCC model. Applying the retrieved parameters for the whole landfill's lifetime, the total produced methane is estimated to be 497 Gg (ranging from 444 Gg to 550 Gg), of this total 48% may have been emitted before the implementation of the collection system, indicating that it was implemented too late, and 81% may have been emitted before the closing date, with only 19% to be emitted after the end of operations. Subtracting the total methane volume burned in the CDM Activity, the Aura landfill may have emitted on total from 9.4 to 9.8 Tg of CO₂ equivalent.