Evaluation of Landfill Gas Decay Constant for Municipal Solid Waste Landfills Operated as Bioreactors

摘要

Prediction of the rate of gas production from bioreactorlandfills is important for the optimization of energy re-covery and for estimating greenhouse gas emissions. Toimprove the predictability of gas production, landfill gas(LFG) composition and flow rates were monitored for 4 yrfrom one conventional and two bioreactor landfill cells atthe Outer Loop Landfill in Louisville, KY. The ultimatemethane yield (L0) was estimated from the biochemicalmethane (CH4) potential of freshly buried refuse and thedecay rate constant (k) was estimated from measured CH4collection. The site-specific Lo was estimated to be 48.4m~3-CH_4wet Mg~(-1). The estimated decay rate in the con-ventional cell (0.06 yr~(-1)) was comparable to the AP-42default value of 0.04 yr~(-1), whereas estimates for the twobioreactor cells were substantially higher (~0.11 yr~(-1)).The data document the ability of the bioreactor operationto enhance landfill CH4 generation, although the esti-mated decay rate is sensitive to the selected Lo. The morerapid decomposition in the bioreactor cells reduces the length of time over which gas will be produced and em-phasizes the importance of having a LFG collection sys-tem operational once the waste receives added moisture.