Estimation of microbial methane generation and oxidation rates in the municipal solid waste landfill of Kaluga city, Russia.

Using a theoretical model and mass isotopic balance, biogas (methane and CO(2)) released from buried products at their microbial degradation was analysed in the landfill of municipal and non-toxic industrial solid organic waste near Kaluga city, Russia. The landfill contains about 1.34 x 10(6) tons of waste buried using a 'sandwich technique' (successive application of sand-clay and waste layers). The delta(13)C values of biogenic methane with respect to CO(2) were-56.8 (+/-2.5) per thousand, whereas the delta(13)C of CO(2) peaked at+9.12 per thousand (+1.4+/-2.3 per thousand on average), reflecting a virtual fractionation of carbon isotopes in the course of bacterial CO(2) reduction at the landfill body. After passing through the aerated soil layers, methane was partially oxidised and characterised by delta(13)C in the range of-50.6 to-38.2 per thousand, evidencing enrichment in (13)C, while the released carbon dioxide had delta(13)C of-23.3 to-4.04 per thousand, respectively. On the mass isotopic balance for the delta(13)C values, the methane production in the landfill anaerobic zone and the methane emitted through the aerated landfill surface to the atmosphere, the portion of methane oxidised by methanotrophic bacteria was calculated to be from 10 to 40% (averaged about 25%). According to the theoretical estimation and field measurements, the annual rate of methane production in the landfill reached about 2.9(+/-1.4)x10(9) g C CH(4) yr(-1) or 5.3(+/-2.6)x10(6) m(3) CH(4) yr(-1). The average rates of methane production in the landfill and methane emission from landfill to the atmosphere are estimated as about 53 (+/-26) g C CH(4) m(-2) d(-1) (or 4 (+/-2) mol CH(4) m(-2) d(-1)) and 33 (+/-12) g C CH(4) m(-2) d(-1) (or 2.7 (+/-1) mol CH(4) m(-2) d(-1)), respectively. The calculated part of methane consumed by methanotrophic bacteria in the aerated part of the landfill was 13(+/-7) g C CH(4) m(-2) d(-1) (or 1.1(+/-0.6) mol CH(4) m(-2) d(-1)) on average.