Methane emission estimation from landfills in Delhi: A comparative assessment of different methodologies

Landfills are important anthropogenic sources of methane (CH4) emission especially in fast urbanizing countries. This paper presents the CH4 emission estimations carried out using the in-situ CH4 measurements, IPCC 1996 Default methodology (DM), Modified Triangular Method (MTM) and First Order Decay (FOD) method for the three landfills currently operational in the capital city Delhi of India. The in-situ methodology has yielded the landfills specific methane emission factors (EFs). The annual average methane emission rates from three landfills namely, Ghazipur (GL), Bhalswa (BL) and Okhla (OL) are 14.6, 23.6 & 7.5 Gg y−1 by DM; 13.3, 10.6 & 7.2 Gg y−1 by the FOD; 17.0, 13.7 and 10.7 Gg y−1 by the MTM; and 4.6, 4.2 and 1.4 Gg y−1 by the in-situ measurement method respectively. The CH4 EFs have been found to be 9.7 ± 2.6, 5.5 ± 1.6 and 5.5 ± 1.7 g kg−1 of waste respectively for the GL, BL and OL landfills in Delhi. The study reveals that in-situ methodology seems to provide better representative emission estimation compared to other methods. The FOD method also yields comparable results with that of in-situ methodology in cases where good waste composition data is available.

► Methane emission from landfill sites show large spatial and temporal variability.
► Development of landfill specific methane emission factor reduces uncertainties in estimation.
► Different methodologies for emission estimation result in different values.
► Usefulness of FOD method depends upon the quality of waste composition data.