Use of Models and Facility-Level Data in Greenhouse Gas Inventories

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Use of Models and Facility-Level Data in Greenhouse Gas Inventories Comparison of model parameters with field investigations The parameters that were obtained from error function analysis and information from each study site based on information at each site including waste composition, waste in place, history and operation practice were used to calculate methane emissions in the IPCC Waste Model again. Total methane emissions were calculated by summarizing seasonal emissions that was calculated by multiplying daily methane emission in each season with the period of the season. The calculation results and field measurements of methane emissions at all sites are summarized in Table 3. The comparison results show that the methane emissions from the IPCC Waste Model gave fair results compared to field measurements in both cases of managed and unmanaged landfills as seen in Figure 5 with the R 2 of 0.65. The differences between calculations and field measurements at the MD1, MD2, MD4 and MS1 were -2.53%, 16.50%, - 11.08% and -7.11%, respectively. At MD3, the calculated value was about 65.51% lower than field measurement. This big difference may be caused by the uncertainty of waste loaded to the site dealing with MSW and other non-hazardous waste from industry while the input parameter used in IPCC Waste Model was only MSW composition because of the lack of non-hazardous waste compositions data. However, the calculations of methane emission from dumpsite were close to field investigations in the cases of US and UD2 revealed by a very low error. At UD3 and UD1, errors of estimation amount to about 50%. These errors may be caused by incorrect data of waste quantity because some parts of waste were moved to other landfills in the case of UD3. At UD1, the quantity of waste was estimated by base on waste delivery vehicle capacity, uncertainty is higher and may effects to emission inventory. Table 3 Comparison of methane emissions in 2006 (Mg) from FOD model and field measurements Site MD1 MD2 MD3 MD4 MS1 UD1 UD2 UD3 US1 Operation practice Managed – deep (Active) Managed - deep (Active) Managed - deep (Active) Managed - deep (Active) Managed – shallow (Active) unmanaged - deep (Active) unmanaged - deep (Active) unmanaged - deep (Inactive) unmanaged - shallow (Active) Default MCF Selected MCF Default OX Selected OX IPCC Waste Model Field measurement 1.00 0.65 0.10 0.15 1,523.30 1,485.75 -2.53% 1.00 0.65 0.10 0.15 127.76 153.01 16.50% 1.00 0.65 0.10 0.15 715.62 2,074.87 65.51% 1.00 0.65 0.10 0.15 420.11 378.21 -11.08% 1.00 0.2 0.10 0.15 60.07 56.08 -7.11% 0.80 0.15 0.10 0.70 42.45 73.89 42.55% 0.80 0.15 0.10 0.70 106.12 106.52 0.37% 0.80 0.15 0.10 0.70 97.67 63.26 -54.39% 0.40 0.1 0.10 0.70 20.60 20.65 0.25% Diff. IPCC Expert Meeting Report 60 TFI
Use of Models and Facility-Level Data in Greenhouse Gas Inventories Figure 5 Relation of estimate methane emission and field measurement (Mg) ratio of estimate form waste model /field measurement 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 5 10 15 20 25 30 Landfill age (years) Figure 6 Ratio of methane emission from waste model versus field measurement The ratio of estimate emission from IPCC Waste Model to field measurement is showed in Figure 6. In general, most of the ratios are between 0.8-1.1. There are three points that are departing from the others, MD3, UD3 and UD1. Ratio of MD3 is 0.3 which may due to the reason explained above. UD3 (ratio 1.5) is a 24 years old unmanaged deep which poor operation system that lead to difficultly during measurement. The site at UD1 with the fair ratio of 0.6 is also unmanaged deep landfill. Despite the site at MD3, calculation of methane emission using IPCC Waste Model with the local value of MCF, OX and site specific waste composition has shown the good relationship. The MCF, half-life time, OX and delay time that were obtained from this study can be used as country-specific parameters in the FOD model that will be used for landfill methane emission inventory in the subsequent section following the Tier 2 methodology of the IPCC. Figure 7 illustrated the application of waste model in managed landfills and unmanaged landfills in relation to landfill age and the quantity of waste in place. It is observed that emissions from managed landfill either by IPCC Waste Model and field measure show lower emission in different age at the close proximity value and corresponded to their waste in place except MD3 where specific composition of waste in place per day is uncertain. The results from unmanaged landfill sites follow the same pattern of managed landfill except for UD3 where low emission is observed despite the large amount of waste in place per day. This may be due to the long life time of this landfill and the improper operation of this specific site. However, it is note that the MCF used in managed landfill sites here is 0.65 which is lower than that recommendation from IPCC 2000 Good Practice Guidance and that OX of 0.15 is applied due to local experiment and conditions IPCC Expert Meeting Report 61 TFI
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