This project has compiled and improved the Taiwan National Greenhouse Gas Inventory for Waste Sector from 1990 to 2014 using methodologies consistent with those recommended in the 2006 Intergovernmental Panel on Climate Change Guidelines for National Greenhouse Gas Inventories (IPCC 2006 Guidelines). The methodologies for estimating greenhouse gas (GHG) emissions from the Waste Sector described in the National Inventory Report submitted by the Annex I parties in 2015 and 2016 have been reviewed and analyzed to understand and identify the latest international trends.
The following efforts were made to accurately estimate GHG emissions and improve the inventory quality for future potential GHG inventory revisions. For a reasonable choice of emission parameters, 3 solid waste disposal sites were visited to understand the history of landfill gas collection and utilization. On-site GHG emissions from 3 categories of industrial wastewater treatment plants were also measured to compare the differences between the local emission factor and default value given in the IPCC 2006 Guidelines. To evaluate for incorporating excluded emission sources and improve the accuracy of emission factors, several tasks were implemented, including the evaluation of CH4 emissions from domestic wastewater treatment plants, evaluation of N2O emissions from industrial wastewater treatment plants, determination of the fraction of methane in generated landfill gas based on the reporting data, and adjustment of the source of activity data for waste incineration. In addition, both Approach 1 (propagation of error) and Approach 2 (Monte Carlo method) were used for the uncertainty analysis of emission estimates. Detailed results of both approaches are presented and compared. Concrete conclusion and suggestion with respect to the above survey results and evaluation for incorporating excluded emission sources have been made after 3 review meetings with the experts.
With reference to the reporting guidelines on annual greenhouse gas inventory under the Kyoto Protocol and National Greenhouse Gas Inventory tables, the Taiwan National Greenhouse Gas Inventory for Waste Sector from 1990 to 2014 consistent with the IPCC 2006 Guidelines has been compiled and submitted by the inventory review process.
The changes in greenhouse gas emissions from the waste sector show that emissions were the highest in 1996 and there was a general downward trend since 2000. The largest contributor to the emissions by category was changed from solid waste disposal to wastewater treatment since 2009. Over the past 10 years, emissions from solid waste disposal and domestic wastewater treatment have decreased substantially, while emissions from industrial wastewater treatment have increased. In 2014, emissions from the waste sector resulted in 4,264.3 kt-CO2 eq. Among the waste sector emissions in 2014, the largest contributor was domestic wastewater treatment accounting for 38.1%, followed by solid waste disposal accounting for 33.5%, industrial wastewater treatment accounting for 25.2%, incineration of waste accounting for 2.3%, and biological treatment of waste accounting for 0.9%. Breakdown of emissions in 2014 by gas shows that the largest contributor to the emissions is CH4 accounting for 89.9%, followed by N2O accounting for 7.9%, and CO2 accounting for 2.1%. The emissions from this sector had decreased by 53% compared with 1990 levels and decreased by 5% compared with 2013 levels.