Seungjin Kim

According to the IPCC (Intergovernmental Panel on Climate Change) guidelines, when calculating CO₂ emissions, CO₂ emissions from biomass should be excluded from the total amount of CO₂ emissions and should be separately reported due to their “carbon neutrality”. Sewage sludge is one of the representative biomass fuels. It is mixed with fossil fuels to achieve greenhouse gas reduction or is used by itself as a fuel to replace fossil fuels. According to the results of this study, biomass fractions of both the sewage sludge and the sewage sludge incineration exhaust gases did not amount to 100%. At present, in many countries (South Korea, Japan, and Germany), when calculating greenhouse gas emissions from sewage sludge incinerators, all CO₂ emissions from sewage sludge are judged to be biomass and only the greenhouse gas emissions that correspond to non-CO₂ gases are calculated as greenhouse gas emissions. However, since, according our results, the content of sewage sludge is not 100% biomass, if CO₂ emissions are excluded according to the existing greenhouse gas emission calculation method, the amount of emissions may be underestimated. Therefore, to accurately calculate greenhouse gas emissions from a sewage sludge incinerator, CO₂ emissions should be calculated in consideration of the fossil carbon fractions of sewage sludge.

In this study, to determine the biomass fraction to apply to the estimation of greenhouse gas (GHG) emissions from the waste incineration sector, municipal solid waste, industrial waste, and sewage sludge incineration facilities were selected and analyzed, and the biomass fractions found in these facilities were compared. The biomass fractions of Municipal solid waste, industrial waste, and sewage sludge in incineration facilities were shown to be 57%, 41%, and 78%, on average, respectively. In the case of municipal solid waste and industrial waste incineration facilities, the values were similar to those of previous studies. However, the biomass fraction of wastes and sewage sludge except for municipal solid waste was found to be significantly different from the IPCC default. Accordingly, we believe that the biomass fractions used to estimate the GHG emissions of different incineration facilities should reflect the characteristics of each waste type. At present, the basic value given by the IPCC for biomass fraction is used in Korea to estimate the GHG emissions of each waste incineration facility. Some studies have found a difference between the value obtained using the basic value given by the IPCC and the value obtained using values that reflect the characteristics of Korea. In common with previous studies, in this study the biomass fraction of waste incineration facilities and sewage sludge incineration facilities except for municipal solid wastes showed a large difference, which is also expected to affect the estimation of GHG emissions. If further studies collect additional data on the biomass fraction of each waste type, this study along with the additional data collected will assist in the development of a state level greenhouse gas emission factor and contribute to the improvement of the reliability of the national GHG inventory.

According to the IPCC guidelines, CO₂ emissions from biomass should be excluded from the entire amount of CO₂ emissions when calculating CO₂ emissions and should be separately reported due to the “carbon neutrality.” Sewage sludge is one of the representative biomass fuels. And it is mixed with fossil fuels in terms of greenhouse gas reduction or is used as fuel to replace fossil fuels by itself. According to the results of this study, biomass contents of both the sewage sludge and the sewage sludge incineration exhaust gases did not amount to 100%. At present, in many countries(South Korea, Japan, and Germany), when calculating greenhouse gas emissions from sewage sludge incinerator, all CO₂ emissions from sewage sludge are judged to be biomass and only those greenhouse gas emissions that correspond to Non-CO₂ gases are calculated as greenhouse gas emissions. However, since, according our results, the content of sewage sludge is not 100% biomass, if CO₂ emissions are excluded according to the existing greenhouse gas emission calculation method, the amount of emissions may be underestimated. Therefore, to accurately calculate greenhouse gas emissions from sewage sludge incinerator, CO₂ emissions should be calculated in consideration of the fossil carbon contents of sewage sludge.

N₂O, which is emitted mainly from nitrogen decomposition via bacteria, livestock manure, agricultural fertilizer use, fossil fuel combustion and waste incineration, is classified as a substance that causes significant destruction of the ozone layer. The N₂O measurement methods for these emission sources may be divided into chromatography, optical, and electrical current measurements. Chromatography has been widely utilized for analyzing N₂O. However, up until now, few studies have been conducted on N₂O using photoacoustic spectroscopy. Therefore, this study aimed to evaluate performance of photoacoustic spectroscopy in this regard based on laboratory and field test results. The repeatability of photoacoustic spectroscopy was measured at 1.12%, which is lower than the repeatability of 3.0% suggested by the ISO 1564 standard, so, it has shown an excellent repeatability. The detection limit was determined to be 0.025 ppm, and the response time was confirmed to be 3 min and 26 s. The results of comparison between these measurements and GC show that the latter has superior accuracy, but mobility and convenience are superior for PAS. On the contrary, GC has a continuous measurement limitation, but PAS makes it possible to conduct continuous measurements. Therefore, PAS can be extremely useful to confirm the characteristics of N₂O emissions and to quantify their amount.