Evaluation and reduction of greenhouse gas emissions from waste incineration plants
Apart from classic pollutants, also greenhouse gases like nitrous oxide (N2O), methane (CH4) and fossil carbon dioxide are emitted by waste incineration plants operated in Germany. In order gain deeper knowledge about the formation and release of greenhouse gases in waste incineration plants, literature research and measurements of nitrous oxide and methane were carried out on behalf of the Federal Environmental Agency (FKZ 3714 42 313 3). The measurements were carried out on plants using different combustion technologies: two sewage sludge incineration plants with fluidized-bed combustion, one sewage sludge incineration plant with grate firing, one waste incineration plant with grate firing and one waste wood incineration plant with fluidized-bed combustion.
The formation of nitrous oxide mainly depends on the nitrogen content of the waste, on the combustion temperature and the oxygen content during the combustion process. As a result, it clearly showed that a high amount of nitrous oxide can be created during the combustion of sewage sludge with a high nitrogen content. In the fluidized-bed combustion plants and for furnace temperatures of more than 850 °C, nitrous oxide emission values of up to 200 mg/m³ were measured. This value doubled to up to 400 mg/Nm³ when the furnace temperature was reduced to below 850 °C. For sewage sludge incineration with grate firing, nitrous oxide emissions of between 360 mg/m³ and 800 mg/m³ were measured for post-combustion temperatures of 850 to 900 °C. On the other hand, the nitrous oxide emissions of a domestic waste and commercial waste incineration plant with grate firing were below 5 mg/m³, and for a waste wood incineration plant with circulating fluidized-bed combustion values of 20 to 50 mg/m³ were measured for temperatures in the post-combustion zone of 930 to 960 °C. The methane emissions measured in the plants in the course of the project were between 5 and 20 mg/m³ for sewage sludge incineration plants and below 5 mg/m³ for the combustion of domestic and commercial waste as well as waste wood.
In order to evaluate the impact of waste incineration plants on the climate, furthermore knowledge of the biogenic share of the waste is required. For this purpose, three methods on the measurement and determination of carbon isotopes were described and published in the standard EN ISO 13833 in 2013.