Seasonal Changes in the Composition and Thermal Properties of Municipal Solid Waste: A Case Study of the City of Perm, Russia
The paper presents experimental studies of municipal solid waste (MSW) composition and its thermal properties (moisture and ash content). Measurements were taken to track seasonal changes in the composition of MSW. For example, in spring, the content of organic waste was 17.0% and, in autumn, it reached 31.5% due to considerable consumption of seasonal vegetables and fruits. The share of paper in MSW changed from 21.4% in spring to 9.7% in autumn. More paper in spring is due to discarded student notebooks at the end of a school year, as well as spring household cleaning. These data indicate significant changes in waste composition during the year, which should be taken into account when planning technologies for waste management.
Laboratory studies of moisture and ash content by season allowed the range of these changes to be determined. In autumn for instance, the moisture and ash content of organic waste was about 82% and 14%, respectively, while in winter, it was approximately 73% and 22%, respectively. These figures can be explained by the organic waste origin: autumn organic waste often comes from fruit pulp and, for example, watermelon peels, and winter organic waste tends to consist mostly of dry vegetable peels such as potato peelings.
The low calorific value of certain components is based on their composition and the level of moisture and ash in different seasons. Therefore, it is important to take into account the moisture and ash content of individual components, not average values, in order to calculate the waste calorific value.
MSW thermal characteristics change significantly over the seasons: the MSW moisture content is the highest in autumn (about 49%) and the lowest in winter (32%). The ash content in MSW ranges from 20% in spring and autumn to 27% in summer. The lowest calorific value per working mass in different seasons varies from 7 to 10 MJ/kg, which must be taken into consideration when developing waste management systems in general and when designing specific energy recovery facilities.