Quantitative Carbon Changes of Selected Organic Fractions during the Aerobic Biological Recycling of Biodegradable Municipal Solid Waste (MSW) as a Potential Soil Environment Improving Amendment—A Case Study

The aim of the investigation was to determine the quantitative changes of selected organic compounds during composting of municipal solid wastes (MSWs). The object of the study was a differently matured compost produced according the to open pile/windrow semi-dynamic technology from selectively collected biodegradable municipal solid waste. During the experiment, the temperature and moisture of the composted wastes were monitored. In the collected samples—taken from differently matured compost—the total organic carbon (TOC) and total nitrogen (TN) were determined. The organic matter fractionation method described by Stevenson and Adani et al. was adopted, which allows to determine the carbon content of the following groups of organic compounds: hydrophobic (HSC), hydrophilic (WEOC), acidophilic (C AC ), cellulose (CCEL), core-HA (ligno-humic, CALK) and residual carbon (non-hydrolysing, CR). The TOC and TN content, as well as the origin and quality of the starting materials, allow the product tested to be classified for fertiliser purposes. The most intense changes were observed during the thermophilic composting phase. In spite of the optimal technological conditions of the process, the predominance of the CR and CCEL fraction was observed, and the share of humic compounds did not exceed 30% TOC. The investigated compost met legal, ecological and economic criteria for products of biological recycling, thus can be used as a good organic amendment to improve the soil organic matter balance, stimulate the soil biodiversity and carbon sequestration.