The Spatial and Temporal Distribution of Process Gases within the Biowaste Compost

Abstract

Composting is generally accepted as the sustainable recycling of biowaste into a useful and beneficial product for soil. However, composting processes can produce gases that are considered air pollutants. In this dataset, we summarized the spatial and temporal distribution of process gases (including rarely reported carbon monoxide, CO) generated inside full-scale composting piles. In total 1375 cross-sections were made and presented in 230 figures. The research aimed to investigate the phenomenon of gas evolution during the composting of biowaste depending on the pile turning regime (no turning, turning once a week, and turning twice a week) and pile location (outdoors, and indoors in a composting hall). The analyzed biowaste (a mixture of tree leaves and branches, grass clippings, and sewage sludge) were composted in six piles with passive aeration including additional turning at a municipal composting plant. The chemical composition and temperature of process gases within each pile were analyzed weekly for ~49–56 days. The variations in the degree of pile aeration (O2 content), temperature, and the spatial distribution of CO, CO2 and NO concentration during the subsequent measurement cycles were summarized and visualized. The lowest O2 concentrations were associated with the central (core) part of the pile. Similarly, an increase in CO content in the pile core sections was found, which may indicate that CO is oxidized in the upper layer of composting piles. Higher CO and CO2 concentrations and temperature were also observed in the summer season, especially on the south side of piles located outdoors. The most varied results were for the NO concentrations that occurred in all conditions. The dataset was used by the composting plant operator for more sustainable management. Specifically, the dataset allowed us to make recommendations to minimize the environmental impact of composting operations and to lower the risk of worker exposure to CO. The new procedure is as follows: turning of biowaste twice a week for the first two weeks, followed by turning once a week for the next two weeks. Turning is not necessary after four weeks of the process. The recommended surface-to-volume ratio of a compost pile should not exceed 2.5. Compost piles should be constructed with a surface-to-volume ratio of less than 2 in autumn and early spring when low ambient temperatures are common.

Analysis of the Spatial and Temporal Distribution of Process Gases within Municipal Biowaste Compost

“…In a wintertime experiment of composting with passive aeration [45], cooling began at the ends of the pile, which was explained by the increased surface area of the material and therefore increased heat loss. In this study, a similar pattern of temperature drop was observed only in piles A1 (36th day of the process, [43] ( Figure A4)), A2 (15th and 23rd day, [43] (Figures A8 and A9)), and A3 (15th and 52nd day, [43] (Figures A17 and A22)), where it took place on just one end. Also, in some cases, areas that had previously cooled down reached a higher temperature at later stages of composting (e.g., the end of the left side of pile A6 at day 29 [43] ( Figure A43)).…”

“…In this study, a similar pattern of temperature drop was observed only in piles A1 (36th day of the process, [43] ( Figure A4)), A2 (15th and 23rd day, [43] (Figures A8 and A9)), and A3 (15th and 52nd day, [43] (Figures A17 and A22)), where it took place on just one end. Also, in some cases, areas that had previously cooled down reached a higher temperature at later stages of composting (e.g., the end of the left side of pile A6 at day 29 [43] ( Figure A43)). It was also observed that low temperatures (prevailing in the piles in autumn and winter) were caused by an unfavorable surface-to-volume ratio, which resulted in faster heat loss (Table 3) [46].…”

“…Four cross sections and two longitudinal cross sections (the left and right sides of the pile) were made for each of the six piles. In total 1375 cross sections were made and presented in 230 figures in a companion manuscript [43]. A small subset (16 cross sections) illustrates the chimney effect in the A1 pile and the temperature effect on CO distribution is presented in this manuscript.…”

“…In addition, only 31.1% of locations in a cross section reached thermophilic conditions (defined as T > 60 • C, necessary to kill pathogens). The entire dataset of the temporal and spatial variation of temperature is presented elsewhere [43].…”

Waste to Carbon Energy Demand Model and Data Based on the TGA and DSC Analysis of Individual MSW Components

“…The software will optimize the carbonized refuse-derived fuel (CRDF) production process before its valorization in the torrefaction process. In addition, the appropriate selection of the MSW mixture will help determine the cost-effectiveness of MSW mechanical pre-treatment and torrefaction of individual, site-specific wastes, waste streams, and their mixtures, such as municipal sludge [9] or compost [10].…”