Modeling of CO Accumulation in the Headspace of the Bioreactor during Organic Waste Composting

Abstract

Advanced technologies call for composting indoors for minimized impact on the surrounding environment. However, enclosing compost piles inside halls may cause the accumulation of toxic pollutants, including carbon monoxide (CO). Thus, there is a need to assess the occupational risk to workers that can be exposed to CO concentrations > 300 ppm at the initial stage of the process. The objectives were to (1) develop a model of CO accumulation in the headspace of the bioreactor during organic waste composting and (2) assess the impact of headspace ventilation of enclosed compost. The maximum allowable CO level inside the bioreactor headspace for potential short-term occupational exposure up to 10 min was 100 ppm. The composting was modeled in the horizontal static reactor over 14 days in seven scenarios, differing in the ratio of headspace-to-waste volumes (H:W) (4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4). Headspace CO concentration exceeded 100 ppm in each variant with the maximum value of 36.1% without ventilation and 3.2% with the daily release of accumulated CO. The airflow necessary to maintain CO < 100 ppmv should be at least 7.15 m3·(h·Mg w.m.)−1. The H:W > 4:1 and the height of compost pile < 1 m were less susceptible to CO accumulation.

Biological treatment of biowaste as an innovative source of CO—The role of composting process

“…Taking into account the previously mentioned information on excessive CO production in bioreactors (both without ventilation and those opened to release process air), the safety aspect of composting plant employees becomes important. Having direct contact with composted waste, they are exposed to CO, the concentration of which significantly exceeds the acceptable generally limit values indicated by the WHO (Sobieraj et al, 2021). Therefore, it is necessary to develop personal protective equipment for workers currently working with the aerobic processing of organic waste in composting plants; however, it is also important to consider this problem in future facilities that interconnect composting plants with lines for further processing of the obtained CO, especially due to the intensification of this gas formation during the waste composting stage.…”

“…Frontiers in Bioengineering and Biotechnology frontiersin.org its concentration can reach 3.2% (31,600 ppm) and 36.1% (360,000 ppm) for reactors with the daily release of accumulated gas and without ventilation, respectively (Sobieraj et al, 2021). High CO production in the initial stage of the process correlates with the temperature increase in the compost piles and shows the most significant increase in thermophilic conditions (Stegenta et al, 2019a).…”

Application of Optimization and Modeling for the Composting Process Enhancement

“…In developing the new software tool, the authors assumed that all available raw materials would be used as much as possible and also proposed a successful minimization of the production cost of the composting mixture. Sobieraj et al [122] created a model to predict carbon monoxide accumulation during composting of organic waste (dairy manure, grass clippings and pine sawdust) in a horizontal static bioreactor. The first-order kinetic model was used to describe carbon monoxide formation during the composting process.…”

The Influence of Low-Temperature Food Waste Biochars on Anaerobic Digestion of Food Waste

“…The maximum methane potential and process kinetic is highly dependent on substrate, inoculum, equipment, and process conditions such as TS and pH. Deepanraj et al [52] analyzed the kinetic of biogas production from kitchen waste at different TS concentrations (5-15%) and pH (5)(6)(7)(8)(9). The result of Deepanraj et al [52] showed that first-order model kinetic (Gompertz model name by author) fit well to experimental data and had a determination coefficient > 0.994.…”