Characterization of the Gaseous and Odour Emissions from the Composting of Conventional Sewage Sludge

Abstract

Many different alternatives exist to manage and treat sewage sludge, all with the common drawback of causing environmental and odour impacts. The main objective of this work is to present a full inventory of the gaseous and odorous emissions generated during the bench-scale composting of conventional sewage sludge, aiming at assessing the process performance and providing global valuable information of the different gaseous emission patterns and emission factors found for greenhouse gases (GHG) and odorant pollutants during the conventional sewage sludge composting process. The main process parameters evaluated were the temperature of the material, specific airflow, average oxygen uptake rate (OUR), and final dynamic respiration index (DRI), resulting in a proper performance of the sewage sludge composting process and obtaining the expected final product. The obtained material was properly stabilized, presenting a final DRI of 1.2 ± 0.2 g O2·h−1·kg−1 Volatile Solids (VS). GHGs emission factor, in terms of kg CO2eq·Mg−1 dry matter of sewage sludge (DM–SS), was found to be 2.30 × 102. On the other hand, the sewage sludge composting odour emission factor (OEF) was 2.68 × 107ou·Mg−1 DM–SS. Finally, the most abundant volatile organic compounds (VOC) species found in the composting gaseous emissions were terpenes, sulphur compounds, ketones, and aromatic hydrocarbons, whereas the major odour contributors identified were dimethyldisulphide, eucalyptol, and α-pinene.

Gaseous Emissions from the Composting Process: Controlling Parameters and Strategies of Mitigation

“…Similarly, elevated temperatures result in increasing CH 4 emissions. This could be explained by the high rate of microbial activities that result in increasing the temperatures, and these conditions are associated with high oxygen consumption, which ultimately leads to forming anaerobic conditions and the formation of CH 4 [45,[72][73][74]. The same trend was also observed regarding CO 2 and N 2 O emissions that exhibit an increase with increasing temperature [63,75].…”

“…For instance, GHGs' emission factor, in terms of kg CO 2eq .Mg −1 dry matter of sewage sludge (DM-SS), was found to be 2.30 × 10 2 . On the other hand, the sewage sludge composting odor emission factor (OEF) was 2.68 × 10 7 ou.Mg −1 DM-SS [45]. Different emission factors could be found in the literature, depending on the characteristics of the feedstock or the composting technology [46][47][48][49].…”

Comparison and Evaluation of GHG Emissions during Simulated Thermophilic Composting of Different Municipal and Agricultural Feedstocks

“…The S_S treatment produced the lowest total GHG emission equivalent (94.08 kg CO 2 -eq ton −1 DM) owing to the lowest N 2 O emissions (49.89 kg CO 2 -eq ton −1 DM). González et al (2020) controlled the aeration flow rate by the oxygen uptake rate (OUR) during sewage sludge composting and this mode could effectively reduce CH 4 emission but emitted much more N 2 O compared with the present study [ 34 ].…”

“…Among these variables, the type of organic solid waste played an important role in the dynamics and cumulative emissions of GHGs. A series of studies have been conducted and focused on GHG emissions during dairy manure composting [ 19 , 24 , 25 , 26 ], chicken manure composting [ 27 , 28 , 29 , 30 , 31 ], biosolids composting [ 32 , 33 , 34 , 35 ], green waste composting [ 36 , 37 , 38 ] and food waste composting [ 10 , 38 , 39 , 40 ]. However, these studies adopted different aeration methods (continuous and intermittent aeration), aeration rates (high, moderate and low aeration rate), bulking agent types (crop straw, rice hull, sawdust, etc.)…”

Odors Emitted from Biological Waste and Wastewater Treatment Plants: A Mini-Review

“…The authors also systematically studied the main VOCs detected in odors, which were isovaleraldehyde, indole, skatole, butyric acid, dimethyl sulfide, and dimethyl disulfide. In another study by the same authors, the odor emission factors, when composting sewage sludge at a pilot scale, were in the range of 10 7 odor units per kg of composted dry mass, whereas the major odor contributors identified were dimethyl disulfide, eucalyptol, and α-pinene [54].…”