VOCs released from municipal solid waste at the initial decomposition stage: Emission characteristics and an odor impact assessment.

The nuisance from odor caused by municipal solid waste (MSW) is resulting in a growing number of public complaints and concerns. Odor pollution occurs in the initial decomposition stage of MSW, including waste collection, transportation and early pre-treatment. Furthermore, decomposition takes place in waste facilities that are often close to living areas, which can result in odor impacts on local inhabitants. However, this aspect of odor impact from MSW has not been well studied. In the current study, lab-scale waste cells were designed to simulate MSW storage conditions in the early stage. The characteristics of VOCs emissions with different waste compositions were analyzed. The odor concentration (CO, non-dimensional) method and odor intensity were used for the assessment of odor. Ethanol was the substance with highest emission rate. The release rate of VOCs increased with the growth easily biodegradable waste (EBW). VOCs emissions was reduced by 25% when the proportion of EBW decreased from 60% to 45%. Methyl sulfide, ethanol, dimethyl disulfide and ethyl acetate were identified as typical odorants. The EBW proportion in waste is the main factor significantly influencing odor pollution. The CO was 244.51 for the 60% EBW condition, which was only 61.46 for 15% EBW condition. These study results provide important information for the implementation of a garbage sorting policy and the monitoring of odor pollution from waste management.

Emission of odor pollutants and variation in microbial community during the initial decomposition stage of municipal biowaste.

Odor pollution often occurs in the initial decomposition stage of municipal biowaste, including throwing/collection and transportation. However, this aspect of odor impact from municipal biowaste has not been well studied. In this study, a practical dustbin (120 L) equipped with flux chamber and filled with three types of municipal biowaste was used to simulate garbage storage conditions. The result indicated that the emission rate of odor pollutants for uncooked food waste (UFW) represented a nearly linear growth trend, reaching the maximum (3963 ± 149 µg kg-1 DM h-1) at 72 h. Cooked food waste (CFW) increased rapidly from 8 h to 24 h, and then remain fluctuated, reached the maximum (2026 ± 77 µg kg-1 DM h-1) at 72 h. Comparatively, household kitchen waste (HKW) reached the maximum emission rate (10,396 ± 363 µg kg-1 DM h-1) at 16 h. Sulfide and aldehydes ketones were identified as dominant odor contributor to UFW and CFW, respectively. While aldehydes ketones and sulfides were both dominant odor contributor to HKW. Moreover, the microbial diversity analysis suggests that Acinetobacter was the dominant genus in UFW, and Lactobacillus was the dominant genus in CFW and HKW. In addition, it was evident that each odorous pollutant was significantly associated with two or more bacterial genera, and most bacterial genera such as Acinetobacter, were also significantly associated with multiple odorous pollutants. The variation of odorants composition kept consistent with microbial composition. The present study could provide essential evidence for a comprehensive understanding of odorant generation in the initial decomposition stage of municipal biowaste. It could contribute to setting out strategies for odor control and abatement in municipal biowaste management systems.

Emission characteristics and variation of volatile odorous compounds in the initial decomposition stage of municipal solid waste.

The odour pollution occurring in the initial decomposition stage of municipal solid waste (MSW), including collection, transfer and transportation, has not been sufficiently emphasised. Thus the emission characteristics of and variation in odorant generation in this stage were investigated through simulation experiments at different temperatures, waste composition and processing durations. Out of 120 odorous compounds, 52 were detected in seven categories under all tested conditions, with significant variations. In the total concentration and emission rate, ethanol generally showed the largest proportion (larger than 80% on average), followed by unsaturated hydrocarbons which were dominated by propylene (13.1% on average of concentration proportion). The total emissions rapidly increased with processing duration when the temperatures were 15°C to 30°C. The proportion of ethanol increased significantly from 40.1% at 6h to 82.9% at 24h at 30°C. By contrast, a low temperature (5°C) resulted in low concentrations, and propylene accounted for the largest proportion instead of ethanol. With increasing temperature, biogenic compounds with large proportions increased more rapidly than xenobiotic compounds because of accelerated biological process and volatilisation. The emission rates of oxygenated compounds, saturated hydrocarbons, unsaturated hydrocarbons and halogenated compounds significantly increased (by approximately 20% to 50%) with an increase in easily biodegradable portion in the MSW. The proportions were relatively stable with the MSW composition variation, suggesting that most xenobiotic compounds were also derived from easily degradable portions. The olfactory evaluation showed that organic sulphur compounds contributed the most (approximately 75% to 95%) to odour pollution at the beginning of the stage because of their extremely low olfactory thresholds, with methanethiol as the dominant contributor (approximately 50% to 80% when detected). Results of this study can provide useful information for an improved understanding and monitoring of odorant emissions in the initial decomposition stage of MSW.