Impact of Biochar Addition and Air-Flow Rate on Ammonia and Carbon Dioxide Concentration in the Emitted Gases from Aerobic Biostabilization of Waste

Abstract

Application of additives to waste may influence the course of the biostabilization process and contribute to its higher effectiveness, as well as to a reduction in greenhouse gas and ammonia (NH3) emission from this process. This paper presents research on the impact of biochar addition on the course of the biostabilization process of an undersized fraction from municipal solid waste (UFMSW) in terms of temperature changes, CO2 concentration in the exhaust gases, NH3 emission from the process, as well as changes in the carbon and nitrogen content in the processed waste. Six different biochar additives and three different air-flow rates were investigated for 21 days. It was found that biochar addition contributes to extending the thermophilic phase duration (observed in the case of the addition of 3% and 5% of biochar). The concentration of CO2 in exhaust gases was closely related to the course of temperature changes. The highest concentration of CO2 in the process gases (approx. 18–19%) was recorded for the addition of 10% and 20% of biochar at the lowest air-flow rate applied. It was found that the addition of 3% or a higher amount of biochar reduces nitrogen losses in the processed UFMSW and reduces NH3 emission by over 90% compared to the control.

Biostabilization process of undersized fraction of municipal solid waste with biochar addition

“…Its density was 219.6 kg . m −3 , and AFP was over 85% [14,60]. The biochar contained trace amounts of HM, which is characteristic of this substance [27].…”

“…Malinowski [11] discusses the impact of biochar additives and different air-flow rates on temperature changes and O 2 concentration in UFMSW in air-filled spaces between waste and gases emitted during process (for the same experimental conditions). Malinowski [11] and Malinowski and Famielec [60] stated that in each of the conducted experiments, the waste reached thermophilic temperatures (over 45 °C). On the other hand, temperatures above 65 °C were obtained with the air-flow rates 0.2 and 0.4 [60].…”

“…Malinowski [11] and Malinowski and Famielec [60] stated that in each of the conducted experiments, the waste reached thermophilic temperatures (over 45 °C). On the other hand, temperatures above 65 °C were obtained with the air-flow rates 0.2 and 0.4 [60]. Figures 1, 2 and 3 present the changes that occurred in MC, OM and AT4, respectively, during the biostabilization process of UFMSW.…”

“…The exceptions were the experiments with 20 wt% addition of biochar, where in several cases, there was an increase in the abundance of tested microorganisms in relation to the initial value at the final stage (after 21 days of process). It is important to note that the highest microbial counts were recorded mainly in 7 day of the process, when the reached temperatures were the highest [14,60].…”

“…The technological properties of biochar used in this study was described in detail in papers by Malinowski et al [29] and Malinowski and Famielec [60]. The MC of biochar was 4.5%, the OM content was 93.4% and the C content was 81%.…”