The application portfolio empowerment method and ELECTRE-I for optimising the control of ammonia release during the aerobic fermentation process.

Aerobic fermentation composting can transform solid organic waste into biological organic fertiliser, while reducing resource wastage and ecological damage. However, in the composting process, a serious loss of nitrogen occurs, primarily in the form of the release of ammonia gas. The release of ammonia gas not only pollutes the environment, but also diminishes the presence of nutrient elements, resulting in compost products that are lower in quality. Given that many factors influence the release of ammonia gas during the aerobic fermentation process, it is difficult to determine optimal process parameters. In an effort to address this issue, we propose herein a combinational weighting method based on the analytic hierarchy process (AHP) and entropy weighting method to determine the weight of each secondary index. We also establish a parametric optimisation model based on the ammonia release conditions of the ELECTRE-I method that provides a theoretical underpinning and a decision basis for optimising the process parameters that mediate the release of ammonia during the aerobic fermentation process. This method can be widely employed to reduce the release of ammonia gas and may be of significance to the future development of bioengineering-based composting technology.

Effect of fipronil on biogas production performance during anaerobic digestion of chicken manure and corn straw.

Fipronil is a broad-spectrum insecticide that has a good control effect on pests of commercial poultry. Although many studies have reported the environmental fate of fipronil, the influence of residual fipronil in poultry waste on biogas production has not been further explored yet. In this article, an experimental comparative study on anaerobic digestion (AD) of chicken manure (CM) and corn straw (CS) with different fipronil concentrations (FCs) was carried at 8% of total solid (TS) and mid-temperature (35 ± 1)°C. The results showed that fipronil had a significant effect on biogas production during AD of CM and CS. When the FC is at a low level (≤10 mg·kg-1), the biogas production rate is increased and the digestion period was shortened, while higher FC (≥ 20 mg·kg-1) showed an inhibitory effect. During the monitoring of enzyme activity, low FC showed no significant effect on cellulase and saccharase, but the urease activity increased in the early stage. High FC showed inhibition of activity of cellulase and urease, but the saccharase activity was significantly inhibited until FC reached 40 mg·kg-1. This study also confirms that the environment in anaerobic digester is favorable for the degradation of fipronil, and its half-life is about 15.83 days.