A technology to reduce ammonia emission via controllingproteolytic bacterial community and physicochemical properties

Abstract

Proteolysis is the rate-limiting step involved in ammonification during organic nitrogen mineralization, and which relates to the amount of ammonia (NH3) volatilized and ammonium (NH4+) released in the composts. However, the dynamic of bacterial proteolytic communities related with NH3 emissions in composting systems are mostly unknown. This study aimed to examine and compare the effects of hyperthermophilic pretreatment composting (HPC) and traditional composting (TC) on (i) the difference of NH3 loss and nitrogenous compounds; (ii) the dynamics of the proteolytic bacterial community participated in proteolysis in composting systems on the basis of the functional genes (npr and sub); (iii) the link between the proteolytic bacterial community, biophysiochemical characteristics and NH3 loss. Results revealed that the HPC was able to decrease NH3 loss by 41.5% compared to TC during 60-day composting, together with an inhibitory effect on protease activity. Particularly, the relative abundances of proteolytic bacteria (Bacillus megaterium and Staphylococcus cohnii) with high proteolytic capability reduced significantly in HPC. Partial least-squares path modeling suggested physicochemical properties such as higher temperature as well as lower C/N ratio played a dominant role in affecting the abundance of proteolytic bacteria, which may have been an important factor contributing to the lower NH3 loss in HPC. These findings suggest that HPC can significantly reduce NH3 loss and enhance our understanding of proteolytic bacteria in composting systems.

Assessment of the Biodegradability and Compatibility of Finished Leathers: Analysis Using Spectroscopy and Thermal Methods

“…In contrast, IS, NL, and CAS products showed moderate biodegradability, ranging between 50% and 60% (Table 4), due to collagen degradation in the crust leather. Regarding the latter product (CAS), the decomposition of organic materials with a low C/N ratio (Table 2) can produce a series of adverse effects: the excessive release of ammonia during composting via volatilisation can produce an inhibition and imbalance in the microbiota due to its toxicity; and the acidification of the compost due to the excessive production of organic acids via protein decomposition, as noted by other authors [34]. As a result, the chemical bio-based option (AB) requires further investigation, as it showed a low biodegradability (58.38%) due to its chemical structure, which has the same complexity as that of the base product that it replaced and exhibits the same functional properties.…”