Waste Management through Composting: Benefits, New Insights and Challenges

The management of municipal solid waste (MSW) is a global challenge of a complex nature. The organic fraction of rapidly degrading MSW, which can be recycled via composting provided it is segregated at the source, is an incipient or non-existent practice in low- and middle-income countries. This study aimed to identify the barriers and opportunities for composting MSW based on the perception of local stakeholders through a qualitative and quantitative exploratory case study in the municipality of São José dos Campos (SP). The study identified and interviewed local stakeholders engaged in composting in the territory, surveying the local market for organic agricultural inputs. Education, infrastructure, and social influence were the main factors that led to the decision to start composting. For home composting, the efficiency of generated waste diversion is from 42% to 59%, and management difficulties at the beginning of the practice are recurrent. Engaging people is the main challenge of community initiatives and 32% ended their composting activities due to the COVID-19 pandemic. Vermicomposting can be an opportunity to value organic waste in the local market. The insights gleaned from the perceptions of local stakeholders provide valuable input for more effective planning within a municipal composting scheme. Full article

As livestock and poultry farming expands in China, the generation of fecal waste has significantly increased. Inadequate waste management can contribute to environmental pollution. This study seeks to optimize small-scale composting systems to address the inefficiencies and the limited automation of traditional composting equipment. We redesigned the mixing blades and refined the ventilation heating system, establishing an efficient mixing mechanism and an energy-saving ventilation heating system. A control system, incorporating Monitor and Control Generated System and Programmable logic Controller, was developed for real-time monitoring and adjustment capabilities, substantially enhancing automation levels. The optimization proved effective by reducing the composting cycle from 13 days to 11.5 days, increasing the GI value from 83% to 89%, and lowering the humidity from 8.9% to 8.1%. Full article

Compost amendments, apart from improving fertility and the general characteristics of agricultural soils, have known implications for global C cycling and sequestration in soils. Their effects are usually assessed via the quantification of soil organic carbon (SOC) pools, usually labile (fast) and recalcitrant (slow) pools, with varying intrinsic decomposition rates and distinct resident times. However, the real C-sequestration potential of organic additions to soil is still under discussion. In this study, a field trial and a lab incubation experiment were designed to study the C-sequestration mechanism in an agricultural Mediterranean soil. Soil with a history of C3 photosystem crop was amended with two maize composts from maize harvesting surpluses (C4 photosystem) with different maturity stages (AC: aged compost; NC: new, less mature compost). The evolution of SOM was monitored for 6 months using complementary analytical techniques, including analysis of stable C isotopes (IRMS), thermogravimetry (TG) and C-stock and priming effect (PE) modelling. Based on the natural C-isotope labelling, the proportion of new C was calculated. More than 50% of the C added to the soil with the compost was incorporated into the SOM in only 6 months. However, the application of maize compost did not always enhance soil C-sequestration capacity. The addition of compost caused a general PE, enhancing SOM decay and reducing the fast (labile) SOM mean residence time (MRT) (11.2 days). This was more pronounced with the addition of a higher dose of AC, causing a PE up to a 718%. On the other hand, a higher MRT (54.4 days) occurred in soils with NC applied, likely due to its deleterious effects, limiting heterotrophic activity. Despite that, the average MRT of the slow (recalcitrant) SOM pool was lower than usually reported. The application of higher doses of both composts generally showed greater MRT values compared to control (1.7 years vs. 3.8 and 2.9 years for NC and AC, respectively), leading to an increase in this more stable C pool and effective soil C sequestration. The results described in this work may help readers to better understand SOM dynamics and may be of use in designing appropriate management strategies for improving OM quantity and quality and to optimize C storage in Mediterranean soils. Full article