What Is the Best End Use for Compost Derived from the Organic Fraction of Municipal Solid Waste?

Closing the nutrient cycle in urban areas: The use of municipal solid waste in peri-urban and urban agriculture

Cities face the challenges of supplying food and managing organic municipal solid waste (OMSW) sustainably amid increasing urbanization rates. Urban agriculture (UA) can help with this effort by producing local crops that are fertilized with nutrients recovered from compost generated from OMSW. This research aims to determine the potential of OMSW compost to supply the nitrogen-phosphorus-potassium (NPK) demand of UA and the environmental benefits of replacing mineral fertilizer from a life cycle perspective. The Metropolitan Area of Barcelona (AMB) serves as the case study given its commitment to reuse biowaste according to the Revised Waste Framework Directive and to promote UA as a signing member of the Milan Urban Food Policy Pact. Based on crop requirements and farmer surveys, we find that the annual NPK demands of the agricultural fields of the AMB that cover 5,500 ha and produce 70,000 tons of crops are approximately 769, 113, and 592 tons of NPK, respectively. Spatial material flow analysis and life cycle assessment were applied to found that the current waste management system can potentially substitute 8 % of the total NPK demanded by UA with compost, reduce the impacts by up to 39 % and yield savings in global warming of 130 %. The more ambitious future scenario of 2025 can potentially substitute 21 % of the total NPK demand and reduce environmental impacts up to 1,049 %, depending on the category considered. Avoiding processing of mixed OMSW, mineral fertilizer replacement and cogeneration of electricity from biogas are the major contributors to these environmental savings.

Dynamics and functions of biomarker taxa determine substrate-specific organic waste composting

Bacteria are an influential component of diverse composting microbiomes, but their structure and underlying dynamics are poorly understood. This study analyzed the bacterial communities of 577 compost datasets globally and constructed a substrate-dependent catalog with more than 15 million non-redundant 16S rRNA gene sequences. Using a random-forest machine-learning model, 30 biomarker taxa were identified that accurately distinguish between the food, sludge and manure waste composting microbiomes (accuracy >98 %). These biomarker taxa were closely associated with carbon and nitrogen metabolic processes, during which they contributed to the predominant stochastic process and are influenced by different factors in the substrate-specific composts. This is corroborated by the community topological characteristics, which feature the biomarkers as keystone taxa maintaining the bacterial network stability. These findings provide a theoretical basis to identify and enhance the biomarker-functional bacteria for optimizing the composting performance of different organic wastes.

Synergetic benefits of pollution and carbon reduction from fly ash resource utilization-Based on the life cycle perspective

Synergetic reduction of pollution and carbon is a key strategy for the fundamental improvement of ecological and environmental quality and carbon neutrality. Solid waste resource utilization can reduce the secondary pollution caused by conventional solid waste disposal and presents evident environmental potential. Based on the comparable system boundaries, this study adopts life cycle assessment (LCA) to compare the environmental impact of three fly ash utilization paths. The synergy index is then defined according to six environmental impact indicators to quantitatively evaluate the synergetic effects of carbon emission and pollutant reduction. The results confirm the possibility of fly ash resource utilization for synergetic pollution and carbon reduction and demonstrate the synergetic emission reduction potential of the solid waste resource utilization supply chain. This study is both an application of the life cycle assessment model in the solid waste utilization and disposal field and provides insight into the pathway of pollution and carbon reduction in China.

Environmental and economic assessment of the construction, operation, and demolition of a decentralized composting facility

Decentralized waste treatment facilities are recently highlighted for the treatment of solid waste in rural areas for being cheap, flexible, and reliable. Among them, decentralized composting is most commonly used. Many forms of decentralized composting facilities also develop and apply in developing countries, but the environmental and economical performances remain unknown. Therefore, this study analyzed the environmental impacts and cost of a decentralized composting facility through life cycle assessment and life cycle cost. The functional unit was the construction, operation, and demolition the composting facility. Contribution and sensitivity analysis were also performed to find out the most influential processes and parameters. The facility had a 10-year designed life span and could treat about 5840 t organic waste in its life cycle. The life cycle environmental impacts were 646,700 kg CO₂-eq, 8980 kg SO₂-eq, -28 kg P-eq, 7.09 × 10^-3 CTUh, 0.13 CTUh, and 16,754 kg oil-eq for climate change, terrestrial acidification, freshwater eutrophication, human toxicity cancer effects, human toxicity non-cancer effects, and fossil resources scarce, respectively. The life cycle cost was 1080.925 k CNY. When scaling to treating 1 t organic waste, the environmental impacts were close to those of similar decentralized and centralized composting facilities and the cost was lower than those of centralized biological treatment plants when excluding revenues from compost. According to the contribution and sensitivity analysis, the operation stage had the largest environmental impacts. The composting and compost substitution processes in the operation stage were the most sensitive processes. This study proved quantitatively that the decentralized facility was feasible both environmentally and economically and enriched the study cases for decentralized composting facilities.

Material flow and environmental performance of the source segregated biowaste composting system

Life cycle assessment (LCA) is performed to investigate the environmental impacts of two alternative approaches in a biowaste management system. The system inventory is based on actual data and on-site sampling for two consecutive years at the mechanical and biological treatment (MBT) facility at the prefecture of Chania (Greece). The facility pertains as MBT for household waste and material recycling (MR) for the recyclable fractions in two different process lines. The mass balances and environmental performance are assessed from waste generation to end-use. The LCA and ReCiPe 2016 methodology estimate the endpoint environmental impacts on human health, ecosystem quality and resource scarcity. The results show that biowaste source segregation in an integrated waste management system not only significantly benefits its recoverability potential it also improves its environmental performance. Impacts on human health (HH) have reduced by 4.6 times, on freshwater ecosystem quality (EQf) by 6.3 times and resource scarcity (RS) usage by 2.5 times when biowaste is combined with compost production and use, material recovery and reprocessing for fertilizer and raw material substitution.

In-situ removal of odorous NH3 and H2S by loess modified with biologically stabilized leachate

The loess regions distribute widely in Northwestern China, North America and Eastern Europe. For these regions, landfill is a suitable technology for solid waste treatment. However, as a landfill cover material, loess is not very effective in controlling the emission of malodorous gases. The present study modified loess with biologically stabilized leachate, and investigated the capacities and mechanisms of the modified loess to remove odorous NH₃ and H₂S. The removal rates of NH₃ and H₂S at different acclimation time, targeted gas concentrations and temperatures were measured. It was found that the NH₃ removal rate of the modified loess was up to 0.08 μmol/(g·hr), which was 1.8 times that of the virgin loess. The H₂S removal rate of the modified loess was up to 1.74 μmol/(g·hr), which was 1.25 times that of the virgin loess. The half-meter loess layer modified by biologically stabilized leachate achieved nearly 100% removal of H₂S. The improvement of NH₃ and H₂S removal ability was mainly due to the enrichment of relevant microorganisms. This work proposed a novel method for in-situ control of malodorous pollutants in landfills in the loess regions, and proved that the in-situ removal of NH₃ and H₂S using the loess modified with biologically stabilized leachate is feasible and cost-effective.

Abundance and characteristics of microplastics in treated organic wastes of Kaunas and Alytus regional waste management centres, Lithuania

The widespread use of plastic without the sustainable management of the plastic waste has led to its accumulation in the environment. The presence of microplastics even in drinking water and food products is of immense concern. This situation is getting even more complicated due to the limited knowledge about the sources of microplastics and their impact on the environment and human health. This article focuses on a poorly understood but potentially significant source of microplastic-treated organic waste. Quantitative and qualitative analyses of microplastics down to 50 µm in the stabilised organic waste (SOW) output after mixed municipal solid waste (MSW) processing and green and food composts are presented in the article. Nile Red staining and FTIR analysis were adopted for the identification of microplastics. The highest average microplastic abundance was found in the SOW: 17407 ± 1739 particles kg^-1 in autumn and 15400 ± 1217 particles kg^-1 in winter. Nevertheless, even separately collected treated organic waste contained a significant amount of microplastics. Green compost contained 5733 ± 850 particles kg^-1 in autumn and 6433 ± 751 particles kg^-1 in winter, while food compost 3783 ± 351 particles kg^-1 in autumn and 4066 ± 658 particles kg^-1 in winter. Microplastics < 1 mm accounted for 83.8-94.9% of all microplastics, which reflects the need to control not only large but also small microplastics in organic waste fertilisers to prevent soil pollution. The dominant shape of microplastics in compost samples was films, while in the SOW, it was fragments. Based on morphological and FTIR analyses, the majority of microplastics in green and food composts were considered as the residuals of plastic bags and packaging materials.

Utilization of Aerobic Compression Composting Technology on Raw Mushroom Waste for Bioenergy Pellets Production

Raw mushroom waste has been an enormous solid waste, not only causing a huge cut on profit margin of mushroom industries but also leading to environmental pollution. Unfortunately, the current utilization methods, such as pharmaceutical extractions, are unable to keep up with the waste generation rate due to the large-scale mushroom production. Yet, the utilization of raw mushroom waste to produce biomass pellets for energetic purposes and the role of an electric composter on shortening the processing time remain unexplored. This is important because conventional composting, which takes a relatively long period (e.g., weeks to months), is less practical when it comes to commercial use of the biomass pellets. To explore this issue, an industrial composter with initial compost was utilized to process the raw mushroom waste, followed by pelletization. Extraction of the material inside the composter at different timing was carried out to determine the optimal processing time for optimal texture to form pellets. It was found that prolonged composting hour affected the pelletization process since moisture, which acts as a natural binder, reduced when the composting hour increased. The gross calorific value increased from 14.07 MJ/kg to 18.76 MJ/kg for raw mushroom waste and compost pellets at the fifth hour, respectively. This study revealed that the raw mushroom waste compost could serve as a valuable renewable energy source and that the production of energy-rich biomass compost fuel pellets without using any binder within a short composting duration is achievable with the aid of an in-vessel composter.

Life-Cycle Assessment of a Regulatory Compliant U.S. Municipal Solid Waste Landfill

Landfills receive over half of all U.S. municipal solid waste (MSW) and are the third largest source of anthropogenic methane emissions. Life-cycle assessment (LCA) of landfills is complicated by the long duration of waste disposal, gas generation and control, and the time over which the engineered infrastructure must perform. The objective of this study is to develop an LCA model for a representative U.S. MSW landfill that is responsive to landfill size, regulatory thresholds for landfill gas (LFG) collection and control, practices for LFG management (i.e., passive venting, flare, combustion for energy recovery), and four alternative schedules for LFG collection well installation. Material production required for construction and operation contributes 68-75% to toxicity impacts, while LFG emissions contribute 50-99% to global warming, ozone depletion, and smog impacts. The current non-methane organic compound regulatory threshold (34 Mg yr^-1) reduces methane emissions by <7% relative to the former threshold (50 Mg yr^-1). Requiring landfills to continue collecting LFG until the flow rate is <10 m³ min^-1 reduces emissions by 20-52%, depending on the waste decay rate. In general, for landfills already required to collect gas, collecting gas longer is more important than collecting gas earlier to reduce methane emissions.

Research on Environmental Issue and Sustainable Consumption of Online Takeout Food—Practice and Enlightenment Based on China’s Meituan

In today’s society, consumers’ food needs can be satisfied by catering e-commerce platforms. However, the plastic pollution of tableware and packaging caused by a large number of catering orders every day has always been an unsolved environmental problem. (1) Background: At present, China’s three largest catering platforms, Meituan, Eleme and Baidu, receive 20 million takeout orders daily and consume about 60 million plastic products. Plastic pollution will have a sustained impact on the environment. (2) Methods: In this study, we use literature research and case analysis. We use Meituan’s takeout food as an example. We studied the takeout business growth, status of online takeout in the treatment of plastic packaging, harm to environment, humans and animals, as well as specific solutions. (3) Results: There are four main reasons which contribute to the plastic packaging pollution (i.e., high recycling cost, difficulty to deal with mixed plastic packaging, low effectiveness of collecting plastic packing, and immature technology and treatment to incinerate and landfill catering plastic waste). (4) Conclusion: Our findings suggest that regulators, takeout platforms and consumers, which have corresponding responsibilities in the environmental protection consumption of online food, are supposed to work together to get rid of the online takeout pollution for achieving sustainable consumption. Not only is government legislation needed to improve the waste management system and encourage the exploration of new intelligent waste classification tools, but platforms, businesses and users should enhance the environmental awareness of online takeout packaging pollution as well. Theoretical contributions and managerial implications are also discussed.