The efficiency of home composting programmes and compost quality

Household dog fecal composting: Current issues and future directions

Dog feces are a known source of nutrient, pathogen, and plastic pollution that can harm human and ecosystem health. Home composting may be a more environmentally sustainable method of managing dog feces and reducing this pollution. While composting is an established method for recycling animal manures into low-risk soil conditioners for food production, few studies have investigated whether household-scale compost methods can safely and effectively process dog feces for use in backyard edible gardens. A broad range of literature on in situ composting of dog feces is evaluated and compared according to scale, parameters tested, and compost methods used. Studies are analyzed based on key identified knowledge gaps: appropriate compost technologies to produce quality soil conditioner on small scales, potential for fecal pathogen disinfection in mesophilic compost conditions, and biodegradation of compostable plastic dog waste bags in home compost systems. This review also discusses how existing methods and quality standards for commercial compost can be adapted to dog fecal home composting. Priorities for future research are investigation of household-scale aerobic compost methods and potential compost amendments needed to effectively decompose dog feces and compostable plastic dog waste bags to produce a good-quality, sanitized, beneficial soil conditioner for use in home gardens. Integr Environ Assess Manag 2024;00:1-16. © 2024 The Author(s). Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Environmental impact scenarios of organic fraction municipal solid waste treatment with Black Soldier Fly larvae based on a life cycle assessment

Biowaste treatment with Black Soldier Fly (BSF) larvae is an alternative option for organic waste valorization. Its environmental impacts should be assessed and compared with conventional treatment options. The research aims to evaluate the treatment of organic fraction of municipal solid waste (OFMSW) with BSF larvae through a life cycle assessment (LCA). This study employed data inventories from literature and aimed to provide a wide range of production parameter values to identify the potentialities of BSF treatment in the best-case and worst-case scenarios. The SimaPro9, the database Ecoinvent3.5, and the impact assessment method IMPACT 2002+ have been employed for the analysis. A sensitivity analysis of relevant parameters was conducted, considering the avoided impacts that can be obtained thanks to the exploitation of larvae proteins for bioplastics or fishmeal production. Research findings highlight six main environmental impact indicators: respiratory inorganics (kg PM2.5-eq), ozone layer depletion (kg CFC-11-eq), terrestrial ecotoxicity (kg TEG soil), land occupation (m2 organic arable), global warming (kg CO2-eq), and non-renewable energy (MJ primary). The most relevant process generating impacts is BSF breeding, followed by boiling, storage, and OFMSW treatment. The environmental performance is better when the conventional fishmeal substituted, thanks to BSF larvae production, is made from areas 10,000 km far, implementing a 100% renewable energy scenario, reducing the energy consumption by 50%, increasing the lifespan of the equipment to 15 years, and products are employed locally. The current study represents the first attempt to evaluate the global higher or lower environmental impact scenario related to OFMSW treatment through BSF larvae.

Social, economic and environmental benefits of organic waste home composting in Iran

Organic waste management is challenging in low-middle income countries. Environmental impacts and high management costs affect the sustainable development of cities, an issue that is exacerbated by the lack of social involvement. The research conducted in Iran aims to assess the benefits of organic waste home composting in Shiraz to improve solid waste management (SWM) sustainability. The introduction of a pilot project to assess home composting systems was described, together with an economic, social and environmental analysis. The current SWM system (S0) has been compared with the new strategy proposed (S1), where home composting is considered to be introduced to collect about 10% of the municipal solid waste generated in a 10-year horizon. An economic balance related to the capital costs and operational costs of both systems was introduced, in parallel with a life cycle assessment (LCA) of the SWM system, and a questionnaire survey of the local population. Results showed that S1 leads to around 5% economic savings for the municipality due to the avoidance of organic waste transportation and disposal. Environmental benefits include a lowering of CO2-Eq emissions of about 19,076 tonnes year-1. In addition, about 28% of the interviewed (n = 319) agreed to employ the home composting system at home (CI 5.5%, 95% of confidence level) supporting the theory that about 10% of the organic waste can be segregated and home-composted. The research underlines that home composting can contribute to improve the sustainability of SWM systems in developing countries.

Community composting strategies for biowaste treatment: methodology, bulking agent and compost quality

The European Union's commitment to increase recycling and recovery rates of municipal solid waste requires significant changes in current waste management. Local governments are developing various strategies for treating the organic fraction of municipal waste (biowaste) via composting. Community composting centres (CCC), green waste collection, treatment points and community gardens are some of these new approaches. Population density and spatial distribution, together with the existence of community green areas, determine the location of the various infrastructures for recycling local biowaste. The composting process consumes high amounts of bulking agent (BA) necessary to provide the structure that allows, amongst other uses, biowaste aeration and microbial surface colonisation. Shredded green waste from parks, gardens and households can be used as BA in community composting and home composting. In this study, a total of 46 compost samples obtained from CCC with two types of handling were analysed: 22 samples treated by vertical flow (VF) and 24 samples treated by horizontal flow (HF). The HF model allowed better use of the volume of modular composting units and the VF model required less effort and time for the CCC operator. Mature, stable and high-nutrient-content composts were obtained with both models. These composts met the legal requirements to be used as an organic amendment, and they can be delivered to the participants or used in community gardens in the municipality.

Is the co-application of self-produced compost and natural zeolite interesting to reduce environmental and toxicological availability in metal-contaminated kitchen garden soils?

Composting can turn organic waste into a valuable soil amendment that can improve physical, chemical, and biological soil quality. Compost amendments can also contribute to the remediation of areas anthropogenically degraded by metals. However, it is well known that compost, particularly self-produced compost, can show enrichment in metals. An experimental study was conducted to examine the short- and long-term distribution and the mobility of metals in soils amended with a self-produced compost when it was added alone or in combination with different doses of a natural zeolite to soil. The aim was also to study the interest of managing moderately metal-contaminated kitchen garden soils by assessing the chemical extractability, phytoavailability, and oral bioaccessibility of metals. When zeolite was added to compost alone, it had the tendency to better reduce extractability of Cd and Zn at 25%, and those of Pb at 15%. When the self-produced compost alone or in co-application with zeolite at these doses was applied to soils, the results showed (1) a decrease of NH4NO3-extractable Zn; (2) a reduction of Pb environmental availability, but not Pb bioaccessibility, and (3) an increase of ryegrass biomass. Nevertheless, the risk posed by the self-produced compost was minimal when applied at the proper rate (0.6% w/w). In the selected experimental conditions, the study recommends that self-produced compost be mixed with 15% zeolite to maximize vegetal biomass and minimize environmental risk. The question of sustainability of the results with repeated compost addition is also raised.

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.

The degradation of single-use plastics and commercially viable bioplastics in the environment: A review

Plastics have become an integral part of human life. Single-use plastics (SUPs) are disposable plastics designed to be used once then promptly discarded or recycled. This SUPs range from packaging and takeaway containers to disposable razors and hotel toiletries. Synthetic plastics, which are made of non-renewable petroleum and natural gas resources, require decades to perpetually disintegrate in nature thus contribute to plastic pollution worldwide, especially in marine environments. In response to these problems, bioplastics or bio-based and biodegradable polymers from renewable sources has been considered as an alternative. Understanding the mechanisms behind the degradation of conventional SUPs and biodegradability of their greener counterpart, bioplastics, is crucial for appropriate material selection in the future. This review aims to provide insights into the degradation or disintegration of conventional single-use plastics and the biodegradability of the different types of greener-counterparts, bioplastics, their mechanisms, and conditions. This review highlights on the biodegradation in the environments including composting systems. Here, the various types of alternative biodegradable polymers, such as bacterially biosynthesised bioplastics, natural fibre-reinforced plastics, starch-, cellulose-, lignin-, and soy-based polymers were explored. Review of past literature revealed that although bioplastics are relatively eco-friendly, their natural compositions and properties are inconsistent. Furthermore, the global plastic market for biodegradable plastics remains relatively small and require further research and commercialization efforts, especially considering the urgency of plastic and microplastic pollution as currently critical global issue. Biodegradable plastics have potential to replace conventional plastics as they show biodegradation ability under real environments, and thus intensive research on the various biodegradable plastics is needed to inform stakeholders and policy makers on the appropriate response to the gradually emerging biodegradable plastics.

Assessing Physiochemical Characteristics of Agricultural Waste and Ready Compost at Wadi Al-Far'a Watershed of Palestine

The Wadi Al-Far'a Watershed (WFW) is one of the most important agricultural lands in Palestine where considerable amounts of organic wastes are generated. Yet, mismanagement of agricultural waste, including random disposal and/or burning, is a prevalent practice in the WFW. Such a practice might result in greenhouse gas emissions and leachate penetration into underlying soil and groundwater. To encourage compost production in the WFW as an efficient way for organic agricultural waste treatment and emission reduction, this study aims at evaluating the quality of both raw organic agricultural waste and ready compost, locally produced or imported. The evaluation considers the physiochemical characteristics as well as the heavy metal contents. The analysis of 17 samples of raw organic agricultural waste showed a good potential for compost production due to the high content of organic matter and other nutrients such as nitrogen and phosphorus. The analysis of 15 ready compost samples, however, showed that compost quality is relatively low due to the high electrical conductivity and low moisture content measurements as well as the high levels of sodium, chloride, and potassium. Furthermore, heavy metal contents of both raw organic agricultural waste and ready compost samples are less than the limits specified by the Palestinian and international standards. Therefore, local farmers can safely use raw organic agricultural waste generated in the WFW for compost production. Composting will not only enhance soil reclamation and crop production but also protect human health and the environment and promote sustainable economic development.

Synthesis of Integrated Flower Waste Biorefinery: Multi-Objective Optimisation with Economic and Environmental Consideration

The improper disposal of flower waste from cultural activities is one of the main challenges in certain countries such as India. If the flower waste is not managed properly, it causes a number of environmental issues. Therefore, various technologies have been developed to transform flower waste into value-added products. To integrate multiple technologies holistically to maximise the energy and material recovery, an integrated flower-waste biorefinery is required. Since there are a wide range of technologies available that can convert the waste into multiple products, there is a need to develop a systematic approach to evaluate all the technologies. This research proposes a systematic approach to synthesise an integrated flower-waste biorefinery based on different optimisation objectives, e.g., maximum economic performance and minimum environmental impact. Due to the conflicting nature between the two objectives, a fuzzy optimisation approach has been adapted to synthesise a sustainable integrated flower-waste biorefinery that satisfies both objectives at once. The efficacy of the proposed approach is demonstrated through a case study in India based on the optimised results with fuzzy optimisation—a synthesised flower-waste integrated biorefinery with economy performance of $400,932 and carbon emission of 46,209 kg CO2/h.

Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments

Finding alternatives to diminish plastic pollution has become one of the main challenges of modern life. A few alternatives have gained potential for a shift toward a more circular and sustainable relationship with plastics. Biodegradable polymers derived from bio- and fossil-based sources have emerged as one feasible alternative to overcome inconveniences associated with the use and disposal of non-biodegradable polymers. The biodegradation process depends on the environment's factors, microorganisms and associated enzymes, and the polymer properties, resulting in a plethora of parameters that create a complex process whereby biodegradation times and rates can vary immensely. This review aims to provide a background and a comprehensive, systematic, and critical overview of this complex process with a special focus on the mesophilic range. Activity toward depolymerization by extracellular enzymes, biofilm effect on the dynamic of the degradation process, CO2 evolution evaluating the extent of biodegradation, and metabolic pathways are discussed. Remarks and perspectives for potential future research are provided with a focus on the current knowledge gaps if the goal is to minimize the persistence of plastics across environments. Innovative approaches such as the addition of specific compounds to trigger depolymerization under particular conditions, biostimulation, bioaugmentation, and the addition of natural and/or modified enzymes are state-of-the-art methods that need faster development. Furthermore, methods must be connected to standards and techniques that fully track the biodegradation process. More transdisciplinary research within areas of polymer chemistry/processing and microbiology/biochemistry is needed.

Home and community composts in Nantes city (France): quality and safety regarding trace metals and metalloids

Home and community composting are key strategies for local organic waste management. The quality and safety of industrial composts are controlled, but those of home and community composts are not, and this could make them unsafe for use in kitchen gardens. Home (n = 20) and community (n = 41) composts, from urban and suburban areas including mildly Pb-contaminated allotment gardens, were analyzed for quality and safety regarding trace metals and metalloids (TMM) using mid-infrared Fourier transform spectrometry (FT-MIR) and portable X-ray fluorescence spectrometry, respectively. Home composts had a significantly higher Pb content (98 mg.kg^-1 ± 10 mg.kg^-1) than community composts (21 mg.kg^-1 ± 2 mg.kg^-1). Numerous home composts (85%) and a few community composts (17%) exceeded the organic farming thresholds for Pb (45 mg.kg^-1) and Zn (100 mg.kg^-1). The high mineral matter content and the relative abundance of chemical functions attributable to silicates (up to 35%) highly paralleled with TMM contents, mostly concentrated in the fine fraction. Co-inertia analysis highlighted strong and significant links between TMM contents and the whole chemical signature delivered by FT-MIR spectrometry. Pb-contaminated soil could be carried into home compost by green waste or by voluntary addition. Covariance analyses indicated that mineral matter and chemical functions only partly explained the variability in Pb content, suggesting a more complex combination of drivers. Community composting appears as a suitable local solution resulting in high-quality compost that complies with European organic farming regulations, while home composting from allotment gardens should be seriously evaluated to comply with such safety requirements.

Decentralized Composting of Food Waste: A Perspective on Scientific Knowledge

Composting has been demonstrated to be an effective and sustainable technology to treat a wide variety of organic wastes. A particular aspect of composting is the number of technological options that can be used, from full-scale plants to small composters. In this sense, the interest in composting at home or on a community scale is exponentially growing in recent years, as it permits the self-management of organic wastes and obtaining compost that can be used by the same producer. However, some questions about the quality of the obtained compost or the environmental impact of home composting are still in an early stage of development and provide little knowledge. In this review, the main points related to home and community composting are analysed in detail according to the current scientific knowledge by highlighting their advantages and possible drawbacks. Particularly, the composting process performance is analysed, with temperature stratification being one of the main problems related to small amounts of organic matter. Simultaneously, compost quality is determined using parameters such as stability and/or maturity, concluding that home compost can be similar to industrial compost in both aspects. However, sanitisation of home compost is not always achieved. Regarding its environmental impact, gaseous emissions, especially greenhouse emissions, are the most studied category and are generally low. Finally, the effects of pandemics on home composting are also preliminary commented, concluding that this strategy can be a good alternative to have cities that are more resilient.

Barriers and Enablers to Food Waste Recycling: A Mixed Methods Study amongst UK Citizens

We aim to identify influences on UK citizens’ household food waste recycling as a basis for designing strategies to increase household food waste collection rates via local services. Using a UK dataset (n = 1801) and the COM-B (Capability–Opportunity–Motivation–Behaviour) model as a theoretical framework, we conduct quantitative regression and supporting thematic analyses to investigate influences on citizens’ recycling of food waste. Results show that automatic motivation (e.g., emotions and habit) and psychological capability (e.g., knowledge) predict household food waste recycling. Physical opportunity (i.e., dealing with food waste in other ways such as home-composting or feeding pets/strays, time and financial costs) was the main barrier to recycling food waste identified in thematic analyses. Participants also reported automatic motivation-related barriers such as concerns over pests, odour, hygiene and local authorities’ food waste collection capabilities. Based on findings we recommend the development of clear, consistent communications aimed at creating positive social norms relating to recycling and increasing knowledge of what can and cannot be put in food waste bins. Improved functional design and free distribution of bins and compostable caddy liners developed according to user-centred needs for cleanliness, convenience and hygiene are also needed. These will not be sufficient without a nationally uniform, efficient and reliable system of household food waste collection.

Phosphorus circular economy of disposable baby nappy waste: Quantification, assessment of recycling technologies and plan for sustainability

This study assessed the potential for minimizing human excreta bound phosphorus (P) loss through used disposable baby nappies, an area that remained unexplored for nations. Accordingly, it performed a substance flow analysis to assess the national P loss through used disposable baby nappies in the case of Australia. The analysis revealed that approximately 308 tonne P is lost through used baby nappies to landfills in Australia in 2019, which is nearly 2.5% of the overall P excreta as human waste. Although the quantity seems small in percentage term, it could result in the loss of a significant amount of P over several years, as assessed 5452 tonne P over the 2001-2019 period, which is concerning in the context of anticipated future global P scarcity. The review of peer-reviewed literature on available technologies/methods for recycling disposable baby nappy waste indicates that there are some technologies for recycling P particularly through co-composting with food and other organic wastes, while the majority of these are still at the lab/pilot scale. There are also various recycling techniques with purpose ranging from energy recovery to volume reduction, generation of pulp, hydrogel, cellulose, and polymer as well as to increase yield stress and viscosity of concrete, however, these are not effective in P recovery. The study implies that compost made of nappy waste can be used as fertilizer to produce bamboo, cotton, and maize plants to supply raw materials for producing biodegradable nappies, hence, to close the loop. The various product and system design options e.g., designing for flushing, designing for disassembling the excreta containing part, and designing for community composting suggested in this study could be further researched for identifying best suitable option to achieve P circular economy of disposable baby nappies. This study also recommends necessary interventions at various stages of the nappy life cycle to ensure sustainable management of phosphorus.

Effectiveness of Various Types of Bio-Activators to Quality of Compost Fertilizer

<b>Background and Objective:</b> Plant litter or plants that grow naturally and the plant materials of the cultivated plants are quite abundant both in fresh and dry form. In the case of a plant, litter is not processed and left on the surface of the soil as organic material then the process of decomposition and reshuffle requires a long time. The research aimed to find out the effectiveness of bio-activators on the formation and quality of compost fertilizer. <b>Materials and Methods:</b> The study design was used in a factorial pattern with two factors. The First factor is bio-activator consists of four levels, namely: EM-4, PROMI, Orgadec and (EM-4+PROMI+Orgadec). The second factor is organic matter consists of seven levels, namely: <i>Imperata cylindrica</i>, paddy straw, <i>Gliricidia sepium</i> leaves, (<i>Imperata cylindrica</i> + paddy straw), (<i>Imperata cylindrica</i> + <i>Gliricidia sepium</i> leaves), (paddy straw + <i>Gliricidia sepium</i> leaves), (<i>Imperata cylindrica </i>+ paddy straw + <i>Gliricidia sepium</i> leaves). There were 28 treatments, each treatment was repeated three times to obtain 84 treatment units. <b>Results:</b> The result showed that compost fertilizer with Orgadec bio-activator treatment and PROMI is the best quality (pH compost, water content, P-total, N-total, C-organic, C/N ratio). <b>Conclusion:</b> The compost fertilizer with Orgadec bio-activator is the best quality for this research (pH compost, moisture content, P-total, N-total, C-organic, C/N ratio).

The role of waste management in reducing bioplastics' leakage into the environment: A review

Bioplastics are becoming more and more widespread as substitutes for petroleum-derived plastics due to their biodegradability. Bioplastics degradation under different environments has been described and reported to depend mainly on bioplastics' compositions and the environmental conditions. Incomplete degradation during waste management processes and leakage of bioplastics into the environment are becoming major concerns that need to be further investigated. In this context, the present paper aimed to review recent literature dealing with biodegradation of bioplastics under industrial (e.g. anaerobic digestion and composting) and natural (e.g. soil and water) environments, and to link it to the potential bioplastics' leakage into the environment. Reviewed data were used to estimate the potential role of waste management processes in decreasing the potential leakage of bioplastics. Depending on bioplastics' type and processing conditions, waste management can effectively reduce bioplastics' potential leakage, decreasing the concentration of these materials that can reach the natural environments.

Home Bio-Waste Composting for the Circular Economy

The consequence of the current economic development model is the generation of large amounts of waste and energy losses. One way to change this negative trend is a more rational use of raw materials reducing the amount of generated wastes. Biowaste, which may be divided into garden and kitchen waste, constitutes the main part of municipal waste. At the household level, it can be managed through composting—the most sustainable way of biowaste management. In this context, this paper aims to assess the economic and environmental effects of implementing the home composting incentive program introduced by one of the municipalities near Warsaw (Poland). The study is based on the estimation of the amount of biowaste generated in the commune, as well as on the number of households with the potential to compost biowastes. The effects of implementing the composting program were evaluated at different participation levels. The cartographic-based methods (GIS) were used in the analyses. Additionally, willingness to accept home composting by residents and its main determinants were examined. The results of the study indicate that the changes in the current household biodegradable waste management model are practicable and generate positive economic and environmental effects. However, the promotion of home composting requires active support from the local authorities, both in the financial dimension and by increasing residents’ environmental awareness.

Evaluation of compost quality from municipal solid waste integrated with organic additive in Mizan-Aman town, Southwest Ethiopia

Background

The present study evaluated the compost quality from municipal solid waste (MSW) and organic additives of coffee by-products and leaf of Millettia ferruginea. Compost sample (n = 30) was taken from fresh compost materials and MSW and different organic additive treatments (T1, T2, T3, T4, and T5). Compost treatments phytotoxicity test was conducted using lettuce seed (Lactuca Sativa L. var. crispa). Analysis of variance (ANOVA) was performed using SPSS (version 22) on major compost quality characteristics.

Results

The compost Physico-chemical characteristics like temperature (26.4 °C), moisture content (45.5%), electrical conductivity (4.6 mS/cm), pH (7.9), total nitrogen (1.2%) and phosphorous content (2918 ppm) in T4 and T5 were analogous but both are significantly different from T3, T2 and T1 compost treatments. Phytotoxicity test using 100% compost treatment media showed that T4 (101%) and T5 (102%) are phytonutrient for lettuce plant. While, T3 and T2; and T1 compost treatments are non-phytotoxic and moderately phytotoxic respectively to lettuce plant.

Conclusion

Therefore, compost from MSW + M. ferruginea (T4) and MSW + coffee pulp + M. ferruginea (T5) are important for improving the physico-chemical characteristics of compost and are phytonutrient for lettuce plant. Thus, for effectively management of the 75% of organic fraction of waste generated from households in the study area, recycling methods like composting with organic additives must be used at large.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13065-021-00770-1.

Comparison of local and centralized biowaste management strategies - A spatially-sensitive approach for the region of Porto

The increasing concern with greenhouse gas emissions and nutrients cycling creates a need for cost-effective, practical and environmentally sensible biowaste management strategies. Centralized systems have struggled to comply with those needs. Decentralized systems, treating waste at source, promise local nutrient circularity and increased resource sovereignty. The large-scale performance of decentralized systems remains unclear, especially concerning the local sink capacity to assimilate the treatment products. This study aimed to compare centralized and decentralized systems for the region of Porto and assess whether creating additional urban farms could reduce costs and environmental impacts. Spatial analysis was used to assess waste generation, potential compost bin locations, peri-urban and potential urban farmland available, and collection and transport requirements. The carbon footprint of different scenarios was determined using life-cycle assessment. The results show that local composting led to cost savings over centralized systems. However, this system encompassed positive carbon emissions and most districts evidenced limited sink capacity for compost application. Additional urban farms added significant sink capacity, however, their impact on cost and carbon footprint was insignificant. The carbon footprint of centralized systems was heavily dependent on factors influencing collection such as population density, and affected by the renewable content of the electricity grid. Anaerobic digestion was the most climate-friendly option in the urban center and local composting in remote and less dense districts. Municipalities may benefit from tailoring the treatment systems to specific districts, creating additional jobs while reducing cost and climate impacts overall.

Sustainable utilization of biowaste compost for renewable energy and soil amendments

Acceleration of urbanization and industrialization has resulted in the drastic rise of waste generation with majority of them being biowaste. This constitutes a global challenge since conventional waste management methods (i.e., landfills) present environmental issues including greenhouse gases emissions, leachate formation and toxins release. A sustainable and effective approach to treat biowaste is through composting. Various aspects of composting such as compost quality, composting systems and compost pelletization are summarized in this paper. Common application of compost as fertilizer or soil amendment is presented with focus on the low adoption level of organic waste compost in reality. Rarely known, compost which is easily combustible can be utilized to generate electricity. With the analysis on critical approaches, this review aims to provide a comprehensive study on energy content of compost pellets, which has never been reviewed before. Environmental impacts and future prospects are also highlighted to provide further insights on application of this technology to close the loop of circular bioeconomy.

The Circular Economy and Organic Fraction of Municipal Solid Waste Recycling Strategies

Densely populated areas with large incoming populations have difficulty achieving high separate collection rates of municipal solid waste. The manuscript analyzes the link between biowaste collection and circular economy requirements as a fulfilment of the recycling rates and using biogas as a sustainable energy source. Three biowaste collection scenarios and three technical scenarios for its treatment are considered. The first scenario assumes only composting for biowaste treatment, the next includes also anaerobic digestion. In the years 2020–2050, the separate biowaste collection level will increase, depending on the scenario, from 26.9 kg/inh. up to 148.1kg/inh. By 2030, the quantity of biogas generated from biowaste can grow to almost 9 million m3/year, enabling the production of renewable energy at annual levels of almost 17 GWh and 69 TJ. Using the third scenario, the quantity of biogas generated grows more than twice (in 2035). If the capture rate of biowaste increases from 15% to 20% and then to 25%, the quantity of biogas generated grows by, respectively, 65% and more than 100%. Unfortunately, none of the scenarios enables the required municipal solid waste recycling rates in 2030 (60%) and 2035 (65%), which demonstrates the significant need to develop more effective separate collection systems, including biowaste. Methodology applied in the paper can be used for other cities and regions trying to meet circular economy demands.

Development of Technologies for Local Composting of Food Waste from Universities

The amount of biowaste generated by university canteens (BWUC) in the faculties of the University of A Coruña (UDC) varies between 6 and 100 kg/day. In addition, the gardening services of the campus generate even higher amounts of garden waste (GrW), including pruning, which, once crushed, serves as bulking material for composting the biowaste from the canteens. Decentralized composting has been chosen with the aim of producing high quality organic fertilizers for university urban gardens while reducing the environmental burdens of both waste management and agricultural practice. Small static home composters of 340 L (SHC) for smaller amounts of generation (up to 20 kg BWUC/day) were used, while, for faculties of higher generation (up to 40 kg BWUC/day on average), the first composting stage was carried out in a closed and dynamic composter (DC). The dynamic composter was designed and built specifically for this project and its features were improved and optimized throughout the study. The pilot project was carried out in two centers of the UDC, which are known as the Philology Faculty (PF) and the School of Architecture (SA). All the organic waste generated by the canteens of these two colleges from January 2011 to July 2011 (approximately 3000 kg) was treated. Composting in SHC included a thermophilic phase that extended one month beyond the loading period for which thermophilic temperatures were also recorded. The use of the DC as the first stage in combination with static composters (SC) for the maturation stage reduced the overall thermophilic phase to 6–8 weeks. The complete maturation (Rottegrade class IV-V) was achieved after about four months in SHC and after two months when using the combined DC-SC system, if the right conditions of moisture were maintained. The chemical quality of the compost produced was compatible with Class A of Spanish legislation (equivalent to organic farmer quality) and the C/N ratio ranged from 9 to 15 depending on the relation BWUC:GrW.

Decentralized Community Composting: Past, Present and Future Aspects of Italy

Italy is among the top biowaste-generating countries in Europe, and has a well-structured waste management framework with quite a number of centralized composting facilities. In recent years, there has also been huge interest from local communities in decentralized composting. Although decentralized community composting is common in some countries, there is still a lack of information on the operative environment together with its potential logistical, environmental, economic, and social impacts. Considering the national Italian legislation on community composting as well as successfully implemented projects at EU level, Italy can set a model especially for Mediterranean countries that intend to build decentralized composting programs. Therefore, in the context of this review paper, a brief overview of the composting process was presented together with main applications in centralized and especially in decentralized composting, while the main focus was kept on the operative and legislative information gathered from Italian community composting. There is a huge difference in the number of composting plants between the regions, and the lack of centralized facilities in the central and southern regions can be supported by decentralized solutions. Decentralizing waste treatment facilities and thus creating local solutions to urban waste management strategies will help to achieve the resource recovery and valorization targets in line with the circular economy.

Adding value to home compost: Biopesticide properties through Bacillus thuringiensis inoculation

Home and community composting are considered potential tools for the self-management of organic waste. The production of added value products from biowaste is an encouraging step further to valorise this waste stream. To increase the profits of homemade compost, this paper presents a strategy to produce enriched home compost with biopesticide properties through a simple and low-cost process. Bacillus thuringiensis (Bt) was inoculated in a home composter bin through a solid inoculum previously prepared using the same waste as substrate. The process was monitored and compared with a home composting control process without inoculation. Final composts were analysed and compared in terms of physicochemical and microbiological properties, respiration and germination indices, indicating the suitability of both to be used as organic amendments. Also, a standardized toxicity test proved that Bt-enriched compost can be safely applied to the soil. Microbiological analysis revealed highly diverse communities in both cases, with limited differences at phylum taxonomic level, but dissimilar relative abundances of species within phylum. Bacteroidetes and Proteobacteria were dominant, with the presence of species able to transform organic matter from vegetal origin, but not usually related to compost. Bt-cristal toxin was clearly present in Bt-enriched compost, indicating the coexistence of Bt with the different microbial populations till the end of the composting process. Although Bt has been widely investigated due to its biopesticide properties, the incorporation of this microorganism to home composting level has not been previously reported.

Assessment of biowaste composting process for industrial support tool development through macro data approach

This study aims to assess composting efficiency and quality of compost through the study of the parameters of the Catalan Waste Agency (ARC) data-base by developing indicators useful for industrial sector. The study includes 17 composting plants for an 8-years period (2010-2017), the quantities of materials treated and generated in these plants: biowaste, yard trimmings, refuse and compost, as well as chemical characterization of compost: moisture, total organic matter, organic nitrogen, pH, electrical conductivity, self-heating test, pollutants and ammonium. Plant were sorted into 4 size classes depending on size capacity and into 4 technologies employed during thermophilic phase. Different indicators were developed related to improper fraction content, yard trimmings ratio, mass losses, compost production, refuse generation and plant saturation. The main average results indicate that improper fraction is 10%, process losses 68%, refuse generated 25% and saturation 79%. Differences were observed in size and technology; for instance, smaller plants presented lower improper content, refuse and saturation and higher losses while plants with turned windrows during decomposition presented higher improper, yard trimmings ratio and plants with vessel technology showed lower losses and higher saturation. Also, the compost quality is higher if the plant saturation and improper fraction are below 90% and 7%, respectively. The indicators were useful to assess the process and were related to the compost quality obtained.

Optimization of Food Waste and Biochar In-Vessel Co-Composting

As bulking agents (BA) affect the composting process, this work examined the impact of combinations of different organic components in order to obtain an efficient co-substrate for food waste (FW) in-vessel composting. To boost the occurrence of microorganisms inhabiting the compost, mature compost was firstly coupled with wheat straw, added to FW, and considered as a control (BC0). Then, two trials (BC10, BC20) including 10% and 20% of biochar were monitored. The results indicated that the temperature of the amended bioreactors was notably increased compared to the unamended one. Thermophilic temperatures were achieved at 14, 34, and 78 h after the experimental setup for BC20, BC10, and BC0, which lasted for 14, 17, and 12 days, respectively. When it came to an assessment of maturity and stability, the quality of the compost was evaluated against several indicators and compared with the compost quality standards of the UK, France, Canada, the USA, Poland, and Germany. BC10 illustrated a high-quality product in relation to the heavy metal concentration, a C:N ratio which reached 14.97, an AT4 which was lower than 6 (4.36 mg O2/g TS), and a nitrification index of 2.61 (<3). Consequently, the addition of 10% of biochar as a co-substrate showed an improvement of the process evolution and the characteristics of the biofertilizer produced.

Economic analysis of a shared municipal solid waste management facility in a metropolitan region

Municipal solid waste (MSW) management in dense urban areas is a challenge for municipalities, especially in developing countries, which commonly have deficient waste management. For example, the metropolitan region of Goiás State, Brazil, has 19 municipalities that dispose of about 72.5% of total MSW in unlicensed MSW final disposal facilities. Therefore, this study analysed the investment and operating costs, and revenues of a municipal solid waste management facility, projected for 20 years, shared among these 19 municipalities. The economic viability analysis, has shown that, regardless of the management facility type, MSW collection and transport are the most expensive cost components, accounting for about 60% of MSW management operating costs. For an Internal Rate of Return of 0%, anaerobic digestion is 11% more expensive (in total) than using community composting. For 2040 (last year), the monthly MSW management tariffs will vary between 3.5 and 10.8 R$·inhabitant^-1·month^-1, depending on the municipality. So, as the unit price of biowaste treatments lowers with waste quantities, for the municipalities with large biowaste quantities, anaerobic digestion becomes recommended for its economic attractiveness. This study can serve as a model for other municipalities in Brazil and elsewhere, helping public decision makers to establish a strategy for MSW management.

Methodologies to assess biodegradation of bioplastics during aerobic composting and anaerobic digestion: A review

Bioplastics are emerging on the market as sustainable materials which rise to the challenge to improve the lifecycle of plastics from the perspective of the circular economy. The article aims at providing a critical insight of research studies carried out in the last 20 years on the degradation of bioplastics under aerobic composting and anaerobic digestion conditions. It mainly focuses on the various and different methodologies which have been proposed and developed to monitor the process of biodegradation of several bioplastic materials: CO₂ and CH₄ measurements, mass loss and disintegration degree, spectroscopy, visual analysis and scanning electron microscopy. Moreover, across the wide range of studies, the process conditions of the experimental setup, such as temperature, test duration and waste composition, often vary from author to author and in accordance with the international standard followed for the test. The different approaches, in terms of process conditions and monitoring methodologies, are pointed out in the review and highlighted to find significant correlations between the results obtained and the experimental procedures. These observed correlations allow critical considerations to be reached about the efficiency of the methodologies and the influence of the main abiotic factors on the process of biodegradation of bioplastics.

Exhausted grape marc and organic residues composting with polyethylene cover: Process and quality evaluation as plant substrate

In Argentina, wine production is one of the most important economic activities, producing a large quantities of organic wastes. Composting is a viable alternative to treat these residues, with the possibility to obtain high-quality products. The objective of the present study was to evaluate the effect of the addition of goat manure, leaves from garden raking and alfalfa to exhausted grape marc and the influence of plastic cover on the composting process and the quality of the finished product. Composting was carried out in turned piles in a total randomized design. Temperature, moisture, pH, electrical conductivity, micro and macro elements, biological parameters, stability and structure were determined with the goal to assess product quality. Mixture compost presented higher macro and micro elements content (especially P, Mn and Zn) than grape marc compost. Plastic cover showed no significant effect on physico-chemical parameters, while microorganisms were affected, with higher cellulolytic and nitrifying content in uncovered piles. In all composts, parameters indicated stability and no pathogens (Salmonella sp.) were detected. Pot assay with Lactuca sativa suggested that all compost revealed adequate substrate quality, with higher plant biomass values than commercial substrate and sand (Control), even with fertilization. Mixture compost showed significantly higher biomass and nutrient absorption values relative to the remaining evaluated substrates, suggesting that the use of goat manure and leaves added to exhausted grape marc, as raw material resulted in higher compost quality. All together indicated that the use of polyethylene cover negatively affect microorganisms content and a higher diversity of organic residues composted would result in higher microbiological activity and nutritional grade product.

The use of biological waste as a source of low-temperature heat for hotbeds in spring in north-eastern Poland

This article proposes a method for using biological waste, including kitchen waste and garden waste, as a substrate for hotbeds. Hotbeds have been long used in home gardens, but most of them are supplied with animal manure, usually horse manure. In this study, the temperature of ambient air, soil temperature and temperature distribution in a hotbed and a cold frame were measured with a thermographic camera. The measurements were performed in three experimental treatments - one hotbed, one cold frame and in the garden. Each treatment was sown with radishes (Raphanus sativus). The experiment began on 7 April, and temperature was measured until the temperature of garden soil reached the temperature inside the hotbed and the cold frame. After the experiment, the hotbed was left in place until the end of August to complete the composting process and grow other plants. The amount of heat generated inside the hotbed during the experiment was calculated, and the thermal efficiency of the hotbed was compared with the maximum heat capacity of composting. During the experiment, the hotbed generated 98.7 MJ of heat, and its thermal efficiency reached 12% of maximum capacity. Radishes grown in the hotbed were harvested 5 days earlier than those grown in the cold frame and 12 days earlier than those grown in the garden treatment. The compost produced in the hotbed fully meets Polish Standards for organic fertilizers. The proposed solution minimizes the quantity of biological waste collected from households.

Assessment of compost quality and usage for agricultural use: a case study of Hebron, Palestine

Complying with the technical specifications of compost production is of high importance not only for environmental protection but also for increasing the productivity and promotion of compost use by farmers in agriculture. This study focuses on the compost quality of the Palestinian market and farmers' attitudes toward agricultural use of compost. The quality is assessed through selection of 20 compost samples of different suppliers and producers and lab testing for quality parameters, while the farmers' attitudes to compost use for agriculture are evaluated through survey questionnaire of 321 farmers in the Hebron area. The results showed that the compost in the Palestinian markets is of medium quality due to partial or non-compliance with the quality standards and guidelines. The Palestinian farmers showed a positive attitude since 91.2% of them have the desire to use compost in agriculture. The results also showed that knowledge of difference between compost and chemical fertilizers, perception of compost benefits, and previously experiencing problems in compost use are significant factors affecting the farmers' attitude toward the use of compost as an organic fertilizer.

Microbial strategies and biochemical activity during lignocellulosic waste composting in relation to the occurring biothermal phases

Typically, hardly-degradable lignocellulosic waste is a component or a co-component of the composted mass. The aim of the work was to present the dynamics and succession of microbial communities during small temperature changes, conditioned by the availability of lignocellulosic polymer and feather waste (the presence of N) in composts with qualitatively and quantitatively different lignocellulosic waste, but most of all, to draw attention to the previously not considered microbial strategies in the composted mass. Decomposition of lignocellulose during composting was similar to the priming effect in the soil, because it was associated with the successive occurrence of two groups of microorganisms. The first group of microorganisms, using easily accessible fraction of the lignocellulose complex, was named the first-strategist group, i.e., non-nutritionally specialized group of microorganisms. The second group, utilizing the hard-to-degrade fraction of lignocellulose, was named second-strategist microorganisms, i.e., nutritionally-specialized group of microorganisms. Biodegradation of the lignocellulose complex in compost I enriched with grass (42.86% pine bark, 34.28% grass, 20.0% sawdust and 2.86% chicken feathers) was faster than in compost II that did not contain any grass, but included more hardly degradable components (25.54% pine bark, 10.63% wheat straw, 51.07% sawdust, 12.76% chicken feathers). In compost I, a higher temperature in the thermophilic phase was recorded; larger amounts of non-specialized mesophilic and thermophilic bacteria in the first weeks of composting and a higher abundance of ligninolytic, xylanolytic fungi and cellulolytic bacteria were observed already in biothermal phase 3 with limited access to easily available C and energy sources. During this period, phosphatase, dehydrogenase and respiratory activities were higher in compost I than compost II. This work demonstrates that the succession of particular groups of microorganisms may help determine the start of biodegradation of recalcitrant ligninocellulosic components during composting.