An insight to municipal solid waste management of Varanasi city, India, and appraisal of vermicomposting as its efficient management approach

Optimisation of process parameters of a thermal digester for the rapid conversion of food waste into value-added soil conditioner

A novel thermal digester for converting food waste (FW) into nutrient-rich soil conditioner was designed and explored. The process variables, that is, temperature, the volume of the digestion chamber and the rotational speed of the digester were optimised using response surface methodology (RSM). The study revealed that the digester temperature of 150°C and rotational speed of 40 RPM required minimum time (180 minutes) for attaining the equilibrium moisture with a minimum energy consumption of 0.218 kWh kg-1. The process resulted in 80 ± 2.5% reduction in total volume of the FW. Detailed characterisation revealed that the end product was comparable to the organic fertiliser as per the Fertiliser Association of India norms. The digestion helps in breakdown of cellulose content of FW into hemicellulose which supports formation of primary and secondary walls, seed storage carbohydrates, and facilitates plant growth. 1H-Nuclear magnetic resonance (1H-NMR) spectra of the end product revealed mineralisation of organics during digestion. Decrease in ultraviolet (UV) absorbance value at 280 nm also revealed the humification of the end product. X-ray diffraction (XRD) analysis disclosed extremely low crystallinity and non-recalcitrant nature of the end product. A low humification index value (HI-3.43), high fertilising index (FI-4.8), and clean index (CI-5.0) revealed that the end product could safely be utilised as an organic fertiliser. The cost-benefit analysis revealed that thermal digestion technique is profitable and economically viable with benefit-cost ratio (BCR) of 1.35. The study offers a unique approach for the rapid and hassle-free production of value-added soil conditioner from FW.

Passive fungal spore release from fruit and vegetable solid waste

Food substrates in municipal solid wastes processing facilities and open dumpsites are a source for the release of fungal spores into air and can cause potential health and climate effects. Experiments were conducted in a laboratory scale flux chamber to measure the fungal growth and spore release from representative exposed cut fruit and vegetable substrates. The aerosolised spores were measured using an optical particle sizer. The results were compared to experiments conducted previously with a test species (Penicillium chrysogenum) on a synthetic media (czapek yeast extract agar). Significantly higher surface spore densities were observed for the fungi on the food substrates as compared to that on the synthetic media. The spore flux was high initially and then decreased on continued exposure to air. The spore emission flux normalised to the surface spore densities indicated that the emission from the food substrates was lower than the emissions from the synthetic media. A mathematical model was applied to the experimental data and the observed flux trends were explained in terms of the model parameters. A simple application of the data and the model to release from a municipal solid waste dumpsite was shown.

What Influences Home Gardeners’ Food Waste Composting Intention in High-Rise Buildings in Dhaka Megacity, Bangladesh? An Integrated Model of TPB and DMP

Composting is a sustainable way of transforming organic waste into valuable organic fertilizers which have the potential to act as soil conditioners by controlling various biological processes. The prime objective of the current study was to determine the influencing factors behind the intent of home food waste composting, by employing the combined model of Theory of Planned Behavior (TPB) and Dualistic Passion Model (DMP). The combined model showed a higher predictive ability in comparison to the individual TPB model. The fit statistic of the integrated model was deemed good, and 65% of the variance for home composting intention was explained. Using a face-to-face questionnaire survey, a total of 203 valid responses were gathered from home gardeners and tested via a unique two-step methodology: the PLS-SEM and the artificial neural network (ANN). The results revealed that the composting intention can be significantly influenced by attitude, subjective norms, and perceived behavioral control. The study also confirmed the positive effect of harmonious passion and the negative effect of obsessive passion on the intention of food waste composting. Furthermore, the hybrid method produced more reliable results because HP was found to be the most important variable in both ANN and PLS-SEM results, while PBC was observed to be the second most important variable in ANN and the fourth most important in PLS-SEM. The results of the current study not only highlight the importance of passion in determining food waste composting intention in Dhaka, Bangladesh, but also provide helpful information for designing effective, sustainable tactics for encouraging residents to compost food waste at home.

Can support policies promote the innovative diffusion of waste-to-energy technology?

Currently, China is facing severe pressure of environmental emission reduction. As a kind of clean energy, waste-to-energy technology has the advantages of renewability, low pollution, and stable supply. To establish an affordable, effective, and sustainable waste disposable method is critical for the low carbon society transition. Therefore, the innovation diffusion of waste incineration power technology is a problem worth studying. Based on this, in order to answer this question scientifically, this paper constructs a system dynamics model of innovative diffusion, and analyzes the internal mechanism of innovation diffusion. The results show that firstly, the government support policies have a positive influence on the innovation and diffusion of waste incineration power technology; secondly, compared with the R&D policy, feed-in tariffs policy is more efficient to expand the installed capacity of waste incineration power; At last, technological innovation caused by government support policies is the main driving force of waste incineration power industry investment cost reduction.

The Generation and Effects for Recyclable Waste from Households in a Megapolis: A Case Study in Shanghai

Shanghai is one of the world-leading megapolises facing the challenge of ecological sustainable development. The recyclable waste from households (RWH) generated in Shanghai has increased rapidly since the implementation of garbage classification in 2019. However, there are no rigorous data on the generation and collection of RWH, and the corresponding countermeasures are required to be studied. This paper attempted to investigate RWH generation and identify the effects of RWH recycling in Shanghai. We used questionnaires combined with a field survey to investigate the competent authorities and leading recycling enterprises to analyze the characteristics of RWH generation. We conducted a monthly survey of 52 leading recycling enterprises in 11 typical districts for 2020. We also identified the main influencing factors of RWH generation using a multiple linear regression model. In addition, we popularized the model to estimate Shanghai’s RWH generation rate. Results show that data from leading recycling enterprises surveys were more accurate and reached a maximum of 82,104.77 kg/cap/month in November 2020. Higher RWH generation was found in suburban districts at 36,396.20 kg/cap/month. Shanghai’s RWH generation rate was 6253.60 t/d through model calculation. The educational level of household managers, regional economic condition, resident population, and disposable income impact RWH generation. Based on the abovementioned results, the implications for RWH management were discussed. We propose to promote the combination of theoretical simulation and information data platform construction. Meanwhile, it is also necessary to improve the capacity of the collection and transport system and accelerate the construction of pre-treatment bases in Shanghai.

Toward a Cleaner and more Sustainable World: A Framework to Develop and Improve Waste Management through Organizations, Governments and Academia

Waste production is expected to reach 3.40 billion tons annually in 2050. To decrease its negative impacts on the environment generated by human activities, waste management (WM) aims to increase the products life cycle and reduce the use of energy and space. Thus, this work aims to propose a framework with actions to develop and improve WM in the Triple Helix (TH) sectors: organizations, governments, and academia. The framework was developed based on the benchmarking of the technical-scientific scenario and the opportunities and challenges of WM added to the authors' experiences. This study was conducted using a combined method of the literature review and content analysis of articles present in the Scopus database, patents identified in the Orbit database, and governmental actions. As a result, 32 actions have been proposed through the framework, distributed among the TH sectors. The countries analyzed were China, India, and the United States, which highlighted because of the h-index and number of patents published. The main scientific contribution of this work is to add empirical elements coming directly from public and private institutions to the theory about WM, forming a block of knowledge with characteristics closer to reality. The major applied contribution of this work is the proposition of actions to the TH sectors, enabling the development of solutions and technologies to improve WM.

Landfill microbiome harbour plastic degrading genes: A metagenomic study of solid waste dumping site of Gujarat, India

Globally, environmental pollution by plastic waste has become a severe ecological and social problem worldwide. The present study aimed to analyse the bacterial community structure and functional potential of the landfill site using high throughput shotgun metagenomic approach to understand plastic degrading capabilities present in the municipal solid waste (MSW) dumping site. In this study, soil, leachate and compost samples were collected from various locations (height and depth) of the Pirana landfill site in Ahmedabad city Gujarat, India. In total 30 phyla, 58 class, 125 order, 278 families, 793 genera, and 2468 species were predicted. The most dominant phyla detected were Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria in the soil and compost samples. Whereas, in leachate samples, the predominant phyla belonged to Firmicutes (54.24%) followed by Actinobacteria (43.67%) and Proteobacteria (1.02%). The functional profiling revealed the presence of enzymatic groups and pathways involved in biodegradation of xenobiotics. The results also demonstrated the presence of potential genes that is associated with the biodegradation of different types of plastics such as polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS). Present study extablishes the relationship between microbial community structure and rich sources of gene pool, which are actively involved in biodegradation of plastic waste in landfill sites.

Implications for Sustainability of the Joint Application of Bioeconomy and Circular Economy: A Worldwide Trend Study

The joint application of bioeconomy (BE) and circular economy (CE) promotes the sustainable use of natural resources, since by applying a systemic approach, it improves the efficiency of these resources and reduces the impact on the environment. Both strategies, which belong to the area of green economy, provide a global and integrated approach towards environmental sustainability, as regards the extraction of biological materials, the protection of biodiversity and even the primary function of food production in agriculture. The objective was to analyze the implications for sustainability of BE and CE joint application. A systematic and bibliometric review has been applied to a sample of 1961 articles, selected from the period 2004–May 2021. A quantitative and qualitative advance is observed in this field of study. The expansion of scientific production is due to its multidisciplinary nature, since it implies technical, environmental and economic knowledge. The main contribution of this study is to understand the state of research on the implications for sustainability that BE and CE have when combined, in relation to their evolution, the scientific collaboration between the main driving agents, and the identification of the main lines of research developed.

Metabarcoding analysis of the bacterial succession during vermicomposting of municipal solid waste employing the earthworm Eisenia fetida

A culture-independent DNA metabarcoding analysis of the bacterial communities was carried out throughout a complete vermicomposting cycle of municipal solid waste material using the earthworm Eisenia fetida. 16S rRNA amplicons from the initial material (0 days), an intermediate (42 days), and a final stage (84 days) were sequenced in an Illumina NGS platform and compared. A steady increase in community diversity was observed corresponding to a 2.5-fold higher taxa richness and correspondingly risen values of the Shannon and Simpson ecological indexes and the evenness parameter. A total of 49,665 operational taxonomic units (OTUs) were counted. From the qualitative standpoint, a clear successional shift was observed with an initial community dominated by putatively plant-associated groups belonging to the Rhizobiales order within the Alphaproteobacteria class, regressively leaving the scores of relative abundance (RA) to the Firmicutes phylum and in particular to the Bacilli. Vermistabilization of municipal solid waste (MSW) increased (p < 0.001) the TKN and total P content in the final vermicompost, while pH, TOC, and C/N ratio declined (p < 0.001) in the process. Likewise, a progressive decrease was noticed in β-glucosidase, acid phosphatase, and urease activity while protease and dehydrogenase showed a slight increase, followed by a steep fall. A strong positive correlation was observed among the canonical functions of physico-chemical attributes and enzyme activities. The canonical correspondence analysis (CCA) revealed that significant families did not change on the temporal scale; however, their abundance was influenced by the abiotic environmental factors. In comparison to prior studies on vermicomposting that used different earthworm species (Eisenia andrei) and different substrates, results reflect a considerable degree of substrate specificity for the earthworm species used. The results offer clues to optimize the vermistabilization of MSW along with its potential use in agriculture, to foster improved levels of the circular economy.

Effects of improved information and volunteer support on segregation of solid waste at the household level in urban settings in Madhya Pradesh, India (I-MISS): protocol of a cluster randomized controlled trial

Background

Segregation of household waste at the source is an effective and sustainable strategy for management of municipal waste. However, household segregation levels remain insufficient as waste management approaches are mostly top down and lack local support. The realisation and recognition of effective, improved and adequate waste management may be one of the vital drivers for attaining environmental protection and improved health and well-being. The presence of a local level motivator may promote household waste segregation and ultimately pro-environmental behaviour. The present cluster randomized control trial aims to understand if volunteer based information on waste segregation (I-MISS) can effectively promote increased waste segregation practices at the household level when compared with existing routine waste segregation information in an urban Indian setting.

Methods

This paper describes the protocol of an 18 month two-group parallel,cluster randomised controlled trialin the urban setting of Ujjain, Madhya Pradesh, India. Randomization will be conducted at ward level, which is the last administrative unit of the municipality. The study will recruit 425 households in intervention and control groups. Assessments will be performed at baseline (0 months), midline (6 months), end line (12 months) and post intervention (18 months). The primary outcome will be the comparison of change in proportion of households practicing waste segregation and change in proportion of mis-sorted waste across the study period between the intervention and control groups as assessed by pick analysis. Intention to treat analysis will be conducted. Written informed consent will be obtained from all participants.

Discussion

The present study is designed to study whether an external motivator, a volunteer selected from the participating community and empowered with adequate training, could disseminate waste segregation information to their community, thus promoting household waste segregation and ultimately pro-environmental behaviour. The study envisages that the volunteers could link waste management service providers and the community, give a local perspective to waste management, and help to change community habits through information, constant communication and feedback.

Trial registration

The study is registered prospectively with Indian Council of Medical Research- Clinical Trial Registry of India (CTRI/2020/03/024278).

Thermochemical digestate fertilizer from solid waste: Characterization, labile carbon dynamics, dehydrogenase activity, water holding capacity and biomass allocation in banana

Thermochemical digestion is a rapid technology of biowaste management resulting in the instant production of organic fertilizer. Characterization and assessment of its suitability as an organic fertilizer is essential for recommendation for crop application. Biowaste and the thermochemical digestate were subjected to physicochemical and biochemical characterization and the compost maturity parameters assessed. The product integrated with inorganic fertilizers was tested in an Ultisol grown with banana in comparison with farmyard manure based fertilizers. Temporal variation in soil reaction, water holding capacity, carbon dynamics, dehydrogenase activity and plant biomass were determined. The thermochemical digestate fertilizer had a bulk density (0.76 Mg m^-3), pH (neutral), C:N ratio (16.26), CEC (85.70 cmol₍₊₎ kg^-1), CEC/ TOC ratio (3.99), Fertilizing index (4.7) and a Clean index (5.0). Field evaluation revealed enhanced water holding capacity (38.75-83.17%). Total carbon increased with consistently high labile (R² = 0.9551) and non labile carbon fractions and the lowest average lability index (0.78). Dehydrogenase activity at harvest enhanced by 72.81%. An even biomass allocation resulted in 38.84% more biomass production in the fruit over farmyard manure based treatments. In addition to ensuring the safety of the environmental ecosystem, the thermochemical digestate conformed to be a quality resource favoring microbial proliferation and carbon sequestration, thereby restraining carbon dioxide emission. The thermochemical digestate fertilizer based nutrition serves the key deliverables of natural resource management, ecofriendly rapid disposal of biowaste and quality organic fertilizer for banana in Ultisols.

Aeration requirement and energy consumption of reactor-composting of rose pomace influenced by C/N ratio

As the composting industry develops rapidly in the world, the compost producers have focused on the efficiency of energy utilization in production without restricting the quality of compost in the forced ventilation systems. Therefore, this experimental study quantified the impacts of initial C/N ratio on aeration requirement and energy consumption due to aeration for reactor composting of rose pomace through kinetics of the process using fifteen 100-l composting reactors. The results of the study showed that initial C/N ratio significantly affected decomposition rate, compost maturity, and dry matter losses and organic matter losses (P < 0.05). The maximum decomposition rate (0.072 day^-1) and the highest degree of progression of the composting process existed at the mixture with initial C/N ratio of 24.26. The results underlined the importance of the initial C/N of composting of rose pomace in terms of energy consumption due to aeration. In particular, more mature compost within a short time can be obtained when composting was operated with a C/N ratio of 23.7-25.8 in the expense of requiring more airflow rate, fan power, and energy consumption by aeration fan per composting material.

Anaerobic digestion of fourth range fruit and vegetable products: comparison of three different scenarios for its valorisation by life cycle assessment and life cycle costing

Changes in consumer demand due to preferences for a healthier lifestyle have led to a new market offering fruit and salad products ready to eat. This affects the agro-industrial sector and the characteristic of waste streams generated having the organic fraction higher quality and representing a new opportunity of valorisation. This study experimentally evaluated the digestion of wastes derived from the fourth range product sector. It was also proposed the use of this digestate as a fermentation medium for producing plant growth-promoting cultures. Three digestion scenarios were studied: Scenario 1 considered biogas valorisation using a combined heat and power (CHP) unit. Scenario 2 featured biogas upgrading to be used as vehicle fuel. Finally, scenario 3 evaluated the transport of waste materials to the digestion plant by a network of pipes and pumps directly from the production chain. All three scenarios included the land application of a biostimulator based on the production of a plant growth-promoting culture derived from digestate. Life cycle analysis and life cycle costing were used to determine potential environmental impacts and costs over a lifetime of 25 years. The study showed that scenario 1 was the most favourable option for valorising this type of waste, although the economic assessment resulted in negative values for all three alternatives.

Investigation of knowledge, attitude, and practice of Tehranian women apropos of reducing, reusing, recycling, and recovery of urban solid waste

This paper aimed to explore knowledge, attitudes, and practices (KAP) of women towards the municipal solid waste (MSW) management in Tehran, Iran, to provide a basis for experts and decision-makers to develop or improve practical waste management strategies. Women's contribution could markedly promote accomplishment of MSW management strategies, which has been neglected in many developing countries. A cross-sectional study was conducted in two stages: first, a random sample of 384 respondent women was selected from the 22 urban districts of Tehran, then 64 of them were randomly selected and trained face-to-face. The second phase was aimed at determining the effectiveness of face-to-face training and its impact on women's performance in waste management. In both stages, data were collected using a structured self-administered questionnaire containing 21 questions in four categories. Chi square (χ²) and Pearson correlation tests were applied to identify the association among variables. Results indicated that 69.6% and 72.9% of the women had adequate knowledge and attitude, respectively, while only 46.0% performed moderate practice on MSW management. Overall, significant association between education level, occupation, and marital status of the women with KAP towards reduction, reuse, recycling, and recovery of MSW were yielded (p < 0.05). Adequate knowledge and positive attitude did not necessarily lead to the proper practice in this study. However, face-to-face training positively affected women's practice in solid waste recycling and source separation. Conducting training programs and motivation of women by municipalities and decision-makers to elevate women's environmental performance could substantially promote MSW management strategies in developing nations.