Proof of concept of high-rate decentralized pre-composting of kitchen waste: Optimizing design and operationof a novel drum reactor

Decentralized composting: gated communities as ecologically promising environments

The global need to strengthen circular economic chains highlights the importance of composting, since the organic fraction corresponds, on average, to 50% of the municipal solid waste. As centralized composting programs have been showing slow advances, especially in low and middle-income countries, the decentralized scale is a promising tool. Gated communities stand out as potential targets for decentralized composting programs, as they generally have organization, tools, employees, space, and a high density of gardens. This study detected, through online questionnaires sent to residents of gated communities, a high probability of adherence to composting programs in the condominium, predisposition for waste sorting, use of the compost, and participation in meetings to address the issue, in addition to a relevant potential for reducing the disposal of organic waste in landfills. On the other hand, the absence of leaders, lack of knowledge about community projects and fear of unpleasant odors and pests were evidenced. Among 106 respondents, residents of 25 condominiums, no variability was detected between positions of different genders, ages, and education. This diagnosis points out challenges and suggests alternatives to overcome them, based on successful experiences, focused on strengthening leadership, technical training, provision of equipment, improvements in communication and socio-environmental awareness.

Machine learning framework for intelligent prediction of compost maturity towards automation of food waste composting system

Reactive composting is a promising technology for recovering valuable resources from food waste, while its manual regulation is laborious and time-consuming. In this study, machine learning (ML) technologies are adopted to enable automated composting by predicting compost maturity and providing process regulation. Four machine learning algorithms, namely random forest (RF), extreme gradient boosting (XGBoost), Light Gradient Boosting Machine (LightGBM) and Multilayer Perceptron (MLP) are employed to predict the seed germination index (GI) and C/N ratio. Based on the best fusion model with the highest R² of 0.977 and 0.986 for the multi-task prediction of GI and C/N ratio, the critical factors and their interactions with maturity are identified. Moreover, the ML model is validated on a composting reactor and the ML-based prediction application can provide regulation to ensure food waste decompose within the required time. In conclusion, this compost maturity prediction system automates the reactive composting, thus reducing labor costs.

Recent trends and advances in composting and vermicomposting technologies: A review

Composting technologies have come a long way, developing from static heaps and windrow composting to smart, artificial intelligence-assisted reactor composting. While in previous years, much attention has been paid to identifying ideal organic waste streams and suitable co-composting candidates, more recent efforts tried to determine novel process-enhancing supplements. These include various single and mixed microbial cultures, additives, bulking agents, or combinations thereof. However, there is still ample need to fine-tune the composting process in order to reduce its impact on the environment and streamline it with circular economy goals. In this review, we highlight recent advances in integrating mathematical modelling, novel supplements, and reactor designs with (vermi-) composting practices and provide an outlook for future developments. These results should serve as reference point to target adjusting screws for process improvement and provide a guideline for waste management officials and stakeholders.

Decentralized Processing Performance of Fruit and Vegetable Waste Discarded from Retail, Using an Automated Thermophilic Composting Technology

Food waste generation is increasing at an exponential rate, affecting the environment, food security, and causing major economic issues worldwide. The main aim of the current research is to investigate a novel composting technology that is still in its early stages of development. The proposed composting technology combining thermophilic composting with the use of advanced automated processing reactors. Starting from a qualitative and quantitative analysis of the waste generated at retail-stores, the most significant difficulties associated to waste management as well as the main characteristics of the discarded waste were identified. The findings allowed to design and evaluate the real operating performance of an automated thermophilic composting prototype (working in a decentralized regime), with the goal of delivering a faster processing system, improving operational efficiency, reducing expenses, and lowering environmental impacts. The proposed operating technique showed a high capacity for pathogens and seeds removal, the waste input mass reduction of 88%, and efficiency in food processing (2235 kg of fruits and vegetables in a 14-days timeframe).

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.

Microbial succession and degradation during kitchen waste biodrying, highlighting the thermophilic phase

Biodrying in conjunction with compound stone amendment was used to treat kitchen waste, which improved biodrying. After 16 days, the pile moisture content decreased from 68.8% to 23.0%. Lignin, cellulose and hemicellulose concentrations decreased from 104.6 mg g^-1 d.b., 322.9 mg g^-1 d.b. and 155.9 mg g^-1 d.b., respectively, to 74.0 mg g^-1 d.b., 224.8 mg g^-1 d.b. and 134.5 mg g^-1 d.b., respectively. The Shannon index for bacteria increased from 2.5 to 3.1, while for fungi, it decreased from 4.6 to 0.6. The relative abundances of Amino Acid Metabolism and Carbohydrate Metabolism exceeded 7%. The thermophilic phase during the process inactivated the pathogenic microorganisms, increased the bacterial diversity, decreased the fungal diversity, and potentially improved the metabolism of nutrients, including amino acids, carbohydrates, lipids and vitamins. The biomarker analysis and predicated protein sequences provide genetic evidence to elucidate why the thermophilic phase is the peak time for nutrient metabolism.

Synergetic degradation of waste oil by constructed bacterial consortium for rapid in-situ reduction of kitchen waste

Traditional composting of kitchen waste (KW) is cost- and time-intensive, requiring procedures of collection, transport and composing. Consequently, the direct in-situ reduction of KW via treatment at the point of collection is gaining increasing attention. However, high oil content of KW causes separation and degradation issues due to its low bioavailability and the hydrophobicity, and therefore greatly limiting the direct application of in-situ methods for mass reduction. To overcome this, a bacterial consortium of Pseudomonas putida and Bacillus amyloliquefaciens was constructed, which exhibited a synergistically improved oil degrading ability for lipase-catalyzed hydrolysis, fatty acids β-oxidation, biosurfactant production and surface tension reduction, and the degradation ratio reached 58.96% within 48 h when the initial KW oil concentration was 8.0%. The in-situ aerobic digestion of KW was further performed in a 20-L stirred-tank reactor, the content of KW oil (34.72 ± 2.05% of total solids, w/w) was rapidly decreased with a simultaneous increase in both lipase activity and in microbial cell numbers, and the degradation ratio reached 57.38%. The synergetic effect of the two strains including B. amyloliquefaciens and P. putida promoted the decomposition process of KW oil, which also paved the way for an efficient degradation strategy to support the application potential of in-situ microbial reduction of KW.

Pyrolysis of food waste over a Pt catalyst in CO2 atmosphere

In this study, a method of disposing food waste is introduced via catalytic pyrolysis under CO₂ condition. The catalyst and CO₂ hindered the generation of condensable compounds, leading to enhancing non-condensable gas generation. However, they did not affect the amount of solid residues left after the thermal reaction. The amount of condensable cyclic compounds was reduced when the catalyst and/or CO₂ were used. The enhancement of non-condensable gas production and reduction of cyclic compounds formation were maximized when the Pt catalyst and CO₂ were simultaneously applied to the pyrolysis of food waste. For instance, approximately 67.3 % less cyclic compounds, including benzene derivatives, were generated at 700 °C in the presence of the catalyst under a CO₂ atmosphere compared to non-catalytic conditions without CO₂. The results suggest that a CO₂-assisted catalytic pyrolysis is as environmentally benign disposal method for food waste.

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.