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The aerobic composting process is extensively utilized to manage kitchen waste. Nonetheless, the variability in the quality of compost derived from engineering practices which significantly hinders its broader industrial application. This work investigated the final products of kitchen waste compost at multiple industrial-scale treatment facilities utilizing three distinct aerobic composting processes in a bid to explore key factors affecting compost quality. The quality evaluation was based on technical parameters like seed germination index (GI), and limiting factors such as heavy metal content. The results showed that most of the compost products failed to meet the established standards, with GI being the primary limiting indicator. Furthermore, maturity assessments suggested that compost with low GI exhibited reduced humification could not be recommended for agricultural use. The investigation delved into the primary determinants of GI, focusing on risk factors such as the oil and salt of kitchen waste, and the microbial community of the humification driving forces. The results indicated that products with low GI had higher oil and salt content and a relatively simple microbial community. A thorough analysis suggested that excessive levels oil and salt were potential influencing factors on GI, as they stimulated the activity of acid-producing bacteria like Lactobacillus, suppressed the activity of humification-promoting bacteria such as Actinomarinales, and influenced the decomposition and humification processes of organic matter and total nitrogen, thereby affecting product quality. The findings provide valuable insights for improving kitchen waste compost products for agricultural applications., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:DongLei Wu reports financial support was provided by the National Key Research and Development Project. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The seed germination index (GI) serves as the principal determinant that impedes the integration of aerobic composting products into agricultural lands. The current research work predominantly focuses on exploring the correlation between physical and chemical indicators of the compost products and GI, neglecting the fundamental cause. This study systematically analyzed the composition of GI aqueous extracts from compost products derived from kitchen waste under various composting methodologies, with nitrogen, carbon, and inorganic salt as critical factors. The analytical work concluded that acetic acid, formic acid, and ammonium were the inhibitory factors influencing GI. Validation experiments introduced inhibitory factors, yielding a functional relationship formula depicting GI variations due to a single influential factor. This study conclusively identified acetic acid as the primary constraint, establishing that its inhibitory concentration corresponded to 70 % GI stands at 85 mg/L. This study will provide guidelines for the future research on enhancing aerobic composting techniques., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this work, the electrolytic process conditions for the electrochemical oxidation (EO) of composting leachate biochemical effluent (CLBE) were optimized via the response surface methodology (RSM). Meanwhile, a comparative study had been done on the failure characteristics of Ti/RuO 2 -IrO 2 anodes in a single electrolyte solution system (H 2 SO 4 and NaCl) and real wastewater (CLBE) by accelerated life tests, respectively. The RSM optimization results showed that the COD, NH 3 -N and TN removal rates were 50.53%, 100% and 95.61% at 30 min, respectively, with a desirability value of 0.993. In parallel, the electrochemical and material characterizations were carried out on the electrodes before and after failure, by which the failure mechanism of Ti/RuO 2 -IrO 2 anodes was clarified. On the whole, the true failure in the H 2 SO 4 solution was attributed to coating dissolution and Ti substrate oxidation. In contrast, the electrode exhibited "apparent failure" due to the "bubble effect" in both NaCl and CLBE solutions, and the "effective roughness" formed compensated for the loss of activity caused by the absence of the coating. Besides, additional dissolution of the Ti substrate occurred in the CLBE solution due to the current edge effect and the presence of organic matter. This paper takes the actual wastewater as the research object and reveals its electrode failure mechanism, which provides a theoretical basis and reference for the subsequent optimization of the actual electrode service life., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The rural domestic waste (RDW) compost has been widely used in agriculture and horticulture, but little is known about microplastics (MPs) in RDW composting. The current work deals with the abundance and characteristics of MPs in RDW composting, and the effects of composting processes on the composition of MPs. Compost samples from two RDW treatment stations were investigated, and a lab-scale experiment was carried out to verify the possible release of MPs from macroplastics (>25 mm) contained in the RDW during composting. MPs were identified using stereo-microscope and μ-FTIR. The average abundance of MPs (0.05-5 mm) in the RDW compost products was 2400 ± 358 items/kg (dry weight), and the main MPs shapes were fibers and films. Polyester, polypropylene (PP) and polyethylene (PE) were the most common polymer types. MPs having a size <1 mm accounted for more than 50% of the total quantity. With the progress of composting, the proportion of MPs having size <1 mm increased, and more foam MPs were observed in the late stage of composting. Under the influence of mechanical force, oxidation and biodegradation, a piece of expanded polystyrene (EPS), PP and PE macroplastic could release 4-63 MPs particles during the composting. Thus, the RDW compost was a significant source of MPs in soils, and the MPs in compost products were closely related to the quantity and type of plastic waste present in RDW, which helped to suggest better MPs control strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Industrial-scale composting of food waste (FW) was performed at different aeration frequencies (C&#95;5&#95;25: 5 min aeration + 25 min interval, C&#95;10&#95;20: 10 min aeration + 20 min interval, C&#95;15&#95;15: 15 min aeration + 15 min interval and CK: stuffiness) to ascertain the optimal aeration frequency to accomplish polymerization and humification of compost. The tested aeration frequencies affected the oxygen uptake rate, oxygen spatial distribution, and ultimately influenced the humification of compost. Extensive aeration was not beneficial to accumulate nitrogen and phosphorus during composting. Aeration frequency influenced the succession of bacterial community primarily through affecting O 2 concentration and the release of various enzymes by these bacteria. Regulating O 2 concentration by adjusting aeration strategies may provide guidance for accelerating maturity of composting. Considering various factors, this paper recommends the scheme of heating period (C&#95;5&#95;25), thermophilic period (C&#95;15&#95;15) and psychrophilic period (no aeration)., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this paper, the treatment of composting leachate biochemical effluent (CLBE) by electrochemical oxidation (EO) with Ti/RuO 2 -IrO 2 as the anode could achieve concomitantly organic carbon removal (COD) and nitrogen removal (NH 3 -N), taking advantage of CLBE inherent high chlorine content. Under the optimal conditions of the current density of 90 mA·cm−2, A/V= 14 m−1, d= 1 cm, pH= 8.34 and Cl- concentration of 6000 mg·L−1, 92.19% of NH 3 -N and 85.59% of TN could be removed in 40 min, and 100% COD removal could be achieved after 100 min, with energy consumption (EC) of 111.09 kW·h·m−3. And the increase in Cl- concentration could reduce the EC of the EO process. In parallel, constructed simple quantitative accounting models for chlorine-containing and nitrogen-containing species in the EO system and clarified the evolution of them. Cl species eventually exist mainly in the form of free chlorine (by-product AOCL concentration always below 2 mg·L−1), while N species were mainly removed in the form of N 2 (≈95.10% of TN). Additionally, the gas chromatography-mass spectrometry (GC-MS) showed that the dominant component of dissolved organic matter (DOM) in CLBE was degraded from the initial unsaturated C 21 -C 30 to the saturated C 11 -C 20. And the Excitation emission matrix (EEM) showed that the EO achieved the non-selective degradation of DOM, the refractory humic acid DOM reached 90.74% removal and the readily biodegradable non-humic DOM removal 92.02%, respectively. These results indicated that the EO technology has broad application potential in the treatment of chlorinated wastewater, and coupling it after biological treatment would be a promising method. [Display omitted] • 92.19% of NH 3 -N and 85.59% of TN removed in 40 min, and 100% COD removal after100 min. • Cl species eventually exist mainly in the form of free chlorine (with AOCL<2 mg·L−1). • NH 3 -N was mainly transformed into 95.10% [N 2 ] cal for removal. • DOM in CLBE was degraded from the mainly unsaturated C 21 -C 30 to the saturated C 11 -C 20. • EO process achieved the non-selective degradation of non/humic acid DOM in CLBE. [ABSTRACT FROM AUTHOR]

Chinese food waste (FW) production is enormous which brings many economic and environmental benefits. There is an urgent need for proper and efficient treatment technology. Anaerobic digestion (AD) is a popular technology for centralized large-scale treatment of FW. Composting technologies including static composting (SC), forced aerated composting (FC), and machine composting (MC) have been applied in rural areas owing to their low cost and simplicity. The characteristics of products in different FW treatment are still unclear, preventing agricultural use of the products. In order to elucidate the properties of different samples and to realize the resource utilization of products, compost samples (FC, SC and MC) and AD biogas residue samples were collected on site. By analyzing the physicochemical properties (pH, moisture content, maturity, salinity, lignocellulose, etc.) and phytotoxicity, the quality of different products was evaluated to determine the most appropriate rural FW treatment technology. MC products showed poor performance in maturity, salt concentration and plant toxicity. SC products cannot be used due to phytotoxicity. High moisture content limited the prospects of AD products utilization. FC products were of good quality with 32.91% in organic matter loss, good performance in lignocellulose degradation, 6.76% in water-soluble salts, and 79.61% in germination index. FC technology is worth promoting in rural areas of China. • Forced aerated composting showed a superior performance among four technologies. • Machine composting poorly degraded lignocellulose, resulting in strong phytotoxicity. • The correlation between phytotoxicity and physicochemical properties was analyzed. [ABSTRACT FROM AUTHOR]