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Electric field-assisted aerobic composting (EAC) is a novel strategy for effectively mitigating nitrous oxide (N 2 O) emissions, but its deeper effects require further exploration. In this study, the differences in N 2 O emissions between the anode regions (AR) and cathode regions (CR) during EAC were evaluated. The cumulative N 2 O emission from the compost in CR was 32.77% lower than in AR. Compared to AR, the physicochemical properties of CR contribute to the reduction of N 2 O emission. PLS-PM analysis suggested that differences in N 2 O emission are primarily regulated by N-cycling related functional genes and N-containing substances, with different regulatory effects. In AR, functional genes and N-containing substances are significantly positively correlated with N 2 O emissions, whereas in CR, they are significantly negatively correlated. This study highlights the differences and effects of electrode regions in EAC on N 2 O emissions, offering new perspectives for future optimization., 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.)

Hyperthermophilic composting (HTC) with excellent disposal effect is a novel composting technology by inoculating exogenous thermophilic microorganisms. However, the role of exogenous thermophilic microorganisms in HTC remains debated, especially for the applicability of different compost feedstocks. In this study, the role of Parageobacillus toebii during HTC using chicken and pig manure was investigated. The addition of P. toebii could raise the maximum temperature to 78.2 °C and obviously enhanced maturation effect in chicken manure composting. However, the enhancement effect of P. toebii was weaker in pig manure compost, and the maximum temperature only reached 73 °C. Addition of P. toebii could stimulated functional microbial communities for C&N transformation, increased temperature, and promoted the growth of thermophilic microorganisms in chicken manure composting. Component analyses showed that chicken manure had higher bioavailability compared to pig manure. Correlation analysis indicated that P. toebii activated as a "leader", stimulating metabolic activity among functional microbial communities and enhancing organic matter degradation for heat release, while its activation depended on the bioavailability of the raw material. This study provides important insights into the role and application of exogenous microorganisms in promoting HTC., 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.)

A low-voltage electric field assisted strategy is considered to be effective in improving compost effect of conventional chicken manure composting (CCMC), but it lacks a critical assessment of NH 3 mitigation and suitability for complex initial materials. This study firstly constructed an electric field-assisted aerobic co-composting (EFAC) of chicken manure and kitchen waste to evaluate NH 3 mitigation and compost maturity. The results showed that the NH 3 emissions of EFAC were 48.73% lower than those of CCMC. The proposed mechanisms suggest that the combined effect of reduced acidity and electric field inhibited the activities and functions related to ammoniation and ammonia-nitrogen conversion. The germination index of EFAC was 54.29% higher than that of CCMC, due to the enhancement of compost maturation. This study demonstrates that the electric field-assisted strategy for co-composting has a broad potential to reduce ammonia emissions and enhance the disposal of complex feedstocks., 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.)

Electrolytic oxygen aerobic composting (EOAC) is an effective treatment with greater technical superiority and cost advantages for organic solid waste using in situ electrolytic oxygen as a feasible strategy to replace conventional aeration. However, the unclear effects of distribution and variation of in situ electrolytic oxygen on compost maturation in different depth zones of EOAC need further exploration. This study demonstrated that the humification of organic matter was faster at the bottom than in the middle and at the top. The main reason was that the higher oxygen content and lower moisture content in the bottom promoted microbial degradation and heat production, resulting in higher temperatures. The microbial analysis showed that the abundance of typical thermophilic bacteria (such as Cerasibacillus, Lactobacillus, and Pseudogracilibacillus) that could promote compost maturation was higher at the bottom than in the middle and at the top. The finding provided in-depth molecular insights into differentiated humification from bottom to top in EOAC and revealed its further practical engineering applications., 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 © 2022 Elsevier B.V. All rights reserved.)

Electrolytic oxygen aerobic composting (EOAC) effectively treats organic solid waste by using in-situ electrolytic oxygen for aeration. However, the fundamental mechanism of compost maturity is still unclear. Therefore, we comprehensively characterized dissolved organic matter (DOM) transformation closely related to compost maturity during EOAC. Excitation-emission matrix-parallel factor (EEM-PARAFAC) and Fourier transform infrared (FTIR) analysis confirmed that EOAC quickly decreased organic matter and increased humus substances, accelerating the compost humification process compared with conventional aerobic composting. Electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis reveals that the double bound equivalent and aromaticity index during EOAC are higher than in conventional aerobic composting (CAC), suggesting more aromatic compounds in EOAC. DOM's detailed transformation investigation suggested that low O/C and high H/C compounds were preferentially decomposed during EOAC. Our investigation firstly extends the in-depth molecular mechanisms of humification during EOAC, and reveals its practical engineering applications., 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 © 2022 Elsevier B.V. All rights reserved.)

Hyperthermophilic composting (HTC) achieves compost temperatures above 80 °C, usually depending on the inoculated hyperthermophilic bacteria, which has been well used in full-scale plants. However, the scarcity of hyperthermophilic bacteria and the high cultivation cost hinder the development of HTC. Recently, a direct-current electric field applied on conventional aerobic composting raised compost temperature to 70-75 °C, but gradient moisture distribution under the action of the direct-current electric field affected microbial metabolic heat and limited the temperature rise. Herein the effects of alternating electric field (AEF) promoting a uniform water distribution and further raising the temperature to achieve HTC were investigated. Our results demonstrated that AEF raised the compost temperature to 90 °C, and the period with temperatures above 80 °C lasted 4 days. The physicochemical properties and maturity index showed that the AEF improved the biodegradation and humification of organic matter due to the generation of metabolic heat. The AEF enriched thermophilic bacteria (Ureibacillus: by 52.36% on day 3; Navibacillus: by 46.54% on day 41). A techno-economic analysis indicated that the proposed approach with the AEF had a cost advantage over HTC with the inoculation of hyperthermophilic bacteria. Therefore, the AEF composting system represents a novel and applicable strategy for HTC., 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 © 2022 Elsevier B.V. All rights reserved.)

Aerobic composting is an effective recycling method for the disposal and resource utilization of organic solid waste. However, the inappropriate aeration mode used during conventional aerobic composting (CAC) often results in low oxygen utilization efficiency and loss of temperature, which further leads to a long maturation period and large odorous gas (NH 3 ) pollution. Herein, a novel electrolytic oxygen aerobic composting (EOAC) process was invented first using in-situ oxygen generation for aeration by the electrolysis of water in compost. Our results demonstrated that the germination index (GI) significantly increased during EOAC, and the maturation time of compost was shortened by nearly 50% during EOAC compared to CAC, indicating higher oxygen utilization efficiency during EOAC. Meanwhile, NH 3 emissions, N 2 O emissions, and nitrogen loss during the EOAC process decreased by 61%, 46%, and 21%, respectively, compared to CAC. The total relative abundance of thermophilic and electroactive bacteria during EOAC increased remarkably. EOAC inhibited ammoniation, nitrification, and denitrification, and weakened N-associated functional genes. A techno-economic analysis indicated that EOAC had greater technical superiority and cost advantages compared to CAC. This study represents proof-of-principle for EOAC and suggests that in-situ electrolytic oxygen is a feasible replacement for conventional aeration during aerobic composting., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Electric field-assisted aerobic composting (EAC) has been recently believed as a novel and effective process for the resource utilization of organic solid waste. However, the effect of electric field in composting process needs to be further clarified. Herein, moisture migration and compost maturity along electric-field-direction (from anode to cathode) in EAC was first to be explored. It was found that moisture content and compost maturity changed regularly from anode to cathode. At the end of composting, the moisture content of S3 (cathodic zone) was 30% and 62% higher than that of S2 (middle zone) and S1 (anodic zone), respectively. The germination index (a key parameter for compost maturity) in S3 (138.92%) was significantly higher than that of S2 (104.98%) and S1 (84.45%). However, temperatures in S3 were lower than that of S1 and S2, indicating the moisture content played a more important role than temperature for compost maturity in EAC. Furthermore, the microbial activities in S3 were also higher than that of S1 and S2, supporting the trend of compost maturity. This pioneering study demonstrates the electric field can drive moisture gradient migration to control the directional differentiation of compost maturity, showing a great application potential in aerobic composting., 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 B.V. All rights reserved.)

Electric field-assisted aerobic composting (EAC) has been considered as a novel and effective process for enhancing compost maturation. However, the poor conductivity of compost piles affects the efficiency and applicability of EAC. Thus, this study aims to examine how conductive biochar affects compost maturation in biochar-added electric field-assisted aerobic composting (b-EAC). Our results demonstrated that the germination index and humus index significantly increased, and the compost maturation time was shortened by nearly 25% during b-EAC compared to EAC. The total oxygen utilization rate and total relative abundance of electroactive bacteria during b-EAC increased by approximately two and three times those in EAC, respectively. These findings indicated that the addition of conductive biochar has a synergistic effect which facilitated oxygen utilization by reducing resistance and accelerating electron transfer. Therefore, the addition of conductive biochar is proved to be an effective and applicable strategy for optimizing the efficiency of EAC., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Nitrous oxide (N 2 O) emission is an environmental problem related to composting. Recently, the electric field-assisted aerobic composting process has been found to be effective for enhancing compost maturity and mitigating N 2 O emission. However, the insertion of electrodes into the compost pile causes electrode erosion and inconvenience in practical operation. In this study, a novel alternating magnetic field-assisted aerobic composting (AMFAC) process was tested by applying an alternating magnetic field (AMF) to a conventional aerobic composting (CAC) process. The total N 2 O emission of the AMFAC process was reduced by 39.8% as compared with that of the CAC process. Furthermore, the results demonstrate that the AMF weakened the expressions of the amoA, narG, and nirS functional genes (the maximum reductions were 96%, 83.7%, and 95.5%, respectively), whereas it enhanced the expression of the nosZ functional gene by a maximum factor of 36.5 as compared with that in CAC. A correlation analysis revealed that the nitrification and denitrification processes for N 2 O emission were suppressed in AMFAC, the main source of N 2 O emission of which was denitrification. The findings imply that AMFAC is an effective strategy for the reduction of N 2 O emission during aerobic composting., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Nitrous oxide (N 2 O) emission is a serious environmental problem in composting. Previous studies have indicated that electric field assistance results in lower N 2 O emissions in aerobic composting; however, the exact mechanisms involved in electric-field assisted aerobic composting (EAAC) are not clear. In this study, the biological N transformation processes and the N-associated genes were investigated. The results demonstrated that electric field application inhibited nitrification, weakened the nitrifying functional genes (the hao and nxrA genes declined maximally by 86% and 86.8%, respectively), and increased the N 2 O consumption-related gene (nosZ) by a maximum factor of 2.76 compared with that in CAC. The correlation analysis demonstrated that nitrification was the main source of N 2 O emission in EAAC. The findings imply that EAAC is a promising process for mitigating N 2 O emission at the source during aerobic composting., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The long maturation period and greenhouse gas (GHG) emission are two major problems that arise during aerobic composting, mainly due to the low efficiency of O 2 transmission and utilization. In this study, a novel electric-field-assisted aerobic composting (EAC) process was tested by simply applying a direct-current voltage of 2 V to a conventional aerobic composting (CAC) process. Compared with the CAC process, the maturation time and the total GHG for the EAC process were reduced by 33% and 70%, respectively. Furthermore, the analyses of O 2 consumption and microbial communities demonstrated that the electric field had enhanced O 2 utilization by 30 ± 9% and increased the relative abundance of electroactive bacteria by about 3.4-fold compared to CAC. This work has represented a proof of principle for EAC and suggests that the electric field is an effective and environmentally friendly strategy for enhancing compost maturity and mitigating GHG emissions during aerobic composting., (Copyright © 2019. Published by Elsevier Ltd.)

[Display omitted] • Assistance with an electric field has been implemented for food waste composting. • The array electrodes enhanced compost maturity by increasing oxygen. • The array electrodes increase the germination index by 15%. • The array electrodes increase humic acid and fulvic acid by 33% and 37%, respectively. Low composting temperature and long maturation periods are two major problems during food waste composting. In this study, a novel array-based electric field-assisted aerobic composting (Pin-EAC) process was tested on food waste compost. Pin-EAC increase the composting temperature to 69.3 °C, and improved the germination index by 15%. The Pin-EAC took at least 40% less time to reach the standard compost maturity. The fluorescent spectroscopy results showed that Pin-EAC could increase humic acid and fulvic acid by 33% and 37%, respectively. Pin-EAC could increase the diversity of thermophilic bacteria during composting. The co-occurrence network shown that Pin-EAC are more closely related to oxygen and temperature. This work has initially shown that the use of an electric field could improve food waste composting quality, suggesting that the Pin-EAC process is an effective strategy for high-water and high-oil organic solid waste aerobic composting. [ABSTRACT FROM AUTHOR]