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19 pages, 1109 KB

Open AccessArticle

Effects of Biochar and Zeolite on the Co-Composting of Agricultural Waste Under Psychrophilic Conditions

by Maria Fernanda Rios-Mercado, Viviana Sanchez-Torres, German Zafra, Delia Rueda-López, Nelson Rodriguez-Lopez, Cristian Rodriguez, Jonathan Blanco, Karen Vides, Jessica Vargas and Edgar Ricardo Oviedo-Ocaña

Processes 2026, 14(10), 1530; https://doi.org/10.3390/pr14101530 - 9 May 2026

Viewed by 286

Abstract

Biochar and zeolite are promising additives for improving composting; however, their effects during the co-composting of agricultural waste have not yet been sufficiently studied. This study evaluated their influence on the composting of green onion residues and chicken manure under psychrophilic conditions on [...] Read more.

Biochar and zeolite are promising additives for improving composting; however, their effects during the co-composting of agricultural waste have not yet been sufficiently studied. This study evaluated their influence on the composting of green onion residues and chicken manure under psychrophilic conditions on a pilot scale using 200 kg piles. Three treatments were evaluated: a control, 5% biochar, and 2% zeolite. Both amendments increased the maximum composting temperature by approximately 3 °C and improved the germination index, with increases of around 10% for biochar and 26% for zeolite compared to the control. Biochar increased the relative abundance of the amoA gene, associated with ammonia oxidation and nitrification, suggesting greater biochemical potential for nitrification. During maturation, zeolite reduced pH and electrical conductivity, indicating greater compost stability. In fast-growing crops, compost from zeolite treatment did not significantly affect plant growth when applied alone, but improvements were observed when combined with synthetic fertilizer. Overall, both additives improved composting performance and compost quality, with zeolite showing the most consistent effects. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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14 pages, 2490 KB

Open AccessArticle

Release of Dissolved Organic Matter from Sludge Biochar and Its Spectral Characteristics in Different Environmental Media

by Bowen Li, Jianjun Liao, Hao Wen, Lincheng Ma, Bin Li, Wei Song and Caixia Fu

Processes 2026, 14(4), 595; https://doi.org/10.3390/pr14040595 - 9 Feb 2026

Viewed by 551

Abstract

The widespread use of biochar in soil remediation has heightened interest in the role of its derived dissolved organic matter (DOM) in soil nutrient dynamics. However, how pyrolysis temperature shapes the characteristics of DOM released from sludge biochar remains unclear. The study examined [...] Read more.

The widespread use of biochar in soil remediation has heightened interest in the role of its derived dissolved organic matter (DOM) in soil nutrient dynamics. However, how pyrolysis temperature shapes the characteristics of DOM released from sludge biochar remains unclear. The study examined variations in the composition and properties of DOM extracted from sludge biochar under two different solutions—ultrapure water (UP) and artificial root exudates (ARE)—across a range of pyrolysis temperatures. Results indicate that the dissolved organic carbon (DOC) content did not differ significantly between extraction environments. In contrast, pyrolysis temperature markedly influenced both the content and composition of DOM. DOM in sludge biochar was primarily composed of humic-like (C1, C2, C3) and tyrosine-like (C4) components. Specifically, DOM from low-temperature biochar was dominated by C2, C3, and C4, whereas high-temperature biochar contained mainly C2 and C4. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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20 pages, 4707 KB

Open AccessArticle

Study on Degradation of Oxytetracycline in Water by PMS Activated by Modified Macadamia Nut Shell Biochar

by Yixin Lu, Aojie Wang, Yi Wu, Linyun Gu, Shuyuan Liu and Guo Liu

Processes 2025, 13(12), 3867; https://doi.org/10.3390/pr13123867 - 30 Nov 2025

Viewed by 659

Abstract

With a complex molecular structure, oxytetracycline (OTC) has characteristics such as bioaccumulation and poor degradability. As a result, if it accumulates in the environment, it can cause bacteria to develop drug resistance, thereby affecting human health. There is a considerable cultivation area for [...] Read more.

With a complex molecular structure, oxytetracycline (OTC) has characteristics such as bioaccumulation and poor degradability. As a result, if it accumulates in the environment, it can cause bacteria to develop drug resistance, thereby affecting human health. There is a considerable cultivation area for macadamia nuts in southwestern China. This study mainly focuses on macadamia nut shells, preparing macadamia nut shell biochar (MBC) and cobalt-modified macadamia nut shell biochar (Co-MBC) for activating permonosulphate (PMS) to remove OTC in the water. To determine the optimal preparation conditions for the biochar, the effects of the pyrolysis temperature and the mass ratio of biomass to cobalt sulfate heptahydrate were investigated. The study shows that after modification, the surface roughness of the material increased, transforming into a micro-pore structure; thus, the specific surface area increases significantly and new functional groups appear on the surface. The optimal pyrolysis temperature for the biochar was determined to be 600 °C, and the optimal mass ratio of biomass to cobalt sulfate heptahydrate was 15:1. Under such conditions, the removal rate of OTC by a Co15-MBC600/PMS system in 20 min can reach 95.53%. The reaction mechanism involves pathways of the free radical (SO₄⁻) and non-free radical (¹O₂), and the Co²⁺/Co³⁺ cycle can promote the activation of PMS. Finally, the OTC can be mineralized into CO₂ and H₂O by reactions such as demethylation and decarboxylation. Co-MBC is highly effective and green and can be reused; therefore, it has good prospects for the removal of OTC in waste water. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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21 pages, 3275 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Biochar as a Catalyst in Persulfate Activation: A Sustainable Approach to Remove Pesticides from Water

by Tajana Simetić, Tijana Marjanović Srebro, Tamara Apostolović, Jasmina Anojčić, Nina Đukanović, Sanja Mutić, Jelena Molnar Jazić and Jelena Beljin

Processes 2025, 13(6), 1856; https://doi.org/10.3390/pr13061856 - 12 Jun 2025

Cited by 9 | Viewed by 2952

Abstract

This study explores biochar-based catalysts made from hardwood (HW) and wheat straw (WS) biomass for activating persulfate (PS) in the removal of lindane and β-endosulfan from water. The effects of pyrolysis temperature, solution pH, and PS concentration were investigated. The results indicated that [...] Read more.

This study explores biochar-based catalysts made from hardwood (HW) and wheat straw (WS) biomass for activating persulfate (PS) in the removal of lindane and β-endosulfan from water. The effects of pyrolysis temperature, solution pH, and PS concentration were investigated. The results indicated that both feedstock and pyrolysis temperature are key factors influencing biochar composition. Biochars pyrolyzed at 700 °C exhibited higher surface areas compared to those pyrolyzed at 400 °C, suggesting more effective interactions with the target pesticides. Changes in pH had a minimal impact on pesticide removal, while increasing the PS concentration from 0.5 to 3 mM accelerated degradation. However, further increases in PS concentration slowed the degradation of both pesticides. Under optimal conditions (pH of 7.0 ± 0.2 and PS concentration of 3 mM), the HW700/PS and WS700/PS systems achieved > 90% removal of pesticides within 4 h. Quenching experiments confirmed that non-radical species (¹O₂), generated through persulfate activation by biochar, were the key factor in lindane degradation in both systems, supporting the catalytic role of biochar rather than mere adsorption. In the HW700/PS system, SO₄^•−, HO^•, and ¹O₂ acted synergistically to enhance the degradation of β-endosulfan, whereas in the WS700/PS system, the degradation was mainly driven by SO₄^•− and ¹O₂. Notably, HW700 biochar maintained its activation efficiency during β-endosulfan degradation even after five cycles. This research offers new insights into the potential of biochar-activated PS as a green, cost-effective, and efficient method for water treatment, addressing pesticide-contaminated surface water and promoting agricultural waste recycling. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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20 pages, 21249 KB

Open AccessArticle

Enhanced Cadmium Adsorption Mechanisms Utilizing Biochar Derived from Different Parts of Wetland Emergent Plants Iris sibirica L.

by Tongtong Li, Yangyang Wang, Yongchao Niu, Zhonglei Zhang, Jin Liu, Xiaoshu Wang, Jingao Wang, Ji Li and Lei Wang

Processes 2025, 13(5), 1520; https://doi.org/10.3390/pr13051520 - 15 May 2025

Cited by 5 | Viewed by 1590

Abstract

Due to their substantial biomass and rapid growth, emergent plants found in wetlands are viewed as excellent sources for biochar production, which has been demonstrated to serve as an effective substitute for absorbite in the effluent treatment. This article systematically contrasted the physicochemical [...] Read more.

Due to their substantial biomass and rapid growth, emergent plants found in wetlands are viewed as excellent sources for biochar production, which has been demonstrated to serve as an effective substitute for absorbite in the effluent treatment. This article systematically contrasted the physicochemical properties of biochar derived from each section of Iris sibirica L. (designated as BC_R, BC_S, and BC_L) under identical pyrolysis conditions, in order to assess their effectiveness in removing cadmium (Cd) from effluent. Experimental results indicated that the removal efficiencies of Cd among the various biochars followed the order BC_S (19.92 mg/g) > BC_L (19.89 mg/g) > BC_R (13.22 mg/g). The removal of Cd²⁺ by biochar is primarily governed by chemisorption, as described by the Langmuir and Freundlich models. Moreover, different adsorption kinetic models, e.g., first-order kinetics, second-order kinetics, intra-particle diffusion, and the Elovich model, were performed to elucidate the adsorption process. Compared to BC_L and BC_R, the proportions of ion exchange and precipitation were more superior in BC_S, reaching 54% and 31%, respectively, which could serve as an effective adsorbent for metal ions, achieving the maximum adsorption capacity. In addition, precipitation (46%) was predominant during the Cd²⁺ adsorption process through BC_R. Therefore, BC_R was more suitable for the acidic wastewater treatment. This study provided an in-depth understanding of the cadmium removal behavior through biochar obtained from different part (roots, stems, and leaves) of wetland plants and introduced a new option for efficient utilization of waste biomass. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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21 pages, 6121 KB

Open AccessArticle

Sulfidated Nano Zero-Valent Iron Sludge Biochar Composites for Efficient Tannic Acid Removal and Enhanced Anaerobic Digestion

by Qian Gao, Wenxia Zhai, Wencai Fu, Ling Liu, Yunpeng Zhu, Keyang Jiang, Sijia Zhu, Kaize Zhao, Zhaodong Qiu, Congcong Wang, Yuanyuan Zhao and Zhiwei Wang

Processes 2025, 13(4), 1084; https://doi.org/10.3390/pr13041084 - 4 Apr 2025

Cited by 2 | Viewed by 1986

Abstract

Tannic acid (TA), a prevalent polyphenolic contaminant in industrial effluents, significantly inhibits microbial activity in anaerobic digestion, thereby diminishing wastewater treatment efficiency. In this study, a sulfidized nano zero-valent iron (S-nZVI) composite incorporated into sludge biochar (SB), abbreviated as SB-S-nZVI, was synthesized via [...] Read more.

Tannic acid (TA), a prevalent polyphenolic contaminant in industrial effluents, significantly inhibits microbial activity in anaerobic digestion, thereby diminishing wastewater treatment efficiency. In this study, a sulfidized nano zero-valent iron (S-nZVI) composite incorporated into sludge biochar (SB), abbreviated as SB-S-nZVI, was synthesized via a one-step hydrothermal method. The composite’s adsorption capacity for TA and its impact on anaerobic digestion were systematically evaluated. Experimental results showed that SB-S-nZVI achieved a TA removal efficiency of 99.31% under optimal conditions (S/Fe = 0.05, dosage = 0.3 g·L⁻¹), with a maximum adsorption capacity of 337.08 mg·g⁻¹. In anaerobic digestion, the addition of 0.03 g·L⁻¹ SB-S-nZVI enhanced chemical oxygen demand (COD) removal by 3.32%, increased specific methanogenic activity by 62.66%, and improved the microbial community composition, particularly enriching hydrolytic bacteria (Georgenia) and methanogenic archaea (Methanosaeta). The mechanistic analysis revealed that the FeS protective layer of SB-S-nZVI inhibited nano zero-valent iron oxidation and facilitated chemisorption-driven TA removal. This study presents an innovative approach for the integrated treatment of TA-contaminated wastewater by combining adsorption, degradation, and energy recovery. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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13 pages, 6387 KB

Open AccessArticle

Performance of CO₂ Adsorption on Modified Activated Carbons Derived from Okara Powder Waste: Impacts of Ammonia Impregnation

by Tuan-Dung Hoang, Yan Liu and Minh Thang Le

Processes 2024, 12(9), 2024; https://doi.org/10.3390/pr12092024 - 20 Sep 2024

Cited by 10 | Viewed by 3086

Abstract

The activated carbons (ACs) derived from okara powder waste with high surface areas were modified with ammonia aqueous solution impregnation in an autoclave to enhance their CO₂ adsorption properties. The impregnated ACs were characterized, where the chemical composition and properties of the [...] Read more.

The activated carbons (ACs) derived from okara powder waste with high surface areas were modified with ammonia aqueous solution impregnation in an autoclave to enhance their CO₂ adsorption properties. The impregnated ACs were characterized, where the chemical composition and properties of the ACs were analyzed by SEM-EDX and FTIR. Activated carbons were functionalized with ammonia aqueous solution (25%) through a hydrothermal process within 24, 48, and 72 h. The adsorption performance of CO₂ onto carbon samples was experimentally evaluated through a TPD CO₂ measurement. FTIR spectra confirm the N-containing in N-modified activated carbons and the presence of the –C=O stretch and N-H groups. CO₂ uptakes of activated carbons are 0.24; 1.78; 2.24; and 1.26 mmol/g, which are relatively comparable with those of activated carbons studied in the literature. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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14 pages, 2893 KB

Open AccessArticle

Effects of Biochar-Amended Composts on Selected Enzyme Activities in Soils

by Faraj Zaid, Nasruddeen Al-Awwal, John Yang, Stephen H. Anderson and Bouzeriba T. B. Alsunuse

Processes 2024, 12(8), 1678; https://doi.org/10.3390/pr12081678 - 11 Aug 2024

Cited by 16 | Viewed by 3270

Abstract

This study examines the effect of biochar as an agricultural soil supplement on soil quality indicators, specifically enzyme activity in Missouri regions. While the benefits of biochar on soil bulk density, soil organic carbon, and infiltration have been established, its effect on soil [...] Read more.

This study examines the effect of biochar as an agricultural soil supplement on soil quality indicators, specifically enzyme activity in Missouri regions. While the benefits of biochar on soil bulk density, soil organic carbon, and infiltration have been established, its effect on soil enzyme activity has remained underexplored in this region. A three-year field investigation was conducted with six treatments (compost, biochar, compost + biochar, biochar + compost tea, fescue, and control) to evaluate the effects on enzymes such as β-glucosidase (BG), acid and alkaline phosphatases (ACP-ALP), arylsulfatase (ARS), dehydrogenases (DG), arylamidase (AMD), cellulase (CLS), and urease (URS). Furthermore, soil pH, organic matter (OM), and cation exchange capacity (CEC) were determined. The results showed that compost and biochar treatments considerably increased soil enzyme activity compared to other treatments, with nitrogen application further increasing enzyme activity. Soil pH, OM, and CEC were all important determinants in determining enzyme activity, with BG demonstrating strong positive associations with ACP and AMD (99.5%). This study shows that compost and biochar amendments significantly improve soil physicochemical and biological properties, thereby enhancing soil health and assisting farmers’ sustainable soil management practices. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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27 pages, 10110 KB

Open AccessArticle

Sustainable Napier Grass (Pennisetum purpureum) Biochar for the Sorptive Removal of Acid Orange 7 (AO7) from Water

by Anand Kumar Yadav, Abhishek Kumar Chaubey, Shivang Kapoor, Tej Pratap, Brahmacharimayum Preetiva, Vineet Vimal and Dinesh Mohan

Processes 2024, 12(6), 1115; https://doi.org/10.3390/pr12061115 - 28 May 2024

Cited by 9 | Viewed by 5149

Abstract

The unregulated discharge of synthetic dyes from various anthropogenic and industrial activities has resulted in the contamination of different environmental compartments. These dyes can contaminate water bodies, soil, and even the air, resulting in many environmental and health issues. True colors may persist [...] Read more.

The unregulated discharge of synthetic dyes from various anthropogenic and industrial activities has resulted in the contamination of different environmental compartments. These dyes can contaminate water bodies, soil, and even the air, resulting in many environmental and health issues. True colors may persist for long periods, thereby affecting the aesthetics and ecology of dye-contaminated areas. Furthermore, they pose potential risks to aquatic life and human health through the ingestion or absorption of dye-contaminated water or food. Acid orange 7 (AO7) is a synthetic azo dye used in the textile, tanning, food, pharmaceutical, paint, electronics, cosmetics, and paper and pulp industries. AO7 can have various human health implications, such as dermatitis, nausea, severe headache, respiratory tract irritation, and bone marrow depletion, due to its high toxicity, mutagenicity, and carcinogenicity. Efforts to regulate and mitigate dye pollution (AO7) are crucial for environmental sustainability and public health. Therefore, this study aimed to remove AO7 from water using sustainable biochar. This objective was accomplished by pyrolyzing dried Napier grass at 700 °C to develop affordable and sustainable Napier grass biochar (NGBC700). The developed biochar was characterized for its surface morphology, surface functional groups, surface area, and elemental composition. The yield, moisture content, and ash content of the NGBC700 were approximately 31%, 6%, and 21%, respectively. The NGBC700’s BET (Brunauer–Emmett–Teller) surface area was 108 m² g⁻¹. Batch sorption studies were carried out at different pH levels (2–10), biochar dosages (1, 2, 3, and 4 g L⁻¹), and AO7 concentrations (10, 20, and 30 mg L⁻¹). The kinetic data were better fitted to the pseudo-second-order (PSO) equation (R² = 0.964–0.997) than the pseudo-first-order (PFO) equation (R² = 0.789–0.988). The Freundlich isotherm equation (R² = 0.965–0.994) fitted the sorption equilibrium data better than the Langmuir equation (R² = 0.788–0.987), suggesting AO7 sorption on heterogenous NGBC700. The maximum monolayer AO7 adsorption capacities of the NGBC700 were 14.3, 12.7, and 8.4 mg g⁻¹ at 10, 25, and 40 °C, respectively. The column AO7 sorption capacity was 4.4 mg g⁻¹. Fixed-bed AO7 sorption data were fitted to the Thomas and Yoon–Nelson column models. The NGBC700 efficiently removed AO7 from locally available dye-laden wastewater. NGBC700 was regenerated using different NaOH concentrations. Possible interactions contributing to AO7 sorption on NGBC700 include hydrogen bonding, electrostatic interactions, and π–π electron donor–acceptor attractions. The estimated total preparation cost of NGBC700 was US$ 6.02 kg⁻¹. The developed sustainable NGBC700 is potentially cost-effective and environmentally friendly, and it utilizes waste (Napier grass) to eliminate fatal AO7 dye from aqueous media. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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Review

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15 pages, 4245 KB

Open AccessReview

A Critical Review of the Role of Biochar in Mitigating Atmospheric Emissions During the Composting of Organic Waste

by Elena Olivera-Begué, Daniel González and Antoni Sánchez

Processes 2026, 14(1), 71; https://doi.org/10.3390/pr14010071 - 24 Dec 2025

Cited by 2 | Viewed by 1271

Abstract

Biochar has emerged as a promising material for carbon storage, exhibiting properties analogous to those of activated carbon. Biochar has a particularly high absorbance due to its high porosity, surface area, and functional groups, although these parameters depend on the feedstock and pyrolysis [...] Read more.

Biochar has emerged as a promising material for carbon storage, exhibiting properties analogous to those of activated carbon. Biochar has a particularly high absorbance due to its high porosity, surface area, and functional groups, although these parameters depend on the feedstock and pyrolysis conditions. The sorbent properties of biochar make it suitable for many applications, including the biological treatment of organic waste. In the context of composting, biochar addition seems to positively impact the process performance and the final compost characteristics. Furthermore, it reduces greenhouse gas and odor emissions, which is a crucial step in preventing the full implementation of composting. The objective of this review is to provide a comprehensive description of the effects of biochar on composting emissions and the reported mechanisms, highlighting the limitations of current research. In summary, the use of biochar in composting is still in its early stages and requires further research and consensus on fundamental issues, such as the optimal biochar dosage and mitigation mechanisms. Moreover, there is a significant lack of full-scale implementation. Accordingly, future work should focus on overcoming these critical challenges to take a step forward towards a consistent and complete picture of the environmental impacts and a rigorous economic analysis of the use of biochar in composting. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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Other

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17 pages, 2576 KB

Open AccessPerspective

An Overview of the Technological Evolution of Organic Waste Management over the Last Decade

by Esther Molina-Peñate and Antoni Sánchez

Processes 2025, 13(4), 940; https://doi.org/10.3390/pr13040940 - 21 Mar 2025

Cited by 7 | Viewed by 4002

Abstract

Organic waste treatment, including its many strategies and objectives, is one of the most rapidly changing sectors of environmental technology. It is closely related to sustainability and other critical issues, such as global warming. The first years of this century were the time [...] Read more.

Organic waste treatment, including its many strategies and objectives, is one of the most rapidly changing sectors of environmental technology. It is closely related to sustainability and other critical issues, such as global warming. The first years of this century were the time of a transition from traditional technologies for the “disposal of” waste, such as incineration (with poor energy recovery) or landfill (more or less controlled), to biotechnologies that are more profitable, such as composting and anaerobic digestion. However, recent developments are focused on advanced technologies in the framework of a circular bioeconomy, maximizing the production of biomaterials and renewable energy using raw organic waste or digested materials. This perspective paper delves into the second transition in the field of technologies for treating and valorizing organic waste, highlighting emerging technologies such as anaerobic digestion enhanced with nanomaterials or biochar to substitute fossil natural gas, solid-state fermentation to obtain bioproducts that have a “chemical twin” with a high environmental impact, and pyrolysis as a predominant thermal treatment due to the production of biochar, probably the most promising biomaterial in today’s research. All these technologies exploit the potential of organic waste for bioenergy production and material utilization, in line with circular principles. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

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