Effect of Biochar Particle Size and Chemical Activation on the Bioavailability of Some Heavy Metals in Co-Compost of Municipal Solid Waste

Document Type : Research Paper

Authors

1 Department of Soil Science, Faculty of Agriculture, University of Tabriz, Tabriz, Iran

2 Department of Soil Science, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.

Abstract

Biochar is commonly used to mitigate the adverse effects of the composting process and enhance the quality of final co-compost product. In this research, municipal solid waste (MSW) was mixed thoroughly biochar of particle sizes (B2-4mm, B1-2mm, B0.5-1mm), and activated biochars (H2SO4-AB0.5-1mm and NaOH-AB0.5-1mm) and co-composted. Results demonstrated that chemical activation of biochar, which involved surface degradation, created rougher and more irregular structures. In co-composting, NaOH-AB (5%) showed the longest thermophilic period (7 days), the highest temperature (71.5°C), total nitrogen content (1.37%) and germination index (131%). The highest organic matter content (38%) was recorded in B1-2mm (10%). Among the biochar treatments, special attention should be given to the H2SO4-AB (10%) treatment due to its lowest Zn and Mn concentrations, the B1-2mm (10%) treatment for having the lowest Fe and Pb concentrations, and the NaOH-AB (10%) treatment for exhibiting the lowest Cd concentration in final co-compst (p < 0.05). Based on the permissible limits for heavy metals established by the national standard of Iran, the concentrations of Fe, Zn, Mn, Cu, Pb, and Cd in the composts produced in this study were all below the allowable limits. However, the control exhibited the highest total and DTPA-extractable HM concentrations. Overall, the addition of biochar, especially activated biochar (H2SO4-AB and NaOH-AB) and those with smaller particle sizes (0.5-2 mm), led to a reduction in both total concentration and bioavailability of HMs. In conclusion, the addition of biochar—particularly activated biochar and smaller particle sizes (0.5–2 mm)—to MSW during composting reduces both the total and bioavailable concentrations of HMs. Therefore, further research on co-composting and its implications is of great importance.

Keywords

Main Subjects

EXTENDED ABSTRACT

 

Introduction

Municipal solid waste (MSW) management is a global concern due to the continuous increase in MSW generation driven by industrialization and population growth. Without urgent intervention, MSW production is projected to reach 3.8 billion tons by 2050. The environmental impacts of illegal dumping or improper management of MSW include climate change, biodiversity loss, and contamination of air, water, and soil. Therefore, effective MSW management-aimed at minimizing waste generation, maximizing reuse, recycling, composting, and utilizing environmentally friendly alternative materials-must be rigorously implemented. Composting is of interest in various waste management strategies due to its low operating costs as well as social and environmental benefits. However, compost production and application face challenges such as greenhouse gas emissions (CH4, CO2, and N2O), odor generation, nitrogen loss, and contamination of water and soil resources with heavy metals. To mitigate these negative effects and improve compost quality, the use of additives such as biochar at the initial stage of composting-known as co-composting-has been proposed. This study aims to investigate the effects of biochar particle size and its activation by NaOH and H2SO4 on the mobility of macronutrients and heavy metals in MSW compost with a low initial C/N ratio.

Materials and methods

MSW was collected from the Municipal Waste Management Organization, Tabriz, Iran. The waste biomass for the production of biochar, was prepared by mixing the pruning branches of plum and pomegranate trees. Biochar was produced by slow pyrolysis at 400 °C with a heating rate of 10 °C per minute and a one-hour holding time at the target temperature. The biochar was separated using 0.5-1 mm (B0.5-1 mm), 1-2 mm (B1-2 mm), and 2-4 mm (B2-4 mm) sieves. For biochar activation, the biochar (B0.5-1mm) was activated with solutions of 2M NaOH and/or H2SO4 at a solid-to-solution ratio of 1:2 (w/v) with gentle stirring for 2 hours. In this research, the MSW were mixed thoroughly with different-sized biochars (B0.5-1mm, B1-2mm and B2-4mm) and activated biochars (NaOH-AB and H2SO4-AB) and co-composted for 90 days until compost maturity. The biochar properties were analyzed using various techniques, including CHNS, FTIR and SEM, while the co-compost samples were subjected to some physicochemical analyses. Repeated measures ANOVA was used for the statistical analysis.

Results

The results revealed that the activation of biochar with NaOH and H2SO4 solutions caused the appearance of a mesh structure with irregularly sized cavities and deep pores by modifying the biochar surface structure. The activation of biochar with NaOH and H2SO4 compared to biochar each produced a peak of approximately 1260 to 1270 cm-1 related to the presence of C-O in aryl esters (aromatic structure). On the other hand, H2SO4-AB produced a peak of approximately 1384 cm-1 compared to NaOH-AB and NAB (related to the presence of C-H in CH2 or CH3 (aliphatic structure)). In co-compost, NaOH-AB (5%, w/w) showed the highest temperature (71.5°C), the longest thermophilic period (7 days), total nitrogen content (1.37%) and germination index (130.9%). The highest organic matter content (OM) (37.9%) was recorded in B1-2mm (10%, w/w). Among the biochar treatments, special attention should be given to the H2SO4-AB (10%) treatment due to its lowest Zn and Mn concentrations, the B1-2mm (10%) treatment for having the lowest Fe and Pb concentrations, and the NaOH-AB (10%) treatment for exhibiting the lowest Cd concentration (p < 0.05). In this research, biochar particle size had no significant effect on the temperature of compost in the thermophilic phase (P>0.05).

Conclusion

Based on the permissible limits for heavy metals in the national standard of Iran, the composts produced in this study contained heavy metal concentrations below the allowable limits. However, the control treatment exhibited the highest total and DTPA-extractable heavy metal concentrations. High-quality co-compost was produced through the incorporation of 10% biochar rather than 5% biochar (w/w). The addition of biochar, especially activated biochar (H2SO4-AB and NaOH-AB) and biochar with smaller particle sizes (0.5 to 2 mm), led to a reduction in both the total concentration and bioavailable of heavy metals. Therefore, further research on co-composting and its implications is of great importance.

Author Contributions

Kamal Khalkhal: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data Curation, Writing - Original Draft, Writing - Review and Editing. Adel Reyhanitabar: Conceptualization, Validation, Resources, Supervision, project administration, funding acquisition, Writing - Review and Editing. Shahin Oustan: Supervision, Validation, project administration, Writing - Review and Editing. Nasser Aliasgharzad: Supervision, Validation, Writing - Review and Editing.

Data availability

 Data will be available based on request from the authors.

Acknowledgments

This paper is published as a part of a Ph.D. dissertation supported by the Vice Chancellor for Research and Technology of the University of Tabriz, Iran. We thank Dr. Mohammad Moghaddam Vahed Professor of the Department of Plant Biotechnology and Breeding at University of Tabriz for his help in statistical analysis.

Funding.

This work is based upon research funded by the Iran National Science Foundation (INSF) under project No. 4004390.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Competing interests

The author declares no conflict of interest.

References

Ali, I. (2010). The quest for active carbon adsorbent substitutes: Inexpensive adsorbents for toxic metal ions removal from wastewater. Separation and Purification Reviews, 39(3-4), 95–171. https://doi.org/10.1080/15422119.2010.527802
An, Q., Miao, Y., Zhao, B., Li, Z., & Zhu, S. (2020). An alkali modified biochar for enhancing Mn²⁺ adsorption: Performance and chemical mechanism. Materials Chemistry and Physics, 248, 122895. https://doi.org/10.1016/j.matchemphys.2020.122895
Awasthi, M. K., Wang, M., Chen, H., Wang, Q., Zhao, J., Ren, X., Li, D., Awasthi, S. K., Shen, F., Li, R., & Zhang, Z. (2017a). Heterogeneity of biochar amendment to improve the carbon and nitrogen sequestration through reduce the greenhouse gases emissions during sewage sludge composting. Bioresource Technology, 224, 428–438. https://doi.org/10.1016/j.biortech.2016.11.014
Awasthi, M. K., Wang, Q., Chen, H., Wang, M., Ren, X., Zhao, J., Li, J., Guo, D., Li, D., & Zhang, Z. (2017b). Evaluation of biochar amended biosolids co-composting to improve the nutrient transformation and its correlation as a function for the production of nutrient-rich compost. Bioresource Technology, 237, 156–166. https://doi.org/10.1016/j.biortech.2017.01.044
Banegas, V., Moreno, J. L., Moreno, J. I., García, C., León, G., & Hernández, T. (2007). Composting anaerobic and aerobic sewage sludges using two proportions of sawdust. Waste Management, 27(10), 1317–1327. https://doi.org/10.1016/j.wasman.2006.09.008
Barthod, J., Rumpel, C., & Dignac, M. F. (2018). Composting with additives to improve organic amendments. A review. Agronomy for Sustainable Development, 38(2), 17. https://doi.org/10.1007/s13593-018-0491-9
Behera, S., & Samal, K. (2022). Sustainable approach to manage solid waste through biochar assisted composting. Energy Nexus, 7, 100121. https://doi.org/10.1016/j.nexus.2022.100121
Bremner, J. M. (1996). Nitrogen—Total. In D. L. Sparks (Ed.), Methods of soil analysis. Part 3—Chemical methods (pp. 1085–1121). SSSA Inc.
Chen, B. L., Johnson, E. J., Chefetz, B., Zhu, L. Z., & Xing, B. S. (2005). Sorption of polar and nonpolar aromatic organic contaminants by plant cuticular materials: Role of polarity and accessibility. Environmental Science & Technology, 39(16), 6138–6146. https://doi.org/10.1021/es050622q
Chen, X., Du, Z., Liu, D., Wang, L., Pan, C., Wei, Z., Jia, L., & Zhao, R. (2022). Biochar mitigates the biotoxicity of heavy metals in livestock manure during composting. Biochar, 4(1), 48. https://doi.org/10.1007/s42773-022-00174-x
Chen, Y. X., Huang, X. D., Han, Z. Y., Huang, X., Hu, B., Shi, D. Z., & Wu, W. X. (2010). Effects of bamboo charcoal and bamboo vinegar on nitrogen conservation and heavy metals immobility during pig manure composting. Chemosphere, 78(9), 1177–1181. https://doi.org/10.1016/j.chemosphere.2009.12.029
Chun, Y., Sheng, G., Chiou, C. T., & Xing, B. (2004). Compositions and sorptive properties of crop residue-derived chars. Environmental Science & Technology, 38(17), 4649–4655. https://doi.org/10.1021/es035034w
Dehkhoda, A. M., Ellis, N., & Gyenge, E. (2014). Electrosorption on activated biochar: Effect of thermo-chemical activation treatment on the electric double layer capacitance. Journal of Applied Electrochemistry, 44(1), 141–157. https://doi.org/10.1007/s10800-013-0616-4
Enev, V., Pospíšilová, L., Klučáková, M., Liptaj, T., & Doskočil, L. (2014). Spectral characterization of selected humic substances. Soil and Water Research, 9(1), 9–17. https://doi.org/10.17221/39/2013-SWR
Everitt, B. S. (1995). The analysis of repeated measures: a practical review with examples. Journal of the Royal Statistical Society: Series D (The Statistician), 44(1), 113-135. https://doi.org/10.2307/2348622
Fierro, V., Muñiz, G., Basta, A.H., El-Saied, H., & Celzard, A. (2010). Rice straw as precursor of activated carbons: Activation with ortho-phosphoric acid. Journal of Hazardous Materials, 181(1-3): 27-34. https://doi.org/ 10.1016/j.jhazmat.2010.04.062
He, X., Yin, H., Han, L., Cui, R., Fang, C., & Huang, G. (2019). Effects of biochar size and type on gaseous emissions during pig manure/wheat straw aerobic composting: Insights into multivariate-microscale characterization and microbial mechanism. Bioresource Technology, 271, 375–382. https://doi.org/10.1016/j.biortech.2018.09.104
IBI (International Biochar Initiative). (2015). The Use of Biochar in Composting. URL www.biochar-international.org.
Ingle, P., Bhange, H., Gavit, B., & Purohit, R. (2017). Urban organic solid wastes as farmland manure and fertilizers: A review. International Journal of Current Microbiology and Applied Sciences, 6, 1487–1495.
  Iran National Standard Organization. (2007). Compost - Physical and chemical characteristics (1st ed., Standard No. 10716). Tehran, Iran. (In Persian)
Jiang, J. S., Kang, K., Wang, C. J., Sun, X. J., Dang, S., Wang, N., Wang, Y., Zhang, C. Y., Yan, G. X., & Li, Y. B. (2018). Evaluation of total greenhouse gas emissions during sewage sludge composting by the different dicyandiamide added forms: Mixing, surface broadcasting, and their combination. Waste Management, 81, 94–103. https://doi.org/10.1016/j.wasman.2018.10.003
Jindo, K., Canellas, L. P., Albacete, A., Figueiredo dos Santos, L., Frinhani Rocha, R. L., Carvalho Baia, D., Canellas, N. O. A., Goron, T. L., & Olivares, F. L. (2020). Interaction between humic substances and plant hormones for phosphorous acquisition. Agronomy, 10(5), 640. https://doi.org/10.3390/agronomy10050640
Jones Jr., J. B., & Case, V. W. (1990). Sampling, handling, and analyzing plant tissue samples. In R. L. Westerman (Ed.), Soil testing and plant analysis (pp. 389–427). SSSA Inc.
Kaza, S., Yao, L., Bhada-Tata, P., & Van Woerden, F. (2018). What a waste 2.0: A global snapshot of solid waste management to 2050. World Bank Publications.
Khajavi-Shojaei, S., Moezzi, A., Norouzi Masir, M., & Taghavi, M. (2021). Investigating the effect of various surface and chemical modification approaches on corn residue and common reed derived-biochar traits. Applied Soil Research, 9(2): 73-86. (In Persian).
Kuo, S. (1996). Phosphorus. In D. L. Sparks (Ed.), Methods of soil analysis: Chemical methods. Part 3—Chemical methods (pp. 869–919). SSSA, ASA.
Lee, H. W., Kim, Y. M., Kim, S., Moon, D. H., Kwon, E. E., & Tsang, Y. F. (2018). Review of the use of activated biochar for energy and environmental applications. Carbon Letters, 26(1), 1–10. https://doi.org/10.5714/CL.2018.26.001
Li, D., Manu, M. K., Varjani, S., & Wong, J. W. (2023). Role of tobacco and bamboo biochar on food waste digestate co-composting: Nitrogen conservation, greenhouse gas emissions, and compost quality. Waste Management, 156, 44–54. https://doi.org/10.1016/j.wasman.2022.10.022
Li, R., Wang, Q., Zhang, Z., Zhang, G., Li, Z., Wang, L., & Zheng, J. (2015). Nutrient transformation during aerobic composting of pig manure with biochar prepared at different temperatures. Environmental Technology, 36(7), 815–826. https://doi.org/10.1080/09593330.2014.963692
Li, Y., Shao, J., Wang, X., Deng, Y., Yang, H., & Chen, H. (2014). Characterization of modified biochars derived from bamboo pyrolysis and their utilization for target component (furfural) adsorption. Energy and Fuels, 28(8): 5119-5127. https://doi.org/10.1021/ef500725c
Lin, X., Wang, N., Li, F., Yan, B., Pan, J., Jiang, S., Peng, H., Chen, A., Wu, G., Zhang, J., Zhang, L., Huang, H., Luo, L. (2022). Evaluation of the synergistic effects of biochar and biogas residue on CO2 and CH4 emission, functional genes, and enzyme activity during straw composting. Bioresource Technology, 360: 127608. https://doi.org/10.1016/j.biortech.2022.127608
Lindsay, W. L., & Norvell, W. (1978). Development of a DTPA soil test for zinc, iron, manganese, and copper. Soil science society of America journal, 42(3), 421-428. https://doi.org/10.2136/sssaj1978.03615995004200030009x
Manu, M. K., Wang, C., Li, D., Varjani, S., Xu, Y., Ladumor, N., Lui, M., Zhou, J., & Wong, J. W. (2021). Biodegradation kinetics of ammonium enriched food waste digestate compost with biochar amendment. Bioresource Technology, 341, 125871. https://doi.org/10.1016/j.biortech.2021.125871
Nguyen, M. K., Lin, C., Hoang, H. G., Sanderson, P., Dang, B. T., Bui, X. T., Nguyen, N. S. H., Vo, D. V. N., & Tran, H. T. (2022). Evaluate the role of biochar during the organic waste composting process: A critical review. Chemosphere, 299, 134488. https://doi.org/10.1016/j.chemosphere.2022.134488
Panwar, N. L., & Pawar, A. (2020). Influence of activation conditions on the physicochemical properties of activated biochar: A review. Biomass Conversion and Biorefinery, 12(3), 1–23. https://doi.org/10.1007/s13399-020-00870-3
Prost, K., Borchard, N., Siemens, J., Kautz, T., Séquaris, J.-M., Möller, A., & Amelung, W. (2013). Biochar affected by composting with farmyard manure. Journal of Environmental Quality, 42(1), 164–172. https://doi.org/10.2134/jeq2012.0064
Puziy, A. M., Poddubnaya, O. I., Martínez-Alonso, A., Suárez-García, F., & Tascón, J. M. D. (2002). Characterization of synthetic carbons activated with phosphoric acid. Applied Surface Science, 200(1-4), 196–202. https://doi.org/10.1016/S0169-4332(02)00883-7
Schimmelpfennig, S., & Glaser, B. (2012). One step forward toward characterization: Some important material properties to distinguish biochars. Journal of Environmental Quality, 41(4), 1001–1013. https://doi.org/10.2134/jeq2011.0147
Schmidt, H. P., Bucheli, T., Kammann, C., Glaser, B., Abiven, S., & Leifeld, J. (Eds.). (2020). European biochar certificate—Guidelines for a sustainable production of biochar. European Biochar Foundation (EBC). http://www.european-biochar.org
Schmidt, H. P., Bucheli, T., Kammann, C., Glaser, B., Abiven, S., & Leifeld, J. (2016). European Biochar Certificate—Guidelines for a sustainable production of Biochar. European Biochar Foundation (EBC). https://doi.org/10.13140/RG.2.1.4658.7043
Singh, B., Camps-Arbestain, M., & Lehmann, J. (Eds.). (2017). Biochar: A guide to analytical methods. CSIRO Publishing.
Tabatabai, M.A., 1994. Soil Enzymes, in: Weaver, R.W., Angel, S., Bottomlet, P., Bezdicek, D., Smith, S., Tabatabai, A., Wollum, A. (Eds.), Methods of Soil Analysis, 2nd Ed. SSSA, Inc, Madison Wisconsin, USA, 775–833.
UNEP (United Nations Environment Programme) & International Solid Waste Association. (2024). Global Waste Management Outlook 2024—Beyond an age of waste: Turning rubbish into a resource.
Vithanage, M., Rajapaksha, A. U., Zhang, M., Thiele-Bruhn, S., Lee, S. S., & Ok, Y. S. (2015). Acid-activated biochar increased sulfamethazine retention in soils. Environmental Science and Pollution Research, 22(3), 2175–2186. https://doi.org/10.1007/s11356-014-3435-1
Wang, Y., Hu, Y., Zhao, X., Wang, S., & Xing, G. (2013). Comparisons of biochar properties from wood material and crop residues at different temperatures and residence times. Energy & Fuels, 27(10), 5890–5899. https://doi.org/10.1021/ef400972z
Wang, Z., Xu, Y., Yang, T., Liu, Y., Zheng, T., & Zheng, C. (2023). Effects of biochar carried microbial agent on compost quality, greenhouse gas emission and bacterial community during sheep manure composting. Biochar, 5(1), 3. https://doi.org/10.1007/s42773-022-00202-w
Yang, J., Yu, M., & Chen, W. (2015). Adsorption of hexavalent chromium from aqueous solution by activated carbon prepared from longan seed: Kinetics, equilibrium and thermodynamics. Journal of Industrial and Engineering Chemistry, 21, 414–422. https://doi.org/10.1016/j.jiec.2014.02.054
Ye, S., Zeng, G., Wu, H., Liang, J., Zhang, C., Dai, J., Xiong, W. , Song, B., Wu, S., & Yu, J. (2019). The effects of activated biochar addition on remediation efficiency of co-composting with contaminated wetland soil. Resources, Conservation and Recycling, 140, 278–285. https://doi.org/10.1016/j.resconrec.2018.10.004
Yeganeh, M., Bazargan, K., Shahbazi, K., Hamedi, F., Keshavarz, P., Bybordi, A., Rahmani, H. and Hasheminasab, K. (2025). Monitoring the quality of municipal solid waste compost produced in Iran. Iranian Journal of Soil and Water Research, 56(2),293-307. https://doi.org/10.22059/ijswr.2024.384512.669824. (In Persian).
Zhang, J., Chen, G., Sun, H., Zhou, S., & Zou, G. (2016). Straw biochar hastens organic matter degradation and produces nutrient-rich compost. Bioresource Technology, 200, 876–883. https://doi.org/10.1016/j.biortech.2015.11.002
Zucconi, F., Pera, A., Forte, M., & De Bertoldi, M. (1981). Evaluating toxicity of immature compost. Biocycle, 22(2), 54–57.
Iranian Journal of Soil and Water Research
Volume 56, Issue 7
October 2025
Pages 1967-1986

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