Title of the Book Chapter: Potential Health Risks Associated with Biochar—From Production to Field Application
Authors: Shamim Mia, Sara Yeasmin Bristy, Keiji Jindo, Md. Nayem Hasan Munna, Mohammad Mahmudur Rahman, Kamal Uddin, Susilawati Binte Kasim, and M. Safiur Rahman
Chapter Summary
Introduction
The chapter titled Potential Health Risks Associated with Biochar—From Production to Field Application offers an extensive review of biochar’s journey from its production to its use in agricultural fields, with a particular emphasis on potential health risks. Biochar is an aromatic carbon-rich material produced through pyrolysis—a process in which biomass is heated under oxygen-deficient conditions at temperatures ranging from 350 to 750 °C. Due to its utility in soil improvement, waste management, bioenergy production, and environmental remediation, biochar has gained significant research attention over the past decades.
However, despite the large volume of literature on the environmental and agronomic benefits of biochar, fewer studies focus on its potential negative impacts. This chapter provides a thorough analysis of the health risks associated with biochar production, modification, and application, with an emphasis on human health concerns.
Health Risks Associated with Biochar Production to Application
The potential health risks of biochar are categorized into three different pathways:
- Health Risks During Biomass Collection and Handling: Exposure to pathogens, heavy metals, and toxic gases during biomass collection can lead to health issues.
- Health Risks from Heat and Toxic Gases During Production: The pyrolysis process involves heating biomass at high temperatures, which produces toxic gases and heat, posing safety risks to workers.
- Health Risks from Dust and Small Molecular Particulate Matter During Application: Exposure to dust and particulate matter from biochar can be hazardous during its field application.
The chapter emphasizes the importance of safety measures during all stages of biochar production and application to minimize these health risks.
Biochar and Its Potential Hazardous Chemicals
Biochar’s production process results in the generation of several intermediate organic substances that are often trapped within the structure of the biochar. The final product contains three major components: fixed carbon, volatile carbon, and ash, with the exact composition depending on the feedstock and production conditions.
Biochar often contains a variety of potentially toxic chemicals such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated aromatic carbon (PCAC), and heavy metals. These substances may either be retained as part of the volatile organic matter or embedded within the biochar’s structure. The risk these chemicals pose to human health depends on the concentration, feedstock used, and production temperature.
Health Risks of Biochar-Originated Chemicals
- Potentially Toxic Elements (PTEs): Elements like cadmium, copper, nickel, chromium, zinc, lead, and arsenic may be concentrated during the pyrolysis process. While their initial concentration may be below permissible limits, environmental conditions can change their availability, posing chronic and acute health risks.
- Volatile Organic Carbons (VOCs): A range of intermediate products, such as methanol, formic acid, and cresols, can be produced during pyrolysis. High concentrations of VOCs can be hazardous to health, crossing occupational exposure limits in some cases.
- Polycyclic Aromatic Hydrocarbons (PAHs): PAHs are persistent contaminants known for their carcinogenic, teratogenic, and mutagenic toxicities. Their concentration in biochar depends on production temperature and feedstock, and their presence is a significant concern for human health, especially during soil application.
Strategies for Reducing PTEs, VOCs, and PAHs Concentrations in Biochar
To reduce the concentrations of PTEs, VOCs, and PAHs, certain strategies can be adopted:
- Adjusting pyrolysis conditions (e.g., temperature, duration).
- Selecting appropriate feedstock that has low levels of contaminants.
- Using post-production treatments, such as washing, composting, or biological treatments, to mitigate contaminant concentrations.
- Modifying the production process, such as using a slower pyrolysis process or increasing carrier gas rates, to minimize the presence of hazardous chemicals.
Health Risks During Biochar Application
During biochar application, exposure to potentially harmful substances can occur through various pathways:
- Dust Particle Inhalation: Biochar particles are small and often classified as dust, posing respiratory risks during handling and application. These risks can be mitigated by using biochar in pellet form or applying it with moisture.
- Human Exposure Through the Food Chain: Biochar containing contaminants such as PAHs and PTEs may enter the food chain, potentially affecting plant tissues and human health when biochar is applied to soil. Proper selection and pretreatment of biochar are essential to minimize these risks.
Health Risks During Biochar Production
- Heat: The process of producing biochar involves heating organic matter under high pressure and temperature. Heat stress can cause fatigue, impair worker performance, and increase the risk of heat-related health hazards.
- Smoke: The pyrolysis of biomass releases gases and particulates that can be harmful if inhaled, including VOCs, PAHs, and PTEs. Proper ventilation and personal protective measures are recommended to reduce exposure.
Management Strategies for Health Risks During Biochar Production
To address these health risks, it is crucial to implement safety measures during production:
- Workers should wear protective masks and appropriate personal protective equipment (PPE).
- Production facilities must be well-ventilated.
- Toxic gases and particulates should be filtered before release into the environment.
Future Research Directions
The chapter concludes by emphasizing the need for more comprehensive research on the health risks associated with biochar. Although there is a large body of research on the positive environmental impacts of biochar, few studies focus on the health risks involved in its production and application. Areas for future research include:
- Generation and fate of volatile organic compounds and particulate organic matter.
- Pathogen exposure and health risks related to heat and smoke during biochar production.
- Management strategies to reduce these risks.
The chapter calls for more attention to be paid to biochar’s health implications, particularly as biochar use becomes more widespread for agricultural and environmental remediation purposes.
Conclusion
This chapter provides an essential perspective on the health risks linked to biochar, covering its production, handling, and field application. While biochar holds significant promise for improving soil health, managing waste, and aiding climate mitigation efforts, its potential health risks should not be overlooked. The chapter highlights the need for further research into these risks, appropriate safety measures during production and application, and the development of safe standards for biochar use to mitigate its negative impacts.