By Amornrat Rangsiwiwat
Aquaculture is a critical source of food and income worldwide. However, it faces numerous challenges, such as water pollution, nutrient accumulation, and high operational costs. The poor water quality often leads to disease outbreaks, making sustainable farm management increasingly difficult, especially for small-scale farmers. Furthermore, if not properly managed, aquaculture can contribute to environmental degradation, including excessive waste generation and greenhouse gas emissions.
A promising strategy for enhancing sustainability in aquaculture is the use of biochar. Derived from the pyrolysis of plant-based biomass such as rice husks or bamboo, biochar possesses remarkable properties that improve water quality, absorb excess nutrients, and mitigate harmful substances in fishponds. Additionally, biochar can serve as a feed supplement, contributing to improved growth performance, nutrient digestibility, and immune response in aquatic species. Studies have shown that biochar supplementation in fish and shrimp diets can enhance mineral absorption and overall health, leading to more efficient and sustainable aquaculture production (Amjad 2024; Konduri 2024). Furthermore, its use can lower farming costs by reducing dependence on expensive water treatment solutions and chemical additives. Studies suggest that incorporating biochar into aquaculture practices can enhance system efficiency, reduce environmental impact, and improve economic viability for farmers (Santos 2022; Mosa 2023).
This article examines the functions, benefits, and applications of biochar in aquaculture while offering practical recommendations for farmers and industry stakeholders. Additionally, it highlights current research gaps and explores potential future advancements in this field.
About Biochar – It’s not Charcoal
Biochar and charcoal differ significantly in their production processes and intended applications. Biochar is produced through pyrolysis, a thermal decomposition process occurring at temperatures between 300-700°C although some studies report temperatures up to 800°C (Sait 2025) in an oxygen-limited environment. This method yields a highly porous material, making it suitable for soil enhancement, carbon sequestration, and wastewater treatment. In contrast, charcoal is produced via carbonization, which involves heating biomass at medium to high temperatures (400-900°C) in a limited oxygen or oxygen-free environment. This process results in a denser and more durable carbon-rich material, primarily used as fuel or for air filtration purposes (Waluyo 2025). While biochar emphasizes environmental benefits such as soil improvement and carbon storage, charcoal is valued for its energy efficiency and industrial applications.
The versatility of biochar extends to various sectors, such as agriculture, aquaculture, and environmental management, making it beneficial for both small-scale and commercial operations. Its ability to upcycle agricultural residues into a valuable resource promotes sustainability by reducing waste and enhancing resource recovery.
Benefits of Biochar in Aquaculture
Biochar has emerged as a significant tool in aquaculture, contributing to carbon sequestration, nutrient management, and bioremediation.
The stable carbon structure of biochar enables long-term carbon sequestration, mitigating climate change effects. In aquaculture, biochar slows organic matter decomposition, thus increasing carbon retention in aquatic ecosystems. This dual functionality supports environmental sustainability while improving aquaculture system management (Santos 2022; Mosa 2023). Biochar effectively adsorbs excess nutrients such as ammonia, nitrite, nitrate, and phosphate, preventing toxic accumulation and reducing the risk of eutrophication. By stabilizing aquatic environments, biochar fosters healthier conditions for aquaculture species (Chen 2023; Elkhlifi 2023). Research indicates that biochar enhances nutrient utilization by improving nitrogen and phosphorus retention while minimizing nutrient leaching, thereby decreasing dependency on intensive water treatment and promoting sustainable aquaculture practices (Murtaza 2023; Wojewódzki 2023).
The porous structure of biochar provides an excellent habitat for beneficial microbial communities that facilitate bioremediation. These microbes break down pollutants such as antibiotics and heavy metals, maintaining water quality and ecological balance (Qui 2022). Furthermore, biochar can be inoculated with specific beneficial bacteria to enhance pollutant degradation, reinforcing its role in aquaculture sustainability (Soffian 2022).
Applications of Biochar in Aquaculture
Biochar has the potential to be used in aquaculture systems to improve water quality, support aquatic animal health, and minimize environmental impacts. Its various applications are summarized in the table below.
| Source of Biochar | Application | Outcome |
|---|---|---|
| Corn Cob (Amjad 2024) | Incorporated at 2% in tilapia diets to improve growth performance, nutrient digestibility, body composition, and mineral absorption. | Significantly enhanced growth rates, improved hematological parameters, increased mineral absorption (Ca, Na, K, Cu, Fe, P, Zn), and better nutrient utilization. |
| Corn Waste (Pueyo 2022) | Used as a biofilter medium in a Recirculating Aquaculture System (RAS) to improve water quality by removing ammonia, nitrite, and other contaminants, enhancing the efficiency of the biofiltration process. | Significantly reduced ammonia and nitrite levels, improving overall water stability and enhancing the health and survival rate of cultured fish species. |
| General Biochar (Various Sources) (Abakari 2020) | Biochar used as a water quality control agent and an alternative carbon source in biofloc-based tilapia farming. | Reduced nitrogenous waste, stabilized water quality, improved microbial balance, enhanced fish growth, and better feed conversion ratios in tilapia biofloc systems. |
| Sugarcane Bagasse (Jateen 2023) | Applied at 52 g/m2 in shrimp pond sediments to improve water quality. | Increased shrimp survival, enhanced water stability, reduced ammonia and nitrite levels, and reduced reliance on frequent water exchanges in shrimp pond systems. |
| Paddy Straw (Konduri 2024) | Used as a 2% dietary inclusion for white-leg shrimp (Litopenaeus vannamei). | Strengthened shrimp immune response, improved feed conversion efficiency, and promoted shrimp growth performance. Decreased mortality rates and improved resistance to common pathogens in aquaculture systems. |
| Submerged Plant-Wheat Straw Biochar Composite (Li 2024) | Mixed into sediments at a concentration of 1.5% to remove hydrophobic organic contaminants (HOCs) and enhance bacterial degradation in aquaculture pond sediments. | Enhanced pollutant degradation, improved sediment quality, and increased bacterial diversity for sustainable aquaculture pond management. |
| Rice Husk Biochar (Robinson 2018) | Applied in aquaponics and wastewater treatment to adjust carbon-to-nitrogen (C:N) ratios, improve nitrogen cycling, and reduce nutrient accumulation in water systems. | Optimized nitrogen retention, increased beneficial microbial activity, reduced eutrophication risks, and improved plant growth in aquaponics. |
These findings suggest that biochar can be a practical and eco-friendly tool in both fish and shrimp farming, contributing to better water stability, improved survival rates, and sustainable production. However, its success depends on the type of biochar, how it is applied, and specific farm conditions.
Producing Biochar: A Simple Guide
Biochar is produced at 300-700°C through pyrolysis, creating a porous material ideal for soil and water enhancement and carbon sequestration. In contrast, charcoal is made at 400-900°C via carbonization, resulting in a denser material mainly used for fuel and air filtration.
Materials Required
- Agricultural waste and heat source (biomass fuel such as rice husks, coconut shells, bamboo, wood chips)
- Metal drum or kiln (200 L drum recommended)
- Ventilation holes or pipes
- Safety equipment (gloves, masks, eye protection)
- Water for cooling
- Storage containers
Step-by-Step Process
- Prepare Biomass: Select dry agricultural residues, cut them into small pieces (2-4 inches or 5 to 10 cm), and ensure minimal moisture content.
- Setup Kiln: Modify a metal drum by drilling air intake and exhaust holes. Place it on a stable surface. Load kiln with biomass.
- Start Pyrolysis: Ignite the biomass and maintain a steady heat while monitoring the smoke color changes as an indicator of pyrolysis progression. White smoke signifies moisture loss (< 350°C), yellow smoke indicates the initiation of pyrolysis (350-400°C), blue smoke represents the optimal pyrolysis phase (400-500°C), and the presence of little to no smoke suggests that most volatiles have been released (> 500°C), signaling the completion of the process (Saletnik 2022; Aon 2023; Nair 2023).
- Cooling and Collection: Allow natural cooling or quenching with water before collecting and storing biochar.
Limitations
The use of biochar in aquaculture faces several challenges, one of the most significant being performance variability. This issue arises due to differences in feedstock types and pyrolysis conditions, which result in biochar with inconsistent properties and effectiveness in aquaculture systems (Lilli 2023). For example, biochar derived from bamboo may perform differently than biochar made from rice husk, depending on the production method used (Aon 2023).
Economic concerns are another barrier, particularly for smaller-scale operations. Biochar production can be expensive, and its application in aquaculture may seem cost-prohibitive without clear evidence of long-term benefits, such as improved water quality and survival rates (Ynfante 2024).
Environmental factors also play a role in limiting biochar’s effectiveness. Conditions like water temperature, salinity, and stocking density can impact its ability to manage nutrients and absorb contaminants.
Recommendations to Stakeholders
Different stakeholders should take specific actions to enhance biochar’s effectiveness, economic feasibility, and long-term sustainability.
Aquaculture farmers should consider incorporating biochar into their production systems to improve water quality and reduce dependency on chemical treatments. Using biochar derived from locally available biomass, such as rice husks or bamboo, can lower input costs while enhancing nitrogen and phosphorus retention in culture water. Farmers should also monitor key water quality parameters (e.g. ammonia, nitrite, and dissolved oxygen) to assess biochar’s long-term benefits in stabilizing the aquatic environment (Ynfante 2024).
Further research studies should focus on optimizing biochar production from different feedstocks to ensure consistent properties that enhance water quality and microbial balance. Researchers should also investigate biochar’s interactions with environmental variables such as temperature, salinity, and organic matter load in different aquaculture systems (e.g. pond, recirculating, and integrated multitrophic systems). Additionally, controlled trials on biochar-enhanced functional feeds should assess their effects on feed conversion efficiency, immune response, and growth performance in key aquaculture species (Nepal 2023).
Governments can support the adoption of biochar by implementing policies and activities that provide incentives, technical training, and funding for sustainable farm management, as well as by establishing quality standards for biochar production and application.
Companies involved in aquafeed production and water treatment solutions can integrate biochar into their product lines. Developing biochar-based filtration media, probiotic-enriched biochar, and functional feeds with biochar additives can provide eco-friendly alternatives to conventional treatments. Collaborative research with academic institutions and demonstration trials in commercial farms will help validate biochar’s efficacy in disease mitigation, nutrient management, and overall farm performance (Li 2024).
By aligning efforts across these sectors, biochar can serve as an innovative tool for improving water quality, enhancing fish and shrimp health, and promoting sustainable aquaculture practices that support both environmental and economic resilience.
Conclusion
Biochar is a sustainable and practical solution for addressing challenges in aquaculture. It can help stabilize water conditions, support microbial balance, and promote better growth and health of aquatic species. Biochar provides an affordable way to improve sustainability. By using locally available biomass, such as rice husks, bamboo, or agricultural residues, farmers can transform low-value waste into valuable biochar through simple pyrolysis methods. This approach aligns with the concept of upcycling, turning waste materials into a useful product that reduces environmental impacts and enhances resource efficiency. By adopting upcycling and focusing on long-term benefits, small-scale farms can integrate biochar into their practices, creating sustainable systems that benefit both the environment and their operations.
AQUADAPT 