Q: What is carbon-based organic fertilizer? How does it differ from traditional organic fertilizer?

A: Carbon-based organic fertilizer is a type of eco-friendly functional fertilizer made from biochar as a matrix, combined with organic or inorganic components. Its core raw material—biochar—is a carbon-rich solid product produced by the thermal decomposition of organic waste such as straw, livestock manure, and bamboo and wood chips under anaerobic or limited oxygen conditions at 400 to 700℃. The biggest difference between carbon-based organic fertilizer and traditional organic fertilizer lies in the introduction of “char”: biochar has a highly aromatic carbon skeleton structure and a well-developed microporous structure, enabling it not only to provide nutrients but also to perform the dual functions of soil improvement and long-term carbon sequestration. Professor Pan Genxing of Nanjing Agricultural University’s “soil biobridge technology” is the core theoretical support in this field, and its basic logic can be summarized as “using waste to produce char, using char to fertilize the soil, carbon sequestration and emission reduction, healthy and sustainable benefits.”

Q: What specific role does carbon-based organic fertilizer play in soil remediation and carbon sequestration?

A: The value of carbon-based organic fertilizers far exceeds that of traditional fertilizers, demonstrating irreplaceable functions in both soil remediation and carbon sequestration.

In soil remediation, the porous structure of biochar significantly improves soil aggregate structure, increases porosity, and enhances water and fertilizer retention capacity. Simultaneously, the abundant functional groups on the surface of biochar can adsorb and fix heavy metal ions, reducing their bioavailability and demonstrating significant remediation effects on degraded soils suffering from acidification, salinization, and heavy metal pollution.

In carbon sequestration, the highly aromatic carbon skeleton of biochar exhibits strong resistance to microbial decomposition, allowing it to stably sequester organic carbon for hundreds or even thousands of years after application. Unlike direct straw return to the field, biochar can reshape the soil microbial community structure, guiding microorganisms towards a stable carbon pool, producing a “negative stimulating effect”—that is, inhibiting the decomposition and loss of existing soil organic carbon. Studies have shown that biochar can increase soil organic carbon storage by 15% to 40%. Currently, biochar, as a long-term carbon sequestration method, has been incorporated into the EU’s carbon credit rating and trading system. my country has also explicitly proposed a policy direction of incorporating farmland biochar carbon sequestration into the carbon market to promote emission reduction and carbon sequestration in the agricultural sector.

Q: What are the main types of biomass carbonization furnaces, the core equipment for producing carbon-based organic fertilizer?

A: Biomass carbonization furnaces are the core equipment for converting agricultural and forestry waste into biochar. Based on technical characteristics, they can be divided into two main categories: fixed-bed and moving-bed. Fixed-bed furnaces include traditional kilns and pyrolysis carbonization kettles; moving-bed furnaces are further divided into cross-flow and vertical-flow moving-bed furnaces.

In actual industrial production, the more mainstream classification method is based on operating mode, dividing them into intermittent (batch) carbonization furnaces and continuous carbonization furnaces. Traditional earthen kilns and some small kilns are intermittent, requiring shutdown, unloading, and reloading after each batch of material is carbonized, resulting in low production efficiency and high energy consumption. Continuous carbonization furnaces represent the current technological direction for large-scale production—they employ a fully automated anaerobic dry distillation carbonization process, enabling 24-hour uninterrupted feeding and continuous discharge. The equipment typically integrates automatic feeding, segmented dry distillation and carbonization, closed cooling, and flue gas recovery systems, and is suitable for various agricultural and forestry wastes such as straw, rice husks, bamboo shavings, fruit shells, and sawdust.

Q: How do the process parameters of a biomass carbonization furnace affect char quality?

A: Carbonization temperature and residence time are the two most critical process parameters determining biomass char quality. The operating temperature range for biomass carbonization is typically between 350 and 850℃. Taking straw as an example, when the pyrolysis temperature is controlled at 450℃ and the average material residence time is 30 minutes, the biochar yield is approximately 34.6%. When the carbonization temperature is increased to around 500℃ and the production capacity reaches 490 kg/h, the biochar yield can be maintained above 37%. Excessively high temperatures can lead to excessive graphitization of the carbon skeleton and collapse of the pore structure; excessively low temperatures result in insufficient carbonization and insufficient fixed carbon content. Therefore, modern carbonization furnaces generally adopt segmented temperature control systems, allowing operators to adjust the internal temperature in different zones according to the characteristics of different raw materials, ensuring stable quality of the produced biochar.

Q: In what aspects are the environmental protection and energy-saving designs of biomass carbonization furnaces reflected?

A: Modern biomass carbonization furnaces have achieved several breakthroughs in environmental protection and energy-saving design. First, the carbonization process is carried out under oxygen-free or oxygen-limited conditions, with no open flame combustion throughout, relying on oxygen-deficient high-temperature dry distillation to achieve material carbonization. Second, the high-calorific-value biomass gas (pyrolysis gas) generated during carbonization is recovered and introduced into the combustion chamber for complete combustion, providing continuous heat for the carbonization process and achieving a “self-heating cycle,” significantly reducing external energy consumption. Furthermore, the flue gas is discharged after multi-stage purification treatment, and byproducts such as tar and wood vinegar can be further collected and utilized. Some skid-mounted equipment can even transport the entire system to the field, enabling on-site collection, on-site carbonization, and on-site return of straw to the field, solving the problems of straw burning and non-point source pollution at the source

Q: What are the future development trends of carbon-based organic fertilizers?

A: The global biochar fertilizer market is experiencing rapid growth. According to market research data, the global market size was approximately US$4.24 billion in 2025 and is projected to grow to US$6.33 billion by 2034. In the future, carbon-based organic fertilizers will upgrade towards precision customization, carbon sequestration certification, and integration with smart agronomy. Soil-based formulation systems can match the nutritional needs of different crops, achieving precise application with a “one-site-one-formula” approach. In the long run, carbon-based organic fertilizers are evolving from simple soil conditioners into core green inputs connecting climate-smart agriculture, circular biomass economy, and sustainable land use. Driven by my country’s “dual carbon” goals, carbon-based organic fertilizers are not only a fertilizer technology innovation but also a strategic path connecting agricultural carbon sequestration and emission reduction with soil health restoration.