A new catalytic hydrothermal synthesis process for humic acid organic fertilizer is opening up a completely new technological path for the resource utilization of organic solid waste. The core achievement of this process is that, under reaction conditions of 250℃ and 2 hours, using sheep manure as raw material and KOH as an alkaline additive (sheep manure to KOH mass ratio 20:3), a humic acid yield of 23.88% is achieved. This yield marks a technological leap in organic fertilizer production from “slow biological fermentation” to “fast chemical catalytic conversion.”

Why is 23.88% a key breakthrough?

Traditional composting has a long humification cycle of 30–60 days, and the humic acid content is greatly affected by raw materials, climate, and turning operations, resulting in poor batch stability. Catalytic hydrothermal synthesis reduces the composting time from several weeks to 2 hours. A yield of 23.88% means that each ton of sheep manure (dry basis) can be directionally converted into approximately 239 kg of humic acid, far exceeding the enrichment efficiency of humic acid in natural composting. Notably, the addition of FeOOH catalyst further enriches the functional groups of humic acid, resulting in a product with excellent growth-promoting properties—pea germination rate reaches 93%, and stem and leaf dry weight doubles compared to the control.

Key Process Conditions for Catalytic Hydrothermal Synthesis The three-step process is clear and replicable: First, raw material pretreatment: sheep manure is crushed and mixed with KOH solution in a specific ratio to adjust the alkaline environment. Second, catalytic hydrothermal reaction: the temperature is raised to 250℃ in a closed reactor and maintained for 2 hours. During this time, KOH promotes the hydrolysis of lignin and hemicellulose, and FeOOH catalyzes the polymerization of humification precursors into humic acid. Third, product separation and stabilization: after cooling, solid-liquid separation occurs, and the solid phase is the humic acid-enriched organic fertilizer product. Compared to traditional fermentation, this process significantly reduces dependence on raw material moisture content, ambient temperature, and turning operations. Process parameters are entirely controlled by temperature and pressure, resulting in significantly improved batch consistency.

New Requirements for Organic Fertilizer Production Equipment The industrialization of this new process places different demands on organic fertilizer production equipment compared to traditional fermentation lines. The core equipment is no longer the turning machine and fermentation tank, but rather the high-pressure hydrothermal reactor and its supporting feeding, heat exchange, and pressure control systems. For existing plants based on the poultry manure fertilizer production process, the front-end fermentation section can be replaced with a hydrothermal reaction unit while retaining the back-end granulation, drying, and screening equipment, forming a hybrid production line of “hydrothermal humification + granulation.” In the chicken manure organic fertilizer production process, the hydrothermal carbonization liquid phase has been proven to promote humic acid formation during composting; adding 10% hydrothermal liquid phase can increase the humic acid content of compost by 27%, providing a new synergistic pathway for chicken manure resource utilization.

Application Value and Prospects Life cycle assessments show that the environmental damage caused by this humic acid organic fertilizer is significantly lower than that of traditional inorganic fertilizers. After being applied to the soil as a fertilizer synergist and soil conditioner, the stability of humic acid allows it to also act as a soil carbon pool, possessing the unique advantage of “synergistic pollution reduction and carbon reduction.” For small and medium-sized organic fertilizer enterprises seeking differentiated products, introducing a catalytic hydrothermal synthesis unit signifies an upgrade from “ordinary organic fertilizer” to “high humic acid functional fertilizer.” Reserving a hydrothermal reaction zone in the organic fertilizer plant design and layout is a forward-looking decision worth considering.