The fermentation stage serves as the "foundation" of the entire chain. If the compost pile becomes oxygen-deprived, aerobic microbial activity ceases, leading to incomplete organic matter decomposition and uneven maturity; consequently, the subsequent crushing and granulation stages must process a batch of "half-raw, half-cooked" material. The double-screw compost turner utilizes two counter-rotating spiral blade rollers to forcibly turn compacted material from the bottom to the surface. This method boosts oxygenation efficiency by over 50% compared to single-screw models, maintaining oxygen levels within the optimal 18%–22% range and shortening the fermentation cycle from the traditional 20–25 days to just 12–15 days. With a turning depth of 1.5 to 3 meters, the uniformity of material decomposition exceeds 95%. The output of this stage—fermented material with consistent decomposition and controllable moisture content—is the starting point for quality across the entire production chain.

The crushing stage is responsible for "particle size standardization." Post-fermentation material typically has a moisture content ranging from 25% to 55%, is highly cohesive, and contains entangled fibers. When traditional screen-equipped crushers encounter such wet materials, the screen mesh becomes clogged, preventing material discharge and causing the motor to idle or even burn out. The solution offered by semi-wet material crushers is to eliminate the bottom screen and adopt a dual-stage rotor structure connected in series; material undergoes coarse crushing by the upper rotor before being propelled into the lower rotor for fine crushing, achieving a particle size suitable for granulation while tolerating moisture content ranging from 25% to 55%. While this step does not alter the material's chemical properties, it determines whether the extrusion granulator's rollers face "uniform fine powder" or "clumps of varying sizes."

In contrast, the dry extrusion process used in fertilizer roller presses places inherently high demands on the stability of the upstream material. It operates on the principle of two counter-rotating, high-strength rollers compressing dry powder into a dense sheet at ambient temperature; inter-particle bonding relies on natural molecular-level attractions—such as van der Waals forces, adsorption, crystal bridges, and mechanical interlocking—without the need for binders or water. This process eliminates the drying stage, reducing overall energy consumption by 30% to 50% compared to wet granulation. However, if the feed moisture content falls outside the 5%–8% range, the wet material slips between the rollers, resulting in uneven sheet thickness; similarly, excessive fluctuations in particle size destabilize the roller nip, causing a sharp decline in particle strength consistency. The core challenge of double-roller press granulation technology lies not in the extrusion action itself, but in the prerequisite of "steadily feeding homogeneous powder into the roller gap."

The new "two-in-one" organic fertilizer granulator addresses this "upstream principle" from a different angle. Traditional modular granulation systems require a series of separate machines—mixers, granulators, and spheronizers—where transferring material between units is not only time-consuming but also leads to heat loss and particle breakage. The two-in-one unit integrates mixing and granulation within a single vessel, allowing raw materials to be processed directly without pre-drying; it maintains a coefficient of variation for mixing uniformity within 5% and achieves a pelletization rate exceeding 90%. The significance of this integrated design lies not merely in reducing the number of machines purchased, but in minimizing the "window of uncontrollability" for materials between process steps—fewer transfer stages mean greater control over the material's state.