The first step takes place in the fermentation tank, where the task is to provide a continuous supply of oxygen to aerobic microorganisms. If the compost pile remains static, oxygen can only penetrate the surface layer; the interior gradually enters an anaerobic state, producing hydrogen sulfide and ammonia. Consequently, the pile temperature fails to rise sufficiently, leaving insect eggs and pathogens alive. The double-screw compost turner utilizes two parallel, counter-rotating screw shafts operating at differential speeds. It offers a turning depth of 1.6 to 2.2 meters and an effective turning span of 6 to 11 meters. During the turning process, the double-screw structure entrains large amounts of air into the material, creating dense, breathable channels. This boosts oxygenation efficiency by over 50% compared to single-screw designs, maintaining oxygen concentration within the optimal 18%–22% range inside the tank. Following this turning process, moisture content variations across the decomposed material are minimized, and fibers soften under the action of microbial enzymes, yielding a stable feedstock for subsequent crushing and granulation.

The second step takes place in the crusher, where the task is to eliminate "coarse particle obstacles" within the material. Decomposed organic materials typically have a moisture content of 25% to 50%, are highly viscous, and contain fibrous tangles; traditional crushers rely on screens to control particle size, but wet material quickly clogs the screen openings. The solution offered by the "half-wet material crusher" is to eliminate the bottom screen and utilize a dual-stage rotor configuration in series: material is first coarsely broken and loosened by the upper rotor, then immediately thrown into the lower rotor for fine crushing, achieving an output particle size suitable for granulation. This step is crucial for providing "qualified intermediate material" with uniform particle size for the subsequent extrusion granulation process; without it, the extrusion rollers would face clumps of varying sizes, significantly compromising compression efficiency.

The third stage takes place in the fertilizer roller press machine, where the task is to impart a permanent physical form to the powder through pressure. Two counter-rotating, high-strength rollers compress the dry powder into dense flakes at ambient temperature, which are subsequently crushed and screened into granules. The entire process requires no added water and involves no temperature increase, with the raw material's moisture content needing to be controlled only within the 5% to 8% range. Extrusion reduces the distance between particles to the point where intermolecular forces come into play; van der Waals forces, adsorption, and crystal bridge connections instantly "bond" the particles, transforming loose powder into a high-density, high-strength physical form. The rapid adoption of roller press granulator production lines in recent years is due to the fact that this double-roller extrusion granulation technology eliminates the drying and cooling systems required for wet granulation. Overall energy consumption is 30% to 50% lower than wet processes, and an installed power of just 7.5 to 45 kilowatts is sufficient to achieve an output capacity of 1 to 15 tons per hour.

These three stages form a complete conversion chain transforming "waste" into "commercial-grade granules." The windrow turner manages "oxygen," converting the anaerobic pile into an active mass undergoing aerobic fermentation; the crusher handles "fineness," turning the wet, sticky, decomposed material into fine powder with controllable particle size; and the extruder manages "shaping," transforming the loose powder into commercial granules that meet density and strength standards. Each piece of equipment addresses only a single physical contradiction; yet, if any link is missing, the material cannot undergo the complete transformation from raw input to finished product. The essence of selecting fertilizer production equipment lies not in comparing the specifications of individual machines, but in understanding the chain of cause and effect connecting these three stages: the quality of the output from one stage directly determines the processing limits of the next.