| Raw Material Compatibility | Feedstock type and variability | Confirm whether the plant can process manure, crop residues, food waste, sludge, or mixed organic materials. Record seasonal changes in moisture, fiber content, and particle size. | Adjustable feeding, mixing, crushing, screening, and blending systems with sufficient capacity for variable materials. | Feedstock analysis reports, material acceptance limits, and a documented process-flow assessment. | High |
| Moisture Control | Initial and final moisture | Composting mixtures commonly require approximately 50–60% moisture at the start. Finished products are often dried to about 20–30% moisture, depending on product specifications and local rules. | Moisture sensors, controlled water addition, forced aeration, and a dryer or curing area with adjustable residence time. | Moisture test method, calibration records, and finished-product moisture results from multiple batches. | High |
| Carbon-to-Nitrogen Balance | C:N ratio of the composting mix | An initial C:N ratio near 25:1 to 30:1 generally supports active aerobic composting. Excess nitrogen can increase ammonia loss, while excessive carbon can slow decomposition. | Recipe calculation, multiple feed hoppers, accurate batching, and the ability to add carbon-rich or nitrogen-rich materials. | Laboratory carbon and nitrogen results, mixing formula, and batch-record history. | High |
| Particle Size | Material size before biological processing | Many plant residues benefit from size reduction to improve surface area and aeration. A practical target is often below 20–30 mm before intensive composting, subject to feedstock type. | Adjustable shredder or crusher, replaceable screens, and overload protection for fibrous materials. | Screen-size specification, throughput test, and inspection of oversized-material discharge. | Medium |
| Aerobic Process Control | Oxygen and airflow management | Aerobic composting requires adequate oxygen. Forced-air systems should allow airflow adjustment to prevent anaerobic odors, excessive drying, and uneven decomposition. | Perforated floors or aeration pipes, variable-speed blowers, temperature monitoring, and automatic airflow control. | Airflow layout, blower capacity data, oxygen-monitoring procedure, and operating records. | High |
| Sanitation and Pathogen Reduction | Temperature and exposure time | For pathogen reduction, many composting programs use a thermophilic phase at approximately 55°C or higher for a defined period. The exact time and standard depend on the feedstock and jurisdiction. | Uniform mixing, temperature probes at multiple points, automatic turning or aeration, and complete batch traceability. | Temperature curves, calibration certificates, turning records, and applicable regulatory compliance documents. | Very High |
| Maturity and Stability | Completion of composting | A mature product should show stable temperature after turning, low odor, no obvious heating in storage, and acceptable maturity indicators such as respiration or germination testing. | Dedicated curing area, controlled residence time, screening after curing, and laboratory testing before packaging. | Respiration or maturity test results, germination index data, and curing-batch records. | High |
| Nutrient Consistency | Total nitrogen, phosphate, potassium, and organic matter | Nutrient values should be declared on a dry- or as-received basis consistently. A plant should demonstrate repeatable results rather than relying on a single high-value test. | Uniform blending, controlled dosing, representative sampling, and routine laboratory analysis. | At least three to six consecutive batch reports with stated test basis and sampling procedures. | High |
| Contaminant Control | Heavy metals, plastics, glass, and stones | Limits vary by country and product category. The plant should identify applicable limits for contaminants such as lead, cadmium, mercury, arsenic, chromium, and physical impurities before production begins. | Source inspection, magnetic separation, trommel screening, manual sorting, and a controlled material-rejection procedure. | Incoming-material inspection records, contaminant laboratory reports, and applicable legal-limit checklist. | Very High |
| Odor and Emission Management | Ammonia, hydrogen sulfide, dust, and odor | Odor problems commonly indicate excessive moisture, poor aeration, or an imbalanced feedstock. Dust control is also required during crushing, drying, screening, and packing. | Enclosed processing areas, negative-pressure ventilation, biofilters or scrubbers where required, and dust collectors. | Emission-control design, workplace exposure assessment, odor-control operating procedure, and maintenance logs. | High |
| Drying and Granulation | Product form and thermal exposure | Choose the process according to the target form: screened compost, powder, pellet, or granule. Excessive heat can increase energy use and may affect biological quality. | Adjustable dryer temperature, granulator or pelletizer, binder-dosing system, and controlled cooling after granulation. | Product specification, moisture and strength results, energy-consumption data, and trial-production records. | Medium |
| Screening and Particle Uniformity | Size distribution of finished product | Particle-size requirements depend on application. Uniform screening reduces dust, improves spreading performance, and helps maintain consistent packaging weight. | Multi-stage screening, adjustable mesh sizes, oversize return system, and dust extraction. | Particle-size distribution report and inspection of undersize and oversize fractions. | Medium |
| Quality Control System | Sampling, testing, and batch release | Sampling should represent the entire batch. Test plans should cover moisture, nutrient content, maturity, pathogens, contaminants, pH, and bulk density when relevant. | Dedicated quality-control laboratory or qualified third-party laboratory, written sampling plan, and batch-release approval. | Sampling SOPs, test methods, laboratory qualifications, nonconformance reports, and corrective-action records. | Very High |
| Traceability | Connection between raw materials and finished batches | Each finished batch should be traceable to its incoming materials, processing dates, operators, equipment settings, test results, and packaging records. | Batch numbering, digital or paper production logs, barcode capability, and retained samples. | Example batch record, recall procedure, retained-sample policy, and inventory traceability test. | High |
| Capacity and Scalability | Actual throughput versus rated capacity | Compare capacity using the same basis: wet feedstock, dry feedstock, or finished product. A practical design should account for moisture variation, maintenance, curing time, and seasonal peaks. | Modular equipment, buffer storage, bypass options, and realistic production calculations based on operating hours. | Mass-balance calculation, guaranteed throughput conditions, utility demand, and reference test data without brand or company information. | High |
| Energy and Operating Cost | Electricity, fuel, labor, and maintenance | Drying normally consumes substantially more energy than screening or compost turning. Compare total operating cost per tonne of finished product, not only equipment price. | Heat recovery, variable-frequency drives, insulation, automated controls, and accessible wear-part replacement. | Utility-consumption estimate, maintenance schedule, spare-parts list, and total-cost-of-ownership calculation. | Medium |
| Packaging and Storage | Protection against moisture and caking | Finished fertilizer should be stored in a clean, dry, ventilated area and protected from rain, condensation, and direct contact with the floor. | Accurate weighing and bagging, sealing equipment, pallet handling, warehouse ventilation, and moisture-resistant packaging options. | Packaging-weight checks, storage conditions, shelf-life test, and warehouse inspection checklist. | Medium |
| Regulatory Readiness | Product registration and labeling | Labels should state product type, nutrient content, moisture basis, application instructions, net weight, production lot, and any legally required warnings. | Flexible labeling system, controlled formulation records, document-control procedure, and support for local certification requirements. | Draft product label, compliance matrix, test certificates, safety documentation, and regulatory submission plan. | Very High |
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