The treatment of cattle manure in cattle farms must balance environmental protection, resource utilization, and economic benefits. The following scientific methods enable efficient processing and circular utilization:

I. Physical Treatment: Basic Reduction and Pretreatment

1. Solid-Liquid Separation
   • Equipment: Use screw extruders, centrifuges, or vibrating screens to separate cattle manure into solid (30%-40% solids content) and liquid (5%-10% solids content) fractions.
   • Purpose: Reduce the difficulty of subsequent treatment. The solid fraction is suitable for composting or fuel production, while the liquid fraction can be further purified or used for irrigation.
2. Drying Treatment
   • Natural Sun-Drying: Suitable for small-scale farms, with low cost but a long cycle (10-15 days).
   • Mechanical Drying: Rapidly dehydrate manure using rotary dryers or hot air furnaces, reducing moisture content to below 15% for easier storage and transportation.

II. Biological Treatment: Core of Resource Utilization

1. Composting (Aerobic Fermentation)
   • Process: Mix solid manure with straw, sawdust, or other bulking agents to adjust the carbon-to-nitrogen ratio (25-30:1) and moisture content (50%-60%). Promote microbial decomposition through turning or forced aeration.
   • Products: Organic fertilizer (NPK content ≥5%) for improving soil structure in farmland.
   • Advantages: Low cost, complete harmless treatment, and compliance with organic farming standards.
2. Anaerobic Digestion (Biogas Engineering)
   • Process: Feed liquid or whole manure into a biogas digester for fermentation at 35-55°C (mesophilic conditions), producing biogas (methane content 50%-70%) and digestate.
   • Products:
     • Biogas: Used for power generation, heating, or cooking (0.3-0.5 m³ of gas per m³ of manure).
     • Digestate: Can be dewatered and used as organic fertilizer or substrate material.
   • Advantages: High energy recovery and reduced greenhouse gas emissions.
3. Vermicomposting (Biological Transformation)
   • Process: Mix manure with humus and introduce earthworm species like Eisenia fetida for organic matter decomposition.
   • Products:
     • Earthworms: Used as protein feed or medicinal resources.
     • Vermicompost: High-quality organic fertilizer rich in humic acids and beneficial microorganisms.
   • Advantages: Achieves a closed-loop "waste-to-resource" system with high added value.

III. Energy Utilization: Clean Alternative Solutions

1. Biomass Fuel Production
   • Pelletizing/Briquetting: Compress dried manure into pellets or briquettes with a calorific value of 12-18 MJ/kg, replacing coal in boilers or drying equipment.
   • Gasification: Convert manure into combustible gas (CO + H₂) via high-temperature gasifiers for power generation or heating.
2. Direct Combustion (Use with Caution)
   • Conditions: Only applicable to dry manure with moisture content below 20%, requiring dust removal equipment to reduce particulate emissions.
   • Limitations: Low thermal efficiency (~30%) and potential dioxin emissions, necessitating strict environmental approvals.

IV. Ecological Utilization: Returning to Natural Cycles

1. Insect Farming
   • Black Soldier Fly (BSF): Larvae efficiently decompose manure into high-protein feed (40%-50% crude protein).
   • Housefly Larvae: Cultivate larvae for aquaculture or poultry feed.
2. Edible Mushroom Cultivation
   • Process: Mix manure with cottonseed hulls or corn cobs as substrate for cultivating mushrooms like Pleurotus or Lentinula.
   • Advantages: High substrate utilization rate; spent mushroom substrate can be further composted.

V. Recommended Integrated Treatment Models

1. "Biogas + Composting" Model
   • Liquid manure → Biogas plant → Biogas for power/heat; digestate → Composting → Organic fertilizer.
   • Solid manure → Direct composting or blending with digestate for land application.
2. "Drying + Fuel" Model
   • Manure → Drying → Pelletizing → Biomass fuel to replace fossil energy.
3. "Vermicomposting + Mushroom" Model
   • Manure → Earthworm farming → Vermicompost → Mushroom cultivation → Spent substrate returned to fields.

VI. Balancing Environmental and Economic Considerations

1. Regulatory Compliance: Ensure treatment facilities meet standards in regulations like China’s Livestock and Poultry Breeding Pollution Prevention and Control Regulations to avoid fines.
2. Cost Optimization: Select methods based on farm scale (e.g., composting for small farms, biogas for large farms).
3. Market Integration: Partner with organic farms, biomass power plants, or feed enterprises to expand product sales channels.
4. Technology Upgrades: Adopt smart equipment (e.g., automatic compost turners, biogas monitoring systems) to improve efficiency.

By combining these methods scientifically, cattle farms can transform manure into clean energy, organic fertilizers, or high-value products, achieving a win-win for environmental and economic sustainability.