Objectives

2

A mountainous areas-adapted model for the full-scale utilization of manure resource was established to solve the problems of the disconnection between planting and farming in the mountainous areas of western Yunnan Province due to the fragmentation of land and the high costs of transportation to provide technical references for the cycling of planting and farming in large-scale pig farms in mountainous areas.

Methods

2

180 valid records of monitoring and 120 samples of manure were obtained from continuously monitoring a large-scale pig farm with 6 000 sows in Shidian County

Yunnan Province from December 2025 to April 2026. The integrated process of "solid-liquid separation-up-flow anaerobic sludge blanket (UASB) anaerobic digestion - secondary anoxic/oxic (A/O) biochemical treatment - high-temperature biodegradation"

the mountain-adapted model of "fixed pipeline + tanker combined transport + terrain coefficient correction"

and the "enterprise + cooperative + farmer" benefit-linked mechanism was systematically analyzed.

Results

2

The average chemical oxygen demand (COD) of the influent and effluent was18 200 mg/L and 182 mg/L

achieving a removal rate of 99.0% with a standard deviation (SD) of 1.2% and the index of tail water treated meeting the standard

GB 5084－2021 (Farmland Irrigation Water Quality Standard). The reduction rate of solid waste reached 63%. The substitution of chemical fertilizers with biogas slurry achieved a 42% reduction in fertilizer usage

equivalent to a savings of 750 yuan/hm² in the costs of planting. The average daily production of biogas was 1

185 m³

and replacing coal with biogas reduced carbon dioxide (CO₂) emissions by 562 t annually. The results of sensitivity analysis showed that the internal rate of return (IRR) of the project maintained at 6.2%

higher than the industry benchmark rate of return against the backdrop of a carbon price of 50 yuan/t

a 20% decrease in the price of organic fertilizer

and a 15% increase in electricity bills. Compared with the traditional models

the processing time for a single batch of manure was reduced by 43.3%

the cost of treatment was reduced by 45.7%

and the removal rate of COD increased by 21%(

P

＜0.05).

Conclusions

2

The model established has preliminarily achieved the dual pathway of "energy-based carbon reduction + resource-based return to the field". Its technical characteristics are consistent with the requirements of the Methodology for Greenhouse Gas Voluntary Emission Reduction Projects - Biogas Recovery and Utilization Project for Manure from Large-scale Pig Farms (CCER-15-001-V01). The project can still operate at break even when the load of processing is reduced to 62% of the capacity designed according to the break-even analysis

indicating that the resistance to risk is strong. It is recommended to prioritize the promotion of the model established in large-scale pig farms in mountainous areas with a relatively large sow inventory

sufficient land for nutrient assimilation

and a cooperative organizational foundation.