Cost Accounting and Product Costing for Farm Biogas: Evidence from a Dairy Farm in Uzbekistan

Biogas plants on livestock farms turn manure into electricity, heat and digestate, yet farm cost accounting in Uzbekistan has no rules for recording such plants or costing their outputs. This study develops a costing methodology for farm biogas production and tests it on a project model built on the manure of a dairy farm in Samarkand region (18,307 t/yr). Following ISO 14051, physical flows are measured first and costs are then assigned to products. The plant is treated as a separate segment for processing secondary resources; manure and digestate are carried at the same nutrient value, so manure valuation passes through and does not affect energy cost; heat is a by-product credited at the replacement cost of natural gas, only for the metered part used on the farm; the cogeneration unit is depreciated by engine hours. The model yields 977,609 kWh of net electricity a year at 827.9 UZS/kWh, 15.7% below the grid tariff. Allocation by energy content would overstate the cost of heat 3.2 times. Unit cost is most sensitive to investment (±19.6% for ±30%). A real internal rate of return of about 4.5% explains why farms do not invest without grants. Journal entries and disclosures are proposed.