Options to reuse sludge from striped catfish (Pangasianodon hypophthalmus,Sauvage, 1878) ponds and recirculating systems

This paper compares the quantity and quality of solid waste obtained from traditional ponds and recirculating aquaculture systems (RAS) for striped catfish and evaluates methane and compost production from these wastes. Striped catfish sludge was collected from four commercial ponds along the Mekong river and from three indoor RAS. The amount of sludge dry matter produced per kilogram of fish in ponds was 6 times higher than that in RAS. However, the concentration of nutrients in solid waste from RAS was much higher, with better compost quality and higher methane yield than that of sludge from ponds. Out of the collected 381 L biogas, the methane yield of striped catfish’s solid waste in RAS systems was 201 L per kg chemical oxygen demand (COD). In ponds, the collected 267 L biogas yielded 125 L CH₄ per kg COD. The higher methane production from RAS sludge concurred with higher digestibility of COD: 58% for RAS versus 38% for ponds. The quality and quantity of methane from striped catfish sludge were lower than that for other animal manures, and the resulting electricity yield was low. Considering the higher nutrient concentration in RAS-sludge, we recommend the combination RAS and composting in reusing sludge, which is presently the best option for a more sustainable and cleaner striped catfish production system.