Anaerobic co-digestion of bovine manure and residual sludge from tilapia fish (Oreochromis niloticus) breeding ponds

Abstract

Tilapia production was 4.2 million tons in 2016, and almost half of the production came from aquaculture. At the same time, organic waste from breeding increases as the demand for tilapia production. An alternative to using such waste is the production of energy and organic fertilizers. The use of a co-substrate can help to achieve the moisture content necessary to feed the digester. The aim of this study was to determine the effect of the anaerobic co-digestion of bovine manure with residual sludge from tilapia fish breeding ponds in the production of sludge. Methane and CO₂ production, chemical oxygen demand (COD), total solids (TS), total fixed solids (TFS), total volatile solids (TVS), volatile fatty acids (VFA), total nitrogen (TN), total phosphorus (TP) content, and microbiological parameters (fecal coliforms and salmonella) during composting were determined. The organic fertilizer obtained was evaluated by a germination and seedling growth assay. The results of this study showed that the mixture of bovine manure and residual sludge from tilapia fish breeding ponds (1:1) produced high methane and low CO₂ in the composting process compared to the when these raw materials were composted individually. Alfalfa germination and seedling growth were significantly boosted by the application of sludge from the mixture of bovine manure with residual sludge from tilapia fish breeding ponds.