Organic Matter Composition and Phosphorus Speciation of Solid Waste from an African Catfish Recirculating Aquaculture System

Abstract

Recycling of phosphorus (P) from feed input in aquaculture systems gains increasing importance, especially relating to sustainable agriculture and food production. In order to find possible areas of application of African catfish solid waste, the purpose of this study was to characterize the elemental and organic matter composition and P speciation in the aquaculture fish waste. Pyrolysis-field ionization mass spectrometry (Py-FIMS) was used to investigate the composition of organic matter and P K-edge X-ray absorption near edge structure (XANES) spectroscopy to describe the occurring P-containing compounds in African catfish solid waste from an intensive recirculation aquaculture system (RAS). The solid fish waste was mainly composed of sterols, free fatty acids and alkylaromatics, as it is common for digestive systems of animals. Ingredients such as the phytosterol beta-sitosterin confirm plant-based feed ingredients and some recalcitrance against digestion in the African catfish gut. The P in the solid fish waste was exclusively bound as calcium-phosphates. These calcium-phosphate minerals as major constituents of African catfish waste may have beneficial effects when applied to soils, suggesting the use of this waste as possible soil amendment in the future.

Enhancing energy recovery from aquaculture residual materials: a focus on anaerobic digestion of African catfish (Clarias gariepinus) sediment sludge

“…The determined C/N ratio of the African catfish sludge was consistent with values from previous research (C/N 7.4-7.9: 1 and 8-9: 1 in Prüter et al, 2020 andStrauch et al, 2018) however, its range was wider than the very narrow C/N ratio of sludge from salmon aquaculture reported by Brod et al, 2017 (C/N 2.8: 1;Brod et al, 2017). This also results from the enormous and rapidly changing stocking densities in African catfish RAS (Palm et al, 2018), changing the formation of solid sludge.…”

Bacterial community in African catfish (Clarias gariepinus) recirculating aquaculture systems under different stocking densities

“…The FishGlassHouse at Rostock University allows experimental studies of commercial African catfish cultivation under different stocking densities. Its RAS has been studied for nutrient dynamics, element and energy pathways (Palm et al, 2018), and organic matter composition and phosphorus speciation of solid waste (Prüter et al, 2020). The present study aims to describe the microorganisms' community composition during a C. gariepinus rearing trial, testing three different stocking densities (extensive, semi-intensive and intensive), by sequencing the 16S rRNA genes amplified from water samples.…”

The Effects of Dissolved Organic Matter Derived from Agricultural Waste Materials on Phosphorus Sorption in Sandy Soils

“…Crop residues, animal manures, composts, and other organic materials are frequently used to improve soil quality and enhance soil organic matter levels. An additional benefit to the agricultural ecosystems of these soil amendments may be an increase in the bioavailability of soil P. However, the impacts of these types of exogenic organic matter still need extensive studies [14,15].…”