Ideally, Aquaponics is a sustainable food production system that integrates plants and fish by cycling nutrients from fish effluent to plants. In practice, aquaponic systems are not entirely sustainable because solid fish waste, collected in filters, is typically discarded despite still containing a considerable level of nutrients. More recently, commercial aquaponic growers have begun to aerobically digest or mineralize their solid waste, which helps to emancipate the nutrients in this untapped resource, thus providing increased levels of nutrients that can better meet the plants’ needs. This study evaluates cost-effective carbon amendments to promote mineralization of aquaponic sludge and create a more enriched nutrient fertilizer for hydroponic crops.
Fish waste from a decoupled aquaponic system at the University of Arizona’s Controlled Environment Agriculture Center was used as the base material. Pre-trial analysis indicated a low carbon-to-nitrogen ratio, suggesting additional carbon would be required for efficient mineralization. Two pure carbon sources, glycerin and methanol, were chosen for their simplicity and low cost. Additionally, hemp leaf litter, which naturally defoliated, was tested at two concentrations (3 g and 6 g per treatment) to assess its potential as a sustainable amendment. Each trial lasted 30 days and included control treatments for comparison.
Results are preliminary but suggest that carbon additions affect nutrient levels. Leaf litter treatments appear to be the most promising for promoting mineralization and developing sustainable fertilizer. This work highlights a practical strategy for enhancing nutrient recovery from solid fish waste in aquaponic systems, with potential benefits for plant growth efficiency and environmental sustainability.