Comparative nutrient analysis of food-waste-based hydroponic fertilizers derived from vermiliquer and individually fermented food items

Developing food-waste-based hydroponic fertilizers (FWBHF) addresses growing urban sprawl and the growing adoption of urban horticulture, improving nutrient cycling and sustainability in our food production systems. This study profiles plant-available nutrients across a range of food products, divided into three main groups (protein-rich, carbohydrate-rich, and fiber-rich) after exposure to anaerobic and aerobic fermentation and vermicompost techniques. Leachates were analyzed for inorganic nutrients and heavy metals to compare with a conventional synthetic hydroponic fertilizer. Key findings identified deficiencies in nitrogen and calcium across all treatments. Nutrient availability in the protein-rich group (beef and chicken) was consistent across both aerobic and anaerobic treatments, with the exception of aerobic fermentation producing a significantly higher level of phosphorus and potassium compared to the control. This was contradicted by the high variation between treatments in the carbohydrate-rich group (pasta and bread), which often produced contradicting nutrient outcomes in the same treatment group, this was attributed to differences in wheat varieties and value-added processes affecting the inorganic nutrient availability in this group. The vermicompost leachate, vermiliquer, contained statistically similar levels of potassium, phosphorus, magnesium, and zinc when compared to the control, but was significantly deficient in nitrogen, calcium, and sulfur. Despite this, it was identified as a potential ‘all-in-one’ solution, being low in heavy metals, elemental toxicity, and odorless when compared to fermentation treatments. These results aim to assist future developments in FWBHF by profiling inorganic nutrient availability across food groups when exposed to vermicomposting and aerobic/anaerobic fermentation techniques.