Agricultural Waste Valorization in the Circular Economy Using Sunflower Husk Ash as a Secondary Resource

<title>Abstract</title> <p> This study aims to substantiate the feasibility of using ash accumulated at industrial facilities (in Ukraine alone, this is more than 100 thousand tons per year) in agriculture. Ash (a by-product of agricultural production) instead of disposal in landfills and environmental pollution can be used as fertilizer. Such an alternative approach to waste management in the circular economy contributes to the formation of new added value, increased food production and the implementation of environmental initiatives. The research studied the impact of applying fertilizers from sunflower husk ash at a rate of 200 and 300 kg/ha compared to conventional fertilizers and unfertilized control plots. Field studies lasted 3 years. The main performance indicators of the evaluation were: yield, quality indicators of the grown crops and agrochemical indicators of the soil. In the experiments, different methods of application were tested: main application and pre-sowing application. Hordeum vulgare, Zea mays, Helianthus annuus, Solanum tuberosum, Solanum lycopersicum and Cucumis sativus were grown in the studies. The size of the accounting plot for one crop is 0.1 ha. It has been proven that when ash is applied, the yield of agricultural crops increases by an average of 10–18%. The content of mobile phosphorus and exchangeable potassium increases by 10–22%; pH changes by an average of 0.3–0.5. An increase in the content of dry matter (proteins, fats) in the products is observed. The study found that fertilizer from sunflower husk ash contains K ₂ O − 28–35%, P ₂ O ₅ − 3-7%, CaO − 9–14%, MgO − 5–7%, S − 4–6%. Does not contain chlorine. The implementation of this waste management model in the practice of agricultural enterprises will allow solving the issue of processing more than 40 thousand tons of industrial waste per year only within Ukraine. This approach is an alternative to a simple, inexpensive and accessible solution to the complex problem of waste disposal and environmental improvement. </p>