Self-Sustaining Double-Stage Circularity Through Utilization of Sunflower Agriculture's Waste in Bio-Fertilizers: Commissioning of a Full-Scale Facility  
[PERSON]  
1 Technical College of Sofia, Technical University of Sofia, 1000 Sofia, Bulgaria; [EMAIL_ADDRESS] (V.  
households. The need to achieve a circular economy is not only driven by environmental considerations--fast-increasing industrialization is also leading to a gradual depletion of natural resources [4; 5]. Considering the waste materials as by-products and their further utilization will allow environmental benefits to be achieved and will increase the availability of natural resources. Unlike agriculture, which generates mostly biodegradable residues, the wastes from different industries are generally hazardous. Therefore, efforts to process and utilize wastes in many countries have focused mainly on industrial types, while the circular management of agriculture has not been considered [6]. Some of the widely used approaches to reduce environmental damage from different types of waste include waste-to-energy and improving composting, storage and, processing methods [7]. Combined with the introduction of stricter waste management policies, these approaches can lead to positive outcomes, but a key element involves increasing the self-awareness of producers and consumers regarding the need for sustainability. An additional mechanism to incentivise the reprocessing of waste and its transformation into valuable resources could be the creation of economic benefits [8]. The implementation of the conversion of agricultural by-products and/or waste products, such as crop residues, animal waste, etc., into valuable resources will not only lead to a significant reduction in the amount of final waste going to landfill, but may also lead to the reintroduction into the production cycle of organic and inorganic products, such as fertilizers, improvers, dyes, etc. [9; 10]. Nowadays, in traditional agriculture, synthetic compounds are used in place of these materials, which is associated with significant pollution [11]. Organic fertilizers, on the other hand, have been proven to be a sustainable alternative that preserves soil integrity, enriches it with essential nutrients, and, at the same time, significantly improves plant productivity and sustainability [12; 13; 14]. The implementation of this approach to utilizing agricultural waste through the production of bio-fertilizers will represent significant progress not only in terms of achieving the goals of the circular economy, but also in terms of meeting the needs of modern society for organic agriculture [15; 16; 17]. A significant part of the materials suitable for these purposes are currently landfilled or incinerated, but the realization of their full utilization and the implementation of a transition from a linear to a circular model of the economy will unlock the full potential of agricultural waste [18; 19]. Regulatory restrictions on the use of synthetic fertilizers, due to the environmental risks, together with the growing interest in organic farming, are leading to an increase in the demand for organic fertilizers [20]. This leads to new challenges, including the ability to secure the necessary quantities of bio-fertilizers and to ensure their environmentally friendly production. One suitable measure has already implemented through the regulation of the European Commission, targeting a 30% reduction in the non-renewable resources used in fertilizer production by 2030 [21]. The next steps should be aimed at securing sufficient quantities of raw materials suitable for the production of bio-fertilizers. One of the researched approaches is the potential of sunflower husks as a raw material for bio-fertilization production. Sunflower, as one of the most widely grown crops, plays a crucial role in the agricultural economy of many countries in Europe and the region, and the production of vegetable oil and biodiesel from sunflower seeds are key industries.