Abstract The valorization of food processing waste is critical for sustainable development and circular economy frameworks. Although Turkish delight waste (D), a high-volume byproduct of the confectionery industry in Turkey, holds significant potential for valorization within the circular economy framework, this potential remains largely unexplored. This study evaluated the valorization potential of Turkish delight waste in anaerobic digester systems by co-digesting it with sunflower heads (S) and tea stalks (T), common agricultural wastes in Turkey, in addition to mono-digestion. Economic evaluations were also conducted on the products obtained at different stages of anaerobic digestion (AD). The highest methane yield of 388 mL CH4/g VS was obtained from Turkish delight waste in mono-digestion, and this substrate enhanced methane production when co-digested with the other substrates. However, co-digestion in the DST digester combining all three substrates yielded 234 mL CH4/g VS, indicating a limited synergistic effect. Metagenomic analyses revealed substrate-dependent variations in microbial community dynamics, particularly in digesters containing only Turkish delight waste. Acidogenic fermentation aimed at increasing VFA yield resulted in total acetic acid productions of 2828, 1707, and 1261 mg/L for D, DS, and DST, respectively. Economic assessments demonstrated that the value derived from VFA production was nearly double that obtained from methane production, even in cases where co-digestion resulted in lower overall yields. Thus, Turkish delight waste emerges as a promising candidate for both mono- and co-digestion in AD systems, offering a potentially more economically viable alternative to methane production through the generation of value-added chemicals such as VFAs. Graphical Abstract
Read full abstract