Lignin is one of the three fractions of lignocellulosic biomass, with a heterogeneous structure that is not fully resolved. However, this macromolecule can contribute as a precursor to several renewable products, for instance, carriers for agrochemical molecules for sustainable agriculture. This chapter evaluates the photodegradation, or photolysis in aqueous media, of a previously developed supramolecular nanoformulation composed of a carrier obtained from acetylated kraft lignin (AKL) and the fungicide prothioconazole (PTZ) as the active ingredient (AI). The PTZ-AKL nanoformulation was subjected to photodegradation studies according to an internationally recognized method, using high-performance liquid chromatography (HPLC) as the primary analytical technique. The results demonstrated rapid degradation kinetics of the AI, resulting in a short half-life (t1/2), and indicated that the AKL did not exhibit a protective effect on the incorporated AI when the nanoformulation was exposed to solar radiation. Thus, it could be inferred that the studied nanoformulation poses a lower risk to the environment.