The increasing demand for food has intensified agricultural practices, leading to environmental degradation and economic loss. Simultaneously, the need for sustainable energy has spurred research into alternatives like potassium-ion (K-ion) batteries, which have emerged as a promising substitute for lithium-ion batteries. This systematic review evaluates the current methods of extracting potassium from biomass, with a focus on its application in K-ion batteries (KIB). Following PRISMA guidelines, a systematic search was conducted across major databases using broad keywords related to biomass-derived potassium extraction and its use in energy storage. Articles were reviewed for relevance, and a subset was selected based on criteria such as extraction techniques (pyrolysis, acid leaching, and alkaline hydrolysis), biomass types, and battery applications. The review highlights the potential of agricultural waste, particularly in developing sustainable energy solutions through KIBs. However, challenges remain, including the need to improve extraction methods and address scalability issues. Further research is required to refine these processes, explore alternative biomass sources, and evaluate long-term battery performance. Linking waste management with K-ion battery technology, this review outlines a pathway toward more sustainable energy solutions benefiting both the environment and economy. Continued research is vital to fully unlock the potential of biomass-derived potassium in renewable energy.