Global environmental concerns, depletion of fossil energy resources and the recent energy crisis and security, especially due to the Russia-Ukraine war, are among the main reasons for promoting a shift from fossil fuels to sustainable renewable energy. However, today, to support the sustainable market position of renewable energies, it is necessary to encourage the transition from the traditional linear model to the circular one. In this scenario, the use of waste shows a huge potential to enhance this change. While the implementation of circular principles represents an opportunity for companies, this entails several barriers. Therefore, this chapter aims at identifying and analyzing the main barriers and opportunities to circular economy adoption in European and Brazilian agroindustry based on case studies. In detail, the chapter focuses on the Brazilian case of sugarcane ethanol and on an Italian frozen vegetable company because they are strategic sectors, they produce considerable quantities of waste, and both produce renewable energy from waste. The implementation of circular practices in companies could represent a business opportunity and a source of value creation. However, policymakers need to first better understand the complex challenges faced by small and medium enterprises to develop appropriate policies to encourage a sustainable transition.