In the heart of Navarre, in northern Spain, stands the E-Cogeneration Cabanillas plant. Here, waste and organic residues (livestock effluents and by-products from the agri-food industry) are given a new life, being transformed into biomethane ready to be injected into the gas distribution network. The plant represents a technological conversion: since 2012 it had been dedicated to the production of electricity and heat from biogas, and in 2025 it was converted to biomethane production. It can process approximately 220 million tonnes of by-products per year and generate 320 Sm³ of biomethane every hour. But the benefits do not stop there: the process also produces 60,000 tonnes of digestate per year, a valuable natural fertilizer distributed on local farmland at the request of farmers, thus closing the sustainability loop.