The research has been carried out in collaboration with ONITEK, a company devoted to technological management and development in energy and environment matters for the agri-food industry, and has had the support of the Department for Economic Development and Competitiveness of the Basque Country. Neiker-Tecnalia specialists have analysed the upgrading as fertilizer of the by-products resulting from the anaerobic digestion process –a process in which biodegradable material decomposes in the absence of oxygen– of the organic waste management plants being promoted by ONITEK. The tests, carried out over the last three years in Arkaute and Larduia (Alava-Spain), indicate that the application of the digestate achieves the same results as conventional mineral fertilizers for maize feed and soft winter wheat. The tests have highlighted that the same yield and grain quality is obtained, so the digestate is emerging as a good alternative for the phosphorus and potassium and to a considerable extent for the nitrogen provided by mineral fertilizers. The Neiker-Tecnalia researchers estimate that the use of the digested matter could lead to potential savings of about 200 euros per hectare compared with the purchase of mineral fertilizers, besides being of considerable benefit to the environment. The digestate comes from the plants that manage organic waste and looks very much like cattle slurry. Its content in terms of nutrients like nitrogen, phosphorus and potassium make it suitable for use on crops. The first of these tests was carried out in 2011 with the application of three doses of digestate (20, 29 and 39 tonnes per hectare) on a maize feed crop with spray irrigation in Arkaute. In the 2011-2012 campaign, a trial using soft winter wheat was set up in Arkaute with the application of 20 and 30 t/ha. Finally, in the 2012-2013 campaign, the research was carried out in Ilarduia, also on soft winter wheat with the application of 30 t/ha of digestate.