A compost pile was created using the windrow method in a plot of land in the municipality of Foz (NW Spain). Fish waste from the Pescados Ruben, S.L Company, which processes several varieties of extracted fish (mackerel,sardine, tuna, squid) into fresh and frozen fish products, were mixed with seaweed found on nearby beaches (primarily Laminaria sp. Cystoseira sp.). To increase the C/N ratio in these materials, pine bark (particle size 10-35 mm) from a local sawmill were added. The various materials were spread in a trapezoidal pile 2 m wide at the base, 1 m high and 6 m long, with a total final volume of 10 m3. To avoid lixiviation and nutrient washout, the pile was set on an impermeable base and sheltered above. The proportion of fish, seaweed and pile bark was 1:1:3.