Waste paper and macroalgae co-digestion effect on methane production

Highlights: • Pelvetia canaliculata was used as a feedstock for anaerobic co-digestion with waste paper. • Methane yield during co-digestion was 30% higher compared with mono-digestion. • Maximum biodegradability index of 0.87 achieved at C/N ratio of 26. • Synergistic effect was present for waste paper and macroalgae co-digestion. The present study investigates the effect on methane production from waste paper when co-digested with macroalgal biomass. Both feedstocks were previously mechanically pretreated to reduce their particle size. The study was planned according two factors: the feedstock to inoculum (F/I) ratio and the waste paper to macroalgae (WP/MA) ratio. The F/I ratios checked were 0.2, 0.3 and 0.4 and the WP/MA ratios were 0:100, 25:75, 50:50, 75:25 and 100:0. The highest methane yield (386 L kg⁻¹ VS_added) was achieved at an F/I ratio of 0.2 and a WP/MA ratio of 50:50. A biodegradability index of 0.87 obtained in this study indicates complete conversion of feedstock at an optimum C/N ratio of 26. Synergistic effect was found for WP/MA 25:75, 50:50 and 75:25 mixing ratios compared with the substrates mono-digestion.