Mechanical pretreatment effects on macroalgae-derived biogas production in co-digestion with sludge in Ireland

Cell walls and lignin component disruption treatments are needed to enhance the hydrolytic phase and the overall biodegradability of lignocellulosics during an anaerobic digestion process. Given their abundant availability in nature, low impact on food market prices and low lignin content, aquatic plants result in being particularly suitable for biofuel conversion. A preliminary study on the effects of a Hollander beater mechanical pretreatment has been conducted in batch mode focusing on biogas yields from five different species of Irish seaweeds in co-digestion with sludge. A second experiment on Laminaria Digitata species has been carried out using a Response Surface Methodology (RSM) with treatment times (0–10 min), mesophilic range of temperatures (35–39 °C) and sludge amounts (100–300 ml). Results from biogas yields of treated macroalgae have been found to be up to 20% higher when compared to untreated ones. A mathematical model of the biogas volume behaviour has been developed and the ideal conditions identified.