Thermo-acidic pretreatment of marine brown algae Fucus vesiculosus to increase methane production-a disposal principle for macroalgae waste from beaches

Marine biomass is washed ashore on beaches used for recreational purposes causing problems for local and spa authorities. The present management of marine waste biomass does not include a sustainable disposing policy and biomass is dumped inadequately. Since macroalgae are receiving increasing attention in the field of biofuel production, this spare biomass may present a potential feedstock in biogas plants. The present study shows an increase in methane production from macroalgae Fucus vesiculosus collected from the beach by applying thermo-acidic pretreatment to enhance hydrolysis of polymeric molecules in biomass. Flue gas condensate (FGC), an industrial acidic waste product accumulating in power plants, was used for acid hydrolysis as well as technical HCl and water. Biomethane potential tests were carried out on pretreated samples. Pretreatment conditions of 80 A degrees C using 0.2 M HCl and a reaction time of 24 h resulted in a +140 % increase of methane yield in biogas production. FGC and hot-water pretreatment at 80 A degrees C for 24 h yielded +38 and +51 % more methane than untreated biomass, respectively. Lower temperature pretreatment (20 and 50 A degrees C) did not show considerable improvement of methane yield neither in water nor in acidic media except when using 0.2 M HCl at 50 A degrees C (+83 %). An extended pretreatment reaction time of 24 h did not reveal any additional recovery of methane compared to a reaction time of 2 h. The full pretreatment effect is already deployed below 2 h. To attain maximum efficiency in the pretreatment process, the amendatory combination of both heat and acidity is necessary.