MacroFuels demonstrated the technical feasibility of producing fuels from seaweed and validated them in commercial engines. This is an important step towards reaching the RED-II targets and providing opportunities for a growing seaweed industry in Europe. Expanding the availability of sustainable biomass as well as a plant-based protein source has a large contribution potential towards the 2050 EU climate goals. MacroFuels’ concepts and results have been presented via the project’s website, social media, conferences and large public events (EXPO2017, EUSEW2019). Brochures and flyers, 8 open access publications, abstracts and book chapters resulted from the project. Policy Briefs and Fact Sheets, press releases and videos on seaweed cultivation, fuel production and testing and social and environmental impacts led to >70 press articles and a Euronews TV feature as part of the Futuris science program (1st broadcast: 17th Feb 2020).
•Seaweed cultivation, seeding and harvesting processes: A novel year-round cultivation approach for seaweed was developed. Production yield of 19 kg/lm of brown seaweed was achieved. The exposed off-shore Danish site was better for seaweed cultivation compared to sheltered sites, which is promising for upscaling European offshore seaweed cultivation. Direct seeding on advanced cultivation substrates with novel binders reduced cost of operation. A prototype automated harvester was constructed and demonstrated. Novel seaweed storage bags allowed simultaneous storing and ensiling of seaweed at sea.
•Conditioning of seaweed: Chemical and biological ensiling processes were developed and optimized. Biological ensiling was promising as a cost-effective operation for long term storage of seaweed.
•Hydrolysis of seaweed sugars to fermentable substrates: Fermentable sugars were obtained by using commercial 2G bioethanol enzymes directly on brown seaweed or on extracted laminarins. Hydrolysis by recombinant enzymes and mild chemical treatment combined with membrane filtration for salt removal was also tested successfully. As such MacroFuels reached fermentable sugar content at 60 g/L in hydrolysate.
•Fermentation to biofuels: Commercial and novel strains have been developed and tested for production of ethanol and butanol from all seaweed sugars. Novel strategy of combined biorefinery and biofuel production was developed including extraction of laminarins under mild conditions. Baker’s yeast converted the extracted laminarins to ethanol rapidly and efficiently with achieved yield up to 78%. The novel strains show higher butanol production yields after adaptating to seaweed hydrolysates. Biogas production of up to 60% methane and conversion of 70% of the total carbon in seaweed and residues of biofuel production were achieved. Pilot production of ethanol and ABE from seaweed sugars were demonstrated. 9.4 L of distilled ethanol and 9.6 L of purified n-butanol were delivered for real engine test.
•Thermochemical fuel production: High yields of furfural, 5-methylfurfural and other furfural derivates were obtained from model sugars and seaweed hydrolysates from xylose (red/green seaweed), laminarin (brown seaweed) and rhamnose (green seaweed) respectively. Furfural was further catalytically upgraded to a furanic fuel blend by reacting it with ethanol or butanol at lab scale, producing a furanic based fuel blend. in high yields. P. palmata was converted via furfural and butanol to a novel furanic fuel at kg-scale.
•Engine tests: The MacroFuels’ produced fuels (vide supra) were tested with a stationary engine as well as road tests. Bioethanol and biobutanol were used as 10% blends (cf. E95). The furanic fuel was used as 5% blend with diesel as reference. All the blends performed well in both stationary engine test and realistic road test, with emissions lower than acceptable limits.
•Techno-economic and sustainability assessment: A multi-criteria assessments of MacroFuels’ biofuels, compared to fossil fuels and terrestrial biofuels, has been completed. Economic and environmental lifecycle impacts were greater than for fossil fuel and terrestrial biofuel transport fuels in the assessment of this early stage development due to the increased costs/impacts from seaweed cultivation. Improved cultivation designs and a focus on co-production of value-added components from seaweed were identified as key for improvement. Impacts to the local environment are strongly site dependent, so to maximise environmental benefits and minimize risks, sound site selection and site specific monitoring are crucial. Social impacts are largely positive and residual social risks can be mitigated by social standards and involvement of civil society.
