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Title: MAB3 – MacroAlgae Biorefinery 3

Type: Research project

Funding program: Danish program for research and innovation – Innovationsfonden

Timeframe: March 2012 – February 2016 (48 months)

 

Objective.

Worldwide, researchers work to limit the increase of carbon in the form of CO2 in the atmosphere and excess of nutrients  – in particular nitrogen and phosphorus – in our aquatic environment – both “pollutants” being the consequence of human activities. However, nitrogen and phosphorus serve as essential nutrient components for the growth of terrestrial and aquatic plants, which are needed for the production of food, feed, and for future energy carriers.

In the MAB3 project, an integrated biorefinery concept was developed for conversion of two selected (based on their sugar and amino acid composition) candidates of brown macroalgae, i.e. Saccharina latissima and Laminaria digitata into energy carriers (ethanol, butanol, and methane), and a protein and lipid enriched fish feed derived as a residual from the energy conversion processes.

The bio-remediation potential was addressed by cultivating the algae through capturing CO2 from the atmosphere and anthropogenic nutrients from eutrophic coastal seawater.

Life cycle sustainability and feasibility assessment documented the nutrient and CO2 reduction potentials of the two algal species.

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Outcomes.

Results from the environmental assessment demonstrated that renewable energy sources, such as marine biomass, can be a suitable and efficient solution for sustainable development of coastal areas. The project evaluated in laboratory and pilot scale the feasibility of producing energy carriers from macro-algae, such as ethanol, butanol and biogas, besides other products such as fish-feed. Ethanol and butanol are obtained by fermentation of sugars and biogas through anaerobic digestion of the biomass. Results show that the high sugar content in Laminaria digitata makes this feedstock ideal for production of biogas and ethanol.

The production of bioethanol and biogas from seaweed would decrease the consumption of fossil fuels leading to a saving for the national fossil fuel consumption.

The life cycle assessment showed that the production of biomass and bioethanol-biogas can provide climate change mitigation and also highlighted the effects of alternative seaweed production and conversion systems on marine and freshwater eutrophication.

In particular, LCA was performed on four different systems:

1. seaweed cultivation and fertilizer production;

2. seaweed cultivation and bioethanol, protein and fertilizer production;

3. Seaweed cultivation and biogas and fertilizer production;

4. Seaweed cultivation and protein production.

The ReCiPe methodology was used to calculate the impact on climate change, marine eutrophication, and freshwater eutrophication. The USEtox methodology was used to evaluate the impact on human toxicity cancer and non cancer.

Moreover, it was calculated the cumulative energy demand (total and fossil fraction) necessary to cultivate and process the seaweed.

 

A few out coming observations follow:

- The cultivation of Saccharina latissima in two sites in Denmark (i.e. Limfjorden and Horsens Fjord) shows that in Denmark it is possible to reach a productivity of 1-2 ton of seaweed dry weight (7-13 ton of wet weight) per hectare.

- Saccharina latissima can bioextract on average 48 kg of nitrogen and 4 kg of phosphorus per hectare of seawater, bringing back to soil the nutrients in the form of biofertilizers.

- When processed in a biorefinery, 1 ton of seaweed dry weight can provide between 0.6 GJ and 5 GJ of energy in the form of bioethanol while at the same time producing 0.1-0.4 ton of protein.

- The conversion of this aquatic biomass into biogas generates higher energy production than ethanol, namely 7-11 GJ per ton of seaweed dry weight. The best case scenario, where Laminaria digitata harvested in summer is converted into biogas, provides climate change mitigation service quantified as -662 kg CO2 equivalents per ton of seaweed dry weight.

- Variation of composition of seaweed biomass across seasons and species was identified as a critical factor. Laminaria digitata has higher dry matter content than Saccharina latissima, and has, therefore, a more efficient exploitation of the marine water surface. Seaweed harvested in spring show a higher concentration of nitrogen and phosphorus which makes them more suitable for bioremediation purposes while the sugar concentration is higher in summer which enhances the production of ethanol.

- Variation in composition affects also the content of micropollutants bioextracted from seawater. While providing a water purification service, seaweed transfer heavy metals to agricultural soil or fish feed. According to the technology used in seaweed processing, the micropollutants can follow different pathways. A precise measure of the concentration and the speciation of the element should be further assessed in order to balance the research efforts among the different biorefinery outputs. Technology for isolation of heavy metals could be then used to reduce the impacts on human toxicity.

 

Project partners.

• Danish Technological Institute (Project coordinator, WP1,2,3,7,8) with expertise in biomass handling, harvesting, pretreatment, extrusion, pelletizing, liquid bio fuels and enzymatic hydrolysis. Partner in AlgaeCenter Denmark, R&D facility for cultivation of algae.
• Aarhus University, Department of Bioscience (WP1): Expertise in cultivation, optimisation and characterisation of macroalgae for energy conversion, high value products and environmental mitigation, and partner in AlgaeCenter Denmark.

• Aarhus University, Department of Environmental Science (WP6): Expertise in Socio Environmental System Analysis; sustainability analysis of cross sectoral resource flows (EIS), LCA and welfare economic analysis, environmental aspect for the production of marine biomass, energy system scenarios and quantification of emissions.

• National University of Ireland, Galway (WP1): R&D in cultivation and harvesting of various species macroalgae, management of natural seaweed resources incl. brown algae hatchery and long line, on-growth facilities.

• Danish Shellfish Centre (WP1). Independent R&D facility situated in Limfjorden Denmark with focus on development of sustainable production in coastal waters. DSC has experience in R&D and in practical aquaculture.

• DTU-Environment (WP4): DTU environment has expertise in biological conversion of biomass to bioenergy and biochemicals, such as bioethanol, biogas, biohydrogen, amino acids etc.

• DTU-Chemical Engineering (WP2,3): Enzyme hydrolysis and kinetics and fermentation techniques.

• University of Siena (WP6): Sustainability analyses with special expertise on macroalgae.

• University of Hamburg (WP2): Expertise in pretreatment technologies, physical and enzymatic hydrolysis. World leading expert in chemical characterization of biomass sugar polymers.

• Orbicon A/S (WP6): Danish experts in feasibility studies and business development for future EUDP application.
• Aller Aqua A/S (WP5). Aller Aqua (DK) produces fish feed for a range of freshwater and saltwater fish species. The fish feed cover the basic metabolism of the fish and includes all needs for nutrients, vitamins and minerals to ensure healthy growth.

• DONG Energy A/S (WP3): Energy producer in Denmark with R&D expertise in Biorefinery, production of energy carriers and feasibility studies.

• Vitalys I/S (WP4): Danish SME working with high-tech amino acid production based on newest methods in fermentation and biotechnology.

• DanGrønt Products A/S (WP2). Denmark’s largest grass drying company owing factories in Ringkøbing and Gredstedbro. Work in cooperation with Danish farmers grass and Alfalfa with large scale production of fodder pellets.

 

References.

Seghetta M., Tørring D., Bruhn A., Thomsen M., 2016. Bioextraction potential of seaweed in Denmark—An instrument for circular nutrient management. Science of the Total Environment, 563-564, pp 513-529.

 

 

Keywords: Seaweed, macro-algae, biorefinery, biofuel, biogas

Methods: LCA

Website: http://www.mab3.dk