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RELEVANCE

Global fossil fuels supplies dwindling


SUSTAINABILITY

Fast-growing, easily utilised marine algae which fix carbon dioxide


BIOTECHNOLOGY

Oil production from cultivated micro-organisms


BIOFUEL

Energy readily convertible from marine plants

BioMara science progresses at Dundalk meeting

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An exciting and varied BioMara scientific and technical meeting was held in October 2010 to enable researchers from the six institutes in the BioMara project to discuss progress.

Hosted by CREDIT at Dundalk Institute of Technology, a group of twenty BioMara researchers attended.  Four talks were presented followed by discussion of technical and scientific developments.  The formal presentations are summarised below:

Anaerobic digestion and volatile fatty acids

Paul MacArtain from the Centre for Renewable Energy at Dundalk IT (CREDIT) presented results of his preliminary work on volatile fatty acid (VFA) production during anaerobic digestion (AD) of Ascophyllum nodosum.  The work was done in laboratory-scale 2 litre digesters at 35⁰C with VFA determination by headspace analysis using a Gasdata LMSxi portable gas tester.  White rice was used as a control.

Ascophyllum produced larger quantities of gas than the control throughout the test period (69 hours) and the proportion of methane was also consistently higher.   Having established an extremely effective methodology, future work will extend to other seaweed species and will include extending the digestion period for up to 100 days, investigation of the relationship between specific carbohydrates and specific VFA concentrations and of acidification of the substrate on VFA concentration.

Molecular investigation of oil production in algae

Carole Shellcock, a PhD student from SAMS’ Scottish Marine Institute explained her molecular investigation of oil production in algae aimed at using gene probes to select oil producers.  Phaeodactylum tricornutum was used as the study species and an experimental cultivation system was designed incorporating 360 ml culture tubes and temperature, aeration and light control.  Methods to evaluate oil content were developed based upon staining the oil with Nile Red, a fluorescent dye which can be used to microscopically examine the cells for oil bodies and also permits flow cytometry to quantitatively assess oil accumulation.   The GC-FID method for extraction and purification of fatty acid methyl esters (FAMEs) allowed the fatty acid profile to be determined.   Samples were taken and cell counts made daily. 

As the literature suggests, oil production lags growth: little oil is produced during the exponential phase and the largest amounts of oil are seen once cells are in the stationary phase.  Replicates produced very variable results but growth and oil production generally occurred more quickly at 20⁰C than at 15⁰C with a maximum concentration of FAME of around 19.5% in both instances, the former after about 15 days and the latter after about 20.  2.5% CO2 introduced to the aeration resulted in higher oil production and reduced pH dramatically in the culture medium.  Assessment of fatty acid profiles has produced some early results and continues.

Upstream Choices: Downstream Costs

Elaine Groom & Simon Murray from Questor gave the final presentation at the workshop.  They contrasted the upstream choices considered by the petrochemical industry with those that will confront algal oil producers.  Major challenges to the upstream stages of conventional oil production – exploration, drilling and extraction – and downstream activity – cracking, refining and distillation – include energy conservation and water availability, clean up and reuse. Algal fuel production will need to address similar issues of energy use and water availability as well as nutrient supply during cultivation.  Water availability and nutrient recovery during the harvesting and fuel extraction phases will require consideration. 

Some solutions to the challenges of extracting oil from microalgae were examined: harvesting might involve flocculation, sedimentation, centrifugation or membrane filtration though each has pros and cons.  Cell rupture is essential for effective recovery of oil.  The preferred methodology will depend upon cell size and culture conditions.  Methods may include mechanical extraction (about 80% recovery), use of solvents (up to 95% recovery) or supercritical fluid extraction using CO2 as a solvent at high temperature and pressure (around 100% recovery). These options require an evaluation of resource use; the aim is to inform the project of the optimum energy return on energy invested (EROEI), depending on the scale of the application.

Ecosystem effects of harvesting seaweed

Kyla Orr is a PhD student at SAMS’ Scottish Marine Institute who bravely spends much of her time on the beaches of the west coast of the Uists studying the role occupied by beach-cast seaweeds on the local ecology.  Her presentation was based on preliminary results to date and was an eye-opener for those who might have seen beach-cast as a useful source of material for biofuel production.  Of the three sources of biomass - harvested, cultivated and beach-cast seaweed – beach cast appears to provide large quantities of easily accessible and historically available feedstock.  Its supply is, however, weather dependent and thus somewhat unpredictable from year to year.

More significantly, beach-cast supports a diverse coastal community of bacteria, detritivores, epiflora and deposit feeders which, in turn, support carnivorous invertebrates, all of which provide feed for large crustaceans, fish and seabirds.  Up to one million oligochaete worms per square metre of seaweed can be found: beach deposits of seaweed are clearly a very important feeding ground for migratory shorebirds, as well as breeders inhabiting inland habitats. Clear relationships are demonstrable between shorebird numbers and beach-cast cover but many questions remain unanswered and will form the basis of further work. It is expected that construction of a mass balanced tropho-dynamic food web model will allow its manipulation to assess the impacts of seaweed removal at different levels on food webs on sandy beaches.  The impact and appropriateness of beach-cast removal may then become measureable.


PDFs of the posters presented at this meeting are available here…

Bioethanol from seaweed

Upstream choices, downstream costs

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