15th October

Seaweed biomass cultivation likely to replace finite fossil fuels

Stefan Kraan, Ocean Harvest Technology

Total worldwide energy consumption today is roughly 480 exajoules with almost 90% derived from the combustion of fossil fuels. Fossil fuels such as coal, oil and natural gas are limited in supply and will one day be depleted. As a result, the quest for renewable energies – being energies generated from sustainable natural resources such as sunlight, wind, tides, etc and from industrial or urban waste and biomass – began decades ago.

In 2007, the 27 member states of the EU decided that 20% of its energy should come from renewable sources by 2020 (Lisbon Treaty).

Global biomass potential versus worldwide energy consumption



The table above shows global energy consumption and its estimated increase by 2050, and the worldwide potential of biomass for energy production based on recent studies. This clearly indicates the need for aquatic biomass to fulfil our energy consumption in a renewable and sustainable way

At sea biomass production

Since the available area for cultivation at sea is so much greater than on land (70% of the earth’s surface is ocean) and with macroalgae growth rates being much higher than of conventional land crops, the potential for biomass production at sea is enormous.


In addition, aquaculture for energy production can avoid the often heated debate surrounding food crops for fuel (food-energy nexus); sustainability; water usage; pesticides and land use change.

Equally, fertilisation, which has a major affect on greenhouse gas balances of crops on land, can be altered or even diminished when cultivating in an aquatic environment. Greenhouse gas emission worldwide using aquatic biomass for energy and fuel is, in most cases, much less, compared to the more conventional biofuels,produced from land-based crops.

Seaweed cultivation is a traditional practice in East Asia. A total of 15 million tonnes wet-weight is cultivated per annum, making it the biggest aquaculture venture on the planet. Of all seaweed harvested, 93% is produced from aquaculture. Seaweed cultivation in Europe is still in a developmental phase with only a few commercial farms in operation, notably in France, Germany and Ireland, where the focus is on small-scale production for high added-value seaweeds.Total combined production of these farms is less than 100 tonnes wet-weight per annum.

Multi-purpose usage

Seaweed is a source of food; food additives and high added-value specialty products such as pharmaceuticals and cosmetics. It also has huge potential as a biomass source. Therefore, the combination of bio-refinery, with the isolation of valuable seaweed components for high-value products and renewable energy production, will be necessary in future years.

Today, aquatic biomass cultivation is a logistically complex multi-step process onshore and offshore, and is mainly based on small volume production on long ropes and manual harvesting. As a result, production costs per biomass unit are much too high. Urgent research is therefore needed to develop near shore and offshore cultivation in the western world, to produce a sustainable, consistent and cheap feedstock with a high carbohydrate level.

No matter the species, it usually takes significant time to develop into a booming aquaculture industry. With oysters for example, it took almost 30 years. Seaweed too is likely to go through a similarly lengthy developmental process, despite significant breakthroughs such as the biochemical process to convert algal carbohydrate into ethanol.

Indeed, several initiatives have already been funded, amongst them the MERMAID and Energetic algae (ENALGAE) projects in Denmark – the latter with Irish participation lead by Dr Maeve Edwards of NUI, Galway.

Seaweed as feedstock

Another EU project with Irish involvement that is looking at seaweed as feedstock for biofuel production is the € 3.5 million EU funded project, AT~SEA which commenced this month. The project involves partners from The Netherlands, Portugal, Belgium, France, Norway, UK and Oceanfuel Ltd from Ireland. The project will explore high-volume cultivation on large textile substrates, with the aim of reducing production costs, thus making offshore production of biomass a high-potential source for renewable energy.

It is generally accepted that Europe’s industries must become more efficient, more environmentally sustainable and more competitive. With the AT~SEA project we want to implement and realise this objective via a tangible case.

Expertise from four sectors: textile; offshore; renewable energy and biotechnology, will be combined to generate new knowledge (textile for offshore use; textile-seaweed interaction), which will be used to develop an innovative technological solution (textile-based offshore production of aquatic biomass) to respond to one of the grand challenges (sustainable and renewable energy supply).

This project will focus mainly on cultivating the native brown seaweed Laminariaceae in North Western European Atlantic waters. These brown algae are known to grow rapidly and produce a high biomass, and to have high carbohydrate content suitable for fermentation into ethanol or furans and could be a sustainable alternative to biofuels and plastics.

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