Seaweed as abundant energy … the most available, scalable and productive source of sustainable biofuel lies in our oceans … and it absorbs carbon dioxide too

October 12, 2024

Seaweed is amazing!

Seaweed, and other microscopic algae, are amongst the fastest growing organisms on the planet (the giant kelp Macrocystis Pyrifera, can grow nearly a metre a day, attaining lengths in excess of 50m) .

Seaweed outnumbers land-based plants 9 times, absorbs minerals directly from the water around it and is thought to be
the single most nutritious foods that you eat (rich in trace elements and vitamins, it typically contains more protein than meat and more calcium). It also contributes around 90% of the world’s oxygen.

There are over 12,000 seaweed species.

Seaweed is an algae, not a plant. It has no roots, leaves or stems to transport water or nutrients. Instead each cell derives what it needs directly from the seawater around it. The only similarity between seaweed and land plants is that both rely on sunlight to create energy through photosynthesis. In fact seaweed could be an incredible source of sustainable energy.

Not only is seaweed a potentially great source of energy, it can reduce the amount of carbon in our atmosphere too. Having a seaweed forest covering 9% of the ocean would absorb more CO2 than human activities produce.

Ancient Greeks used seaweed for healing purposes. Long before we were putting seaweed in our skincare products, they were using it in their heated baths to draw out toxins from the body and rejuvenate their skin. Known as Thalassotherapy (thalasso is Greek for ‘sea’) they believed it could restore good health and cure illness.

And it tastes like bacon. This has opened doors in the vegan and vegetarian market. Seaweed-based bacon is not just vegan-friendly, but also gluten-free, low carbohydrate, organic, and sustainable. A seaweed diet is linked to an increased life expectancy, Japanese Okinawa diet (low salt, high seaweed).

You can read more about seaweed here, but let’s focus on its potential as a great source of sustainable energy:

Seaweed as biofuel

Kelp, a type of seaweed, is a promising source of biofuels, if sustainably produced and used.

Compared with, for example soya, which is also used for the production of biofuels, growing seaweed is faster, more space-efficient and does not require the use of fresh water or the addition of fertilizer. Furthermore, seaweed does not compete for land area. On the contrary, seaweed can be grown in exactly the area we have the most of: the sea.

Europe today meets 90% of its renewable transport target with land-based biofuels, which in many cases are at least as bad as fossil fuels. Meanwhile, climate science shows that fighting climate change will necessarily involve bioenergy, though the sustainable scale remains one of climate science’s most unsure areas.

As a source of sustainable energy, seaweed has some key benefits:

  • Available: Though seaweed is plentiful, it is an under-used source of biomass. The sea covers almost three-quarters of the world and half of the world’s biomass grows here. However, we only get 2% of our energy from food that comes directly from the sea.
  • Scalable:  Seaweed can be grown on straight or circular ropes, horizontally and/or vertically, (ideally) down to 10m depth to retain optimal sunlight conditions. There are also integrated solutions to growing seaweed that make best possible use of
    the available space. For example, seaweed could be grown in circular systems, like Integrated Multi-Trophic Aquaculture that brings together other sea production, like fish farming and offshore energy. This makes the involved industries both more sustainable and cheaper as, amongst other benefits, it’s easier to recycle nutrients, seaweed grows better when it can use waste nutrients from fish farming, and sharing infrastructure minimises costs.
  • Suitable: Between 85 and 90% of seaweed is water, which means seaweed is very suitable for biofuel-making methods like anaerobic digestion to make biogas and fermentation to make ethanol. In addition, many seaweed species, like sugar kelp, have high carbohydrate and low lignin content that is perfect for making bioethanol.
  • Efficient: especially in absorbing nutrients like phosphorous and nitrogen. Because seaweed grows very fast, it can absorb a lot of CO2, in fact up to 66 tonnes CO2 per hectare, which can help tackle ocean acidification. Fast growth also means CO2 emissions from for instance seaweed biofuel are quickly reabsorbed by new growth. In addition, seaweed doesn’t need fresh water or fertilising.
  • Productive: growing about 26 tonnes dry weight per hectare, compared to 2.3 tonnes soya and 5.1 tonnes corn.

With an effective business model for the harvesting of seaweed as a sustainable energy source, it has the potential to deliver huge benefits. The model will need to address issues such as ocean conservation, development of production facilities on land, and the costs. These factors will be important to address in order to ensure that seaweed becomes a net zero, or even net positive, future source of energy.

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