Offshore algae

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Algae are bred and provided with a lot of nutrients, then grow rapidly in open water, and are finally harvested and prevented from decomposing.

The intention is to utilise the rapid growth rate of algae as well as the resources of open water (sunlight, nutrients and water) to sequester greenhouse gases, while minimising unwanted impacts. The economics may be improved by using some of the algae, for example as food, fuel or fertiliser.

The algae breeding, feeding and deployment could be performed in fixed locations with prevailing currents, or with ships. Fixed locations are likely to be more economical and may be particularly palatable in marine deserts. Ships may facilitate utilisation of substantial areas while reducing sensitivity to weather and environmental issues (with any given location being impacted for a short period of time on each occasion).

The harvested algae would be dealt with in a way that prevents the greenhouse gases from re-entering the atmosphere. This is currently being considered as a separate challenge in it's own right, which at least seems more achievable than dealing directly with greenhouse gases in the atmosphere. To illustrate, ideas for dealing with the algae including converting it to oil or drying and burying it - these ideas have not been thoroughly thought through. It might be practical to extract some of the nutrients for re-use in the cycle.

Algae would likely be selectively bred for the purpose.


This is just an idea.

It currently seems physically possible. If it could be proven to work in a test environment and the economics seemed promising, we would still anticipate environmental and political challenges.

There is likely to be difficulty in obtaining appropriate algae.

In the areas where the algae is growing, the algae would consume much of the sunlight and nutrients. We hope that the detrimental impacts could be minimised by operating in each area for a short period of time.

There would be risk of failure to sufficiently harvest the algae, which would result in an area receiving prolonged exposure and the algae decomposing in the water (which would be likely to consume much of the oxygen in the water, causing other marine life to suffocate). We hope that these risks could be mitigated by safe operating practises, using algae that is easy to harvest, using algae that struggles to reproduce outside the artificial breeding conditions, and perhaps using an algae the decomposes at a rate or in a way that is less harmful to other marine life.

If selective breeding of algae turns out to be inadequate, genetic engineering may be justified. Either way, there is no guarantee that suitable algae would result.

There may be difficulty in suitably disposing of harvested algae.

The harvested algae may be sufficiently valuable or desirable that economics or politics facilitate roll-out.


If this works and were to be deployed at scale, we think it stands a chance of significantly reducing global greenhouse gas levels.


[Please help with any useful information or metrics on current and expected economics.]

See also[edit]

Other comments/feedback received[edit]

  • From Adam Kirk on I'd like to see this idea used in conjunction with deep sea oil wells. Specifically, once extraction is "completed" and the well has run dry, it would be a neat idea to turn the pump upside down and start pumping an algae-water slurry back into the well. As much algae as possible. Use the algae to collect carbon from the atmosphere, and then the pump to sequester the carbon below bedrock. Fill in the line and leave it to turn into oil once again in a few thousand years.
  • From Martin Wolterding on (Paraphrased) Rather than genetically engineering algae, it may be possle to bring nutrient right water from great depths to the surface - with the nutrients causing algal growth that will remove CO2 from the atmosphere.
  • From Tony Nony on We need to remove CO2 from the air as permanently as we can. So long as the algae remain alive, healthy and growing, then they're another form of plant life 'sequestering' carbon. One form (phytoplankton) does -half- of all photosynthesis on Earth. The WPedia articles says that 40% of them have gone missing since 1950 (possibly due to ocean warming). So to use algae as one carbon solution, you'd need to find out which species are hardiest. Some of them are among the fastest-growing renewable biomass sources (WP:see Algae#Energy_source), a resource that's expected to take off in the next decade.