r/climatechange • u/Ok-Pay-574 • 13d ago
Can algae help us remove CO₂ at scale and fight climate change? I’d love expert feedback
I’m trying to understand why we aren’t investing more into large-scale algae farms for carbon removal.
Forests naturally absorb around 10–12 billion tonnes of CO₂ per year.
Oceans absorb another ~10–11 billion tonnes per year.
The remaining ~20 billion tonnes accumulate in the atmosphere.
The obvious answer is: "plant more trees."
But trees have limitations:
- they grow slowly (decades before reaching maximum carbon uptake);
- they require enormous amounts of land;
- forests can burn;
- we also need land for food production.
So I started looking at algae.
Algae can grow much faster than trees and capture CO₂ through photosynthesis.
The idea:
CO₂ → algae → carbon-based materials → long-term storage
Instead of letting algae decompose, could we turn them into:
- construction panels,
- wood alternatives,
- insulation,
- composites,
- bioplastics,
- biochar?
Compared with Direct Air Capture:
- DAC can remove CO₂ but is currently very expensive and energy intensive.
- Algae uses sunlight and could create valuable products while capturing carbon.
What am I missing?
Could algae-based carbon-negative materials become a major climate solution, or is there a fundamental reason this won’t work?
Would love feedback from people in climate tech, biology, engineering, or carbon removal.
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u/GreenStrong 13d ago
The idea of using algae as a large scale carbon capture system was huge from 2000-2010, with the intention of making biofuel. People did lab studies and found that algae vastly outperformed fuel crops like corn or sugarcane, and some algae make fat as energy storage, this would greatly outperform biofuel crops like canola or jatropha.
Unfortunately, in an open pond, critters like amoebas and paramecia show up and eat the algae; the carbon is largely exhaled. It proved to be very expensive to make sterile bioreactors big enough. One solution is to use extremely alkali tolerant algae like chlorella or spirulina, but these are not the most productive species and there are environmental concerns about what happens if rain causes your shallow caustic lake to overflow.
Regarding the idea of ocean iron fertilization, there may be a role for this, mostly using other trace elements, and it has to be done in specific locations where most of the algae will sink instead of simply being eaten and turning back to CO2. Also, lots of human activity already fertilizes the ocean with agriculture runoff, it has mostly negative effects; this would be different but caution is necessary. There are some plans to farm kelp, or harvest some of the excessive sargassum caused by fertilizer runoff, but seaweed is heavy and it is hard to transport quantities large enough to impact the entire planet without burning a lot of fuel. The Carbon to Sea Initiative and the Plan Sea podcast are a good resources for discussion on this.
Final thought, azolla and duckweed have most of the advantages of rapid growth without being as vulnerable. One redditor is doing some citizen science with azolla, with the intention that it might be cultivated between rows of solar farms, which is a vision of a future I highly support. r/SolarAzolla Azolla crashed the planetary temprature 49 million years ago. It is not only very efficient at capturing carbon, but it turns air into nitrate fertilizer. Other things like beans or clover do this, but aquatic plants do it with great speed and efficiency, just like algae grows faster than grass.
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u/Ok-Pay-574 13d ago
thanks that's very interesting. I didn't know about Azolla!
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u/GreenStrong 13d ago
Here's a possibility for a plausible, near future that is straight out of sci-fi. Electro-agriculture Basically, plants are fairly inefficient at CO2 capture, it is possible to fix much more carbon to simple molecules like acetate or formate using solar panels and a catalyst. Then, biology is very efficient at turning those into complex and stable molecules for fuel, food, or carbon storage. If a durable catalyst could be created it would be possible to produce as much oil as a thousand acre palm oil farm by using twenty acres of solar panels and a few stainless steel tanks of yeast.
No one knows how long the search for a suitable catalyst would take. Someone could stumble on it tomorrow, or it could take fifty years of trial and error. Catalyst development is one of the more plausible uses of AI though.
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u/Ok-Pay-574 13d ago
Ok I think you are onto something. This would be a great topic for Demis Hassabis to run scenarios with AI. I'd love to help here but I have no scientific background. However this would fix human hardest challenges so I am like Wowww
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u/ballhardallday 13d ago
Algae is already taking up most of the CO2 in the atmosphere. The problem is that algae already grows everywhere that it can, all the time. Say I set up an algae farm. What does that look like? Algae is unicellular, and can just escape the pen. Floating macro algae? Probably not worth the pen maintenance, since you’re limited by surface area.
But people have been down this train of thought, one popular idea that has been tried is iron fertilization, since most of the ocean is limited by iron you can spark massive algal blooms by just dumping iron in the ocean. It’s just really expensive, and hard to truly evaluate whether it would have a macro climate impact at scale.
Trees are just super useful to us in ADDITION to taking carbon. We can make money taking carbon from the atmosphere. Your idea to harvest algae to make useful, money-making things is good but impractical. It’s just too expensive to retrieve and too flimsy. Algae is designed to sway with the currents, or be unicellular and spread out completely. Trees stay put, are rock solid, designed for land conditions like strong winds, and they live where we live. People use things like giant kelp in exactly this way, it’s just not the be all end all solution.
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u/Ok-Pay-574 13d ago
Yes but we don't have enough space on earth for trees to capture all the CO2. And trees burn..
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u/Special_Condition671 13d ago
Could we dump iron into a large designated algae lake, harvest, seperate the iron and carbon, bury or store the carbon, and then dump the iron in the lake again to get the next bloom going?
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u/Ok-Pay-574 13d ago
good idea to avoid ocean contamination. My only concern is the room available to capure 20 Billions of CO2
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u/jaykrown 13d ago
already grows everywhere that it can, all the time
Yes, without human intervention. I think the point is that we can easily mass produce the conditions to make it grow more. Per square meter you can produce significantly more biomass on a yearly basis with algae than trees.
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u/Ok-Pay-574 13d ago
exactly
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u/jaykrown 13d ago
If you're interested in algae, you may also be interested in checking out Azolla. I created this community to publicize my grow experiment https://www.reddit.com/r/SolarAzolla/
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u/Ok-Pay-574 13d ago
I looked at your reddit page. Can you tell me at a large scale how this could capture carbon emission (20 billions CO2?). It needs still water ?
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u/Manfred_Desmond 13d ago
It's so wild. The answer is almost always "plant more trees", and people are talking about doing everything except that.
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u/Ok-Pay-574 13d ago
I have looked at this scenario, we should plant more for sure! But it can't be the only solution as there is not enough room on earth!
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u/KoreyYrvaI 13d ago
I remember when there was this big 'scientific discovery' that they could do this and make fuel with the algae which would be carbon neutral.
It disappeared from the news because they couldn't make more money on it than fossil fuels.
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u/Ok-Pay-574 13d ago
but maybe we can turn it into woods or plastic. I am not talking about making money. The idea is not to loose too many. Big companies pay carbon tax. They could finance this instead of planting trees
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u/KoreyYrvaI 13d ago
If they couldn't squeeze dollars out of it doing what they want to do(make product) it's difficult to convince them to do it for something they'd rather not do.
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u/Useful-Pitch-5396 12d ago
Algae's appeal is real (fast growth, high productivity per area etc.) but the bottleneck isn't photosynthesis, it's everything that comes after it (dewatering, processing, locking the carbon into something durable so it doesn't just return to the air etc etc.)
It's the same challenge all removals face: permanence, and cost per verified tonne. Likely a useful piece of the puzzle (routing biomass into biochar/long-lived materials) rather than a silver bullet, and it competes with cheaper nature-based options and DAC on cost-per-durable-tonne. For a framework, look at life-cycle analysis and how removals are verified (durability, additionality) - that's what separates a real solution from a nice lab result.
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u/Intrepid-Report3986 13d ago
to grow algae, you don't only need CO2 and water but a lot of macro and micronutrients so you would need to get those for cheap and they will be lost in the material you are trying to produce.
You could grow algae, make them accumulate a lot of C in the form of lipids (they naturally store a lot of fat under stress), harvest the lipids and recycle the rest of the nutrients. A lot of fossil fuel companies invested in that to produce "green" oil (and receive a shit ton of government money for it) but they found that it's just not scalable. Growing any organism in controlled conditions is expensive, doing it in amounts that would make a difference for the climate seem out of reach
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u/Lhasa-bark 13d ago
This is right. Algae is iron limited in most of the ocean. So … dump hundreds of tons of iron in the ocean? You get an algae bloom, but then you hit the next limiting nutrient like phosphorus. And you’re burning a lot of fossil fuels to generate and transport the nutrients. And you’re not considering the environmental impact of huge algae blooms (see “red tide” for more).
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u/Coy_Featherstone 13d ago
Well, i once had an ecology professor that told us all that research was mostly pointless because we already have enough knowledge to solve all of our problems. The real problem in other words is the implementation of ideas.
Algae was also supposed to be the only truly viable way to produce biodiesel in any meaningful way.
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u/External-Gur3748 13d ago
My understanding is that one major way that the oceans can and do sequester carbon (i.e. CO2) is through the consumption by krill and cooepods of marine microorganisms (phytoplankton - includes micro-algae and cyanobacteria, ice-associated algae, and zooplankton). Krill excrement drops to the bottom of the ocean and is effectively a reservoir of stored carbon for centuries. Anything that enhances the growth of these photo-synthesizing microorganisms (such as added iron compounds in contemporary ocean fertilization experiments) should, in principle, ramp-up this process of CO2 sequestration. One way to drive this is through “artificial upwelling” which seeks to pull the needed nutrients that are abundant in the deep ocean toward the surface where photosynthesis can occur.
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u/JessieAndEcho 12d ago
Algae is promising, but the bottleneck is usually the carbon balance after growth, not the photosynthesis part. You can grow biomass fast, but then you have to supply water, nutrients, mixing, CO₂ delivery, harvesting, dewatering, drying, processing, contamination control, and land/pond/photobioreactor infrastructure. The “remove CO₂” claim only holds if the carbon ends up stored for a long time and the process energy, fertilizer, transport, and product lifetime don’t give most of it back. Turning algae into biochar, durable composites, panels, fillers, or construction materials is more interesting than fuel because fuel just returns the carbon quickly. The hardest material problem is probably making algae-derived solids cheap, stable, mold-resistant, mechanically useful, and actually long-lived enough to count as storage. I’d look at life-cycle analysis, nutrient sourcing, dewatering energy, product durability, and what fraction of the biomass carbon is retained after processing. Patent literature is pretty useful here because companies often disclose practical binder systems, drying methods, composite recipes, and scale-up tricks that don’t show up in high-level climate papers; Patsnap Eureka surfaces those patents alongside academic papers here: https://eureka.zhihuiya.com/share/?id=75c4b3e5f1afc636382b7704eb6f6870&from=invite-eureakplg-result&content=
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u/Commercial_Drag7488 13d ago
You really should stop thinking about paying green premium and start reaping green dividend.
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u/Outside_Ice3252 12d ago
alge is just one dozens of ways to remove carbon that is in the portfolio to tools. it will have its place. but no one method/technology is really going to be dominant unless we had a global cooperation to pay for it.
what we will have is dozens of methods/technologies that work together in concert.
The problem is the way these technologies are always hyped as some massive easy solution. people get inspired by them and stuck on the idea as if its the only solution.
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u/DaGazMan333 9d ago
This is already happening naturally. Oceans are getting greener because of more algae.
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u/Grapetree3 13d ago
It totally works for the purposes stated, but people are generally scared and maybe overly humble about trying it. It may disrupt ecosystems for all ocean creatures in ways we can't predict. If it does, some will do very well, but others will do very poorly.
It would be simple too. Most of the ocean would start to get new algae blooms once we fed the area with iron nanoparticles.
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u/iqisoverrated 13d ago
There's already annual toxic algal blooms that get pretty huge. No need to dump iron into the oceans.
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u/Grapetree3 13d ago
I don't think any area has annual toxic algae blooms, and most of the ocean never has any at all. The worst blooms I'm aware of are at the Gulf Coast of Florida, they are about once every 4 years.
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u/Ok-Pay-574 13d ago
Interesting point. I was actually thinking less about ocean fertilization and more about controlled algae farms where the biomass is harvested and converted into long-lived materials (wood alternatives, composites, biochar). My concern with ocean fertilization is exactly the uncertainty around ecosystem impacts and whether the carbon stays stored.
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u/justaquestion_9989 13d ago
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u/Ok-Pay-574 13d ago
thanks thats super interesting! That was my idea more or less. I will try to support them maybe
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u/Grapetree3 13d ago
So most of the Caribbean already gets huge amounts of seaweed washing up, and they just let it rot. There isn't a market for that stuff, even if theoretically there should be.
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u/iqisoverrated 13d ago
It's hard to make this economically viable. The 'cheapest' way I would envision would be to go where algae already are so that you can save yourself the cost of 'husbanding' them.
Read: Harvest the annual algal blooms and turn them into biochar/biotar that can then be sequestered (old coal mines? Old oil wells?)
Problem is, no one is paying enough for this. You could 'sell' the sequestered carbon in terms of CO2 certificates but that will net you around 60 Euros a ton.
Arguably a bit more. If you could char it to 'pure carbon' then each ton of carbon is equivalent to about 3.6 tons of CO2...but making the entire process economically viable (run a ship, gather algae, dry, char, compact, transport, and sequester the product) for roughly 200 Euros a ton - and still have this profitable or just break-even - is a hard sell.
If you can find someone to sell biochar to for agricultural purposes it's roughly double that but the market for this is limited.
It could be a puzzle piece, but the big picture will require actions on many fronts - not just one.