Picture of Simple Algae Home CO2 Scrubber - Part 1
I created this instructable to show how to build a simple algae based CO2 scrubber for home or apartment use. The basic design shown here will scrub its own consumption and approximately 24 pounds of carbon dioxide from the atmosphere every year. This is approximately the CO2 produced in the production of 17kW of electricity. This device may be scaled up to process larger quantities of CO2.

The carbon dioxide is consumed by the algae which release oxygen. In part I the scrubber consists of a 2 liter reactor vessel and a small aquarium air pump. The bottle contains a solution of water, algae and nutrients. Room air is passed through the bottles using a standard aquarium bubbler stone where the CO2 is absorbed by the algae and oxygen released.

In later parts this basic design will be expanded provide more flexibility and increased production.

Maintenance is simple and straightforward as any house plant. About twice a month I add a couple drops of liquid plant food. The color of your home scrubber may be kept at any desired color range by controlling the food. If the algae gets too dark for your taste simply wait until the color begins to lighten before feeding again, if its too light try adding another drop of nutrient or feeding more often to increase the population.

Once or twice a year its probably not a bad idea to clean the scrubber. Save enough medium from one of the lightest bottles to reseed them. Then empty them into your compost heap, the sink or the toilet and restart them using tap water and the reserved medium.

All that being said, let's take a quick look at the tools and materials we'll be using then we'll get started.
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slinkiestpopi3 months ago

to get more light into a 6" wide tank, could i use a fiber optic cable?

egbertfitzwilly (author)  slinkiestpopi3 months ago

You'd have to make some sort of light tree to disperse I think. You might be better off using battery driven red and blue LEDs and a solar recharger. This would also open the door to using a battery driven pump.

Also rotating the tank may be sufficient, you might be able to replace the air pump with a small fountain pump or waterfall type aerator that rotates the medium periodically. Algae requires approximately 6 seconds for a full cycle but only needs to be exposed to light for about 1/100 of a second to absorb a photon. The balance of the time is spent on internal processes which are not light based.

ok, thanks.
one side is facing a wall, but most of it will be receiving light. Also, can rain have algae in it?
egbertfitzwilly (author)  slinkiestpopi3 months ago

I would say in general rainfall itself does not contain algae, other than whatever might be picked up on the way down. Rain drops are condensed water vapor. However there is an excellent chance that any creek or streambed swollen by rain will contain some local algae. As will most standing water, particularly in soil, after a couple of days.

Would rotation still be useful for a 5-6' tall tank, who's light source will be mainly from the side?
egbertfitzwilly (author)  slinkiestpopi3 months ago

Depends on the width and the light source(s). Light will penetrate approximately 6 cm if I recall correctly. Some sort of circular rotation might work well.. I believe that rotation will significantly increase your yield and that the optimal is about a 6 second cycle.

Is there light on one or both sides of the tank?

gallactronics3 months ago

Effective method. Here's another model of a solar-powered CO2 scrubber:

jboboblob8 months ago

I've been trying to research how to keep oxygen levels, where food (i.e. water for DIY Soylent) and waste/sanitation (i.e. health club membership) are externalized, up in a theoretical scenario. I'm wondering if this would be applicable?

Specifically, I'm wondering how feasible it'd be for an individual to live in a 12' x 24' self-storage compartment (purely from a thorough research standpoint for my novel since it's illegal and non-fun sounding. It'd take place in a small northern city without most of the usual security systems) with good air quality (not air tight, but certainly undesirable).


1) The room would have very bad air flow.

2) There would be one human needing (good) air/oxygen for ~22 hours each day.

3) Electricity would be limited. This is still being researched separately, but think daily charged portable batteries small enough to be packed into a backpack (where they're hooked up to a power strip for less conspicuous charging).

4) Temperature is a huge variable. It'd have to take into account that there may be cold temperatures with the occasional strong cold snap. I'm unsure as to how much a human would be able to keep a unit heated up (keeping oneself warm would be very easy; down jacket, etc). Magnets could be used to keep blankets or sleeping bags on the walls & ceiling, and a thick curtain could be placed a foot away from the entrance, but since it's still encased in thin metal there's a concern for bio-matter. Additionally, any soundproofing efforts would offer some amount of insulation as well.

* 5) A small propane stove could be used briefly to increase temperatures. The consequent oxygen consumption could be problematic.

6) For light, per the Wikipedia page on grow lights, "Recent experiments show that providing plants with white LED is also viable because LED colour is achieved by using multiple compounds; thus, it is possible to provide all the wavelengths required with a white LED." Consequently, I think that there are plenty of low energy options for the character to realistically use, i.e.

My research began at normal household plants, and then to c4 plants as photorespiration is less of an issue. Unfortunately, c4 plants wouldn't be tolerant of the temperature variance. Figuring out how to keep a bottle (or bottles) with water warm would be much simpler than ensuring the warmness of a plant. Also, algae produces more oxygen than either c3 or c4 plants. But does that sound feasible?

I'd appreciate any feedback. Specifically I'm interested in how much oxygen this would generate, and also the algae's health/function when faced with temperature variance (the occasional brief but very cold snap & more prolonged but less extreme coldness).

Also, FYI: I don't plan on publishing said book (in the unlikely event that I even finish it) - it's not for profit - but I'd be sure to reference this specific instructable if it seems the most viable :)

egbertfitzwilly (author)  jboboblob8 months ago

NASA identified algae tanks as the solution for CO2 recycling during long term space travel so I believe something similar would work. There will also need to be a secondary lab for keeping new cultures so the colony can be rebuilt.

Anje Albertyn10 months ago

hi there. I am trying to build an algae CO2 scrubber for a science project. I am trying to pass off the idea that it would be able to absorb some carbon dioxide given off by fires people make in confined places like their houses. How would it be possible for me to measure how much CO2 my scrubber can absorb?

egbertfitzwilly (author)  Anje Albertyn10 months ago

The calculation to search for is "Gas Uptake in Water". This is a complex calculation based on the surface area of gas exposed to water. This may be surface area or bubble size. When bubbling through a tank which is the normal mechanism for this sort of project its a function of bubble size ( surface area ) and the height of the tank you are bubbling through. Surface area absorption is also interesting as the uptake only goes down about 6 cm requiring some form of rotation.

In the Alabama algae feasibility study ( the PDF is attached to the instructable ) the author does some calculations. You might consider using that paper as the basis of your science fair project. Although it doesn't specifically scrub power plant emissions it does demonstrate the role of algae and how it can be used to sustainably manage CO2 recycling ( air - algae -fertilizer - plants - decay - air ).

Scrubbing emissions is an extremely challenging problem which must deal not only with the trival problem of algae tanks but also heat and toxic waste produced which also condense out of the exhuast plume.

Anje Albertyn10 months ago

hi there. I am trying to build an algae CO2 scrubber for a science project. I am trying to pass off the idea that it would be able to absorb some carbon dioxide given off by fires people make in confined places like their houses. How would it be possible for me to measure how much CO2 my scrubber can absorb?

Anje Albertyn10 months ago

hi there. I am trying to build an algae CO2 scrubber for a science project. I am trying to pass off the idea that it would be able to absorb some carbon dioxide given off by fires people make in confined places like their houses. How would it be possible for me to measure how much CO2 my scrubber can absorb?

bio-boy4 years ago
I am looking to make my household carbon neutral. I am intrigued by the solution you are suggesting. After other green initiatives such as increased insulation, my carbon foot print is around 10,000kg of carbon per annum.

If I understand what you are saying

1 2ltr bottle will consume 24lbs of CO2 PA or 10.88kg

So 1ltr will consume 5.4kg approximately. (Call it 5 kg to keep the maths simple. & I may not be able to achieve the same growth rates as you)

There fore to offset 10,000kg of CO2 I need 2000ltrs of water/algae/nutrients?

I have a large garden. At the bottom of my garden is an overgrown pond, (installed by the previous owner) its filled with leaves & other organic matter, witch I have recently dug out. It is south facing & gets sun all day long. After a quick calc I have determined that this has a volume of, a little over, 2100ltrs

Would this work either as an open pond or covered with some sort of clear plastic sheeting? If so what sort of size of pump would I need?

1 way too get your house carbon nuetral is to go solar with deep / universal / golf / specailized batteries. then wired them up with grid tie inverters. if its done properly an well uill be able too stop your meter from turning at all.
egbertfitzwilly (author)  bio-boy3 years ago
Did you make any progress on this?
egbertfitzwilly (author)  bio-boy4 years ago
Sorry it took so long to reply, I had to sort out some information.When one moves from a tank to a pond a whole range of new possibilities opens up.

Breeding algae in a pond presents two challenges, light penetration and harvesting. With a tank based system harvesting is a trivial matter, with a pond based system one must deal with the issue of how to manage a 20 micron object.

The other challenge is light penetration. Sunlight will only penetrate to about 6 cm ( in terms of algae usable light ) due primarily to shadowing. So it is necessary to rotate the tank contents by some mechanism.

Fortunately there are at least two major studies that are worth considering as they provide a well thought out solution space.

The most recent is from the University of Alabama regarding the production of algae as biodiesel feedstock and the other is from the NREL Aquatic Species Program.

I've attached these two files to the instructable so you can review them. Please keep us informed of your progress and consider doing an instructable if you do something to make your pond an algae farm.

aashley641 year ago
hey I wanted to ask you how did you estimate how much amount of carondi oxide is been used up by the algae.. also i want to do carbon sequestation in a pond. plz give some ideas
hpetrow1 year ago
So if the pump can pump for example 50l/h and atmosphere has 0.033% of CO2. That would make only 114l of CO2 passing the device in a year. That would make something like 0.3 kg/year of CO2 passing the scrubber. So I guess most of the CO2 should come from the surface interface with atmosphere.

In that case isn't the design quite ineffective? The out flow of the air prevents the atmosphere to enter the bottle. Shouldn't the top be open and the algae solution have as much exposed surface as possible?

Feel free to point out if I have gone somewhere wrong with my thinking. Planning to design my own scrubber, so would be nice to know if my thinking is right or not before buying the materials for it.:)
Prodiver2552 years ago
I have tried a couple times to get algae to culture from samples from my fish tank (a freshwater tropical setup) and have yet to get any algae proliferation. Each time the bottle turns a nasty grey color and I get an off-white sediment that forms. I have tried aerating and conditioners to remove chlorine/chloramines and add plants food. Any ideas what I may be doing wrong?Thanks
egbertfitzwilly (author)  Prodiver2552 years ago
I have never seen the symptoms you describe. Have you tried with water from the tank? You should also be able to use water from a stream, pond or lake. You could also use bottled, distilled water.

If you are using liquid plant food remember a little goes a long way.
novice1016 years ago
This is a quick flow chart. The residual could be converted to charcoal (pyrolysis), and buried. (google Terra Preta )
Could the resulting charcoal be used in turn to filter water in your fish tank? Or would it have to many other 'residual' ingredients to make it safe for your fish? Thinking on larger scale for smal home fish farm appropriate for prepping.
ebcat5 years ago
I am studying algae for a school project, I have cultivated some kinds of algae but, when I extract it from its habitat, they die. I thing the cause of algae die it's the turbulence of the air pump? it can be that?
egbertfitzwilly (author)  ebcat5 years ago
What kind of water are you using? Try filling your container with the same water you take your algae sample from. If your using tap water (or bottled water) let it stand for a day or two then boil it to drive out any remaining gasses. The container you fill from the natural source should get a good healthy growth, you can use samples from this to create other cultures. If your air pump to way too big for the container I suppose it might damage the algae. If so then using a larger container (like a gallon milk jug) might do the trick for you. I've attached a picture of another version I've got at home. This one uses an aquarium filter (without any filter cartridge) to aerate the water.
Although this can work it is less efficient than your first model due to only the top being the suitable area of algae growth compared to your first filling the bottle. second of all if the algae gets sucked into the pump (if that were to happen) it might get too agitated in the mechanism it could die.(maybe put a finer strain cover on the end) Plus the aqua filter would seem to use more energy than an air pump. But yes it can aerate the water and that what I use for my ten gallon fish tank for aeration, and a good bacteria set up for filtration. ( i hate buying filters all the time). And also what is the suggested time to keep air pump on if turbulence is an issue (like for ebcat)
egbertfitzwilly (author)  OruKun5 years ago
Actually its much more efficient, the biowheel rotates the medium from the bottom of the tank up into the light (and aeration). Studies have shown that algae need only about 1X10-23 seconds to absorb a photon but about 6 seconds to complete photosynthesis.

Of course I remove any filter elements so the pump(s) merely rotate the water into the photic/gas uptake zone.

This particular pump is the same as the air pump I was using but much more effective in this configuration. Conceptually I think this is much better than the raceway pond for large scale configurations.

Since I don't have a fish tank I can't speak to what cycles might be appropriate. I use an 18/6 light/dark cycle which is optimal for the algae.
Using bio balls is a good way to give your algae I way to anchor down and remain more stable, you can always add more lighting with submerge able lights, just a thought. • • • Fuzzee Dee OUT • • • }~{ <> }~{ ^~^ :-> 
egbertfitzwilly (author)  FuzzeeDee2 years ago
Yeah, I was thinking LEDs on a wire rack with some capacitors so they fire a limited number of times a second.
Amazing the level of efficiency that can be achieved with a little effort.
"If your using tap water (or bottled water) let it stand for a day or two then boil it to drive out any remaining gasses."

I don't think the gasses are the problem here. I think chlorine might be the problem, and to fix that you must use a dechlorinator from your pet shop or pond shop. Old style chlorine will remove itself from standing water in 24-48 hours, but chloramines, now in use in most US city water supplies, is stable and will not remove itself from the water. Both prevent the growth of algae, bacteria, and fungi.

egbertfitzwilly (author)  chuckr445 years ago
OruKun ebcat5 years ago
ebcat, if you are worried about turbulance ask the suggested time for keeping the air pump on for aeration.
If your answer to ebger's suggestion is "I did all of that" the algae you may have gotten into shock with the new environment, thus if you are cultivating it from its habitat get some of the water from it before switching to yours.
And if the algae you extract still dies, its either unidentified human error or a weak organism  sample that is not suitable for your school project.
bigt46165 years ago
wait, my town uses ozone to clean the water(way more cleaner way) all it does is add oxygen to clean the water, so it should be safe to use, right, if not tho, theres a stream that runs by my house from a mountain so i could always use that. i was just wondering tho.
egbertfitzwilly (author)  bigt46165 years ago
Should be fine, I'd let it breathe for a day or two so that the dissolved excess oxygen can evaporate.
eh, im going to get it from the stream just in case. i somewhere that someone was doing this with water bottles, i think thats better to put it on a windowsill, im probaly going to do that and my pump has 2 ports, also my dad has a pond that he never cleans, so that should be crawling with algae. i also made a hydroponic system in my room last week. im feeling green this month, rofl.
k, i got the algae from my dads pond, its kinda clumpy and i turned on the pump and its just circulating arround. is that ok? also, can i put a timer on it so it only does is when theres light? cause they wont use photosynthisis at night.
egbertfitzwilly (author)  bigt46165 years ago
Yes, that should be a fine source of algae. A timer to turn off the light at night is also a good idea. You can probably run multiple bottles off of each port. If you run down to PetSmart you can find an aquarium manifold that will distribute air to multiple lines. Keep in mind that the bigger the pump the more power it uses. On the pump it should have somewhere the rated power in Watts. I use a pump rated at 1.8W (about 15kW/year). If you use a more powerful pump you may need to have some extra algae to consume the additional power. Also I found that when running multiple bottles from a single air line getting the back pressure correct in each bottle was critical. So fill the bottles and carefully adjust the opening to make sure everyone seems to be getting about the same amount of air.
You can get pressure balanced manifolds, but cost twice as much.
• • • Fuzzee Dee OUT • • • }~{ <> }~{ ^~^ :-> 
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