Simple Algae Home CO2 Scrubber - Part 1

Intro: 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.

STEP 1: Bill of Materials

Okay here's what we'll need:

Tools:

Drill or drill press with 3/16" bit
Razor knife or scissors
Hot glue gun - Optional
Funnel - Optional for filling bottles

Materials and where I got them. I have no relationship with any of these stores or products. They are inexpensive and should be commonly available:

1 X 8' 1/4" aquarium airline tubing - PetSmart Top Fin brand or ACE Hardware flexible plastic tubing
1 X 3' 1/8" inch rigid plastic air hose (3/16 outer diameter) - PetSmart Top Fin brand
1 package 6 air stones - PetSmart Top Fin brand (also available individually)
1 x 2L Clear Plastic soft drink or water bottle with screw on top - Recycled
1 x 2L de-chlorinated water for breeder reactor

On the next page we'll learn more about dechlorination

STEP 2: Preparing Tap Water for Use in Algae Cultivation

Most (if not all) municipal water supplies, and many holding tanks for wells in rural communities, farms, and ranches, are treated with chemicals to kill off any harmful bacteria or other pathogens which may get into the water. The most common of these chemicals are chlorine and chloramine.

Though the dosages of these chemicals in the water supply are low enough that they are not harmful to a land animal (including people, dogs, cats, hamsters, horses, etc) or house plant, they are high enough to eliminate or inhibit the growth of micro-organisms including algae

Chlorine is very volatile, so it will evaporate very quickly from your source water. If your water is only treated with chlorine, then letting it stand over night should allow the chlorine to evaporate from the water and make it safe to use. In fact, you can even speed this up by bubbling air through the water with an air stone. This will increase the surface area of the water and allow the chlorine to evaporate even faster.

However, this is one of the primary reasons for switching form chlorine to chloramine treatment of water supplies. Unlike chlorine, chloramine is non-volatile. It doesn't evaporate quickly. If your source water is treated with chloramine, it is important that you get a dechlorinator that will neutralize chloramine.

I would try letting the water stand overnight. If algae fails to grow in the medium after a couple of weeks try again with bottled or collected rainwater.

Okay, we've let the water sit out overnight and are ready to begin our adventure in algae cultivation.

First we'll need to gather some algae and nuture it until we have enough to get our scrubber going.

STEP 3: Obtaining an Algae Culture

In many documents about growing algae the concept of how to get algae is arguably the most intimidating step. Practically all of the sites have recommended scientific supply houses which offer exotic algae culture specimens suitable for advanced use in the latest biotechnology project.

Fortunately we're not doing that and therefore we can take advantage of the fact that algae will grow anywhere in water unless one works actively to prevent it. Ask any aquarium owner.

So first we will obtain an algae sample.

If you know somebody who has a fish tank the simplest solution is to ask them for an algae sample before they clean it next time. Scrape the green stuff off the side of the aquarium along with a little bit of fish tank water. Trust me, that's all the algae you're going to need.

As an alternative you might check with a friend or neighbor who has a hot tub. Algae like warm temperatures so a healthy sample might easily be available before the hot tub cleaning cycle. Different folks have different tolerances for chemicals and some folks might have more or less aggressive chemical policies. The hot tub at your spa probably isn't going to yield a good sample....and if it does you might consider changing spas....also remember to be a tactful when asking that neighbor you don't know so well if they've got a hot tub full green, floating goo...

Alternatively algae cultures may be obtained by getting a little water out of a natural stream, creek, pond or lake. In this case it's been raining here lately and a nice algae culture has taken root in the birdbath. I drew out a small sample, trying to keep it clean. While we're not concerned with pure algae cultures at this time we want to reduce the number of miscellaneous micro-organisims we include.

Once we've obtained a reasonable sample we're going to breed the algae in order to produce the feedstock for the scrubber. In order to do that we're build a high volume breeder reactor in our next step.

STEP 4: My First Breeder Reactor....

No, a breeder reactor is not the cornerstone of a secret WMD project. The word reactor is used in this context as shorthand for "reactor vessel". In this case the reactor vessel will hold algae, water and nutrients for the purposes of breeding the algae, hence the name "breeder reactor".

We'll start with the 2L soft drink or water bottle and the 3/16" drill bit. We're going to drill a hole in the center of the plastic cap, insert a piece of 1/8" rigid plastic tubing, glue that in place. Then we will fill the bottle with water, add the algae culture and nutrients and wait for nature to take it's course.

Fit the drill bit into the drill and drill a 3/16" hole in the center of the plastic cap. Cut off a 10" section of rigid plastic tubing with scissors. Feed that through the hole in the cap until approximately 1" projects from the top.

Cut off a 1" piece of the flexible plastic air hose and remove one of the air stones from the 6 pack. Attach the flexible tubing to the bottom of the air hose and attach one of the air stones to the other end.

Fill the bottle most of the way with dechlorinated or fresh water. Now add the algae sample we took earlier. A funnel isn't strictly required as long as most of the culture makes it into the reactor.

Fill the bottle up the rest of the way with dechlorinated water and insert the cap bubbler assembly. Your breeder reactor is now charged and ready.

Now take out the air pump. I selected the Tetra 799 based on its low capacity, inexpensive price and being in stock at PetSmart. Any air pump will suffice.

Decide where you will place your reactor, remember that this is a plant which uses photosynthesis. The more direct sunlight it recieves the better. Locate an outlet for the pump. Cut a length of flexible tubing that will reach from the air pump to the input located on the cap. Attach the pump to the reactor with the tubing. Tighten the plastic cap down and then open it 1/4 turn. This will allow the scrubbed air and generated oxygen to escape.

At this point you are actively scrubbing carbon and breeding algae for the next phase of the reactor.

STEP 5: Scrubbing CO2 in the Window

Now loosen the top at least a1/4 turn and plug in the pump. Leave enough space at the top of the bottle that the water doesn't bubble out.

With a couple of days the water will begin to turn murky and then green. The intro picture shows this reactor after approximately 1 week.

Watch the water level for evaporation and top it off periodically, preferably at the same time as feeding. Mineral water is an excellent supplement for trace minerals not found in Shultz nutrients.

In Part II we'll talk more about culturing and cultivating algae and learn how to make a true algae nutrient medium.

STEP 6: For More Information

For more information regarding this I used the following sources:

Carbon Dioxide Emissions from the Generation of Electric Power in
the United States available from the Department of Energy:

http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2report.html

and "Gas Exchange of Algae" available via the National Library of Medicine (pubmed.gov) at
http://www.pubmedcentral.nih.gov/pagerender.fcgi?artid=546951&pageindex=1#page

or the PDF is attached.

Comments

[james 11111]

By going vegan you apparently save 600LBs of CO2 a month...that's 7200LBs a year for you math wizz kids. so say you just ate meat and dairy every other day that would be...?

[H3xx]

Old post is old, but I felt the need to reply. The meat that you would have bought before going vegan is literally just being bought by someone else. The only way going vegan will help is if, say, an entire town went vegan. And that would be a drop in the bucket. If all of America went vegan, it would have a drastic effect on CO2, but unless we took care to eliminate the excess cow population as it happened (humanely of course) it would have a very BAD effect. If the number of cows and pigs we consume during a year were suddenly released into the wild, they would graze the plant life in the environment down to extinction and then starve to death on mass.
Don't get me wrong, I support the ending of industrial farming, but we have responsibilities as apex predators in our ecosystem to keep the herbivorous life in that ecosystem in check. And the easiest way to do that is by eating what we cull so that the death isn't meaningless. That said, we absolutely could do with far less meat consumption. Meat culture is pretty insane.

[one.kender]

Are you pulling more cow out of the air than your pump is burning in electricity?

[james 11111]

I am doing the same thing but have come across a 1 watt USB pump and have bought a solar power bank. I used a spagetti jar i wasnt using instead of a plastic bottle. For the medium i used a chlorella capsuel. I have sat a bath sponge on top of the water and a piece of activated carbon from a cooker hood filter as i mainly wanted it just to be an air purifier in winter when i don't have the windows open. i have also added a few aquarium moss balls for decoration and some non toxic glow stones as i wanted it to be an ornamental feature as well. Now i have an air purifier and a bit more oxygen and a little less CO2. My original idea was just to bubble air through water and add essential oils but this is far more interesting and organic. Thanks egbertfitzwilly, much appreciated guide.
James

[smertrios2007]

The fatal flaw in your plan... assuming you have a 2 watt air pump (very small i'm guessing its bigger) then your cabon footprint *just* for the pump is 17,520 watts for a year that 520 watts more than you scrubber can absorb!

[Jolly]

I'm inclined to think that part of the solution should include a green power source then you're good. Having stated that, you always need to take that first step towards something better 😉

[sspence]

only if your power generation produces carbon.

[Azilys]

Hello.
How did you calculate the level of carbon dioxide absorption? Do you still have sources that give the coefficients that allow you to make such calculations?

[jhorthos]

I'm afraid this is the equivalent of a perpetual motion machine. The carbon has to go somewhere - if you removed most of the algae every few days and poured it down the drain, letting the remainder regrow, the scrubber would work because the fixed carbon (in the form of algae) would go down the drain. I suspect it wouldn't fix enough carbon to be worth it, but at least it would do something. The reactor as described would fix carbon as the algae grows to saturation (a few days) and after that net carbon flux would be zero. The principle of fixing carbon with plants depends on the plants growing and storing the fixed carbon in some fairly stable manner (for example as wood).

[sspence]

fartilizer for plants, or if using spiruline, food for you.

[AspiringEngineer]

I imagine scooping out and dumping ~90% of the algae every few days or so and tossing it on the ground or burying it would work. I imagine it could be used as a fertilizer for terrestrial plants, too.

[caston81]

Will this measurably reduce the reading of CO2 ppm in a room?
Does it release converted oxygen into the room?

[sspence]

34 of these would counter one person's co2 exhalation.

[sspence]

I was curious if I could practically cleanse the air in a sealed habitation. 1 person releases approximately 1000 grams of CO2 daily. One 2 liter bottle of algae can remove 30 grams of CO2 daily, so I figure 34 bottles per person. Algae grow great using human pee as the medium, so no need to purchase "nutrients".

[TinaIgnacio]

Hello, may I ask why did you use algae? Is there any other plants that can be used?

[cburgess7x]

Hello, I'm constructing a bunker and have the idea of, instead of using air ventilation to and from the surface, use oxygen scrubbers instead, which a bing search lead me to this instructable. So lets say I got 20 or 30 or 40 standard 30gl aquariums with algae cultures, would it be possible to support life just on that, or would I need more or less, or a different approach to the idea. I'm planning on said bunker to comfortable support up to 6 people should my family become that large.

[Mrs. KathleenA]

Will you be able to provide sunlight for your aquariums or grow lights? Light is needed for the process.

[cburgess7x]

Holy sh*t, I forgot all about this :D I've done my due research also. There have been 2 biosphere experiments, which, as massive as they were, 3 acres in size, were not self sustaining. The first one lasted 2 years, and the second lasted about the same time, both facing similar issues. The end results were that you could not live indefinitely in an enclosed ecosystem. So I basically can just forget about having my own little cavern sealed off from the rest of the world. I still think it could be possible, but it just isn't practical.

[mr.lilliken]

Theoretically yes, but i have done some research and some damn how, no one anywhere has every successfully supported themselves by plants only within a closed environment. ((Or search engines are shipt)). There may eventually be some nitrogen balancing issues though, and idk about more exotic things, but oxygen and CO2 will be easily regulated.

this will help, but i'm not going into the rest of my calculations and guestimations unless someone replys https://en.wikipedia.org/wiki/Photosynthetic_efficiency
Anyways, i guestimate you'd need around 4000watts of power continously lighting plants for minimum viability of this idea, you may require much more. That is a lot of power, but it is also a lot of crops that you can grow (though land crops are less efficient than algea). Hope you have power!

Edit: I am assuming 100 watts of food energy is properly processed by the human and that the CO2 and oxygen emitted are proportional to that (idk, but wat is an order of magnitude between friends). between 1% (all land crop plants mildly pessimistic) and 8% (good algea and LED lights, i though i heard a 30% once upon a time?) light to plant biomass. which means 100 watts * 100/1 TO 100 * 100/8 = = = = 10,000 watts TO 1,250 watts. Of course, i'm no expert in this feild and i still have many questions these each maybe off multiple times over.

[BushrahK]

I have built one of these using the steps provided, but my only question is how do you know it's actually working?