How to Make CO₂

Reviewed by Anne Schmidt

Last Updated: November 7, 2024 References

CO₂ is the chemical symbol for carbon dioxide. Carbon dioxide provides the fizz in soda and many alcoholic beverages, the lift that makes bread rise, the propellant in some aerosols, and the suppression in fire extinguishers. CO₂ can be produced deliberately or as a by-product of other chemical reactions.

Part 1

Part 1 of 2:

Making CO₂ At Home

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1
Get a 2-liter plastic bottle. Use plastic instead of glass; if you should build enough pressure to rupture the bottle, a plastic bottle will not explode the way a glass bottle would.
- If you're planning to use the generated CO₂ to supply carbon dioxide for the plants in your aquarium, a bottle of this size will provide an adequate supply for a 25-gallon (94.64 l) aquarium.
18 ml) of sugar. Use raw instead of refined sugar, as it has more complex sugars that will take longer for the yeast to break down. It's also cheaper.

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Warm tap water is sufficient; hot water will kill the yeast.
46 ml) of sodium bicarbonate. Sodium bicarbonate is the principal ingredient in baking soda, available at most stores.
5
Add 1/2 teaspoon (2.46 ml) of any yeast extract. If available, this will help the yeast last longer.
- An example of a yeast extract is Vegemite, found in Australia. Other yeast extracts include Bovril, Cenovis, and Marmite.^{[1]
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64 ml) of yeast. Brewer's yeast lasts longer than baker's yeast, but baker's yeast lasts long enough for the reaction and is cheaper than brewer's yeast.
You should see a slight foaming at the top of the water.
10
Wait 2 to 12 hours. The water should start to bubble during this time, showing that CO₂ is being released. If you don't see bubbling after 12 hours, you either had the water too hot or your yeast is no longer active.
- Your solution should bubble at about the rate of 2 bubbles every second. Any faster, and you may upset the pH of the water.^{[2]
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Part 2

Part 2 of 2:

Other Ways CO₂ is Produced

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1
Exhale. Your body uses the oxygen you inhale to react with the proteins, fatty acids, and carbohydrates you ingest. One of the results of this reaction is the carbon dioxide you exhale.
- In contrast, plants and some forms of bacteria take carbon dioxide from the air and, with energy supplied from sunlight, make simple sugars (which are carbohydrates).
2
Burn something with carbon in it. Life on Earth is based on the element carbon. To burn something requires a spark, a fuel source, and an atmosphere to burn it in. The oxygen in our atmosphere readily reacts with other substances; put it with burning carbon, and you get carbon dioxide.
- Calcium oxide (CaO), also known as quicklime, can be produced by burning limestone, which contains calcium carbonate (CaCO₃). The CO₂ is driven off, leaving the calcium oxide. (For this reason, it is also called burnt lime.)
3
Mix carbon-containing chemicals. The carbon and oxygen that make up CO₂ are found in a number of chemicals and minerals classified as carbonates or, when hydrogen is also present, bicarbonates. Reactions with other chemicals can release CO₂ into the air or mix it with water to form carbonic acid (H₂CO₃). Some of the possible reactions include the following:
- Hydrochloric acid and calcium carbonate. Hydrochloric acid (HCl) is the acid found in the human stomach. Calcium carbonate (CaCO₃) is found in limestone, chalk, eggshells, pearls, and coral, as well as some antacids.^{[3]
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  Go to source} When the two chemicals are mixed, calcium chloride and carbonic acid are formed, and the carbonic acid breaks down into water and carbon dioxide.
- Vinegar and baking soda. Vinegar is a solution of acetic acid (C₂H₄O₂)^{[4]
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  Research source}, while baking soda is sodium bicarbonate (NaHCO₃). Mixing them produces water, sodium acetate, and CO₂, usually in a foamy reaction.
- Methane and water vapor. This reaction is performed industrially to extract hydrogen by using steam at high temperatures. The methane (CH₄) reacts with the water vapor (H₂O) to produce hydrogen (H₂) and carbon monoxide (CO), a deadly gas. The carbon monoxide is then mixed with water vapor at lower temperatures to produce more hydrogen and turn the carbon monoxide into safer carbon dioxide.^{[5]
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- Yeast and sugar. When yeast is added to sugar in solution, as in the instructions in Part One, it forces the sugar to break down and give off CO₂. The reaction also produces ethanol (C₂H₅OH), the form of alcohol found in alcoholic beverages. This reaction is called fermentation.

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Question

Can I make dry ice with homemade CO2?

Shubham Nanche

Community Answer

It is nearly impossible to make homemade dry ice, as CO2 starts liquefying under pressure and as low as -65°C.

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Tips

To use the bottle-made CO₂ with your aquarium, you will need to drill a narrow hole into a 2-liter bottle cap, run rubber tubing through it, and cement it in place. You should also have an airline valve to keep water from being sucked in as the carbon dioxide escapes and a pressure release of some kind to prevent the bottle from exploding if the CO₂ doesn't release properly. In addition, you can hook up a bubble counter to check how fast the carbon dioxide is escaping.^{[6]
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Warnings

Many times, the by-product CO₂ is produced in quantities too small to be captured. Unfortunately, this carbon dioxide, released into the atmosphere in sufficient quantity, will trap heat from the sun and prevent it from escaping back into space, thus raising Earth's temperature. This is considered by many scientists to be the leading cause of climate change.

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