CO2 Supplementation, Simplified.

Plants grown indoors often consume more CO₂ than what enters the grow space naturally. These same plants become more productive when CO₂ levels are maintained at higher levels than atmospheric concentrations.

For these reasons, indoor gardeners provide supplemental CO₂ to their growrooms using a variety of methods. Compressed tanks, burners and the gardener’s own breath are all effective at providing the CO₂ necessary for growth, but mycelial CO₂ production is the easiest and most cost-effective means of maintaining beneficial CO₂ levels in gardens up to a certain size.

Mycelia are the fibrous, root-like networks formed by fungi throughout a substrate. Fungi are more closely related to animals than to plants; like animals, they exhale CO₂ as they grow. This CO₂ mixes throughout the grow space for use by plants. Mycelia come in small, pre-inoculated bags, buckets, pads or bottles already producing CO_2, without giving off any excess heat or requiring complicated set-ups.

While mycelial CO₂ is low maintenance, it is important to place it in the correct area in a grow space to get optimal results. It should be placed high enough in the room so the CO₂ cascades over the plants instead of pooling at the bottom of the grow space where plants cannot reach it. Some forms of supplemental CO2 can be placed on or near the grow lights, which also helps optimize mycelia productivity, as this location increases heat and oxygen flow to the bags.

For any supplemental CO₂ to be effective, it’s important to ensure the growth of your plants is not significantly limited by other variables. Considering mycelial CO₂ doesn’t provide as much of the good stuff as compressed gas or burners, it is important to set your ventilation fan to run only when the grow space thermometer reaches the highest temperature tolerable by the plants.

This ensures the CO₂ produced by the mycelia remains in the grow space long enough to be taken up by the plants. If the grow space contains multiple, high-power lights, they should be water-cooled rather than fan-cooled to ensure the CO₂ produced by the mycelia can be used up, while keeping the lights and the grow space from overheating.

Eventually, the size of a grow space limits the effectiveness of mycelial CO₂ supplementation. With large growrooms containing many lights, compressed gas or burners remain the most cost-effective means of providing the extra CO₂ plants need.

However, there are ways to maintain or even improve the cost-effectiveness of mycelial CO₂ supplementation. Try adding them to a new substrate or experimenting with different species of fungi, for example.

The Extra Mile

Mycelia eventually stop generating CO₂ once they have consumed all of the usable material within their package, at which point they become inactive, but not “dead.” By providing mycelia with a new food source, they become active again and are happy to continue growing and producing CO₂ while they decompose the new material.

Hay, manure, coffee grounds, rye pellets and many other materials are suitable for consumption by mycelia and can be prepared/sterilized at home or bought prepackaged online. Older mycelia can be broken down and mixed into the new media manually, or via syringe if adding liquid media to pre-sterilized bags.

Gardeners using soil substrates can also mix mycelia directly into the dirt before adding plants. These mycelia will produce more and more CO₂ as they grow throughout the soil during the entire lifetime of plants, and will remain active even when new crops are added into the mix.

For those looking for more than just the additional CO₂ in their growrooms, mushrooms like oysters, shiitake, wine caps and lion’s mane not only produce CO₂ while they grow, but can also be eaten. All of these edible mushrooms enjoy warm indoor environments and provide delicious rewards for the oxygen they get from the plants. These fungi can produce several flushes of mushrooms before they finish decomposing their substrate, if they are given more water after each flush.

To recap, mycelia CO₂ can be of great benefit to indoor gardeners if used correctly. Mycelia placed high in the grow space with minimal ventilation will generate a helpful boost in CO₂ levels for extended periods of time for smaller grow spaces without the need for complicated, expensive equipment.

Mycelia can also be reused by adding them to new grow media and, with some extra effort, can even grow edible mushrooms. Fungi and plants have an ancient partnership and the gases they exchange throughout the grow space greatly benefit the plants within.