6 Best Greenhouse Carbon Dioxide Generators For Plant Growth On a Budget
Boost plant growth and maximize yields on a budget. We review the 6 best cost-effective CO2 generators to enhance photosynthesis in your greenhouse.
You’ve dialed in your lights, your nutrients are perfect, and your watering schedule is down to a science, yet your plants seem to have hit a ceiling. If your greenhouse is sealed up tight, the limiting factor isn’t what you’re putting in the soil—it’s what’s missing from the air. Supplemental carbon dioxide is the key to unlocking the next level of growth, and you don’t need a commercial budget to make it happen.
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Why Your Greenhouse Plants Need More Carbon Dioxide
Plants build themselves out of thin air, literally. They use carbon dioxide (CO2), water, and light to create sugars through photosynthesis, which fuels their growth. In an enclosed greenhouse, especially one sealed for winter, your plants can use up the available CO2 surprisingly fast. Once the ambient CO2 level drops, photosynthesis slows down, and plant growth stalls, no matter how much light or fertilizer you provide.
Think of it this way: light and nutrients are the fuel, but CO2 is the oxygen that lets the engine run. Standard atmospheric CO2 is around 400 parts per million (PPM). By raising the level inside your greenhouse to 1,000-1,500 PPM, you’re essentially turbo-charging the photosynthetic process. This can lead to faster growth, stronger stems, and significantly increased yields.
However, adding CO2 isn’t a magic bullet. If your lighting is weak or your plants are nutrient-deficient, they can’t use the extra CO2. It’s a holistic system. Enriching your air with CO2 only works if you also give your plants the increased light, water, and nutrients they’ll need to support that accelerated growth. It’s a fantastic tool for breaking through plateaus, but only after you’ve mastered the fundamentals.
Titan Controls Ares 2: Reliable Propane CO2 Burner
When you’re ready to move past passive methods, a propane burner is a reliable and effective workhorse. The Titan Controls Ares 2 is a popular choice for small to medium-sized hobby greenhouses because it’s straightforward and built with safety in mind. It works by burning clean-burning propane, which releases both carbon dioxide and water vapor—a nice bonus for maintaining humidity.
This unit comes with two burners, allowing you to adjust the output for different-sized spaces, typically up to a 10′ x 10′ room. Installation is simple: hang it, connect it to a standard propane tank (like the one for your grill), and plug it in. The electronic ignition means no pilot light is constantly burning fuel, and it includes crucial safety features like a tip-over switch that automatically shuts the unit off if it gets knocked over.
The main tradeoff here is the ongoing cost of propane and the need for proper ventilation. You must ensure your greenhouse has some air exchange to prevent the buildup of heat or other gases. A burner is an active system, so it’s best paired with a CO2 controller or at least a timer to prevent wasting fuel and running CO2 levels dangerously high. It’s a fantastic step up for the serious hobbyist who wants consistent, powerful CO2 enrichment.
ExHale 365 Self-Activating CO2 Bag for Simplicity
If you want the absolute simplest entry into CO2 enrichment, you can’t beat a mycelial CO2 bag. The ExHale 365 is the original and still one of the best for small, enclosed spaces like a grow tent or a tiny greenhouse. There is no setup, no power, and no maintenance. You just hang the bag above your plants and walk away.
The bag contains a living, breathing block of mycelium (the root structure of mushrooms) growing on a sterilized substrate. As the mycelium consumes the substrate, it naturally exhales CO2, 24 hours a day. The "365" model is designed to produce a steady, low-level stream of CO2 for up to nine months, making it a true "set it and forget it" solution.
The downside is a complete lack of control. You can’t turn it off or adjust the output, so it’s not ideal for spaces that require ventilation, as you’ll just be venting the CO2 outside. These bags are most effective in small, completely sealed environments where a slow, steady release can build up over time. For a 4’x4′ tent, one or two of these can make a noticeable difference without any complexity.
TNB Naturals The Enhancer: Just Add Warm Water
Similar to the ExHale bag, The Enhancer from TNB Naturals offers a simple, natural way to generate CO2, but with a different mechanism. Instead of mycelium, it uses a mix of dehydrated yeast and other organic ingredients inside a canister. To activate it, you simply add warm water, shake it up, and hang it in your grow space.
The yeast begins to ferment the sugars in the canister, releasing a steady stream of CO2 through small holes in the lid. It’s an incredibly cost-effective way to get started, with a very low initial purchase price. The reaction typically produces CO2 for about two weeks, after which you can buy an affordable refill pack to start the process over again.
This is a great option for experimenting with CO2 on a shoestring budget. However, its short lifespan means you’ll be replacing or refilling it frequently, which can become a chore. The output can also be a bit inconsistent, peaking in the first few days and then tapering off. It’s perfect for short-cycle crops or for someone who wants to see the effects of CO2 before committing to a more expensive system.
Pro-Leaf CO2 Regulator: Precision on a Tight Budget
This option isn’t a generator itself, but a tool for managing a CO2 tank—the most precise method available. The Pro-Leaf CO2 Regulator is an affordable yet reliable piece of equipment that connects to a standard CO2 tank (the kind used for kegerators or soda machines). It allows you to control the flow of CO2 into your greenhouse with incredible accuracy.
The real advantage of a tank and regulator system is control. The Pro-Leaf includes a high-quality solenoid valve that you can connect to a timer or, even better, a digital CO2 controller. This allows you to set a target PPM level (say, 1,200 PPM) and the system will automatically release CO2 only when needed, shutting off when the target is reached. This is by far the most efficient method, ensuring you don’t waste a drop of CO2.
The initial investment is higher. You have to buy the regulator and source a CO2 tank, which can be purchased or rented from a local welding supply or brewery store. However, the long-term running cost is often the lowest of all methods, as tank refills are relatively cheap. For the data-driven grower who wants to dial in their environment perfectly, this is the ultimate budget-friendly path to precision.
CO2Boost Bucket: A Natural Pump-Driven CO2 System
Easily control your beer's carbonation with this durable CO2 regulator. Featuring an adjustable 0-60 PSI range and a check valve to prevent backflow, it ensures consistent pressure and a clean brewing process.
The CO2Boost Bucket strikes a nice balance between the simplicity of a CO2 bag and the active distribution of more advanced systems. Inside the bucket is a proprietary mix of organic compost ingredients that naturally decompose and release CO2. What sets it apart is the included small air pump and tubing.
Instead of passively letting the CO2 seep out, the pump pushes air into the bucket and directs the CO2-rich output through a tube that you can place directly over your plant canopy. This ensures the CO2 is delivered right where the plants need it most, rather than just pooling near the floor or ceiling. The system is designed to run for 60-90 days and requires no daily maintenance beyond ensuring the pump is plugged in.
This is a great middle-ground solution. It offers better distribution than a passive bag without the complexity or safety considerations of a propane burner. It’s ideal for someone with a small-to-medium greenhouse who wants a natural, hassle-free CO2 source but also wants to make sure that CO2 is being actively delivered to the plants for maximum absorption.
AutoPilot CO2 Generator for Larger Hobby Greenhouses
When you scale up your hobby greenhouse to something larger, like a 12’x20′ or bigger, the smaller generators just can’t keep up. The AutoPilot CO2 Generator is a step up in power and is designed to enrich larger volumes of air effectively. It operates on the same principle as smaller propane burners but is built with more burners (typically four to eight) for a much higher CO2 output.
These units are built for durability and safety, with features like solid-state electronic ignition and dual solenoid valves for redundant fuel control. They are designed to be part of an integrated environmental control system, working in tandem with timers and CO2 monitors to maintain precise atmospheric levels. This isn’t a beginner’s tool; it’s for the hobby farmer who is serious about maximizing production in a larger, well-sealed structure.
The investment is more significant, both in the unit itself and the amount of propane it will consume. But for a large space, trying to use multiple small generators or dozens of CO2 bags is simply impractical and inefficient. Matching the generator’s BTU output to your cubic footage is critical for both effectiveness and safety. The AutoPilot series provides a reliable, powerful solution when your ambitions outgrow the smaller options.
Matching Your CO2 Source to Your Greenhouse Size
Choosing the right CO2 source is less about which one is "best" and more about which one is right for your specific setup. Pumping propane-generated CO2 into a tiny grow tent is overkill and unsafe, while hanging a single CO2 bag in a large greenhouse is like trying to heat a barn with a candle. The first step, before buying anything, is to seal your space as well as possible. There’s no point in generating CO2 if it immediately leaks out.
Once sealed, you can use your greenhouse’s size as a guide to narrow down your options. Here’s a simple framework:
Small Enclosed Spaces (e.g., 4’x4′ tent, small cold frame): This is the perfect environment for passive, natural generators.
- Best Bets: ExHale 365, TNB Naturals The Enhancer, CO2Boost Bucket.
- Why: Low cost, zero complexity, and their gentle output is sufficient to enrich a small, sealed volume of air.
Medium Hobby Greenhouses (e.g., 8’x10′ to 10’x12′): Here, you need more power and control. You’ve moved beyond passive methods.
- Best Bets: Titan Controls Ares 2 (propane), Pro-Leaf Regulator with a 20lb CO2 tank.
- Why: These systems have the output to raise CO2 levels meaningfully in this volume of space and offer control via timers or controllers, preventing waste.
- Large Hobby Greenhouses (e.g., 12’x20′ and up): At this scale, efficiency and power are paramount.
- Best Bets: AutoPilot CO2 Generator (propane), or a larger 50lb CO2 tank with a regulator.
- Why: You need the high output of a multi-burner generator or the large capacity of a big tank to avoid constant propane or CO2 tank swaps.
Ultimately, your budget and desire for control are the final deciding factors. A CO2 bag is cheap and simple, while a tank and regulator offer precision at a higher upfront cost. Start with the option that best fits your space, and you’ll be on the right track to boosting your plant growth.
Supplemental CO2 can feel like an advanced technique, but these budget-friendly options make it accessible for any dedicated hobby farmer. The key is to match the solution to the scale of your operation and remember that CO2 is a growth multiplier, not a substitute for good light, water, and nutrients. Get the basics right, seal your space, and adding CO2 could be the single biggest step you take toward a more productive greenhouse.
