What Are Chemical Scrubbers in Hydroponics?

What Is a Scrubber in Hydroponics?

Today’s blog dives into a misunderstood but increasingly important tool in controlled-environment agriculture: chemical scrubbers. While the term “scrubber” may cause some confusion (especially if you’re British), in horticultural terms, it refers to a chemical or mechanical system used to clean the air inside grow rooms or greenhouses.

But how do these systems work? And more importantly, should you be using one?

Why Air Quality Matters in Grow Rooms

Your hydroponic grow room is a closed system—what happens in the air directly impacts your plants. Most growers are familiar with:

• Inlet filters – to block pests and airborne pathogens.
• Outlet filters (e.g., activated carbon) – to trap odors and VOCs before they leave the room.

But chemical scrubbers go a step further, removing specific gases inside the room—most notably ethylene.

What Is Ethylene and Why Should You Care?

Ethylene is a naturally occurring hydrocarbon gas and also a potent plant hormone. In low amounts, it regulates ripening and flowering. But in excess, it causes:

• Leaf drop
• Flower and fruit drop
• Premature ripening
• Symptoms similar to overwatering

For crops like tomatoes and cucumbers, ethylene exposure in grow rooms can severely reduce yield and cause developmental issues.

How Chemical Scrubbers Work

Most scrubbers work by using potassium permanganate—a bright purple, highly oxidizing solution. The air is bubbled through this chemical, which reacts with and neutralizes ethylene and other organic compounds.

Benefits:

• Effective at removing ethylene
• Reasonably safe compared to other oxidizing agents
• Can be contained to avoid human exposure

Warnings:

• Never use it to treat hydroponic nutrient solution – it strips iron and sulfur from the mix.
• Still hazardous if mishandled – always use within a closed-loop system.

Other Ethylene Control Methods

Aside from potassium permanganate, there are two other advanced ways to reduce ethylene in your grow room:

1. 1-MCP (1-Methylcyclopropene) – Blocks ethylene receptors in plants; used in post-harvest storage for bananas and flowers.
2. ACC Deaminase Bacteria – A microbial solution that reduces ethylene synthesis within the plant itself.

Each method has pros and cons, but for active grow environments, scrubbers remain a cost-effective, low-tech option.

When Not to Use a Scrubber

While removing ethylene is usually beneficial, some crops rely on low levels of it to develop properly:

🚫 Avoid scrubbers in legal cannabis and hop production.
Both require small amounts of ethylene to maintain female flower expression and avoid hermaphroditism.

If you’re growing these crops, interfering with ethylene can result in unwanted male traits or flower loss.

Scrubbers + CO₂ Burners: A Smart Combo

If you enrich your grow room with CO₂ via a burner, there’s a risk the combustion isn’t perfect, which can lead to ethylene build-up. In these cases, a scrubber is not just helpful—it’s essential.

🔥 Bad combustion = excess ethylene = stressed crops.

That’s why CO₂ levels above 1000 ppm often aren’t recommended. The yield benefits flatten, and ethylene toxicity can outweigh the gains.

Bonus: Scrubbers in the Produce Industry

Fun fact: Potassium permanganate is also used in banana shipping crates to scrub ethylene and delay ripening during long hauls. So yes, the same technology helping your grow room could be preserving your supermarket fruit!

Conclusion: Should You Add a Chemical Scrubber to Your Grow Setup?

If you’re growing ethylene-sensitive crops like tomatoes, cucumbers, or peppers—and especially if you’re using CO₂ enrichment—a chemical scrubber is worth serious consideration.

✅ Use it if:

• You’re noticing unexplained leaf, flower, or fruit drop.
• You use gas burners for CO₂.
• You’re running a sealed or semi-sealed grow room.

❌ Skip it if:

• You’re growing legal cannabis, hops, or ethylene-tolerant plants.

Chemical scrubbers might not be flashy, but in the right setup, they quietly protect your yield and create a more stable environment for plant growth.

Article by Dr Russell Sharp

If you would like to keep up to date with subjects just like this, you can listen to both our podcasts! Links can be found bellow:

Hydroponics Daily Podcast: https://open.spotify.com/show/207T7p7fw9sPjINfSjVXW2

Cereal Killers Podcast: https://t.co/eSEbBkTVHl