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Regardless if you are an amateur cannabis grower or are trying to have the best tomatoes in your greenhouse, there is always more to learn. Indoor cultivation requires just the right amount of outdoor ecology combined with a bit of environmental control. After all, beneficial fungi in the soil is good, but mold eating your crop is not.

The cannabis cultivators at HAPA are taking steps to innovate the indoor growing environment. They are using data-driven techniques and plant biology to create growing conditions that mimic the optimum outdoor ecosystem. Everything has to be dialed in just right at the small scale from humidity to the soil microbiome.

Like us, plants also have epigenetics, which is how different genes are activated or deactivated as a result of the environment. So HAPA is looking to create an environment suited to activate all the most desirable traits. They are growing not just the plants but also the fungi, algae, bacteria, and countless vital organisms that contribute to a complete ecosystem.

In addition to simple efficiency for the effort, HAPA also recognizes the need for sustainable growing practices. Synthetic fertilizers, toxic building materials and long supply chains can all have a negative impact on the outdoor environment. For each choice they make, HAPA also considers sustainability to keep their whole operation as a closed ecosystem with a minimal impact on waste streams or other non-sustainable industrial processes.

We had an epic conversation with Marco Teran, HAPA’s lead engineer, about how he and Creative Cultivator Lani Mendez utilize soil, water, and air quality to grow plants to their greatest genetic potential. Let’s take a look at 7 of their favorite tips.

Cannabis farmers tending to plants

1. A Tight Seal

The first step in creating the perfect indoor ecosystem is to make sure it does not mix with the local outdoor ecosystem. While we tend to think of most enclosed and unventilated spaces as practically airtight, even a very small exchange of air with outside can impact plant health and growth by altering the humidity, temperature, or chemical composition.

HAPA didn’t just seal the seam, they used a water-based epoxy on the walls and floor to prevent any exchange. As the epoxy dries the base evaporates, so it’s preferable to have water vapor in the air instead of a VOC solvent like acetone or ethyl acetate. These solvents can stick to other surfaces in the room and slowly re-release well after the epoxy is dry.

Sustainability bonus: Solvent-based epoxies can potentially release airborne chemicals as byproducts for days or weeks, impacting air quality for occupants from any domain of life. A water-based approach is better.

2. Humidity and Temperature

Having the right amount of water is much more complex than ensuring the soil doesn’t dry out. For each cultivar there is an optimum temperature and humidity that will balance transpiration, which is the balance of water evaporation at the surface of the leaf with how quickly the roots can replace it. The goal is to allow the water to flow at just the right rate through the plant. Too little and the plant won’t be able to move nutrients to the tissues that need them which can slow growth. Too much transpiration can use water faster than it can be replenished, leading to dryness.

Close-up of cannabis plant

Sustainability bonus: HAPA uses water from dehumidifiers and their HVAC system to irrigate, reducing reliance on the city’s water supply.

3. Carbon Dioxide

Plants have a more complex relationship with carbon dioxide than we do. They both release it and consume in different parts of their metabolism. Increased carbon dioxide can potentially increase the metabolic rate, leading to larger plants, but it’s not that simple. Marco told us that when a small room is packed with plants, microclimates will develop. Hotter, colder, wetter, or drier spots will be found throughout the space, impacting how much water the plant can use as we mentioned above.

Moving air around can help to mitigate these problems. Marco said If the air is moving too fast the plant may not be able to capture any extra carbon dioxide that is available. So once water capture is just right, carbon dioxide can be increased from the 300 to 400 ppm ambient levels. Marco told us that “1200 ppm seems to be the upper limit before a loss in efficiency,” but they’re aiming for 900 – 1000 ppm for now.

Sustainability bonus: Composting the stems and leaves from previous crops creates a closed-loop carbon dioxide cycle. Fungi in the compost release carbon dioxide that is then used by the plants, reducing or eliminating transport costs for bottled carbon dioxide.

4. What should not be in the air

The atmosphere is complex, so in addition to perfecting the humidity, temperature, and carbon dioxide, it also needs to be free of pollutants. Standard filters of the highest efficiency recommended for the HVAC system are vital, in addition to VOC and particle sensors to ensure a portable air purifier isn’t also necessary. High VOCs (TVOC is over 1500 ppb) or excessive particles (PM2.5 is over 35 ug/m3) aren’t good for people or plants, but can be removed with a purifier in the room that can handle both VOCs and particles, like our Molekule PECO purifiers.

 Molekule Air Pro air purifier next to cannabis plants

HAPA has learned to control for:

Ethylene, which is a plant hormone with a very simple chemical structure that is typically released to ripen fruit, but can also result as a byproduct of incompletely burnt propane. This can cause early maturation and death of plant tissues. HAPA removed a propane heater causing this issue.

Ozone was released from an ozone generator in an attempt to control the smell of the plants. Not only did the human occupants report chest irritation, but the ozone actually dissolved the trichromes on the surface of both living and curing plants. HAPA is now using other methods for smell control such as carbon filters on outlets.

Fungi like mold and powdery mildew are dangerous to plants but most healthy plants can fight them off. Observing standard sterilization procedures to avoid introducing spores and keeping the plants healthy is the simplest way to avoid fungal contamination.

Sustainability bonus: Propane and natural gas appliances contribute directly to climate change by emitting VOCs like ethylene and methane. Carbon dioxide is actually the least problematic of all greenhouse gasses, methane has 25 times more impact.

5. Bring in an ecosystem

Soil from a garden store is full of nutrients, but is missing some key ingredients. The beneficial fungi, bacteria, algae, and all sorts of other microorganisms that cooperate with the plant roots to create a perfect blend of nutrition need to be added.

The team at HAPA harvests this ecosystem from the local forest. Marco seeks out decaying hardwood trees like Redwood, and finds the delicate wispy spider web-like hyphae that represent a healthy soil microbiome. These bits are harvested and fed a carbohydrate solution and “fed” to the plants, though in this case the organisms are actually feeding each other.

Fertilized soil

Sustainability bonus: Eliminating reliance on synthetic fertilizers helps combat water pollution, packaging waste, and transportation pollution.

6. Use the best tools

One of HAPA’s key ingredients is accurate data. They employ sensors more commonly found in institutional research labs, and use them to develop a system that captures data throughout the grow room. Soon they plan to have temperature sensors every few feet to study microclimates.

They also are looking to the latest techniques used in emerging cannabis processing labs. Performing exhaustive biochemical testing can be expensive, but with modern sequencing techniques it can be possible to link specific sets of genes with the chemical products of the plant and vice versa. Combining this type of genetic data with the extensive sensor readings already captured will continue to improve overall crop yield.

This type of accurate analysis is necessary because most plants that are grown for their flowers have a growth cycle of just a few months, around 70 days in the case of cannabis. Marco tells us “one day of life for the plant is like an entire year of life for a person.” One day of deprivation to a plant is like a year of deprivation to a human, with the same lifelong consequences.

Close-up of cannabis plant

Sustainability bonus: Innovating the technology for sustainable cultivation.

7. Conserve electricity

You can use any of the techniques above to enhance the conditions in your greenhouse or any other indoor cultivation environment, and hopefully reduce impact on the outdoor environment. HAPA admits that the one consistent outside input into their system is electricity, which comes from the San Francisco municipal grid. While San Francisco’s downtown is already powered by 100% renewable energy and they plan to extend that to the rest of the city by 2030, reducing energy consumption is still a vital goal.

To conserve power HAPA uses LED lights, which are longer lasting and more efficient than incandescent bulbs. Cannabis requires different amounts of light at different points in its life, so HAPA also analyzes their data to find the optimal light intensity for each segment of the crop cycle. Marco tells us this reduces the electrical demand that would be possible using standard agriculture lighting. Soon they will be gathering data on different wavelengths of light during each interval of the crop cycle to further reduce the electrical load.

Sustainability bonus: Even 100% renewable energy contributes some environmental waste from parts and transport, so reducing electricity use helps to limit the impact.


At Molekule our mission is to spread the science of clean air, wherever the knowledge may be necessary. Keep an eye on our FacebookInstagram, and Twitter accounts for more information.


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