Blinded by the Light
Josh Armitage
Commercial Account Manager
Grow Generation
In our last SCC blog, we discussed the importance of lighting as a system of systems and the role it plays in sustainability and profitability of a cannabis business. After carefully planning, scoping and deploying a lighting system, most operators believe it is the end of the lighting road. Plants should use those photons for photosynthesis, yield and flower will be great, and lighting will be efficiently tuned to the operation. However, nothing could be farther from the truth.
A critical element that is missing from the above equation is light measurement. Measuring lighting levels in your cultivation facility could be the difference between making the most use of your investment and energy or literally leaving money (and yield) on the cultivation tables.
One of the authorities in horticultural and cannabis lighting, Dr. Bruce Bugbee, frames the root of the issue in one simple cause: humans and our visual system are not very good at quantifying light intensity.
What may look very bright from a human perspective, is dim for a plant. To put it in perspective, typical office building codes specify 300 lux (lumens/m2) of light as an acceptable level for safe human activity. That is 4 to 6 umol/m2s. A “bright” environment for humans is actually terrible for plant growth. If the rooms appear “bright” a cultivator may not measure light levels since it may appear to our eyes that there is sufficient enough light, but in reality it could actually be an order of magnitude or a significant percentage off-target from the desired PPFD level.
What are some of the practical implications of not quantifying light levels in a grow?
First and foremost, you may be leaving yield quite literally on the table. If a grower believes that they are growing in a 1000+ PPFD light environment but are actually operating 20 to 30% below, that is 20% to 30% yield that is essentially lost per growth cycle. Depending on the size of the grow, that could mean millions of dollars in annual revenue.
Conversely, if you are growing in a high PPFD environment and not measuring your light levels, you have no guide to adjust other parameters like CO2 to compliment high PPFD. Measuring light is a first step in understanding the photosynthetic environment your crop experiences day-in and day-out and having the knowledge to do something about it.
Measuring light levels also ensures you have an understanding of whether the light plan provided by your lighting vendor was accurate and that there is uniformity of light throughout your rooms. Fixture spacing, distance to crop and the optics of the fixtures are a few of many parameters that come into play when creating a lighting design. If any of these elements are not consistent with the lighting plan then you may have significantly different results from what you are expecting. You may have hot spots or significant dips in PPFD when you expect a uniform environment. Measuring light in space both throughout the room and at different levels, will ensure that you can accurately correlate your light environment to plant outcomes.
In the context of sustainability, not measuring and not knowing light levels in your grow rooms means that your operation is consuming energy (and money) and not deploying them optimally.
Lighting systems consume tens of thousands of kilowatt hours per day, whether it be LED or HPS. If you are missing your targets by 20 to 30%, it does not imply your power consumption is proportionally lower. A 1000W or 600W fixture will always consume that amount of power unless it is dimmed. Wasting wattage to obtain a suboptimal lighting environment will end-up squeezing cannabis business on both ends - on the revenue side with less yield to sell to the market and on the operational side since there is no relief on the energy costs. This results in a higher energy use, higher cost of production (g/ft2/kWh), and narrower profits.
Given the outsize impact lighting has, it appears the industry is increasingly paying attention to light measurement. The 2020 State of Cannabis Lighting Report shows a clear trend of cultivators paying attention to light measurement. The percentage of cultivators measuring light has grown steadily over the last five years from 55% in 2016 to 72% in 2020.
There is a growing awareness in the industry that cultivators will not be able to control, harness and maximize their lighting systems in the absence of measurement of lighting levels and the understanding of the intensity of light being shed on a crop. Bottom line, light measurement can optimize revenue and minimize profit (and product) loss.
