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In the first four installments of this calibration science series, we covered sources of error, signal-to-noise ratio (SNR), precision, accuracy, reducing noise, how to plot a calibration line, and how to measure calibration quality (1-4). In this, the fifth installment, we will continue the calibration quality control theme. Sometimes in a data set used to generate a calibration, one or more data points will stand out as being not like the others and these data points are called outliers. How to spot outliers and potential ways to correct them will be discussed here.

Back in the day on the American children’s show Sesame Street (5) they played the game “Which of These Things is Not Like the Others”. For example, they might show pictures of a duck, a hen, a pigeon, and a dog. In this case, the thing not like the others was the dog since it is a mammal and not a bird, making the dog an outlier. In calibration science spotting outliers is like this, spotting data points that are not like the others.

For our purposes we will limit ourselves to a discussion of outliers in the types of analyses performed in a cannabis analysis lab. Probably the most important thing measured in these labs is total tetrahydrocannabinol (THC) or potency. Two of the most common potency methods are high pressure liquid chromatography (HPLC) with ultraviolet-visible (UV-Vis) detection (6) and mid-infrared spectroscopy (7). In both these cases, spectral absorbance readings and concentration data are used to plot calibration lines. Thus, we will restrict our discussion to spotting concentration and spectral outliers.

A good way to spot concentration outliers is to first calculate a set of concentration residuals

 A concentration residual is the difference between the known and predicted concentration for a standard used in a calibration. This quantity is calculated using 

 is the concentration residual; C is the actual concentration; and C’ is the predicted concentration.

The concentration residual measures how well the concentration in a specific standard was predicted.

The next step in spotting concentration outliers is to plot the residuals versus sample number as seen in 

. The data in this case are for the isopropyl alcohol (IPA) calibration discussed in a previous column (4), thus the units of the residuals are volume percent IPA.

Under normal circumstances this plot should be a random scatter of points with no apparent structure and with the magnitude of all the residuals approximately the same. Note in the plot that for samples 1,3,4, and 5 the residuals are all right around 1% IPA, but that for sample 2 the residual is -15.9% IPA; this thing is certainly not like the others! This residual is 15 times bigger than the others.

Once we spot an outlier, the question we have to ask is whether to include that standard’s data in a calibration or not. Ideally, we need to find the assignable cause as to why something is an outlier. This term is statistics speak for the reason why something is an outlier. If we understand why something is an outlier, we can fix the problem or justify not using the data in a calibration.

In the case of sample 2 in Figure 1 the assignable cause was easy to find: I typed the wrong concentration value for sample 2 into the spreadsheet used to generate the calibration line. Correcting this typo gave the concentration residual plot seen in 

With the typo corrected the concentration residual for sample 2 was reduced from -15.9% IPA to 0.3% IPA, illustrating the power of concentration residual plots to improve calibrations.

There are a number of reasons why concentration outliers happen including:

1. Transcription Errors: In other words, typos. Often times the absorbance and concentration data for a calibration have to be typed into a spreadsheet or some other computer program. It is very easy to mess up the transcription of these numbers, i.e. to commit a typo. This is exactly what we saw with Figures 1 and 2 above.

2. Poorly made standards: In calibrations that use concentration data, the error in the known concentrations in the standards is often times the biggest source of error in the analysis, and lack of care and poor technique when making standards can condemn you to always having poor calibrations. Hence,anything you can do to improve the quality of known concentrations in your standards will pay dividends in calibration quality.

3. Sample Problems: If the concentration of the analyte in your standard changes between when you make the standard and when you measure its absorbance that is a problem. Things that can cause this to happen include reactions taking place within the sample, evaporation of the sample, or analyte precipitating out of the sample. A good way to check this problem is to monitor your standard samples over time. For instance, once you make a fresh standard measure its absorbance every few minutes, then hours, to see if it is stable or not.

Remember our calibration consists of concentration data and spectral absorbance data. Spotting concentration outliers involved calculating concentration residuals, similarly, spotting an outlier in the spectral absorbance data is done by calculating a spectral residual, the formula for which is seen in 

 is the spectral residual; A is the actual absorbance; and A’ is the predicted absorbance and where the actual and predicted absorbances may be peak heights or peak areas.

For the calculation of concentration residuals we had the predicted concentration, C’, already in our hands since we needed it to calculate calibration metrics. Where do we obtain the predicted absorbance? From the calibration line equation itself. The calibration line for our IPA method is seen in 

We discussed calibration lines in previous articles (1-4). Briefly, 0.165 is the slope of the calibration line, and -0.6834 is the 

-intercept. Since peak area (spectral absorbance) is on the 

-axis, if we know the concentration of any given IPA sample (X), we can calculate its corresponding peak area by plugging the concentration value into Equation 3 and then solving.

Now, to obtain the predicted peak area as needed for the spectral residual calculation we would use the predicted concentration as the X in Equation 3, and solving for Y would give us the predicted absorbance. The predicted absorbance represents the peak area the calibration says would correspond to a given predicted concentration.

For example, in Figure 2 the concentration residual for sample 1 is -1.4% IPA. The known concentration for sample 1 is 9% (4). If we rearrange Equation 1 we can solve for the predicted concentration as seen in 

In our example then C = 9%,
R = -1.4%, and the predicted concentration C’ is then 10.4%. To predict the peak area that corresponds to this concentration we set X = 10.4 in Equation 3 and to obtain 

to see that the predicted peak area that corresponds to a concentration of 10.4% IPA is 1.03. The right-hand column in 

 shows the measured peak areas for each IPA standard.

To calculate the spectral residual for the 5 standards used to determine the calibration line seen in Figure 3 one would repeat the exercise seen above for sample 1 for all 5 samples. This will yield a set of five spectral residuals. Like with concentration residuals, it is useful to plot spectral residuals versus sample number to look for outliers. Such a plot is seen in 

Note in Figure 4, that all the residuals are small, about the same magnitude, and do not have a discernible pattern. This is unlike Figure 1 where the sample with the concentration residual of -15.9% was clearly an outlier.

: Same as for concentration outliers, typos happen. This is the first thing to check when any outlier of any type is spotted.

: The peak height or area to be used in the calibration must be measured properly. More on that in a future column.

: Recall (1,2) that all measurements have noise/error, and this is true of spectra as well. Calibrations are always a garbage in/garbage out process, and noisy spectra will give inaccurate predicted concentrations. How to improve the SNR of spectra was discussed previously (1-4).

: Analytical instruments are finicky beasts and don’t always work properly leading to incorrectly measured data. Before using any analytical instrument for quantitative work make sure it has been calibrated, passed its quality control checks, and that you are following the method standard operating procedure (SOP) properly.

: If a molecule other than the analyte absorbs light at the same wavelength where we are measuring the peak height or area, this will interfere with the correct determination of the concentration of the analyte, hence the term interferents. Traditionally we dealt with interferents by making sure only the analyte contributed to the peak being used in the calibration. More recently, algorithmic methods known as chemometrics can get around the problem of interferents (8). However, this discussion is beyond the scope of this column series. Thus, for our purposes, it is important to choose a calibration peak that is known to be free of interferents.

: As always humans are fallible and make mistakes. Make sure the person using the instrument has been properly trained, the method has an SOP, and that it is followed properly.

What if There is No Assignable Cause for an Outlier?

This gets tricky. A data point may be an outlier because there is truly something wrong with the measurement, or it might contain information important for the calibration model that is not consistent with the other data points. Statisticians have spilled much ink as to what to do in this case, here is my rule of thumb based on my understanding of the literature. The first thing you should do is calculate the average of the residuals by using 

 is the average residual; i is the sample index; |R

| is the absolute value of an individual residual; and N is the number of residuals.

The purpose of using the absolute value is to keep positive and negative residual values from cancelling each other. For the five concentration residuals seen in Figure 2 their absolute values are 1.4, 0.3, 1.0, 0.2, and 0.9 % IPA, and their average is 0.76%.

In general, outliers whose residual is 10x that of the average can be discarded without an assignable cause, which would have been the case with the -15.6% concentration outlier, although we did find an assignable cause for it. Outliers of 3x or less should almost always be included in the calibration. The gray area is where the residual is >3x but <10x the residual average. In the absence of an assignable cause some judgement for these is needed. What I tend to do is remake the standard, measure its peak height or area, calculate its residual, and see if the residual value is reproducible. If so, I tend to keep this data point.

Outliers are data points in a calibration not like the others. They can be spotted by calculating residuals and plotting them versus sample number. Calculating the average residual and comparing it against individual residuals can be used to judge whether an outlier should be included or excluded from a calibration. Assignable causes of concentration and spectral outliers were discussed.

Smith, B., Calibration Science, Part I: Precision, Accuracy, and Random Error, 

Smith, B., Calibration Science, Part II: Systematic Error, Signal-to-Noise Ratios, and How to Reduce Random Error, 

Smith, B., Calibration Science, Part III: Calibration Lines and Correlation Coefficients, 

Smith, B., Calibration Science, Part IV: Calibration Metrics, 

https://en.wikipedia.org/wiki/Sesame_Street

Giese, M. E; Lewis, M. A.; Giese, L.; and Smith, K. M.; 

Smith, B., A Proposed Representative Sampling Plan for Hemp Grows, 

Quantitative Spectroscopy: Theory and Practice

Smith, B., Calibration Science, Part V: Spotting Outliers, 

, PhD, is Founder, CEO, and Chief Technical Officer of Big Sur Scientific. He is the inventor of the BSS series of patented mid-infrared based cannabis analyzers. Dr. Smith has done pioneering research and published numerous peer-reviewed papers on the application of mid-infrared spectroscopy to cannabis analysis, and sits on the editorial board of 

. He has worked as a laboratory director for a cannabis extractor, as an analytical chemist for Waters Associates and PerkinElmer, and as an analytical instrument salesperson. He has more than 30 years of experience in chemical analysis and has written three books on the subject. Dr. Smith earned his PhD on physical chemistry from Dartmouth College.
Direct correspondence to: 

Cannabis Analysis 

Here, we discuss how to spot outliers and potential ways to correct them in data sets.

Calibration Science, Part V: Spotting Outliers

In indoor cannabis cultivation, increasing lighting penetration is crucial to maximize yield and ensure quality and consistent phytochemical content. Many factors influence how light penetrates the canopy, impacting photosynthesis and overall plant growth. We discuss methods to increase plant canopy penetration for indoor cannabis cultivation, increasing crop size while enhancing cannabinoid, terpene, and flavonoid production.

Shortcomings of Lighting in Indoor Horticulture

In the realm of cannabis cultivation, sunlight remains unmatched in its ability to penetrate plant canopies effectively. Despite advancements in indoor lighting technologies, these systems fail to achieve the same depth and uniformity of light penetration that sunlight provides. The inadequacies of lighting penetration in indoor horticulture can be attributed to deficiencies in lighting intensity, spectrum, and distribution, as well as thermal management of the grow environment. Moreover, certain plant functions, such as tropisms, photoreceptor and pigment protein saturation and activation, adversely influence light penetration, affecting plant health in indoor cannabis operations. For the purposes of this discussion, this paper addresses the use of full-spectrum light emitting diodes (LEDs) lighting in indoor grow operations. Although the term “full-spectrum” is used, LED lighting systems fall short of delivering the true full spectrum of light delivered by the sun.

Lighting intensity is a critical factor that directly influences photosynthesis, impacting yield and phytochemical composition in cannabis cultivation. Cannabis plants require a specific light intensity range for optimal growth. Insufficient lighting can stunt growth, reduce biomass, and accelerate leaf shedding by impairing photosynthesis and hormone signaling. Excessive light intensity can cause photoinhibition, which damages the photosynthetic apparatus and induces a stress response. Interestingly, these stress responses are not always detrimental; in some cases, they can lead to the enhanced production of secondary metabolites. Since these responses occur at the subcellular level, they present significant challenges for study and analysis (1).

Lighting intensity, quantified in micromoles per square meter per second (µmol/m²/s), is a fundamental metric in cannabis cultivation. During the vegetative growth phase, cannabis plants typically require light intensities ranging from 400-600 µmol/m²/s. This requirement increases to approximately 600-900 µmol/m²/s during the flowering stage to support flower development and resin production.For reference, sunlight within the Photosynthetically Active Radiation (PAR) spectrum of 400-700 nanometers (nm), strikes the Earth at an intensity of around 2000 µmol/m

In contrast, LED lighting seldom achieves intensities exceeding 1000 µmol/m

/s at the plant canopy, and when it does, the lighting footprint provided is very limited. Several factors influence LED lighting performance, including the efficacy of the LEDs, typically measured in lumens per Watt (lm/W), and the ability to control lighting output to achieve uniform coverage with minimal waste. Although the efficacy of LEDs is improving, the theoretical maximum for full-spectrum LEDs stands at 300-400 lumens per Watt (2).

Incorrect lighting placement is a common issue in cultivation. LED lighting has an output that is either too wide causing “spill” or wasted light that doesn’t strike the plant canopy, or too narrow, providing adequate lighting to only a limited portion of the plant canopy. The height at which lights are mounted is a critical factor as well, especially with horticultural fixtures that were designed to be mounted very close to the plant canopy. For instance, one manufacturer recommends a mounting height of 8 in above the plant tops. If this distance is doubled, the light intensity, and therefore photon delivery, decreases by 75% (refer to the Inverse Square Law for Lighting). This demonstrates how small variations of just a few inches can significantly change lighting delivery.

“Lighting spectrum” refers to the wavelengths emitted by a light source, encompassing the visible light spectrum and extending into the ultra-violet (UV) and infrared (IR) regions. Blue light (400-500 nm) is essential for vegetative growth, regulating stomatal opening and chlorophyll synthesis. Red light (600-700nm) is pivotal in driving photosynthesis and influencing flowering and photomorphology. Far Red light (700-800nm) increases growth and helps to regulate photoperiod. Amber light peaks at 620 nm and provides protective properties, which we identify later.

Despite the high configurability of LED spectrum delivery by manufacturers, their ability to compete with natural sunlight in terms of intensity and spectrum remains constrained by high costs and current technological limitations. Nevertheless, LED technology has significantly advanced, offering superior capabilities that far outweigh those of more traditional horticultural lighting solutions, such as High Pressure Sodium (HPS), Metal Halide (MH) including Ceramic Metal Halide (CMH), and fluorescent technologies. It is now common knowledge that LED lighting produces higher quality cannabis in greater yields than the industry’s previously adopted lighting solutions.

The advantages of LED lighting stem from its ability to tailor the light spectrum to the specific needs of cannabis plants at different growth stages. This generally requires a combination of broad-spectrum and discrete frequencies to create an optimal light recipe for cannabis growth. This means some frequencies are underserved while some frequencies may provide too much light. The underserved frequencies lack the power to penetrate deep into the canopy and maximize yields. On the other hand, the overabundant frequencies can lead to photoreceptor and pigment saturation, causing plants to activate protective mechanisms or suffer from growth and quality issues.

An overabundance of light can lead to the saturation of photoreactive plant elements, which play vital roles in growth, development and stress responses of plants. These elements include pigments such as chlorophyll, carotenoids, anthocyanins and flavonoids, as well as photoreceptors like phytochromes, cryptochromes, phytotropins and UVR8.

Chlorophyll, the most crucial pigment in plants, is essential for photosynthesis, where it converts light energy into chemical energy, transforming water (H2O) and carbon dioxide (CO

). Excessive light can saturate chlorophyll, causing growth to plateau and potentially damage leaves. Photoinhibition results when the plant's photosynthetic machinery is overwhelmed, decreasing photosynthesis efficiency and energy production. Photoinhibition can also generate reactive oxygen species (ROS), including free radicals and peroxides, which may oxidize vital cellular components like proteins, lipids, and nucleic acids, leading to significant cellular damage or death (4).

Carotenoids are critical for protecting chlorophyll from photooxidation and facilitating non-photochemical quenching—a process that turns excess light energy into heat. If this pigment experiences light saturation, carotenoids can undergo photobleaching. This degradation results in the loss of their color, light absorption capabilities, and antioxidant functions (5).

Anthocyanins absorb blue-green and ultraviolet light, functioning as photoreceptive agents to mitigate cellular damage. Additionally, they also produce red and blue hues in plants. However, when these pigments become saturated, their protective properties diminish, potentially leading to altered or faded coloration within the plant tissues (6).

Flavonoids, a diverse group of phytonutrients, encompass various pigments including anthocyanins, and are renowned for their antioxidant properties. They play a vital role in neutralizing ROS and protecting plant cells from oxidative stress. Prolonged exposure to excessive light can cause flavonoids to become saturated and could damage enzymatic pathways. This may also disrupt their structural integrity and functionality thus affecting the overall plant health and resilience.

Phytochromes are photoreceptors that are sensitive to red and far-red receptors. Phytochromes help regulate processes such as seed germination, stem elongation, leaf expansion, and the timing of flowering in response to changes in light conditions. During seed germination, where they detect light quality and quantity, which is crucial for breaking seed dormancy and initiating growth. They are also able to detect the light environment, distinguishing between shaded and full light conditions. Furthermore, phytochromes are integral in photoperiodism, influencing the timing of flowering based on day length.

Cryptochromes are photoreceptors that are sensitive to blue-light and to ultraviolet-A (UV-A) radiation.They control several functions, including seedling development, flowering time, and circadian rhythms. They play a crucial role in enabling plants to gauge the overall quality of light, important for growth and development.

Phototropins, another group of blue-light responsive photoreceptors are primarily involved in mediating phototropism—the growth of plant organs towards or away from light. They influence chloroplast movement, stomatal opening, and possibly light-induced water uptake mechanisms.

The saturation of these photoreceptors can lead to a range of issues, from altered growth patterns and developmental timing to reduced photosynthetic efficiency and stress responses.

The following discusses the importance of maintaining high photosynthetic photon flux density (PPFD) levels for optimal plant growth and details strategies to maximize light penetration within a plant canopy effectively. It highlights various methods to ensure plants receive sufficient light without risking light saturation or damage, essential for achieving high yields and superior phytochemical content in cannabis.

High PPFD levels ensure that plants receive adequate light for maximum photosynthetic activity, leading to higher yields, and higher quality phytochemical content. However, maintaining an optimal PPFD without causing light saturation or damage is crucial to plant function.

Here are the primary methods for maximizing canopy penetration without harming plants:

Use LED Luminaires: LEDs can increase penetration due to their lower waste heat output, allowing them to be placed closer to the plant canopy without causing heat stress. If purchasing new lighting, make sure you have enough lights to cover your crop correctly. Adjust the power settings to meet the PAR requirements for all stages of growth. Purchasing LED fixtures that utilize Total Internal Reflective lensing will further increase PPFD and penetration with minimal wasted light.

Optimize Light Placement and Mounting Height: Arrange your lights to maximize coverage over your canopy with minimal spill and wasted light. Use enough light fixtures to cover your crop, then increase your luminaire density until PAR values required by your plants for their specific stage of growth are met. Use an LED-specific extended PAR lighting meter (400-750 nm) to verify accuracy of your setup.

Use Under Lighting: Not a common practice but worth mentioning is the use of under-lighting specifically designed to illuminate plants from below is worth considering. Though a costly endeavor, it may prove advantageous for high-end boutique cultivation operations. Great care must be taken to ensure these lighting fixtures are built for the task: they should be water and dust proof, possess excellent thermal management to prevent LEDs from overheating, and include robust electrical protection.

Adjust Lighting Intensity as Plants Grow: Increasing light intensity gradually as plants mature can maintain highest penetration possible while minimizing light stress. There are several methods to accomplish this:

1. Some LED fixtures have dimming capabilities, either manually adjusted or automatically tuned via various equipment and applications. 

2. Traditionally, non-LED lighting technologies have required manual adjustment of height for each light. This can become quite a chore if the operation uses many lights.

3. Automated light movers can be used for height adjustment, but their use is generally not recommended due to their high cost and potential maintenance challenges.

4. To accomplish this task with minimal capital and operational (labor) costs, it is highly recommended to place lights at a height far enough above the plants to cause them to “stretch” into the lighting. As plants stretch towards the light source, PAR values will increase. Once plants reach their maturity height, the lights may be raised or lowered to tune the PAR values. After the first few crops run in your facility, with known genetics and specific light fixtures, growers can usually place lights and never have to touch them again during the flowering stages.

Use Reflective Materials: Use reflective surfaces to bounce light under and around plant canopies. Flat white paint covering walls and flooring is inexpensive and helps spread light evenly. For those using grow trays, some manufacturers build them in flat white for this purpose.

Control Plant Density and Canopy Management: Regularly tend plants to manage canopy density and branch positioning. Techniques like topping, low-stress training (LST), and defoliation can help create a more open canopy, allowing light to penetrate deeper. This not only improves light penetration but also air circulation.

Monitor and Adjust Environment: Ensure temperature, humidity, and CO

 levels are optimized. Waste heat (energy converted to heat instead of light) can increase leaf temperature, so adequate ventilation and air conditioning may be necessary to keep temperatures within an ideal range (typically 70-85° F during the light period). Monitor this by ensuring proper Vapor Pressure Deficit (VPD) is maintained (7).

Using these spectrum strategies, you can further improve light penetration in an indoor cannabis operation, while minimizing the risk of light-induced stress or damage due to saturation.

Use Full-Spectrum LEDs: Full-spectrum LED lights attempt to replicate natural sunlight and provide a balanced spectrum that includes wavelengths that target the known photoreceptors and pigments. Although full spectrum LEDs cannot entirely replicate sunlight, they offer other advantages. These LEDs, which consist of blue base LED coated with an excitable phosphor material, provide smooth and continuous transitions across an extended PAR curve (usually 425-750 nm). Leaving no gaps in spectrum coverage is extremely beneficial to plants, particularly since most photobiologists agree that science is far from fully understanding a plant’s use of light.

Supplement with Discrete (targeted narrowband) Red and Far-Red Light for Flowering Cannabis: Adding discrete red and far-red lights can improve light penetration and stimulate deeper canopy growth due to their longer wavelengths. These wavelengths are absorbed less superficially and have fewer receptors than blue light, allowing them to reach further down into the plant, enhancing photosynthesis in lower leaves without the risk of light saturation. It is important to note that plant photosystems require only 1 or 2 blue photons to process a CO

molecule while the red end of the spectrum requires 8-10 photons to process CO

Make Sure Your LEDs Take Advantage of the Emerson Effect (9): By understanding and applying the Emerson Effect, cultivators can significantly improve both the efficiency of photosynthesis and the overall productivity of plant crops. The Emerson Effect is a phenomenon in photosynthesis whereby the rate of photosynthesis is significantly increased when red light (~660 nm) and far-red light (~730 nm) are provided simultaneously, compared to each light wavelength supplied alone. This effect highlights the synergistic interaction between two photosystems involved in the light-dependent reactions of photosynthesis: Photosystem I (PSI) and Photosystem II (PSII).

Optimizing lighting penetration in indoor cannabis cultivation is essential for maximizing yield and ensuring high-quality phytochemical content. While indoor lighting systems, particularly LEDs, offer significant advantages over traditional methods, they still face challenges in replicating the intensity and spectrum of natural sunlight. Effective strategies to enhance light penetration include proper light placement, utilizing full-spectrum LEDs, supplementing with red and far-red light, and employing reflective materials. Additionally, managing plant canopy and environmental conditions are crucial for achieving the best results. By implementing these techniques, cultivators can overcome the limitations of indoor lighting and improve both the productivity and quality of their cannabis crops.

Alves, P.; Magalhães, A.; Barja, P. The phenomenon of photoinhibition of photosynthesis and its importance in reforestation. 

Schubert, E. F. Solid-State Light Sources Getting Smart. 

McCree, K. J. The Action Spectrum, Absorptance and Quantum Yield of Photosynthesis in Crop Plants. 

https://doi.org/10.1016/0002-1571(71)90022-7

Mansoor, S.; Ali Wani, O.; Lone, J. K.; Manhas, S.; Kour, N.; Alam, P.; Ahmad, A.; Ahmad, P. Reactive Oxygen Species in Plants: From Source to Sink. 

Lima-Melo, Y.; Alencar, V. T. C. B.; Lobo, A. K. M.; Sousa, R. H. V.; Tikkanen, M.; Aro, E.-M.; Silveira, J. A. G.; Gollan, P. J. Photoinhibition of Photosystem I Provides Oxidative Protection during Imbalanced Photosynthetic Electron Transport in Arabidopsis Thaliana. 

Hildenbrand, Z. L.; Mendoza-Dickey, H.; Manes, R. Enhancing Anthocyanin Levels in Cannabis: Environmental Factors at Play. 

Mendoza-Dickey, H., Manes, R., & Hildenbrand, Z. L. Intensity and spectrum: The role of lighting in vapor pressure deficit. 

https://doi.org/10.1007/978-1-4612-6024-0

EMERSON, R. Dependence of yield of photo-synthesis in long wave red on wavelength and intensity of supplementary light. 

 is a research Professor at the University of Texas at El Paso, the principal founder of Inform Environmental, a partner of Medusa Analytical, and is a director of the Curtis Mathes Corporation (OTC:CMCZ). Direct correspondence to: 

 has a MS degree in Chemistry and is the founder of Green Matter Consulting. 

 is the CEO and CTO of the publicly-traded Curtis Mathes Corporation, where he specializes in the creation and manufacture of frequency-specific lighting for horticulture and phototherapy purposes.

Hildenbrand, Z., Mendoza-Dickey, H., Manes, R., Lighting Penetration in Indoor Cannabis Cultivation, 

The Cultivation Classroom

A look at how some cultivation methods are used to increase plant canopy penetrationfor indoor cannabis cultivation, increasing crop size while enhancing cannabinoid, terpene, and flavonoid production.


Lighting Penetration in Indoor Cannabis Cultivation

The regulatory landscape for hemp-derived cannabinoids is undergoing significant transformations, driven by both federal and state legislative actions. This article provides an analysis of current regulations and proposed changes that could impact the hemp industry. The 2018 Farm Bill initially provided a legal framework for hemp cultivation and the production of non-intoxicating cannabinoids. However, recent amendments to the 2024 Farm Bill paired with major regulatory changes on the state level seek to redefine hemp and increase regulations for hemp consumer goods. This article examines these regulatory shifts, their motivations, and the potential consequences for farmers, producers, and consumers in the hemp industry. The analysis underscores the need for balanced regulations that ensure product safety without stifling industry growth and innovation.

The hemp industry has seen substantial growth and transformation since the passage of the 2018 Farm Bill, which legalized the cultivation of hemp and the production of non-intoxicating cannabinoids like cannabidiol (CBD). As the industry matures, the regulatory environment continues to evolve, presenting both opportunities and challenges for stakeholders. This article aims to provide a comprehensive overview of the current and emerging regulations impacting hemp-derived cannabinoids, with a particular focus on recent legislative developments at the federal and state levels.

The Farm Bill is a comprehensive piece of legislation that governs an array of agricultural and food programs in the United States. These bills are typically passed every five years by the US Congress and are critical for setting the country’s agricultural and food policy. The Farm Bill encompasses a wide range of topics including farm subsidies, food assistance programs, agricultural conservation, rural development, and more.

The 2018 Farm Bill: A Foundation for Hemp

The 2018 Farm Bill marked a pivotal moment for the hemp industry, removing hemp (defined as cannabis with less than 0.3% tetrahydrocannabinol [THC]) from the list of controlled substances. This legislation allowed for the legal cultivation, processing, and sale of hemp and its derivatives, leading to a surge in the production and commercialization of hemp-derived products, particularly CBD.

: The bill federally legalized hemp, distinguishing it from cannabis based on its THC content.

: States and Native American tribes were required to submit hemp production plans for approval by the United States Department of Agriculture (USDA).

: The bill protected the interstate commerce of hemp and hemp products, preventing states from prohibiting the transportation of legally produced hemp.

Building on the framework established by the 2018 Farm Bill, the 2024 Farm Bill introduces several amendments aimed at addressing regulatory gaps and ensuring the safety and quality of hemp-derived products. These amendments reflect growing concerns over the rapid expansion of the hemp industry and the need for more robust oversight.

: The 2024 Farm Bill proposes a redefinition of hemp to include not only the plant itself but also any derivatives, extracts, and cannabinoids, regardless of their THC content, as long as the final product contains less than 0.3% THC.

Enhanced Testing and Labeling Requirements

: To ensure consumer safety, the bill mandates rigorous testing for contaminants and accurate labeling of hemp-derived products.

: The amendments emphasize stricter enforcement of THC limits, requiring more frequent and comprehensive testing of hemp crops and products.

: Increased funding for research into hemp cultivation, processing, and product development is included to support industry innovation and address agricultural challenges.

While federal legislation provides a broad framework for hemp regulation, states have significant autonomy in implementing and enforcing their own rules. Recent state-level regulatory changes reflect diverse approaches to managing the hemp industry.

California has introduced stringent regulations on hemp-derived cannabinoids, particularly CBD. These include:

: Mandatory registration and licensing for all hemp cultivators, processors, and retailers.

: Comprehensive testing for contaminants and accurate labeling requirements.

: Prohibition of hemp-derived cannabinoid sales to individuals under 21.

New York’s regulatory framework focuses on consumer protection and product quality. Key regulations include:

: Enforcement of GMP standards for the production of hemp-derived products.

: Requirements for clear labeling and traceability of hemp products from cultivation to sale.

: Retailers must obtain permits and comply with strict advertising and marketing standards.

Colorado remains a leader in hemp regulation, with a focus on fostering industry growth while ensuring public safety. Notable regulations include:

: Voluntary certification program for hemp producers to promote best practices.

: Support for research into hemp cultivation and product development.

: Streamlined licensing process to encourage industry participation.

The evolving regulatory landscape presents both opportunities and challenges for the hemp industry. The amendments to the 2024 Farm Bill and state-level regulations have significant implications for farmers, producers, and consumers.

: Stricter testing and labeling requirements will enhance product quality and safety, fostering consumer trust and market growth.

: Increased funding for research and development will drive innovation in hemp cultivation and product development, opening new market opportunities.

: Clear regulatory frameworks can facilitate the expansion of hemp markets domestically and internationally.

: Enhanced testing, labeling, and licensing requirements may increase compliance costs for producers, particularly small and medium-sized enterprises.

: Variations in state regulations can create uncertainty and complexity for businesses operating in multiple jurisdictions.

: Rapid market growth and increased competition may lead to market saturation and downward pressure on prices.

The regulatory landscape for hemp-derived cannabinoids is in a state of flux, shaped by ongoing legislative developments at the federal and state levels. The 2018 Farm Bill laid the groundwork for the industry’s growth, but recent amendments to the 2024 Farm Bill and state-level regulatory changes reflect a move towards more stringent oversight to ensure product safety and quality.

These regulatory shifts present both opportunities and challenges for the hemp industry. While enhanced regulations can improve consumer trust and product quality, they also pose significant compliance costs and complexities for businesses. The future success of the hemp industry will depend on balanced regulations that promote innovation and growth while ensuring safety and protecting consumer interests.

As the hemp industry continues to evolve, stakeholders must stay informed about regulatory changes and actively engage in the policymaking process to advocate for fair and effective regulations. By doing so, the hemp industry can achieve sustainable growth and realize its full potential as a valuable component of the agricultural and consumer goods sectors.

 is the founder, CEO, and Chief Extractor of Heylo. With a background in chemistry and clinical research, Lo was inspired to explore cannabis as a medicine and to enter the emerging industry. She joined Eden Labs, a leading CO

 extraction equipment manufacturer to support and expand a Research and Development department. There she managed the development of their latest and greatest CO

 extraction system. In 2017, after working with Eden Labs and another cannabis processor, Lo launched Heylo with a mission to help people get more out of life with cannabis.

Friesen, L., Current and Emerging Regulations for Hemp-Derived Cannabinoids: Implications for the Hemp Industry, 

Extraction Science

This article provides an analysis of current regulations and proposed changes that could impact the hemp industry.

Current and Emerging Regulations for Hemp-Derived Cannabinoids: Implications for the Hemp Industry

When it comes to packaging, there are several variables that need to be considered. Some of these points to take note of are cost, safety, and if it's environmentally friendly. All these things play a role in the sustainability of packaging. In this interview, Raphael Wechsler, Founder of Wroots Botanicals LLC, Sustainability Lead for Studio Voltaire LLC, and former Director of Partnerships and Operations and Sustainability Committee Chair for the Cannabis Association of New York, discusses the challenges of cannabis packaging and its sustainability in the industry.

How does your experience and education give you a unique understanding of cannabis packaging and sustainability?

 I have unique views on this subject because I have served in different roles whereby I have gained perspectives from business and brand owners, cultivators, academics, policy and regulatory, and consumer perspectives. Additionally, even though it may sound completely irrelevant, working in corporate finance in Iceland or technology with Apple, you gain a broad knowledge, experience, and perspective capability to see things through different lenses. Every dimension needs to be considered and the more diverse your experience is, the greater the vantage points, and—very importantly—the more you can understand what drives decision making in each universe. From an evidence-based decision-making model, your dataset is more expansive, and you are exposed to more ideas at the margin. These may seem nonsensical today, but if they are given the respect they deserve, in time they can be game changers—I’ll dive into some of these later.

What are some regulations and standards for cannabis packaging?

 First and foremost, packaging regulations are designed around the intent of serving the public with such aspects including labeling that is clear, details about cannabinoid content such as tetrahydrocannabinol (THC) or cannabidiol (CBD) in grams per serving, warnings such as the impairment of driving ability with consumption, and labeling that does not entice children. For example, a brand cannot create images or artwork on a mylar bag for edibles making it look like it belongs in a drug store candy section. Another example, and I have some unique views on this, but if we look at regulations in the NortheastUS, all packaging for any product with THC/A must be child resistant.

What are the main elements of sustainable cannabis packaging?

Sustainable cannabis packaging, to me, is domestically or locally sourced, designed and made by a company that itself is sustainable and treats its employees well with sustainable incentives, is made from materials that have a traceable audit with public results, has a low packaging weight to contents ratio, obviously is nontoxic, in most cases is child-resistant, and has a clear way to either reuse or ensure true recyclability.

What are some current and upcoming innovations in cannabis packaging?

 I must be transparent in terms of my model for ideal packaging: a banana peel, an orange peel, or, put differently, how nature packages. The beginning and end of life are where I start because like most packaging, the product is quickly consumed but the packaging and impact remain. Having said this, the innovations that excite me the most are non-petroleum based, or created without great waste whether it be plastic, glass, or metal. Specifically, carbon-based packaging built by materials that are grown rather than extracted and manufactured, is the ideal. Examples include hemp, hemp-based polymers, polyhydroxyalkanoates (PHA)

 mycelium, seaweed, plastic captured from our oceans, and pulp from sustainably grown materials such as bamboo or wood. On top of that, and this is an area I am particularly passionate about, is in reusable packaging; because ultimately single use cannabis packaging is what we should all work to replace or ban. Ever eat at a restaurant? I’m pretty sure the glass you drank out of, the plate your food was on, and the silverware that put food in your mouth were all previously used by hundreds of people.

How sustainable is packaging in the cannabis/hemp industry currently?

 As I read this question, I can’t help but think of the dedicated members of the sustainability committee I had the privilege to chair, their expressions ready to burst with ideas and insights. The short, hard, and tough pill to swallow is: in general, it is not [sustainable] and there are several real reasons for this. To start, let’s do some quick math. If we take one cannabis product in dried whole flower, which would include pre-rolls, and look at a developed market such as Massachusetts, together they account for about a 63% share of retail sales (1). If we take a common stock keeping unit (SKU) such as a 1/8 oz or 3.5 grams (an eighth) that comes in a virgin plastic polypropylene (PP) or high-density polyethylene (HDPE) dram jar made in China, that brings with it a slew of environmental problems:

a) Packaging Weight to Content Ratio: a plastic jar will on average weigh around 70 grams to store 3.5 grams of plant material.

b) Sourcing and Sustainability Standards: Being produced with little to no sustainability oversight in China and then shipped to the US is, no matter how you look at it, terrible for the environment.

c) Lifecycle: The cannabis product will likely be consumed somewhere between 1-5 days, but the plastic packaging will remain, for all intents and purposes, forever.

d) Recyclability: At this point, most consumers in the US assume that plastic is not only recyclable, but recycled regardless of size, color, or object. The reality is around 90% of plastic is NOT recycled and ends up all around and now inside of us (2). If I were to hold up a black HDPE or PP dried flower jar and ask 100 consumers in Massachusetts or New York if that packaging is recycled in their state, I am willing to wager at least 50% believe it is. But the reality is that at most Material Recovery/Recycling Facilities (MRFs or ‘merfs’) the infrared scanners that identify and sort cannot detect black, so it goes to landfill.

If a consumer finds a cannabis brand that they love, for many they soon overlook the waste associated, thus ensuring future demand and creation of more single use packaging waste. But this problem is also one of the biggest opportunities. I wish everyone in the cannabis industry printed this in their offices because if they did, and truly understood this, they could help change the world (3): 

“According to Deloitte, Gen Z is adopting more sustainable behaviors than any other group: 45% stopped purchasing certain brands because of sustainability or ethics concerns.”

What are some challenges and solutions to sustainable packaging?

If I could fix a few problems, the priority list might look like this:

Education of both consumers and business owners:

 While working on sustainability initiatives at a packaging company and with a large trade association, I spoke with hundreds of brand owners. I would say 90% wanted to be sustainable, but when the conversation shifted to the ‘how’, the response will often sound like this: 

“I can get Mylar bags for around 11 to 12 cents, depending on the quantity. But going biodegradable often increases that cost anywhere from 10 to 15 cents apiece.”

 On the one hand this is their economic reality and I get that. At the same time, let’s be real, and not use that as a convenient way to make the easy, self-serving choice. What they either do not know, or are unwilling to invest in to achieve, is that studies have shown that consumers will pay a meaningful premium, as in over 25% more, for sustainable products and according to a New York University (NYU) study, grow at 2x the rate of those that are not (4).

 Let’s get deeper into perhaps the largest impediment to a marketplace filled with sustainable packaging. The number of conversations I’ve had with companies that started all “sustainable this” and “eco-friendly that” were fine until they see the increased "cost" is well over 100x. I can tell you specifically that the price insensitivity level for sustainable packaging is right around the 15-20% threshold. If 45% of Gen Z consumers—as in 31 million—will drop you completely when they find you are not committed to saving the planet, in what world is increasing your packaging cost by 30% not worth it?

 Consumers need to have an economic incentive to not only choose products with sustainable packaging, but also it must be easy to do so. For example—and I am very proud of the regulatory work we did at Cannabis Association of New York (CANY) with our sustainability committee—every New York dispensary can have a loyalty program built around sustainable packaging and reusability.

What steps would a cannabis company need to take to implement more sustainable packaging for their products?

 Make sustainability an integral part of your mission and DNA…full stop. Very simple, have sustainability focused positions that are involved top to bottom in decision making, local or domestic sourcing unless there is a valid sustainability reason for international sourcing, conducting lifecycle assessment (LCAs) on vendors and supply chain, having an internal sustainability plan with radical and public transparency, prioritizing non-petroleum materials with a benign beginning and end of life, and lastly, a campaign to help brands showcase their sustainable packaging with impact case studies to motivate other companies.

Would rescheduling or descheduling of cannabis affect cannabis packaging?

The short answer is yes. This may be unpopular, but I believe a key solution to making cannabis packaging more sustainable and increase both recyclability and reusability is some standardization in a bottle/packaging bill. Look at Maine, Vermont, and Connecticut or other states that have some sort of bottle bill with standardization. States with bottle bills have a beverage container recycling rate of around 60%,while non-deposit states only approach about 24% (5). Standardization will make it easier for MRFs to invest in state-of-the-art sorting machines or new technologies so less get spat out to a landfill where a lot of glass ends up. With rescheduling, cannabis will become normalized just like beer, and with that, bring more sustainable packaging options.

Do you have any advice/recommendations for both beginner and advanced cannabis manufacturers who specialize in packaging?

First and foremost, my advice is to prioritize offering only truly sustainable packaging solutions. No plan B! Second, no matter how appealing it may be short term, do not greenwash in any way. For example, and this is why it is important to have an in-house sustainability subject matter expert, you might see a company offer plastic jars or pre roll tubes with a claim that they are ‘biodegradable’. When you see this your antennae should stand right up. Passing ASTM D5511, for example, is not the solution nor in my view a sustainable solution. Third, focus on either licensing, funding, or developing in-house proprietary packaging solutions with raw materials that are grown organically or without the use of malignant chemicals. Fourth, build solutions around reusable packaging and if that is not possible, focus on materials that have high capture rates in the MRFs, such as aluminum.

I have a friend who used to be the #1 salesperson for a cannabis packaging company. When we met, he was filled with passion for sustainability but, over time, that changed and one day—with great frustration—he said, “we sell trash.” Not surprisingly that person left. When you do good work and truly commit to being a sustainable company that is not focused on today’s profit margins, something amazing happens. Your employees develop a sense of pride in working for you, in doing good work themselves, and then they tell everyone they know. When a packaging company is focused on making money for its owners first, that is one of the purest forms of not being sustainable that I know of, and it is a matter of time before employees and consumers catch on.

In closing, I have great faith in North American and European consumers who are, more than ever, demanding that the products that they purchase and put into their bodies are made sustainably, with natural ingredients, by companies that give back, prove their positive environmental impact, and finally care more about our fragile world more than their wallets. The most important force in the world to me is the United States consumer. Every waking day a company has a choice in whether to create sustainable goods and solutions people will love or wait for the market to force the issue. All I know is…leaders go first.

Retail sales share of recreational cannabis in Massachusetts as of May 2024, by segment. Statista. 

https://www.statista.com/statistics/1469982/massachusetts-marijuana-retail-sales-share-by-product/#:~:text=Flower%20made%20up%20a%20nearly,of%20roughly%2018.6%20percent%20each

A whopping 91 percent of plastic isn’t recycled 

In this interview, Raphael Wechsler, Founder of Wroots Botanicals LLC, Sustainability Lead for Studio Voltaire LLC, and former Director of Partnerships and Operations and Sustainability Committee Chair for the Cannabis Association of New York, discusses the challenges of cannabis packaging and its sustainability in the industry.

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