Top 5 Factors That Can Influence Botanical Extraction Yield

Among the essentials of botanical extraction is the question of how much essential oil a plant can produce. Producers of botanical extracts have a vested interest in getting the greatest possible yield from plant biomass. Optimizing ROI demands it.

Percentage yield of an extract can be calculated by dividing the weight of a dry extract by the weight of the dry plant biomass and multiplying by 100. It sounds so simple, doesn’t it?

So, how much essential oil can be extracted from an acre of plant biomass? The answer’s not so simple.

First, countless plant species are cultivated and/or harvested for their extracts and used for aroma, flavor, color, and medicinal or therapeutic purposes. Floral botanicals such as lavender, vanilla, rose, jasmine, geranium, rosemary, and hemp derive their highest-value extracts from the plants’ flowers. For example, it’s been estimated that an acre of hemp may produce about 200 pounds of CBD crude — but that estimate is a far cry from predicting ROI on a crop.

Many factors influence extraction yields from biomass, and some of these factors can even influence one another in interdependent ways. Following are a few of the most influential factors when it comes to botanical extraction yields:

1. Factors within the plant itself
2. Environmental influences
3. Harvest practices
4. Post-harvest storage and processing
5. Extraction method

1. Factors Within the Plant Itself

Long before the introduction of genetically modified crops, growers had been selecting and hybridizing for different qualities like drought tolerance, resistance to pests, and proficic production. Rose oil production is a good example. While there are over 400 species in the family Rosaceae, just five species are targeted for essential oil extraction, and a single species, Rosaceae damascena, has been widely cultivated, bred, and hybridized for its valuable oil.

In addition to the plant strain, there is also the question of which parts of the plant are the source of the most desirable extract — whether roots, leaves, flowers, seeds, or another part. Often, extracts can be derived from multiple plant parts, but in varying amounts.

Hemp growers are also familiar with the question of strains, breeding, and phytochemical production, as some strains reliably produce higher concentrations of CBD, while others may not. In addition, much of the CBD produced in a hemp plant comes from the flower, with smaller amounts extracted from stems and leaves.

2. Environmental Influences on Essential Oil Production

Obviously, different crops are suited to widely varying climates, geological settings, and soil types. Crops cultivated in ideal conditions may grow faster and produce substantially more biomass. But does that necessarily point to a better return on the agricultural investment? Maybe not.

In many cases, the desirable phytochemicals plants produce are part of their own response to environmental stressors — phytochemicals that are sought out for their beneficial effects, such as ɑ-pinen, D-limonene, eucalyptol, and camphor. In one plant, drought conditions might increase one essential oil compound and interrupt production of another. In another plant, the effect could be the opposite. 

In short, plants are dynamic, complex organisms, and their growing environments can impact the quantity and quality of their biomass, sometimes in unpredictable ways. Nearly limitless variables include sunlight, exposition, rain, irrigation, plant spacing, soil quality, air quality, humidity, temperature, fertilizers, pest exposure, altitude, and much more.

3. Harvesting Practices Can Affect Extraction Yield

Studies have long been done to determine the ideal stage for crop harvest. In a study comparing four harvest dates at 20-day intervals on lemon balm, one of the four dates was a clear winner. Not only was quantity affected, but so was essential oil quality.

Plants should be harvested at the optimal time based on the convergence of many factors: plant size, whether the plant is an annual or perennial, optimal quality of the primary part associated with the target phytochemical, season and weather, and availability of labor and/or equipment. Even time of day can matter, due to the presence of dew or extreme heat. Jasmine, for example, should be harvested early in the day while the flowers are tightly closed. Large-scale producers often sample and test plants for yield before harvesting.

Many plants used in essential oil manufacturing are harvested by hand. The skill of an individual farm worker can actually have an effect on the quality of the final product.

Testing for Contaminants

Agricultural practices like use of fertilizers, pesticides, herbicides, and antifungals may have an impact on plants’ oil production. Just as important, they can pose a risk of contamination. Talk to your extraction specialist about testing and analysis.

4. Post-Harvest Practices Can Impact Yield & Quality

The choices involved in cutting, drying, chopping, storing, and transporting biomass can all have an impact on extract yields and essential oil quality. Plants that need to be properly cured and dried before extraction need to be handled with care to prevent spoilage and/or mold growth.

In fact, hemp grown for CBD needs to be properly cured to enhance and maximize cannabinoid production, for optimal potency and quality. Storage conditions also need to protect biomass from pests, dirt, bird droppings, etc., which can expose the final product to adulterants and affect the value.

That’s why it’s equally important to know the storage conditions your botanical extraction partner uses for plant biomass. Look for an expert who understands the value of your biomass and protects it from cross contamination or exposure to other risks, like high temperatures, moisture, or dust.

5. Extraction Method Matters, Too

Just as there are countless plants cultivated for their valuable essential oils, there are numerous ways of extracting these important phytocompounds. Some of the most commonly used and well known include:

• Cold pressing
• Steam distillation
• Solvent extraction
• Supercritical fluid extraction

There are also many other extraction methods, but the four listed here provide a nice illustration of technological progress from, essentially, squeezing valuable oils from plant biomass (as in cold pressing) to the advanced use of carbon dioxide in its subcritical and/or supercritical state as a solvent.

Between these extremes, steam distillation and solvent extraction can dependably extract decent yields. But steam distillation requires high energy inputs and can expose delicate phytochemicals to high temperatures … and many solvents can be dangerously toxic and leave residue behind.

Carbon dioxide extraction, on the other hand, is environmentally benign, relatively inexpensive, reclaimable from the extraction process, and leaves behind no toxic residue. It has also been shown to achieve high yields on a wide range of floral and other types of biomass.

Don’t Leave Yields or Quality to Chance

Clearly, the factors influencing essential oil yields are numerous, interdependent, and complex. But your choice of extraction, processing, and bottling partner should give you greater confidence in the yield and quality of your final essential oil and botanical extract products.

You can learn more about the steps involved in producing some of the most in-demand floral and botanical extracts with our free guide, From Biomass to Bottled Extracts. Click below to claim your copy now.