While in Denver, Colorado we were given the opportunity to tour the award-winning cannabis extract company Emotek Labs, which has developed an industry-standard closed-loop system for extracting resins from cannabis using butane, while avoiding the risk of fire and explosion that can occur with traditional ‘open’ systems.


While in Denver, Colorado we were given the opportunity to tour the award-winning cannabis extract company Emotek Labs, which has developed an industry-standard closed-loop system for extracting resins from cannabis using butane, while avoiding the risk of fire and explosion that can occur with traditional ‘open’ systems.

What is butane honey oil (BHO)?

Butane honey oil is a high-purity cannabis extract that is created by ‘blasting’ cannabis plant material with pressurised butane gas. In appearance, it may range from a fluffy, opaque and yellowish (usually termed ‘wax’ or ‘budder’) to an almost-transparent, glassy sheet—this is the most highly-prized form, and is usually known as ‘shatter’. Wax and budder is often whipped to achieve its consistency, and its appearance may disguise impurities that would be more visible in the shatter form.

In general, a cannabis extract or concentrate is cannabis resin that has been fully separated from residual plant material through use of a solvent. Lipid-based cannabis resins cannot dissolve in water, but are capable of dissolving in non-polar solvents, as well as some polar solvents.

What are closed-loop extraction systems?

Closed-loop systems such as those created by Emotek are far safer and more effective than older methods
Closed-loop systems such as those created by Emotek are far safer and more effective than older methods

A closed-loop system is one which does not leave any ‘gaps’ through which solvents can escape. The advantages of a closed-loop system are various; primarily, the risk of explosion is reduced drastically as the flammable component is kept in a secure system that does not allow leaks, and secondly, gas usage is drastically reduced as it is recirculated back through the system and used more than once to blast the plant material.

The rudimentary ‘open’ systems that previously dominated the extract-making world are gradually being displaced, now that modern, professional systems such as that developed by Emotek have begun to take hold. However, the high initial outlay for machines such as Emotek’s is seriously off-putting for all but the best-financed operations, so many amateurs—and more than a few professionals—still utilise the unsafe ‘open’ methods that waste a huge amount of butane (itself a petrochemical and a non-renewable resource) and carry a high risk of causing explosions and fires. In Denver, there were several relatively major fires caused by unsafe extraction methods in the months following legalisation in January 2014.

What Emotek does

While Emotek Labs has produced some award-winning extracts themselves, their primary purpose is to supply a superior class of extraction systems that are safe, effective and user-friendly. To this end, they have designed a closed-loop system that can be made to order in several different sizes—from the home-use 250g model to the industrial 2500g version.

Currently, Emotek makes its extraction systems to order, and does not hold excess stock; in the future, as supply lines for parts become more efficient, the team hopes to clear the already long waiting list and reach a point where stock can be made in anticipation of orders.

What is the Emotek closed loop system?

The system, which is priced at $26,980, consists of a stainless steel base with circular holes cut into it to accommodate two stainless steel containers, of which one holds a canister of n-tane (high purity butane) and the other comprises the blasting chamber of the device—where the gas is passed through the ground cannabis to release the resins.

The blasting chamber itself is made up of several sections that must be assembled correctly prior to use; the fixings themselves are high-quality and precisely fit together so that it is effectively impossible to set the device up incorrectly, as the screws will not tighten unless correctly aligned.

A complicated series of tubes connect the gas canister to a vacuum pump (which at various points throughout the process is crucial to ensuring no oxygen or gas remains in the system) and then to the blasting chamber itself.

The key to a closed-loop system is that no gas should ever escape the system; thus, a recycling tube sends the butane back into the canister once it has passed through the cannabis material. The gas may be passed through the material several times before the canister is replaced, and sent to be recycled (usually such recycled butane will be sold as a lower-grade product, suitable for industrial but not medicinal purposes).

How does the Emotek system work?

Wax or budder is whipped to achieve its consistency
Wax or budder is whipped to achieve its consistency

Once the system has reached the correct pressure (just over -1 bar), the valves are opened and the gas is allowed through the chamber. A small Plexiglas window directly beneath the chamber allows the operator to view the progress of the gas—when the canister is almost exhausted the level of liquid drops visibly.

Below, another stainless steel container collects the liquid butane and dissolved resin. Two view-holes at the top of this container allow the operator to visually ascertain the extent to which the butane has evaporated (shining a flashlight in one hole and looking through the other is the best way to ensure a clear view).

Once the butane has evaporated and been channelled back into the canister, the whole process may be repeated once or twice more. Usually, the gas is run through the chamber at least once; when run through each subsequent time, the colour of the liquid passing through the window can usually determine the amount of resin left in the material.

Purging the cannabis extract

When the plant material is exhausted and the butane evaporated off for the last time, the chamber is detached from the container below and set aside to be cleaned. The container is now covered with a layer of sticky cannabis resin, which is scraped off and spread onto a silicone baking sheet. Some traces of sticky resin usually remain adhered to the container; to clean it, butane is rinsed through the otherwise empty system.

Shatter, the glassy, almost transparent form of honey oil that is most highly prized
Shatter, the glassy, almost transparent form of honey oil that is most highly prized

The hashish extract, now spread thinly and evenly on the silicone baking sheet, is placed inside a vacuum oven to go through the process known as ‘purging’. First, the oven is depressurised to create a vacuum; when this occurs, the residual bubbles of butane left in the hashish expand and burst, evaporating completely and ‘cleaning’ the hashish so that trace impurities are removed.

Next, the hashish is left in the oven, which is heated to around 110°F, for up to eight hours to allow the final residual traces of butane to evaporate. Once the purge is complete, the extracted hashish should be glassy in appearance, firm (although possibly slightly sticky) to the touch and with no bubbles trapped within it. Bubbles indicate that the product was insufficiently purged and that there is residual butane trapped within.

Why is butane seen as the best solvent?

Butane is the solvent of choice for most extract artists. It is a non-polar solvent, and thus does not carry an electrical charge in its molecules. It is cheap and easy to source, and due to its very low boiling point of around -1°C, it is easy to remove from the finished product—at least in theory. In practice, the finest-quality butane is essential, as trace impurities including heavy metals are present in many lower grades of gas.

There are various downsides to using butane as a solvent. Without specialised, high-cost equipment, using butane can be extremely dangerous: amateur extract artists have suffered serious burns, and in some cases lost their lives in butane explosions, and many properties have been severely damaged or destroyed. Furthermore, butane is a petrochemical, and as such, perpetuating its use negatively impacts on the environment and is highly unsustainable.

However, butane is generally seen as the superior of the available options. Many other solvents that can dissolve cannabinoids do not evaporate at low enough temperatures to preserve the cannabinoids themselves, and can only realistically be used to make tinctures—where the active ingredient remains in solution. The alcohols propyl and ethanol can also be used to make cannabis extracts, but often contain 1% or more of impurities which can be impossible to remove.

A note on polarity of solvents

Chemical polarity refers to the overall electric charge present in a molecule, as defined by the sum of the charges of its component atoms. A polar molecule (such as H2O) is made up of a positively charged oxygen atom (+1) and two negatively charged hydrogen atoms (-2); thus, it has a ‘dipole’ (two unequal and opposing poles) and an overall charge of -1. A non-polar molecule (such as methane; CH4) has equal charge in its component atoms; thus, it has no overall dipole and carries no charge, either positive or negative.

In general terms, non-polar solvents dissolve non-polar solutes, and polar solvents dissolve polar solutes: butane dissolves oil, and water dissolves sugar. However, this rule does not always hold true, as polarity is a relative scale, and polar molecules vary in charge according to their component atoms. Furthermore, both polar and non-polar solvents are capable of dissolving cannabis resin—but not all are equally effective. Non-polar solvents generally are favoured for making cannabis extracts, but various polar solvents, including ethanol and propyl alcohol, are capable of dissolving cannabinoid compounds.

Dielectric constant and polarity

Complex glass piecs like these are used to 'dab' honey oil
Complex glass piecs like these are used to ‘dab’ honey oil

Perhaps a more useful measure when comparing different solvents and their ability to dissolve cannabinoid compounds is to ascertain the dielectric constant (DK) of the solvent. Rather than directly adding the charges of the component atoms to measure polarity, DK measures a substance’s electrical capacity against that of a vacuum, under certain conditions—a specific voltage must be applied, and temperature must remain constant.

Non-polar solvents have a DK of 15 or less, while polar solvents range anywhere from 15 to 100. It seems that the closer a polar solvent is to the cut-off of 15 DK, the more effective it is as a solvent for cannabinoid compounds. This explains water’s ineffectiveness as a solvent for cannabinoids—water has a DK of 80.4 at 20°C, while ethanol and propyl alcohol have DK of 24.3 and 21.8 at 20°C.