By Nikki Yeager

Essential oils have enjoyed a boom in sales over the last decade as Western consumers search for alternatives to chemical-laden products that are toxic both to their bodies and to the planet. Since the first recorded essential oil blend was recorded in Egypt in 1,500 BC, people around the world have been using essential oils for their perceived medicinal properties. A market research study by Grand View Research estimates that the global essential oils market is expected to reach $11.67 billion by 2022. Such a high level of demand raises two vital questions: Where are all these essential oils coming from, and what is their impact on the environment?

To begin with, in order to produce a single pound of essential oil, enormous quantities of plants are required: 10,000 pounds of rose petals, 250 pounds of lavender, 6,000 pounds of melissa plant, 1,500 lemons and so forth. According to Nicole Nelson, marketing coordinator for herbal distribution retailer Mountain Rose Herbs, due to a variety of factors, large amounts of produce are needed to produce oils. For example, some oils are more difficult to extract because instead of being externally secreted by the plant, the oils are stored in tiny cavities or ducts within the plant. Other oils provide small yields in general. For example, Bay Leaf can be expected to provide a 3 percent yield during distillation, whereas Rose Petals typically provide only a .006 percent yield. "Weather can also greatly affect the amount of oil that a plant produces from year to year," Nelson added.

In light of this, it's important to understand how plants for these resource-intensive products are farmed. The majority of popular essential-oils companies source their raw materials from corporate farms that turn out large quantities of plants. As with the cultivation of products on many large farms, pesticide usage is common. And there are currently no organic certifications specifically for essential oils, which large companies like YoungLiving and DoTerra cite as a reason for foregoing organic certification all together. In the end, consumers are left largely on their own when it comes to discovering which pesticides are used on crops that are used for essential oils—especially since most companies aren't voluntarily giving up that information.

One solution to large, corporate farming is wild harvesting, but this too has its downsides—some plants used for essential oils are listed on the International Union for Conservation of Nature Red List of Threatened Species, including sandalwood (Santalum album), which is listed as vulnerable, and rosewood (Aniba rosaeodora), atlas cedarwood (Cedrus atlantica), and rosewood (Dalbergia abrahamii), which are all listed as endangered. The commonly accepted rule by harvesting communities, including guidelines set by the Living Earth School of Herbalism and the San Juan National Forest Service, is that no more than 10 percent of any wild crop should be removed during a single harvesting session. Audits on wild harvesters can be done independently with a witness to the harvest, or by a third party company like Quality Certification Services to ensure wild harvests are done ethically. Still, overharvesting continues due in large part to a lack of information and regulation. And as plants become hard to find, prices rise, and in some cases, oils are adulterated to meet demand. Sandalwood, for example, has become one of the hardest to find essential oils. It also the most adulterated oil on the market.

However, there is good news to be had. It is possible to produce organic and/or pesticide- and herbicide-free oils, as well as wild harvested oils that do not damage plant species' survival. Companies like Mountain Rose Herbs provide oils that are certified "organic" by Oregon Tilth whenever possible, as well as oils that are wild harvested according to ethical harvesting guidelines.

Consumers can also check to see if a particular plant species is native to the land it's grown on. Native species typically grow with less intervention, because they are suited to the amount of rainfall, the type of soil, and the climate they are grown in. Non-native plants may need artificial climate control, chemical soil preparation and/or additional water due to the foreign environment they're being grown in.

Aside from the environmental impacts associated with producing essential oils, essential oils themselves can have an impact. Each pure oil comes with its own set of potential ecological and disposal issues. Each essential oil should have a Material Safety Data Sheet (MSDS) that provides toxicity information, flammability warnings and disposal directions. While this information is required of all essential oils in the U.S., many essential-oils companies, such as Young Living, DoTerra and Mountain Rose Oils, require consumers to contact the company directly to request MSDS information. By comparison, in the UK most MSDS information is posted directly on the company's website.

Most essential oils are extremely flammable—particularly tea tree, clove, frankincense, eucalyptus, lavender, lemon and peppermint—requiring extra precautions when disposing of them or cleaning up a spill. Flammable oils are considered household hazardous waste in small quantities, and the containers holding those items cannot be recycled unless the oil is washed from the container. Some cities require that containers of flammable liquids be thrown in the trash rather than recycled, as even trace amounts of flammable liquid can pose a danger to recycling plant workers.

That being said, removing essential oils from a previously used container must be done carefully. Many oils—including the same ones listed above as flammable—are toxic to aquatic life, and can have long-lasting impacts on marine ecosystems according to their MSDS sheets. Most also come with a warning that the oils themselves should not come in contact with a water supply or groundwater, meaning they should never be dumped down the drain or toilet.

So how should essential oils be cleaned from a container, or disposed of, in case of expiration or contamination? If a bottle of oil has expired and is no longer good for therapeutic use, the best options for disposing of the remaining oil is to use it with a passive diffuser (a porous, nonflammable material that can soak up the oil and allow the scent to linger over a period of time) or to add it to homemade cleaning products for the scent alone.

If an oil is contaminated or rancid and cannot be used, it must be disposed of through a hazardous-waste collection service. Most cities offer hazardous household waste programs, which can be found through local waste-management programs. For large or bulk quantities of essential oils and carrier oils (oils like Jojoba and Sweet Almond oil that are used to dilute essential oils in oil blends), biodiesel salvage companies like SeQuentialPacific Biodiesel will accept oils for biodiesel production so the waste ends up being used productively.

Container recycling can also pose challenges. All quality essential-oils products come in glass containers, since pure essential oils can degrade plastic. Glass bottles can be recycled in most cities, though some cities, such as New York, require all glass that previously held flammable or hazardous materials be thrown in the regular trash. With 106 kilotons of essential oils produced in 2014 alone, that's a lot of glass bottles potentially ending up in the trash! Essential oils sold to consumers come with a plastic lid and either a rollerball or drop-dispenser—due to recycling constraints, these typically end up in landfills as well.

So how can essential oil aficionados best reduce their waste? Some companies allow customers to return bottles for recycling. If that service isn't available, the best way to recycle essential-oils packaging would be to dispose of the oils following the recommendations of your local waste-management company.

Essential oils are here to stay and can be a more natural solution to common discomforts and ailments than traditional chemical and pharmaceutical cures. However, it's the responsibility of consumers to question companies on farming practices and to commit to proper disposal and recycling habits. Without consumers taking the extra steps to vet their essential-oils companies, it's easy for this resource-intensive industry to fall into harmful ecological practices.