Essential Science: Researchers Patent a New and Natural Frugal Fungicide


A selection of different composite wood products both untreated and treated with essential oil. The samples dipped in essential oil exhibit far less mold growth.

Sitting at the Forest Products Laboratory (FPL), microbiologist Vina Yang recounts a news story that took Madison, Wisconsin by storm. Fourteen years ago, more than 35 students and faculty mysteriously fell ill at Caesar Chavez Elementary School. Although the school had only been open for two months, it quickly and inexplicably turned from Madison’s newest educational institution into a health nightmare. Ailments ranged from sudden onset asthma, to respiratory problems, to severe allergic reactions, and it was only after the school’s inevitable closure that officials found the source of the problem—hidden behind the pristine drywall and gleaming floor tiles of the new building, inadequate ventilation had caused mold to take a firm hold at Caesar Chavez.

Today, Yang and fellow researcher Carol Clausen are working hard on developing new techniques to combat the mold plaguing the world’s wood-containing residences, businesses, and storage facilities. More than seven years of research recently culminated in a patented method of using essential oils derived from plants to inhibit mold on cellulose-containing materials such as paper, lumber, and ceiling tiles.

Yang and Clausen’s Durability and Wood Protection unit traditionally studies preservatives for wood in exterior applications, but it quickly became apparent that there was demand for a less toxic solution for indoor use as well.

“We would always take calls from consumers asking for ways to prevent mold on the inside of houses,” Clausen recalls, adding that essential oils can be as effective as chemical fungicides without the associated health concerns, which are elevated when used in a household environment. Perhaps the biggest, albeit subjective, drawback of using the oils indoors is the odor, as they tend to smell strongly of the parent plant. “One person came by the lab and just loved the smell—others came by and told me to close the door,” added Yang.

From the original arsenal of seven oils that Yang and Clausen began to study in 2007—thyme, ajowan, dill weed, Egyptian geranium, lemongrass, rosemary and tea tree—only the thyme oil compositions received the patent earlier this year. Patent Number 8,986,757 now awaits licensees and industry partners to deliver new products to consumers.

Yang suggests that applying the oil to wood stored in warehouses or lumber yards could prolong its storage life, while Clausen foresees the treatment as an easy way for companies to provide peace of mind to consumers. “I especially foresee a lumber or construction company using our technology as a way to provide inexpensive protection to customers,” Clausen said.

The oil can be dipped, sprayed, or brushed onto wood surfaces, and in some cases, simply exposing the material to oil vapor is enough to inhibit mold growth, making it the ideal process for fumigating large spaces or large volumes of material.

A photograph illustrating the effectiveness of essential oil as a mold inhibitor when applied to wood as an oil vapor. The treated wood stakes (left) experienced far less mold growth than their untreated counterparts (right).

A photograph illustrating the effectiveness of essential oil as a mold inhibitor when applied to wood as an oil vapor. The treated wood stakes (left) fared much better than their untreated counterparts (right).

Essential oils cost roughly $18.00 per pound, and when they are diluted for use, the cost is about two cents per gallon, and fractions of a penny per square foot. Essential oil technology becomes even more affordable when one considers that health problems caused by interior mold accounted for $2.8 billion in 2002 alone.

The research may have come a bit late to rescue the doomed Caesar Chavez Elementary School and prevent the legal action that resulted from the building’s poor construction, but both researchers hope that in the future, new buildings will benefit from these surface treatments.

Clausen cautions that although effective, essential oils are not a replacement for public education or good building practices such as the proper installation of ventilation systems or flashing.

“Prevention is the key, and educating the consumer is huge, especially in flood prone areas or in regions that face seasonal problems with mold,” Clausen said. “If they could just keep the buildings dry, that would solve all of their problems.”