The question of whether Diatomaceous Earth (DE) is organic is complex, as the answer depends entirely on which definition of the word “organic” is being used. Diatomaceous Earth is a natural, powdery substance derived from the fossilized remains of ancient aquatic organisms. To the average person, “organic” often implies natural, minimally processed, or approved for use in organic farming, which is where the confusion arises. This natural material sits at the intersection of chemistry and regulation.
The Geological and Chemical Composition of Diatomaceous Earth
Diatomaceous Earth is a soft, siliceous sedimentary rock formed from the accumulated remains of tiny, single-celled algae called diatoms. These microscopic organisms secreted cell walls, known as frustules, which are primarily composed of silica. Over millions of years, these shells settled into deposits that are mined and processed into the fine, white powder known as DE.
The chemical composition is predominantly silicon dioxide (\(\text{SiO}_2\)), typically 80% to 90% by weight. Most of this silica is in an amorphous, or non-crystalline, state, which is considered to have low toxicity. Since DE is fundamentally a mineral oxide lacking carbon-hydrogen bonds, it is chemically classified as inorganic.
Understanding the Two Meanings of ‘Organic’
The confusion surrounding DE stems from the two distinct meanings of the word “organic.” The first is the chemical definition, which classifies compounds based on the presence of carbon atoms covalently bonded with other elements. Since DE is a mineral composed of silica, it is chemically inorganic, despite its origin from formerly living organisms.
The second, and more common, interpretation is the regulatory or consumer definition, which refers to materials approved for use in certified organic farming systems. This definition is established by regulatory bodies like the USDA National Organic Program (NOP). Under these standards, a product can be naturally occurring and inorganic, yet still be allowed as an input in organic agriculture if it meets specific criteria.
Diatomaceous Earth in Certified Organic Applications
When people ask if Diatomaceous Earth is organic, they are typically asking about its regulatory approval for use in homes and gardens. The answer is yes, specific grades of DE are permitted for use in certified organic production. This approval is not universal for all DE products, however, and depends on the processing and the resulting crystalline silica content.
Only Food Grade DE is generally approved because it is minimally processed, uncalcined, and contains less than 1% crystalline silica, the form that can be hazardous when inhaled. In contrast, Filter Grade DE, often used for industrial purposes like swimming pool filtration, is heat-treated through a process called calcination. This high-temperature treatment increases the concentration of crystalline silica, making Filter Grade unsuitable and prohibited for organic gardening or use around food.
The primary function of approved Food Grade DE in organic systems is as a mechanical insecticide. It works by absorbing lipids and waxes from the exoskeletons of crawling pests, causing the insects to dehydrate and die. This non-chemical mode of action aligns with organic principles, confirming its status as an accepted material in certified organic practice.