Bioremediation

The umbrella term refers to a variety of techniques that use organisms to remove harmful substances from an environment or break them down into nontoxic compounds. Because the availability of certain resources can limit the growth of these organisms and impair bioremediation efforts, nutrients such as fertilizers can be deployed to accelerate cleanup.

Molecules such as DDT, a synthetic insecticide, and PFAS—"forever" chemicals used to make products resistant to heat, water, and grease—have historically been used across various industries but are now known to be harmful. Microbes that can convert some of these substances into nontoxic products, such as water and carbon dioxide, have already been identified, with ongoing research to find others.

Depending on the contamination's complexity, in situ—onsite—options may be preferred and can include supplying oxygen or nutrients into the existing soil to accelerate the microbial breakdown already present in the environment. Ex-situ methods instead displace contamination for treatment away from the environment and may be used for volatile chemicals that require isolation.

Biochemical reactions that decompose complex molecules into simpler ones have occurred on Earth for as long as life has existed and have gradually transformed the planet into a celestial body that is increasingly habitable to greater biodiversity. Along the way, modern, human-made bioremediation techniques began to take shape in Santa Maria, California, in the 1960s.

A bloom estimated to contain about 100 sextillion microbial cells broke down much of the 4.1 million barrels of spilled crude oil into nontoxic compounds in what was one of the most significant bioremediations of a human-made disaster. The microbes involved acted similarly to the first patented genetically modified organism in US history: an oil-eating bacterium engineered in 1971.

Through a series of processes that collectively make up phytoremediation, plants can take up pollutants from soil and water through their roots, then break them down, release them as less harmful gases, or store them within their cells. Any plants that sequester heavy metals or other toxins must be removed and managed after the environment is decontaminated.

After the nuclear disasters, sunflowers have been planted for their ability to extract large amounts of heavy metals from soil, including radioactive cesium and strontium, which their biochemistry confuses with potassium and calcium, respectively. Sunflowers' rapid growth and large biomass enable them to isolate contaminants and survive long enough to be safely harvested and disposed of.

As organisms such as mushrooms grow, they develop large networks of root-like structures called mycelium that spread underground and release enzymes that break down contaminants. By absorbing these chemicals, fungi limit the damage caused by these toxins and localize them within the organism for easier collection and disposal.

The burning of homes, cars, and other objects in wildfires produces toxic ash that can be spread across land and into water sources through runoff. Myco-wattles—cylinders used for stormwater runoff management and erosion control that have had fungi stuffed into them—act as post-wildfire ash decontamination devices and have helped remove petrochemicals, lead, arsenic, and other harmful heavy metals.

Physical manipulation, such as collecting and moving contaminated material to a landfill, or chemical applications, which use strong, expensive substances and produce harmful byproducts, can be costly. While bioremediation leverages naturally occurring degradation processes that can be augmented without disrupting impacted ecosystems, these processes may be less effective in places that are largely dissimilar to those where they naturally occur.