On this page (11 sections)
- Garden soil and contaminated soil are judged differently
- What counts as a natural method
- Where biology works best
- What natural methods cannot do
- “Without chemicals” needs a footnote
- How a responsible project runs
- Natural attenuation after a derailment
- Natural and engineered methods side by side
- Where Elm Dirt fits
- Testing it on your ground
- Sources
Often it can, for the right contaminants, because microbes already living in soil eat fuels, solvents and some pesticides, so those compounds can be treated with biology instead of harsh chemicals [1][2]. Metals are a different story, since biology cannot destroy them, and it also works slowly on some organic compounds, and a typical project runs months to years [1][2][3]. Whatever the method, the result gets measured on your site.
Garden soil and contaminated soil are judged differently
Search “natural soil remediation” and half the results are about healthier garden beds. This post covers the other case, where a named contaminant is in the ground and a regulator, lender or landowner needs it dealt with.
Garden soil is judged by how plants grow. Remediation is judged by a lab result for a specific compound against a cleanup target, and a plot can grow excellent tomatoes and still fail that test.
What counts as a natural method
Four approaches usually travel under the label. They differ mainly in how much the project intervenes.
| Method | What happens | Where it fits |
|---|---|---|
| Natural attenuation | Microbes already in the soil degrade the contaminant with no amendments. The site is monitored. | Sites where the biology is demonstrably already working. EPA notes this takes careful assessment and monitoring [2]. |
| Biostimulation | Air, nutrients, or carbon are added so the native microbes work faster [2][4]. | Sites where the right microbes exist but conditions limit them. |
| Bioaugmentation | Microbial cultures are added, usually after biostimulation [2][4]. | Contaminants that native organisms do not degrade well [2]. |
| Phytoremediation | Plants take up, store, or convert contaminants, or support microbes in the root zone [5]. | Low concentrations and shallow soil. EPA says it may take several years [5]. |
How a project picks between the middle two is covered in biostimulation vs. bioaugmentation.
Where biology works best
EPA lists oil and other petroleum products, solvents and pesticides among the contaminants bioremediation treats [1]. A 2006 EPA technical paper reports successful bioremediation of halogenated and non-halogenated volatile and semivolatile organic compounds at many sites, and puts PAHs, pesticides, herbicides and PCBs in a group with a thinner performance record [2].
The best candidates are organic compounds microbes can use for energy and carbon, in soil with enough oxygen. Our contaminant fit chart sorts the common ones.
Every organic compound comes with two cautions. Some only partly break down, and some pass through by-products more toxic than where they started [2][3]. A good project samples for those by-products along with the parent compound.
What natural methods cannot do
Natural methods cannot destroy metals, and FRTR, the federal remediation technologies roundtable, says bioremediation is not applicable to inorganic contaminants [3]. Lead, arsenic, cadmium and mercury are elements, and microbes can only change a metal’s chemical form, which may make it less mobile or, sometimes, more mobile. EPA notes that aerobic treatment can shift the ionic form of arsenic, for example, so the new form has to be checked [2].
Plants and fungi can pull metals out of soil and into tissue. In one study of lead-contaminated soil, a nightshade plant paired with a fungus removed 58.6% of the lead, against 47.2% for the fungus alone and 40.2% for the plant alone [6]. None of that lead was destroyed. It moved into the plants, and the harvested plants then have to be handled as waste [5]. More on this on our heavy metals page.
Natural methods are also slow, and EPA says bioremediation may take a few months or several years. It runs longer when concentrations are high, the contaminant is trapped in dense soil, the area is large or deep, conditions have to be modified, or the soil is dug up and treated above ground [1]. Cold slows it as well, and in northern climates it may stop working for part of the year [3]. See how long soil bioremediation takes.
In an emergency, when concentrations pose an immediate risk to people, EPA says excavation with offsite disposal or ex situ treatment is often the fastest response [7]. Biology can come in afterward, since excavated soil can also be treated on site [7]. The two are compared in bioremediation vs. dig-and-haul.
“Without chemicals” needs a footnote
Most projects add something to the soil, and EPA’s list of amendments runs from molasses and vegetable oil to air and oxygen-releasing chemicals [1]. The microbes do the breaking down, and the project decides what goes in to help them. When you read a proposal, ask for every material that will go into the ground and the reason for each.
How a responsible project runs
A natural method still follows an engineering sequence.
- The contamination gets mapped first, since EPA’s green remediation guidance says in situ and ex situ treatment both depend on thorough delineation of the source areas and a conceptual site model that gets updated over time [4].
- The soil gets tested, with bench-scale treatability tests that measure the contaminant and its breakdown products on site, identify the microbes already there, and show which amendments work [4].
- Treatment and sampling run on a schedule, and EPA’s public guide says soil and groundwater are tested regularly to confirm the treatment is working and to track progress [1].
- An independent laboratory measures the result against the cleanup level the regulator or landowner set.
If a proposal skips steps one and two, you are being asked to trust the method without data.
Natural attenuation after a derailment
After a 2023 train derailment, researchers sampled creek sediment downstream and found native microbes able to break down vinyl chloride and butyl acrylate, two of the chemicals released [8]. Only monitoring revealed that, and the same data say whether the biology is keeping up and how fast it is going.
We run our own work that way, including a monitored soil-restoration pilot in East Palestine, Ohio.
Natural and engineered methods side by side
| Natural and biological methods | Engineered physical methods | |
|---|---|---|
| How contaminant is dealt with | Degraded by organisms, or taken up by plants | Dug out, then disposed of offsite or treated above ground [7] |
| Disturbance | Contaminated soil can stay on site, which reduces truck traffic [1] | Truck traffic and earth-moving equipment [7] |
| Speed | Months to years [1] | One day to several years, depending on size and depth [7] |
| Metals | Not destroyed | Soil can be removed [7] |
| Best use | Organic contaminants at moderate levels with time to work | High concentrations, immediate risk, small volumes |
Plenty of sites use both: excavation for the worst spots, biology for the rest.
Where Elm Dirt fits
We make living-soil biological products in Kansas City, Missouri, and work directly with applicators. Biome Makers, an independent lab, identified 291 microbial species in our Plant Juice. That list tells you what is in the bottle. It does not show the product cleans any particular contaminant, and we don’t claim it does. On a site we take a baseline, apply the biology, have an independent lab test the soil over time, and report the numbers. Expect months to a year or more.
Testing it on your ground
A baseline sample and a small treatability test show how your soil responds before anyone commits to a full program, and that is where we start. Talk with us about your site.
Sources
- U.S. EPA. A Citizen’s Guide to Bioremediation. EPA 542-F-12-003, September 2012. Link. Accessed 2026-10-01.
- U.S. EPA. Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites. EPA/625/R-06/015, October 2006. Link. Accessed 2026-10-01.
- Federal Remediation Technologies Roundtable. Remediation Technologies Screening Matrix, section 3.1: In Situ Biological Treatment for Soil, Sediment, and Sludge. Link. Accessed 2026-10-01.
- U.S. EPA. Green Remediation Best Management Practices: Bioremediation. EPA 542-F-21-028, December 2021. Link. Accessed 2026-10-01.
- U.S. EPA. A Citizen’s Guide to Phytoremediation. EPA 542-F-12-016, September 2012. Link. Accessed 2026-10-01.
- Sun L, Cao X, Li M, Zhang X, Li X, Cui Z. Enhanced bioremediation of lead-contaminated soil by Solanum nigrum L. with Mucor circinelloides. Environmental Science and Pollution Research 24(10):9681-9689, 2017. doi:10.1007/s11356-017-8637-x.
- U.S. EPA. A Citizen’s Guide to Excavation of Contaminated Soil. EPA 542-F-12-007, September 2012. Link. Accessed 2026-10-01.
- Chen G, Rosolina S, Padilla-Crespo E, et al. Natural attenuation potential of vinyl chloride and butyl acrylate released in the East Palestine, Ohio train derailment accident. Environmental Science & Technology 58(40):17743-17755, 2024. doi:10.1021/acs.est.4c04198.