Microbial remediation uses microorganisms to either degrade organic contaminants or to bind heavy metals in more inert and less bioavailable forms.

Microorganisms break down contaminants by using them as a food source or metabolizing them with a food source. There are aerobic bacteria, and then there are anaerobic bacteria. Aerobic processes require an oxygen source, and the end products typically are carbon dioxide, water and salts. Anaerobic processes are conducted in the absence of oxygen, and the end products can include methane, hydrogen gas, sulfides, elemental sulfur and dinitrogen gas.

Microbial remediation is done either by:

Breeding bacteria in high numbers and then introducing them into contaminated area.
Creating the ideal conditions in the affected soil or water to become the ideal habitat for bacterial growth to occur (temperature, oxygen, food source, etc).

How do we do this?

Some grassroots microbial remediation tools are:

  • Compost (Thermophyllic)
  • Actively Aerated Compost Tea
  • EM
  • Biochar
  • Mycorhizal Fungi
  • Vermiculture

Using these tools and others, grassroots remediators can recharge the soil food web and inoculate the contaminated or damaged site with beneficial bacteria, fungi, and other powerful soil organisms that can begin to bind and break down different contaminants.

Also, engaging in microbial remediation sets you up for successful phytoremediation, allowing plants to survive under less than ideal site conditions.

It is important that microbial remediation is done properly and effectively. Not all compost is created equal, and not all compost tea is made the correctly. There are specific ways to make these remedies so that they pack a medical and microorgasmic pow for the land you are working with!

For example, lets take a look at compost tea. Actively aerated Compost Tea can be used to inoculate your site with beneficial microorganisms, who can then go to work replenishing the soil food web, and binding and breaking down different contaminants. It takes all the bacteria and fungi that have grown in your compost pile and multiplies their  numbers by extracting them into liquid and feeding them specific foods.

Compost tea allows you to stretch out your compost and make a little go a long way. However, your compost tea will only be as good as the compost you are using in it – so it is critical that you maintain a good, aerated compost pile, that has the proper materials mix. It helps if it undergoes a thermophylic composting process. Which isn’t as hard as it sounds – simply having the right ratio of compost materials, oxygen, moisture, and allowing your compost to attain key temperatures over several weeks, and then letting it sit for 3-6months, allowing it to create the perfect conditions and habitat for a high diversity of beneficial bacteria and fungi. Good compost = powerful compost tea, as the tea can only multiply what organisms are already present in the compost.

Actively Aerated Compost Tea Recipe

  1. Pretreat your compost to increase its inoculant and fungal power. Take your compost inoculant and add some humic acid or fish hydrolase to it. Put it into a shallow tray and mix it up well. Then let it sit for two to three days. This encourages fresh microorganism growth in the tea. Many recipes don’t require you to pretreat your compost: you can treat this as an optional step or you can see it as a way to increase the effectiveness of your brew.
  2. Fill a bucket with non-chlorinated water. Water temperature is ideally between 55-80oF. If you are using tap water, leave it sitting and uncovered for 24 hours to off-gas any chlorine). If your water has chloramine in it, add some humic acid, or consider using rain water.
  3. Put the airstone in the bottom of the bucket, attach the air pump and let it start to bubble. Make sure there is enough oxygen and agitation moving through your liquid; if not, get a more powerful pump. An aquarium pump is likely not strong enough. You are looking for more of a churning or rolling boil, not simply fine bubbles.
  4. Put 1 cup of compost and worm castings (your inoculant) in the stocking or mesh bag, tie off the end and suspend it in the water.
  5. Add the food : ¼ cup of unsulphured molasses, fish hydrolase and kelp. Some folks add humic acid (1 tablespoon) too.
  6. Let the whole brew bubble for 24 hours and for no longer than 36 hours.
  7. Pour the mixture through a strainer to remove large debris so that it doesn’t clog your backpack sprayer or plastic watering can (supposedly bacteria can react with some metal cans). Apply your tea to the soil within 4 hours of finishing it.
  8. Make sure to clean your bucket and pump for your next round of tea. Use a non-toxic, environmentally friendly, biodegradable cleaner.
More detailed information, recipes, and interviews on microbial remediation can be found in Earth Repair.