We are in the dead of winter, a wonderful time to gather thoughts and contemplate the arrival of spring and summer. In the Pacific Northwest we are fortunate to have mild winters.
It is so easy to ferment your food scraps. And it’s a good feeling to know that in the process you save money on your garbage bill, get rich soil in return, and feed your plants natural nutrients. No more smelly garbage, fruit flies, rats or vermin to contend with. But you’ve got to put the fermented material back in the ground.
Bokashi fermenting involves mixing the food scraps with a microbial culture mix in a specialized fermenter that excludes oxygen. The microbes are active when the oxygen levels are brought to very low levels where other microbes perish. The microbes release enzymes (chemicals) that breakdown food waste to a form that is then easily metabolized by soil microbes. It is a two step process.
Fermenting is a pickling process. The food scraps are first pickled in a specialized fermenter, and then the fermented product is put it in the ground. It is 10 times faster than composting and much easier. Greenhouse gases are eliminated. You end up with virtually 100% of the waste material going back to the soil where it is broken down even further.
There are many advantages to this method of disposing of food scraps. Nutrients are put right back into the soil and the population of soil microbes expands in numbers and diversity. Plants do very well in this kind of soil and you no longer need to use fertilizers and pesticides to get vibrant healthy plants.
In the Seattle area we rarely have frozen ground to worry about. We had a few weeks of frozen ground this winter. Lots of people interested in fermenting food scraps wonder what to do when the weather is cold and the ground is frozen. It’s wonderful to ferment your food scraps in the home where it’s warm and cozy.
You don’t have to take the garbage out in the cold and rainy weather and won’t have to empty your fermenter for weeks with a proper fermenting device……………but eventually, depending on how much waste you generate you are going to make that trip to the garden (or planter box) to bury the fermented product to feed your hungry soil microbes.
What do you do when the ground is frozen? That’s a good question. And you might also wonder how cold weather affects the rate of fermented food waste material being broken down in the soil by those hungry microbes. Does it take longer? Can you save the fermented waste material until the ground is thawed out and then bury it?
I want to provide answers to these and other question I often get and have gathered some photographs that I think you will find interesting and helpful.
Winter is here…ground is frozen…what to do?
The most efficient bokashi fermenting is done with two fermenters. One fermenter is being filled layer by layer with food waste and a sprinkle of bokashi culture mix (specialized microbes) while the filled fermenter is sealed and set aside. When the fermenter being filled is nearly full, you normally take the sealed fermenter outside and bury the contents under 8 inches of soil mixing it well into the soil.
The just emptied fermenter is then put into action to fill layer by layer food scraps and culture mix giving time for the just filled and sealed fermenter to complete its process of anaerobic fermenting. It takes most people about 4 to 6 weeks to fill a single fermenter. So you will head to the garden about once every 4 to 6 weeks for a burial and mixing process. This process can continue indefinitely and is truly a sustainable way of disposing of food waste material.
If the weather is cold, and the ground is frozen, most people just dump the batch of fermented food scraps into a large container outside with a lid. It is perfectly okay to let it freeze too. You can fill a container or two all winter if you like and await the spring thaw.
When the ground is once again soft, work the fermented product into the soil and you will observe the soil microbes rapidly metabolize all of the wasted material in short order. All of the nutrients go right to the soil. Your vegetable garden will be great……..and nothing was lost in waiting out the winter. If you have properly fermented the food waste you will have no smelly garbage in the outside container. Animals will not bother it. We have lots of clients in Eastern Canada, Upstate New York, the Midwestern US and Alaska who experience long winters. They know it’s easy even in the winter to process food waste.
Although it is difficult to accurately measure how fast the fermented material is metabolized in the soil because many different kinds of food scraps may be processed, one easy way to gauge the activity is to filter the soil at various intervals after the fermented food scraps are mixed with soil to see how long it takes for recognizable material to disappear. In the summer virtually all material (except pits and bones- see below) will be gone in about 7 – 10 days. In the middle of winter buried in frozen ground the same material will take 20 – 30 days to disappear. Even though it appears that the rate of metabolism is reduced when the weather is cold, the overall assimilation in the soil is quite rapid.
Indoor Bokashi Fermenting:
If you have a heated garage, an underground facility where the temperature is controlled or live in an area where your climate can be controlled indoors, you might want to consider fermenting your food scraps in a plantar box. You don’t need a lot of land or soil to ferment your food scraps and then have them converted to nutrients in the soil. If the temperature is sustained near room temperature, the metabolic rate for uptake by the soil process is rapid.
How much soil is needed to process bokashi fermented food waste?
We’ve made the point that you can bury the fermented food waste in the same place over and over if you like. Earthworms love the fermented food scraps and will migrate to the areas where it is buried and mixed with soil. Put some worms in the container if you want to use a plantar box.
One of the great things about bokashi fermenting is that you can do it in an apartment or condominium with a balcony if you have room for a plantar box on the balcony. You may want to have a couple of plantar boxes so you can mix soil and fermented food scraps in one and move soil from that box to other boxes where you want to grow plants. You can create a very lovely balcony garden.
I have fermented all of the food scraps I produce in a two person household for 8 continuous months in the same 25 gallon size plantar box. I started with the empty plantar box and placed ordinary soil into the box that was screened through a ¼ x ¼ inch wire mesh. I could then check the soil to see how much waste material had not been broken down in the soil by filtering the soil through the mesh at timed intervals after burial in the plantar box.
You can see the empty 25 gallon container, filtered soil, filled container, and 5 gallon fermenter loaded with fermented food scraps ready to be mixed with soil in the container in the pictures taken when I started. In the summer it took about 7 – 10 days to convert fermented food scraps to rich soil.
Every 4 – 6 weeks I would then move the soil to a wheel barrel filtering it through the wire mesh to observe what had not broken down before mixing the next batch of fermented material with the same soil putting it all back to the container.
You can bokashi ferment weeds, grass clippings, flowers, and virtually anything that is derived from plant or animal material and mix it with the soil to restore the soil to a much richer material for your plants to use. You can see the fermented food scraps in the upper left corner, flowers and weeds before fermenting (right side), and in the container after bokashi fermenting (lower left corner). The fermented materials are mixed with the soil and covered with about 8 inches of soil and then allowed to process for a week or two (lower right image).
The flower stems, grass clippings and wood chips took only 7 days to ferment before they were mixed with soil. They were completely taken up by the soil in the next week.
Bones and Pits……How long before they disappear?
People are frequently surprised to hear that bones will disappear when properly bokashi fermented. Larger bones and pits will take a little longer to completely break down and disappear so they are no longer recognizable.
Small bones and cartilage disappear rapidly in less than 10 days in the summer but the larger bones and pits will be observed if you look for them. But they are very different once they have been fermented. There is no harm in leaving them alone but if you want to get rid of them in the soil quickly, it is easy.
You’ve got to do a little work and I have shown you how to do it in the picture below. After 8 months when I filtered all the soil in the container, I had a small pile of bones and pits that were still recognizable as shown on the upper right image. I’ve also observed that grape stems and certain waxy vegetable skins might hang around for awhile if they are not bruised or damaged before fermenting. Cooked food goes very quickly after fermenting.
Back to the bones and pits! If you pull them out and place them on a flat rock (wear safety goggles) and give them a crush with a hammer or other stone, they will easily break into small pieces and fibers that are then put back to the soil. If you leave them a week or two in the soil before the crush, the bones become very soft and fibrous.
This “bone meal” is an excellent source of calcium and phosphorous and other minerals and will help your plants. If you leave them alone it is fine….just a time release type of delivery to the soil. I like to break mine apart. You can see how they crushed into fibers and small pieces that were then put back to the soil surface and mixed in to go the path of all the other nutrients in the soil.
After 8 months of continuous use, the plantar box appears no fuller than when I started. It is in the dead of winter and we’ve had some heavy rain but you can see the soil is dark and rich (although a little clumpy because of the heavy rain). I have observed the rate of breakdown in the cold weather is about half that of what I observe in the summer but still rapid. There are no flies, foul odors or problems in processing all of my material in this single container.
Bokashi fermenting dog and cat poop?
People frequently ask me if they could ferment the pet waste in the fermenters. Although it could be done and would certainly break down and be taken up in the soil, we discourage this process in the containers that are going to be used for a vegetable garden.
Pet waste is generally alkaline and carries with it a number of potential parasites and pathogens that can get into the water supply. It is an important point; how to safely dispose of pet waste without contaminating the ground water.
We have constructed a special fermenter with an accelerant to handle pet waste (Bokashi PetCycle Waste Disposal System) and use the same microbial culture mix in the fermenters to eliminate odors and convert waste into nutrients for the soil.
If you are collecting the waste in plastic bags and putting it in the garbage cans, it will end up in a landfill where it will with the plastic cause a lot of problems. Methane gas will be produced and the potential for ground water contamination persists. Those plastic bags will stay around for thousands of years.
If you put it in the PetCycle™ disposal system to ferment, the smell will be eliminated and the waste material will be converted to a high nitrogen rich “pickled” waste that can then be put safely into the soil where you want to grow ornamental plants. Even though it looks awful…like gravy………it is not smelly and is taken up by the soil microbes quickly leaving rich nutrient soil for your plants. You mix it in the soil in a hole in the same way you process bokashi fermented food scraps after the fermenting is complete.
In summary, it is easy to let the microbes do their work. Even in the winter when the ground is frozen they process material. Just set your fermented material outside and let it sit until the ground is soft and easy to work. Then mix it well with soil and cover it over with about 8 inches of soil so it can be incorporated back to soil.
If you love plants, like to grow your own vegetable garden and build beautiful ornamental gardens and want to get away from chemical fertilizers and pesticides, bokashi fermenting is for you. It’s easy, fun and fast. Remember to dilute your bokashi tea 1 to 100 with water before adding it to your house plants and garden. Give the soil about 2 weeks to process any freshly buried fermented product before planting seedlings.