Compost accelerators, compost starters and compost activators are all terms used for products that are added to the compost pile to make better compost and to make composting faster. What is the difference between these terms? Are they required for composting, and how much faster is the composting process if you use them?
Compost Accelerators, Starters and Activators
Let’s first try to understand the different terms. I spent some time looking for definitions of these terms and looked at a lot of products that use the terms. My conclusion is that the terms are used interchangeably, or they are used incorrectly a lot of the time. I could not find clear definitions for any of the terms.
However, products being sold under these terms do not all contain the same ingredients. Bottom line, I think it is best to ignore the terms, and look at the ingredients in the box which is what I will do in this article. I’ll discuss the ingredients instead of looking at accelerators, starters and activators.
How do you find out what the ingredients are in a certain product? Simple, right – look at the label. Wrong. Almost none of these products list their ingredients. They might say something like “contains bacteria” but they never say which ones or how much. They might also mention fertilizer – but they never give details. This lack of information should be a big red warning sign – DO NOT BUY!
Microbial Inoculant and Soil Inoculant
Microbial inoculants and soil inoculants contain microbes. We all know that microbes are responsible for the composting process and so it seems to make sense that we should add some at the start of the process to speed it up.
All of the organic matter you add to the compost pile is covered with huge amounts of bacteria and fungi spores. You can’t see them, but they are there. It makes no sense to go out and buy some more to add to the pile. Don’t believe claims that microbe inoculants will speed up the process.
The other thing to understand about composting is that it is a very dynamic process—I discussed this in Compost Microbes – Good For The Soil. As the compost pile warms up, the microbe populations change. As water levels change, so do the microbe populations. If the environmental conditions are favorable for a certain microbe, it will find the compost pile and it will prosper. They are everywhere. And if you add microbes that don’t like the current conditions they will die. Purchased microbes may already be dead when you buy them, or they might die as soon as you add them – you have no way of knowing.
Lime and pH Balancers
Many composting recipes advise you to add lime, which will raise the pH of the compost. Some products claim that they include ‘pH balancers’ and or lime.
How important is it to keep a correct pH?
To better understand this, lets look at the changes in pH as the composting process proceeds.
The initial pH of garbage, yard clippings and manure will have a pH of between 5 and 7. Manure tends to be at the upper end of this rage, close to 7, and woody products (woody stems, paper) tend to be more acidic. So the starting pH depends on what goes into the pile. All of these things will compost, so starting pH does not seem to be that important.
In the first few days of composting, acids are produced and these will lower the pH to about 5. Some scientists have suggested that this early acidic phase may be very important for killing pathogens, so adding lime may actually prevent the killing of pathogens.
As composting proceeds, the pH will slowly increase to a final pH of about 7 to 7.5.
The composting process manages its own pH and it does not need our help to adjust the pH during the process. The microbes will adjust their populations to match the pH for us.
Secondly, since most finished compost is neutral or slightly alkaline, it makes no sense to add lime to the process—it will only make your finished compost more alkaline. Most plants prefer a pH below 7. Excess lime will also release more ammonia, and you want to keep as much of the nitrogen in the compost as you can.
Bottom line—don’t worry about the pH, don’t add pH balancers, and don’t add lime.
Fertilizer
The only reason to add fertilizer to a compost pile is to help feed the microbes. They certainly don’t need more phosphorus and potassium, but if your compost pile ingredients are mostly browns (see How to Compost – Browns & Greens), there will be a deficiency of nitrogen. Adding more nitrogen will speed up composting.
Good nitrogen sources include Urea, blood meal, grass clippings and alfalfa meal. These are much better for the compost pile than compost accelerators, compost starters and compost activators – and cheaper!
Energy Source
Some products claim to contain an ‘energy source’. I guess they think you need this extra energy to wake up the microbes so they will do their job. What these manufacturers fail to realize is that almost everything in the compost pile is an ‘energy source’ for microbes.
Some people talk about adding sugar, molasses, or milk for the same reason. Adding food that has spoiled can certainly be composted—there is no problem adding these items. But they are not needed to make compost nor do they speed up the composting process to any great degree. And I think that adding good food to a compost pile is environmentally irresponsible – donate it to someone who does not have enough to eat.
Worms
A number of web sites recommend adding worms to a compost pile—they are wrong. There is a composting process call vermicomposting, or worm composting, that uses worms, but that is a completely different process than using a compost pile. A compost pile gets hot and will fry the worms. Actually, the worms are smart enough to leave as the pile gets too hot.
You might see worms in the finished compost, but that is because they have moved into the pile near the end of the composting process.
Handful of Soil
Earlier in this post I said that you do not need to add a commercial source of microbes, because they are already on the ingredients. If you think that your plant refuge might be too clean—its not—then feel free to add some soil into the compost pile. The soil will add more microbes and costs you nothing.
The soil is not needed, but will not harm the composting process. If it makes you feel good, add a handful or two of soil.
Compost Accelerators, Starters and Activators
I am amazed at how many such products exist—hundreds of different brands. I am even more amazed that many provide no information about their ingredients. Nor do they provide any kind of test results to show that their products actually work. But people must be buying them!
The reality is that composting happens in nature once microbes and organic matter meet. A compost pile provides the mass to produce good heat to speed up the process along, but composting happens even without a pile.
In a future post I’ll look at ways to speed up the process.
Adding compost accelerators, compost starters, compost activators, compost boosters etc, is a waste of money and resources.
References:
1) Photo Source: SKS Bottle & Packaging Inc
I have a green cone digester. We use it to compost our dog’s poop. We’ve had it for a couple of years now and things are piling up. I’m thinking it has enough nitrogen, so maybe some soil?
Soil won’t do much. Try adding some browns – like straw.
Just started my first compost pile and it’s been a couple of weeks and hasn’t started heating up yet. Did a Google search for “catalysts for composting” and your post was one of the first things that came up. Glad it did. I’ll just add some grass and see how that goes. I think I have too much brown.
Thank you for the insightful article. Ive always been told to mix some 10-10-10 into the pile to add heat for over-wintering (I live in Maine), and when I tried this, and then used the compost, my plants grew tall, but were leggy. What is the correct amount of fertilizer to use?
If you don’t have enough nitrogen in a compost pile, adding nitrogen will speed up the composting process and in turn heat it up. Adding P and K does nothing for this process. The correct amount depends on the C:N ratio of the compost pile.
Hi, I have just discovered that the professional, store-bought composted manure that I applied in my garden and house plants contained aminopyralids that poisoned the soil for 3?! years. Short of replacing all the soil in my garden (not), I can only hope to speed up the decomposition of this poison. When I had bats (this year they left after a month–too hot maybe), their guano was recommended for compost activation. I also saw lobster mulch and worm castings at the store today. This trauma is what lead me to your great article. What bio activator would you recommend for garden soil? Good luck to Canada at stopping this broad leaf herbicide from getting into the home garden.
Soil is all you need, and you don’t even need that – you use soil mostly to make you feel better.
If the C:N ratio is off, and high in carbon, add some nitrogen like Urea.
I know this is an older post, but I just came across this….
THANK YOU!! I’m just starting out at composting, and everywhere I turn there are a bazillion products to “help the process”.. and it would be like getting nickle and dimed to death. I was about to give up on the idea, since composting in the desert already has its own challenges… you’ve stopped me from being discouraged!
Don’t buy anything for composting – except maybe some urea fertilizer if you want to speed it up.
Or use your own human urea fertilizer for free
Was searching online for garden compost activator after my local store stopped stocking it, and came across you article, thanks, it’s saved me money as I now realise I’ve been using it in the past thinking it was that alone which made me great compost !
Hi, thank you for writing this article. I have a 5L urban composter with a tap that came with accelerator. It recommended spraying the scraps, every 3 days draining the liquid which can be used as a fertiliser (10ml to 1L water) or drain cleaner and then putting the scraps in a outdoor compost. Would the process be just as effective in making plant fertiliser (I have succulent pot plants and indoor plants), if I did not use the accelerator? Or would you recommend just outdoor composting. Also, I have just been digging a hole in the ground and putting the left over scraps in there, from reading your article and comments it might be more effective to line the hole with cardboard, wet it and put plastic on the top. Any comments, suggestions/advice would be greatly suggested.
Look at the ingredients – I have no idea what is in the bottle.
I have a solar cone (green cone) digester rather than a compost pile to deal with kitchen waste only (no yard waste). The company sells an accelerant/starter. How would I make my own? Thank you.
You do not need one, but if you want one ….. add a handful of soil, and some nitrogen fertilizer.
I add rabbit litter pan waste (droppings and recycled paper litter. A LOT. Also excess hay that she tosses out. I’m also a vegetarian & bunny & I eat a lot of fresh greens. I compost the stems & stalks, carrot peels, apple cores, etc. I live in northeast US, it’s in the 30s. I have a portable turning composter that needs to speed up. I added a little soil prior to composting. Will adding leaves from the woods speed it up? I think my ratio of browns to greens is closer to 1:1 instead of 2:1.
I live in north east (Massachusetts) and collect a lot of foliage for composting every autumn. Autumn followed by brutal winter where composting rate goes down drastically. What is the best practice to compost in cold climate?
You either have to provide heat or wait until spring.