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
Hi – Excellent article. I have been making very good compost for many years now and the only thing I would add is that initial wetting of the heap is very important. I collect materials for compost hep throughout the season, when I have a large heap of these I ‘put the heap to bed’ for six months. An empty compost area is used and lined with cardboard (this stops the heap drying out too much and insulates it. I then layer the brown and green as much as I can, there is usually soil added on discarded plant roots and in spent compost. Thoroughly wet each layer with a hose as you go. By the time the hep is done it will almost wobble when you slap it! Excess water drains away but compost will not rot down unless it is all t wet through. Cover the top with a good layer of cardboard (for some reason this seems to promote worm breeding. Cover with a plastic sheet – this keeps the heat in and stops rain from cooling the heap. I turn the heap out after about 6 months and cover. In another three months it is like crumbly chocolate cake. Its a good soil conditioner but is more nutritious if i can source some raw manure – horse or chicken to go in between the layers. The secret is to keep it wet – if it is dry it will not rot down (or will do but too slowly to be useful).
I live near Seattle WA USA and have a 29,000 square foot lawn and mow it about once a week in the growing season so I generate a LOT of grass clippings. I throw them in the woods behind my house. About 15 feet into the woods it goes downhill pretty steeply so I stand at the edge and throw the grass on the slope. I try to mix in leaves in the fall by blowing them or raking and throwing them but it is mostly grass clippings. Due to the terrain, I am not able to “turn” the clippings. It does not compost but instead just forms matts. Is there anything I can do to accelerate the composting process? Can I assume you feel that homemade compost accelerator of beer, cola, ammonia and water is ineffective? What about adding some “garden soil” or compost from Lowe’s or Home Depot?
Thanks,
Don
grass contains lots of nitrogen – adding more is not going to help. You probably need to add carbon.
The best thing to do is leave the grass clippings on the lawn. There they decompose quickly and help feeding the lawn.
I would love to mulch the grass and leave it on the lawn but I have a few hundred small patches of Poa Annua scattered throughout the lawn. Right now it comprises only a few percent of the total area but if I leave the grass clippings on the lawn I will be helping it to take over the lawn, so unfortunately I have to discard the clippings. How do I add carbon?
straw, fall leaves, saw dust
I greatly enjoyed the article, and the responses. I’ve been making compost successfully for years, and thought I knew enough, but this year its stalled and hasn’t rotted down. I thought it was too ‘woody’, but now I’ll add a bit of soil.
Thanks
This is all wonderful what doesn’t work , but what does work then? My compost won’t rot and I don’t have any brown stuff to add so what do I do?
If it is not composting them you don’t need browns – you need more nitrogen – or greens. Or more air.
Wow, clear and articulate. Very good information provided in simple and unambiguous terms. Thank you so much Mr. Robert Pavlis.
A newbie to composting and was confused to start with, not any more.
Thanks for the informative article,like so many I intended buying all sorts of feed etc. Great article. Thank you
Very good & valuable information
Thank you for the information and your time.
Thank you for the great post! Almost bought some accelerator.
I have a question about composting plastics. There are some bioplastics touted as being compostable. Do you have any experience composting them? Thank you!
No, but from what I have read they don’t decompose any time soon. The problem here is the terminology. The general public sees “compostable” and we think they can be composted along with the other normal kitchen scraps. However, compostable means it does compost some time in the future. It could take 10 years and still qualify as compostable.
Don’t try to compost plastics.
As a novice gardener reading the article seemed interesting but has left me even more confused now. I have a big black composting bin and have been adding household waster, tea bags, eggs shells, vegetable waste (not potato) and occasional paper but it does not seem to be rotting down after over 2 years……………..any suggestions please. I was just looking at buying compost accelerator until I read that you say it is a waste of money
Paper composts very slowly. Try adding fall leaves.
The problem with the black bins is that they are too small to heat up which means slow composting. You also can’t turn the pile – slow composting. Probably not enough air – more slow composting.
Add some soil for microbes, and try to mix it up a bit.
Suggest you use the bin to collect the material and then once a year dump it all in the garden even if not composted.
Great article. We’ve just moved from the city to the country and can now build a couple of big compost bays. In our small garden we had a plastic compost bin that was low enough that we could reach in and turn at least the topmost part of the compost and it got realyy hot for all that it didn’t hold the heat as a larger bin would have. Beside that bin we had a very large tumbler, also pretty efficient. When we emptied one or other bin we transferred the unready stuff into the other bin to give the work in progress a bit of variety. I did add blood and bone from time to time and a handful of lime if it was smelly. Won’t worry about that in future.
Thanks again, Mr Pavlis.