When you’ve finished mowing the lawn and you’ve emptied the clippings from the grass box for the last time of the session, you’re likely to be looking at a substantial heap of fresh grass clippings. Some people send this off to the dump just to get rid of it but those people should ask the question, can you put grass clippings in compost?
Yes, without doubt. Grass clippings are the best material you will ever get hold of for making compost. This is because grass is the easiest material to make compost from. It’s so easy to make compost from grass clippings that it will almost happen just by looking at it.
Given that you have this bounty of grass clippings, there are things you can do to make the process simple. With the most basic approach and input of effort, you can turn, what may seem, a nuisance heap of green grass clippings into the best compost that you will ever make.
Most people see grass cutting as a chore and, somehow, loath doing it. If you ever appreciate the full value of compost, you won’t see grass cutting as a chore but an opportunity to harvest something of value. Don’t see grass clippings as a waste, see it as a crop.
If you manage grass clippings, and other trimmings from the garden, effectively you will have a constant supply of compost that will probably provide for all your organic fertilizer needs.
Do you need to add anything to grass clipping compost?
You don’t need to add anything to grass clippings to encourage rotting. I’ve seen many a heap of chopped grass reduce to something black and useful. But there are ingredients that you can add to grass clippings that will enhance the mix and, possibly, speed up the composting process.
Grass that you cut will be cut from the Spring-time months, through to the Autumn/fall. By the time the fall comes these grass clippings should be well on the way to rotting down into compost. During the fall we will see, of course, a good supply of dead leaves. Treat this as a bonanza. It only comes once a year.
Gather as many leaves as you can and add them to the rotting grass clippings. There are a number of advantages to doing this. The leaves, being dry, will absorb any excess moisture from the rotting grass and then start rotting down. Dry leaves need moisture or they won’t rot. To incorporate the leaves, you will need to dig over the heap of rotting grass.
We have a post that looks at the value of leaves as an organic fertilizer. Check out ‘How to make organic fertilizer from leaves’ to find out more.
As you do this, you can add the leaves. The aim here is to get an even mixture of rotting grass and dead leaves. Digging over any compost will draw air into the mix and by adding dead leaves, these will create pockets of air which will keep the mixture open.
Another ingredient that’s worth adding is hydrated lime. This will neutralise the acids that are formed, particularly in the early stages of the process. To get the best out of hydrated lime you need to introduce it into the mix at the earliest stage. As you construct your heap of grass clippings, build it in layers.
Set out a layer of grass clippings, about 6 to 8 inches deep, then scatter a generous dusting of hydrated lime on top of this. Don’t worry about exact weights and measures. Just scatter around enough lime to make it look white. Then add another layer of grass clippings and repeat the process.
Then leave it for a month or two then dig it over to get air into it. May be wait until the Autumn fall when there are leaves around to add to the mix.
Another addition that may be necessary is water. If you cut your grass in very dry and hot conditions, then there’s a risk that the grass clippings won’t convert into compost. It will just sit there as a dry mass and do nothing. It will be hay. Adding water may be the necessary trigger to get things moving in what, may be, has become a dormant compost heap.
What is the best way of making compost from grass clippings?
The best way to make compost from anything, provided it’s organic and will rot, is to turn it over regularly. There’s an easy way and then there’s the hard way. The hard way is to use a fork and dig it over. It may feel like a lot of work but think about the quality that you will be achieving and, as you are working at it, remember that there will be an end to the digging chore.
The easy way can be more fun. This involves using compost tumblers. Using a compost tumbler you are more likely to turn over the mass of forming compost more regularly. Keeping it moving from very beginning of the process will give you the best chance of making a good quality compost and it will be the quickest way of doing it.
The process will be improved by adding hydrated lime to help maintain a low acid level. Lime is not essential, grass clippings will rot without it but using a compost tumbler you need speed and hydrated lime will help with this.
A compost tumbler can only handle limited sized batches of material. When a batch is looking dark enough and feels anything like compost, you can empty the tumbler completely. Then another batch can be loaded in. All compost tumblers will operate this way except the Rolypig composter which is an ‘in one end and out the other system’.
This may be converted enough to use as organic plant feed or, if it looks like it needs to rot further, put it in a static bin and leave it there. It will carry on rotting until it reaches a constant conclusion.
With the compost tumbler empty you can now load it up with another batch of grass clippings and subject this to the tumbling process. Because grass clippings will deteriorate where ever they are, you will find that much of the grass that you put in a compost tumbler, in batches, will be partly rotten. It will start rotting while waiting for the compost tumbler to be empty.
This isn’t a problem. If organic material has started rotting before it goes in a tumbler then it’s off to a good start. The tumbling action will take it the rest of the way. Be careful when handling partly rotten grass clippings. Fresh grass clippings will be clean to handle with that smell that only fresh cut grass can throw out. Half rotten grass is not so good to handle. It will smell bad and there will, most likely, be fungal spores in the air. It may be necessary to wear a face mask to protect yourself.
Do worms help to make compost from grass clippings?
Worms will get to work on any organic material including grass clippings. They will not attempt to digest fresh grass. They can’t digest any fresh waste, it has to rot down enough to be soft for the worms to bite into.
When the grass clippings start to break down they will generate heat. The temperature can be quite high, especially in the middle of a heap. The worms won’t be able to function in such high temperatures so they will avoid this area of a heap. They will only be found where the conditions are suitable to them. They will wait in the safe peripheral parts of the heap where it’s cooler.
After the heating stage in a heap of grass clippings there will be a cooling period and the grass will carry on rotting. It’s at this stage and onwards that the worms will be inclined to move in and start to digest, what is essentially, grass that has almost completely rotten.
The worms will multiply in numbers, often to a point beyond the available food supply. They will ingest and digest everything around them in the fullness of time. It’s believed that they will ingest waste that has already gone through a worm. Depending on the population of worms on site, they will convert any green waste to something that is beyond compost. It will become vermi-compost.
You will know when this has happened. Vermi-compost is much more dense than conventional compost. It has a solid feel and shows every indication that it’s been broken down to an absolute constant where it can go no further.
There is an argument for not having worms in the compost. If you want a compost that has a fibrous texture then allowing grass clippings to rot down to a constant relying on just the actions of fungi and microorganisms, will achieve this. When the worms move in and build up large numbers, they will grind ever fibre down to a fine level.
There will extract nutrients which they need for themselves. This will deplete the nutrient value of the compost as a plant food but there will be enough to make a contribution in many ways when added to soil
What are the hazards of making compost from grass clippings?
In the early stages of a heap of grass converting to compost, there is usually evidence of heat. You may see steam rising. If you dig it around after a day or two since cutting the grass, you may see clouds of steam rise up. This will depend on the size of the heap that has accumulated. A small heap will show very little heat output but a large heap may put out a spectacular display.
This, on its own shouldn’t pose too much of a problem but there may be problems if you spend much time digging the heap over soon after it has been formed. There will be parts of the heap where the temperature has risen but hasn’t become hot. These parts are where the rise in temperature has triggered the growth of fungi.
If you disturb this part of the heap you run the risk of allowing the spores from the fungi into the air. Then you will, unavoidable, breath in the spores. You will know when you have because you will sense a stale, musty smell. You won’t want to stay around it and will likely move away. There is a real risk that if you expose yourself to much of this then you may develop respiratory problems. You need to try to avoid this completely or wear a face mask.
The safest thing to do is to leave the heap well alone for 2 to 3 months, allowing time for this phase to pass. If you want to dig at a grass compost heap to take some out to put in a compost tumbler, then use a watering can and rose attachment to dampen down the spores. If they are stopped from becoming airborne then you won’t breath it in. This would be a safer way of operating.
What can you do with grass clipping compost?
The compost from grass will be as useful as any compost from any other green waste. There will be the added advantage of it being of a more consistent quality. It will be more of an even, balanced medium, largely because the input material is plain and has no variations of mixture. It will generate a fibrous compost that can be added to soil. It will increase the humus factor of any soil.
If you have soil that needs the addition of humus,you will need to add compost grass clippings as often as possible. The mere presence of this type of compost in the soil will attract worms. This is what you want. Active worms in the soil will open up the soil structure allowing air to get in to the plant roots and excess water to drain away.
The worms will feed on this fibrous material breaking it down completely and, effectively removing it. After a while the soil will revert to how it was originally and will be in be in need of more compost generated from grass clippings. When you bring up the humus level in soil to where you would like it to be, you have to keep going by adding more and more.
After reading this you may be wondering, is it better to leave grass clippings on the lawn?