Mulch will eventually turn into compost if left on top of garden soil, mixed into a compost bin or left in a large pile in an open area to break down. Mulch can be added to a compost bin to help it break down quickly. Mix it in with other compost materials, water and old compost. Fine bark mulch will break down quickly into compost.
How to turn mulch into compost
There are many ways to quickly turn mulch into compost. Here are top 4 ways to turn bark, sugar cane, straw or leaves from mulch into compost.
A pile of mulch
All mulch types will eventually break down and turn into compost. Fall leaf compost can be made by simply pile up the leaves in a wire cage and letting them break down over the winter. The key here is volume to make sure the leaf pile is at least 4x4x4 feet.
This will help the pile to warm slightly and for bacteria to thrive and digest the fall leaves. Small amounts of heat will be created as bacteria break down the leaves.
Bark mulch will also break down in this way too if left in a large pile. Bark mulch will break down from the bottom up. The larger the bark piece sizes, the slower it will break down. Large bark piles with large pieces can take over a year to break down to compost.
Later in this article I will talk about ways to speed up the process of making mulch from bark chips.
Mulch on garden beds
Mulch left on garden beds will break down to compost through microbial activity and worms. Both will come to break down the organic matter from your soil and slowly turn the bottom layers of mulch in to compost.
Adding a thin layer of aged cow manure first will help to offset the small amount of nitrogen that is temporarily taken up by the bacteria in the break down process.
As mulch layers are topped up to 2-3 inches thick, the bottom layers will be broken down and turned into a layer of compost on top of your garden bed.
Lighter mulches like hay and sugar cane mulch can be dug into the soil at the end of a 6 month season as it will be almost completely broken down and will easily mix into the soil adding nutrients.
Mulch in compost bins
Mulch can be added to a compost bin to break down. Mix mulch through with vegetable and fruit scraps to add extra nitrogen. Coffee ground also work well in the compost bins mixed together with mulch.
Mulch is usually a mix of high nitrogen and high carbon material. Tree mulch will have both green material from the leaves of the tree and brown material from the stems and branches.
Together this brown and green mix makes the perfect combination to form a balanced compost on its own. Adding food scraps is not necessary but is a great way to avoid waste.
Adding much to worm farms
Mulch can be broken down in worm farms quickly and efficiently. I like to use mulch as worm bedding including straw, sugar cane and even fall leaves. I like to mix a range of worm bedding materials together including left over or old mulch.
For more on using mulch as worm bedding, check out my previous article.
Depending on the size of your worm farm you may only be able to add a small amount of mulch but this is a very fast way to turn it into compost or worm castings ready for your garden.
I like to use mulch on top of the food scraps in my worm farm to prevent ants and flies. Covering food scraps with a carbon covering will help to reduce the amount of water in the worm farm and stop it going soggy.
How to make mulch into compost quicker
Here are my top tips to turn mulch into compost quicker.
Shred it as fine as possible
Shredding mulch material including bark mulch, fall leaves and straw as fine as possible will help the mulch to turn into compost quicker. Choosing a fine bark mulch or if you have a shredder at home, using a fine setting will create mulch pieces that will break down fast.
Sugar cane mulch can be purchased pre-shredded and the small pieces are quick to turn into compost on top of garden beds or mixed through a compost bin.
Mix the compost mix often
Aerating and mixing the compost pile that contains mulch will speed up break down process. Adding air will help to support bacteria to quickly break down the bark mulch. It will also help to mix the ingredients thoroughly and it will all break down fast.
Add a few secret ingredients
There are a few secret ingredients that can be added to a compost mix to help the mulch to break down faster. Adding seaweed solution to the mix will feed the bacteria and attract worms to the pile. A diversity of bacteria will help the pile to break down quicker so it is worth adding this ingredient if you have it laying around at home.
Worm juice is another great ingredient which will increase the bacteria density and population helping the bark mulch to break down quicker.
Another fantastic secret ingredient to add to mulch to help it break down into compost is to actually add some old compost. Old compost added to mulch will supercharge the break down process. Keeping the pile moist will support the bacteria living in the old compost speeding up the breakdown process.
Does mulch turn into compost? | Summary
Mulch will turn into compost over time whether it is sitting on top of your garden soil or mixed through a compost bin. Th smaller the mulch pieces, the quicker it will break down. Old mulch can be raked up from the top of garden beds and placed in a compost bin to break down.
Old mulch can also be left on top of garden beds, topped with new mulch and the lower layers will break down to compost on the lower layers without doing a thing.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.