Hot composting in winter – it can be done with insulation

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Hot composting in winter

Most of us know that making compost in warm weather is easy. The bugs that turn waste into compost are much more effective in warm temperature. But what about hot composting in winter, is it possible to convert green waste into compost in cold weather?

You can make hot compost in the winter months but the process will vary compared to summer-time composting. You may find that any periods of hard freezing of the waste may provide an advantage. When frozen it will be dormant but as it thaws the material will physically break down giving the bacteria a huge opportunity to work quickly and make up for lost time.

What else?

Can you add waste into a frozen compost bin?

Where can I put waste if my bin is frozen and full?

Should I use a compost bin or compost tumbler?

Can you compost all year round?

Can I make compost indoors in winter?

Do compost bins need to be in the sun?

Can you compost in the winter?

It will depend on where you are in the world. If you regularly have mild winters then none of this will be an issue. If the air temperature is above freezing most of the time then the bacteria and microorganisms that digest the waste will carry on performing. There will be a slowing down of activity with lower temperatures compared with higher temperatures when the composting process will work at optimum efficiency.

Can you compost in the winter?

If there is a cold period of time when the air temperature is well below freezing then you must expect any composting process to stop. Total shut down won’t happen straight away. The outer extremities of a compost heap or bin may be frozen solid but there is still a chance for material in the middle to carry on. The outer layer will provide a level of insulation that will protect the middle.

Pink rose watering can by Rolypig

This situation may only be temporary. If the cold weather intensifies and the cold period extends, then the whole volume of compost will become frozen. At this point nothing will happen. The whole mass will be frozen solid, the waste will be effectively preserved. Frozen waste material is unattractive to vermin. There is no smell generated from frozen organic waste and if animals try to consume it they will find it very difficult to chew what is essentially, solid ice.

Can you add waste into a frozen compost bin?

Yes you can, if there is room. You can ensure that there is room if you plan ahead. If you know that there is likely to be a period of very cold weather then remove as much fully formed compost as possible and store it in bags. Compost that is fully formed, dark and crumbly, can be stored in bags without fear of vermin being interested. There will be no food value for them in this sort of material. With space prepared you will now have somewhere to dump green waste which will freeze with the rest of it but at least it’s out of the way. On the subject of vermin (rats, mostly), we have a couple of posts that you may be interested in. Check out ‘How to keep rats out of the garden’ and ‘Rat-proof garden. Is it possible’?

Adding fresh waste won’t affect the frozen material. The fresh waste will quickly become frozen as part of the main mass. The only complication will be that in a prolonged frozen period, the bin will become full. The compost that would normally be formed can’t be removed from the bottom of the bin to make room at the top.

The same applies to compost tumblers. Keep adding until there is no more room. In doing this you are just putting the waste somewhere to get it out of the way but you can’t expect it to convert to compost any time soon. When your vessel is full you will have to make other arrangements until the air temperature rises and the composting process can get started again.

Can you add waste into a frozen compost bin?

To help ensure that there is space in your compost vessel through the winter freeze, don’t add too many dead leaves from the Autumn/fall. You can justify adding some to help with the ‘green’ and ’browns’ balance but keep it to a minimum. They will take up space. The best thing to do with dead leaves is to store them in plastic bags. They can keep until the early spring when the composting process will get underway again. They won’t attract vermin and, provided you keep them dry, won’t generate any smell.

Where can I put waste if my bin is frozen and full?

There is no choice with this. You will have to store it in other containers or plastic bags. If no composting can happen then material volumes will build up. The only advantage of waste being frozen is that it can be stored without fear of producing a smell, at least for the short term.

One simple way of dealing with the problem would be to get an extra compost bin or tumbler and start loading up.

The advantage of this is that as soon as the weather turns and the air starts to warm up, the waste will break down as part of the thawing process and will be in a perfect condition to begin the composting process. You won’t need to do anything more than wait for compost to appear. If you have waste building up in plastic bags then you will need to get moving quickly when the weather warms up. The bags will have to be emptied into a composting device.

Don’t leave bags of waste lying around after the thaw. It’s no problem when frozen but in warm temperature the waste will smell and will definitely attract vermin. There will also be liquid which will escape from the bag and possibly make a mess.

Don’t forget the importance of using hydrated lime. Frozen green waste will eventually thaw and break down into a mushy material. Having lime in the mix will ensure that the acid level is kept low and decomposition will begin very quickly. The hydrated lime won’t take up any space because you only need to add a small sprinkling as you add fresh waste. Freezing conditions won’t affect hydrated lime. It won’t deteriorate due to any freezing temperature however low it may go,  it will just sit there waiting for conditions to change.

Should I use a compost bin or compost tumbler?

Either will work, at least as a place to dump green waste in a frozen period. See more about static bins and tumblers. But are there any pros and cons? In a harshly frozen time the contents of both will be static. A bin will be static regardless but a tumbler, by its nature, needs to roll to accelerate the composting process. If the contents become one big solid mass then you won’t be able to roll it because it’s likely that it will be too heavy. It’s probably wise not to try rolling it because, depending on the type of tumbler, you may incur some sort of injury in the attempt. This would almost certainly be the case if you have a ‘butter churn’ end-over-end compost tumbler. The problem is that the frozen solid lump will stick in place and as you try to roll it end-over-end there is a risk that it will swing back in place. If your chin is in the wrong place at the wrong time then you will be inline for a clout.

So when it comes to choosing from a standing start between a static bin or a tumbler you need to consider how long the frozen periods are likely to be in your area. If you don’t care too much about the tumbling action accelerating the composting process then put in a couple of static bins. This will provide you the most basic of storage space that will generate compost for you when favourable conditions allow.

When the warmer weather comes and you want to have the benefit of the aeration that a compost tumbler brings then go for a tumbler. A tumbler system will  produce usable compost much faster than a static bin but don’t expect it to perform during a frozen time.

Can you compost all year round?

Yes, provided the temperature doesn’t drop too low. You do have to accept that there will always be more activity in the compost bin during the summer months than in the winter. Warmer conditions mean that the microorganisms and worms will multiply. This is the time to expect the best performance that you can get from any compost system.

The most effective way of making compost all year round is through a tumbler type composter. Introducing air into the waste material will ensure that, whatever life forms are present, they consume and deliver much more efficiently.

A static bin type composter will generate compost through the summer months. To get the best from it you need to remove any made-compost from the base of the bin to allow fresher waste to move down. The falling of waste from top to bottom will do much to draw air into the mix and this will accelerate the composting process.

The ultimate approach would be to occasionally dig out the entire contents of a static compost bin from the bottom of one bin and load it into another empty bin. This would effectively be turning the whole mass of material over completely. If you do this around every six weeks in the summer months, the green waste will quickly convert to compost.

The winter months can be very different. Whatever compost system you adopt, all life forms will become either completely or semi dormant, although it is possible for some microorganisms to be effective all year round. You can expect to see green waste material rot down but not as quickly as it will through the warmer summer months.

Can I make compost indoors in winter?

You can make compost under cover, indoors, away from the harsh winter elements. If you have enough covered space it won’t be a problem if the weather is sub-zero. Provided there is enough insulation to maintain a reasonably agreeable temperature level, compost can be made indoors.

The most effective way to make compost indoors has to be with a wormery system. If you are going to put any effort into housed composting then it’s worth going for a wormery. These are easy to set up. There are ready-made ‘tray’ systems which are specially designed for disposing of green waste with a good population of worms.

Be sure to use the right breed of worms. These are the red worms which are commonly known as ‘Tiger worms’. These breed very quickly in the right conditions and are capable of consuming large quantities of waste. The larger earthworms will be no good for this as they are unable to digest just organic waste, they need to be in soil.

It’s very important to understand that Tiger worms can’t digest fresh green waste. The waste has to rot down to the point where it’s well on its way to becoming compost before the worms can begin to consume. They will, however, graze on the molds and fungi that appear on the green waste in the early stages of decomposition. As soon as there are any signs of this, they will get to work.

As the molds, fungi and a whole range of microorganisms break the waste down, the worms can then move into this material and start to digest it. They will turn it into worm casts which apparently go through the worm’s digestive system more than once. When the worms have finished digesting the waste completely you will not recognise it as the waste that you originally loaded in. It will be a consistent material, dark brown in appearance and quite dense.

The worm casts can be harvested and stored during the winter months to be used as a highly effective organic fertilizer. This will be better than anything that turns up from any other composting system because it is fully broken down. That isn’t to say that standard compost from a compost bin or tumbler isn’t good enough because it is. The point is that when worms get involved when they have the ability to turn any compost into something much better.

Do compost bins need to be in the sun?

No, a compost bin does not need to be in the sun. There is an argument that by being in the sun that it will warm the contents and accelerate decomposition. This may be so but the effect will be minimal. Because of the volume of the mass of waste in the bin, it will only be the outer extremities that will benefit from this. Also, unless you have the bin on some sort of turntable, it will only affect the sunny side.

I think, on balance, that it’s probably better to keep the compost bins in the shade for a number of reasons. A compost bin placed in the hot sun may lead to the contents drying too much. For green waste to rot down into compost the material needs to be moist. Without moisture the microorganisms that do most of the breaking down, can’t function. There is also a potential problem if worms are involved. Worms don’t like heat they move away from hot-spots because they like to be cool.

You also need to consider the compost bin itself. They are usually made of plastic and, although it may have a UV (ultraviolet light) stabiliser in the plastic, it’s not good practice to allow too much sunlight to get at it.You will see indications on the compost bin outer surface if it’s been placed in excessive sunlight.

The colour will often fade on the side that’s been exposed to the sun and after a while you will see cracks appearing on the surface of the plastic. This is more likely to happen if there is no UV stabilizer involved. If this is the case then the plastic will become very brittle and at some point will start to disintegrate. These are good enough reasons for most people to keep their compost bins in the shade.

Find out more about compost bins and tumblers, see: tumbler composter vs bin.

Make compost all year round, winter is just an interlude.”

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Image sources: Frozen leaf | Snow on twigs | Cobwebs


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