What to do with your Spent and Used Compost

Towards the end of the growing season, you may be faced with the dilemma of what to do with all the old spent used compost from your plant containers and grow-bags, especially if you only have a small patio or garden.

I currently grow many of my own vegetables in containers outside our front door, and as most of my vegetables are now finished I have had the problem of how to dispose of the hundreds of liters of old used compost I have leftover.

By the end of the growing season all the goodness from the compost has been used up by the plants, (in fact this is usually used up within 6 weeks, hence why you need to feed your plants), and many people would consider it pretty useless and simply dispose of it with their normal rubbish, so adding to the landfill sites and the rate they fill up, not an environmentally friendly option.

Now on Guernsey in the Channel Islands where I live, the local authorities recently ran a promotion to encourage people to compost their kitchen and garden waste. They provided a large number of compost bins at a greatly subsidized price, so allowing members of the public to only pay £10 per bin, instead of over £30, (the normal price). These bins each came with a small container to keep within your house and use to put any eggshells, carrot tops, vegetable peelings, etc into until you got round to transferring them into your compost bin. They also provided a CD on how to make good compost.

Kitchen Waste Container

I decided to buy three of these compost bins, and using the knowledge I already had of making compost from house and garden waste, I realized I could combine this waste with my spent compost and in effect re-introduce goodness to it so I could use it again next year.

Now if you look at the picture I started this article with you will see I have very few vegetables left growing now. What you may not realize is that originally my growing area had a lot more containers, but these have since been emptied of vegetables, and the spent compost has been incorporated into my bins along with kitchen waste, old vegetable leaves, lettuces that had run to seed (bolted), damaged or nibbled at vegetables, old newspapers, etc. If you look at the picture below this section, you will get an idea of what my growing area looked like at the beginning of the season, and therefore how much old spent compost I must have produced.

My Vegetables in Containers Early in the Season

Tips on Making Good Compost

Now using your old compost is a good idea so long as you remember to alternate layers of the old compost with new stuff that will rot into it and add the goodness you want for the following year. If you simply pile all your old compost into the compost bin all you will have next year is a bin full of useless compost, so make sure you include layers of newspaper, lawn mowings, vegetable peelings, etc.

If you can find some try adding as many worms as possible too, because they will spread the new material in with the old as they tunnel through the compost, plus they will help to break down the material by eating it and then re-depositing it as nature intended.

It is particularly important that there is air between the layers, so don’t pack them down too tightly, and try to keep the layers thin, as materials such as grass mowings quickly turn into a nasty layer of “slime”, if not enough air can get into them to rot them down.

Alternate the types of materials you use too, so, for example, you could start with a layer of spent compost, followed by a layer of crumpled newspaper, followed by hedge-clippings, then more old compost, then grass mowings, kitchen waste, spent compost, etc. Try to keep the layers no more than 6 inches thick each time.

As the materials rot down the level in your bin will drop and you can add further material to the mix.

If you only have a compost heap rather than a bin, then the tips above still apply, although you should regularly “turn” the heap using a fork so that the materials all have access to the warmest part of the heap which is usually in the center. You will also need to cover the heap with a waterproof sheet such as polythene to stop it getting too wet in the rainy seasons, (otherwise, your compost will take a lot longer to be ready as the heat cannot build up sufficiently). Make sure your heap never dries out, and sprinkle with water from a hose if necessary.

To give you some ideas of things you can safely compost I have provided a list below:

1) Hair Clippings

2) Egg Shells

3) Vegetable peelings

4) Newspapers

5) Lawn Mowings

6) Tea Bags

7) Annual Weeds, (not perennial ones as they will grow back next year if you put them in your compost bin).

8 ) Hedge-clippings

9) Rabbit or Guinea-pig/Cavy Bedding (so long as it is straw, hay or paper and not artificial.)

10) Any pets waste that is not from a meat-eating pet such as a dog or cat.

11) Cardboard Egg Boxes

12) Wood shavings

13) Old vegetable foliage such as the potato halums, the remains of bean plants, tomato plants, carrot tops, etc. Do not compost any diseased leaves as the disease will remain in the compost and may infect next year’s plants too.

14) The roots of beans are especially good as they hold nodules of nitrogen which will be great for next years crops.

Things Not to Compost include:

1) Cat Litter

2) Meat cooked or raw

3) Cooked vegetables

4) Plate Scrapings after meals.

5) Any raw vegetables that may have mayonnaise or other dressings on, (this will attract rats).

Two of my Compost Bins full of Contents from the Central Containers Shown.

Your compost should ready for use within about 6 months so long as it doesn’t dry out. You can also improve the rate your compost breaks down by adding your own urine to it, (yes you did read that correctly). Human urine contains certain bacteria that help compost to rot successfully, so if you can add a bit of “pee” to the mix it will help you to make good quality compost more quickly.

Most compost bins have a door at the bottom, so the oldest compost gets used first which ensures it has had time to rot down properly.

Other Uses for Spent Compost
If you really have so much old and spent compost that you can’t possibly put it all into compost bins, then you may want to try these ideas:

1) Use it on top of your flower or vegetable beds as a mulch. This will not only act as a soil improver, (especially if you have either a very clay soil or a very sandy soil), but it will automatically be mixed in with your existing soil by worms as they come and go through between the two layers.

2) Use it to help level a sloping garden or border.

3) Use it to partially fill the bottom of deep plant containers so reducing the amount of fresh compost you need to fill up a pot where the plant may not need a particularly deep root run.

4) If you have a place where you can dry the old compost out you can recycle it as bedding for horses or cows and then it can be composted with the added manure at a later date.

5) Spread it over your lawns and rake it in with a grass rake until it is barely visible. This is good for the lawn and also will be taken down by the worms and improve the soil.

6) Use it the following year to grow carrots in, as they require little nutrient and will actually produce better roots if the compost is old spent used compost. Too many nutrients will result in small carrots with loads of foliage, instead of larger carrots with less foliage.