Home Composting
- You are here:
- Home
- /
- Environment and planning
- /
- Recycling and Waste Service Information
- /
- Waste & recycling
- /
- Green waste
- /
- Home Composting
Want to become a compost advisor?
Set-up a community composting project
Introduction to composting
Home composting is a simple, natural process that turns the kitchen and garden waste you would normally have thrown away into a nutrient rich, cost free product to use on your garden.
By home composting you are taking responsibility for the organic contents of your household bin:
- uncooked kitchen waste
- garden waste
- paper and cardboard.
This makes up almost two-thirds of your bin. Even if paper and cardboard are excluded, you are potentially diverting 20% (1/4 tonne) of your rubbish from landfill sites by composting at home, every year. Remember - composting is not an exact science and what works for some people may not work for others.
You are in control of this recycling process so it is important that you understand how your waste is converted into compost.
What is composting?
Compost results from one group of microorganisms after another eating their way through organic material. Each group creates the living conditions for the next group to use by breaking down biodegradable material into a form suitable for other organisms who then continue the process.
The speed of composting is influenced by a range of factors:
Degradation
This first phase involves microorganisms feeding and then multiplying to create the heat energy needed to raise the temperature of the decomposing material. Microorganisms which survive at this higher temperature then take over and continue the process until the material is degraded to a point where there is no food left.
This process begins again in your compost bin each time fresh material is added. This means that the material in your compost bin is at different stages of decomposition depending on the length of time it has spent in there.
People often say that their kitchen and garden waste does not seem to be composting. If you were to look at the inside of your compost bin you would see that the material at the bottom is in a far more advanced state of decomposition than that at the top as it has been in the bin for a longer period of time.
Conversion
This stage begins when the temperature drops as a result of the reduced activity of microorganisms at the end of the degradation phase. Microorganisms which work at lower temperatures will then move in to complete the decomposition process. The amount of larger insects will increase and become more noticeable. At this point the original organic material is mostly unrecognisable.
In your compost bin, this process will be taking place near the bottom as it works on the material that has been in there for some time.
Maturation
During this final stage, the activity of microorganisms decreases and the material cools down providing the ideal conditions for earthworms, insects and mites to complete the process. The result is compost; a dark brown material with a rich earthy smell.
Home produced compost will contain some undecomposed material such as twigs or eggshell fragments. It will, therefore, be visibly different from most people's image of compost which is based on what you buy from the garden centre. The commercially available peat-free multi-purpose composts have been made by shredding organic material then composting it in large batches.
Finally, the compost itself is screened to remove over-size particles. You can get a fine texture with home produced compost simply by separating the larger particles out with a sieve.
Why should I compost?
When organic waste decomposes in an aerobic (with air) environment, it is converted into compost. If organic waste is sent to landfill, this natural process can cause serious environmental problems.
The lack of oxygen available within the compacted layers of waste causes the organic waste to decompose anaerobically. This process produces methane gas and toxic leachate. Methane is a highly potent greenhouse gas, whilst leachate can contaminate water supplies.
Fortunately, UK landfill sites are engineered to ensure that these potential problems are avoided, but these pollution control measures are very costly to install. The key, therefore, is to harness and control this entirely natural process of decomposition through home composting.
What can I compost?
The food of the the composting process needs to be a mixture of carbon and nitrogen materials. The microorganisms that turn the materials into compost use carbon (browns) for energy and nitrogen (greens) for growth.
Basically anything that once lived will decompose and can be put in a compost bin, however there are things that are best left out as they can attract vermin.
Put in | Leave out |
|---|---|
grass cuttings/fresh plant trimmings | droppings from meat eating animals |
fruit scraps/ vegetable peelings | cooked food |
other uncooked kitchen wastes | dairy |
tea bags | nappies |
coffee grounds and filters | plastic |
vegetarian pet droppings | glass |
weeds (treated) | metal |
chopped woody pruning's/twigs | meat and fish |
sawdust | |
finely shredded paper/cardboard | |
vacuum cleaner dust (soak before adding) | |
stalks from dead plants | |
leaves (add sparingly) |
What does composting need?
Composting needs food (materials), water (moisture) and oxygen (air) - just like us.
Materials
This is the food of the composting process and needs to be a mixture of carbon and nitrogen materials. The microorganisms use carbon (browns) for energy and nitrogen (greens) for growth.
Greens are materials that are soft and sappy. Most of our kitchen wastes are greens as are grass clippings and freshly dug weeds. These nitrogen-rich materials contain proportionately less carbon and high levels of moisture and decompose more easily.
Browns are the drier, fibrous materials such as paper, cardboard, and woody pruning's. They contain proportionately higher levels of carbon and lower levels of moisture and tend to decompose more slowly as a result. This is not a disadvantage however. Browns provide structure to your compost heap by keeping open the spaces which store the air and moisture essential to the composting process.
You will find that your finished compost contains a proportion of undecomposed browns which you should put back into your bin to continue decomposing.
Successful composting depends on combining these greens and browns in balance.
Unpleasant smell
A bin that is made up predominately of greens can become slimy. The absence of carbon browns during decomposition causes much of the nitrogen to be converted to ammonia due to the microorganisms being unable to keep up with the decomposition process. This produces the unpleasant smell. The high moisture levels contained in greens can clog the valuable air spaces in the material.
Slow composting
A compost bin that contains a predominately high proportion of browns decomposes very slowly. The material in the compost bin will keep its original structure for a long period because the microorganisms are unable to easily decompose the material if there aren't enough greens. This can be reason why the material does not seem to be composting.
Balance of materials
A balance of materials is important but during the summer household waste tends to be predominately greens. Until the autumn brown materials are generally in short supply. Some brown materials such as paper and cardboard are available all year round and can be used to balance the green materials, but they must be cut up thinly. Leaves can also be used, but sparingly, as they take a long time to decompose
The quantity of greens and browns in your compost bin is not important - it is simply necessary to understand how each type of material influences the process so that you can confidently make your own decisions about what you need to put into your bin.
Moisture
Water is essential to the composting process but a balance must be struck. If the material becomes too wet, the air spaces become clogged up, which limits the oxygen available to the composting microorganisms. The process then becomes anaerobic which is the common cause of unpleasant smells.
If the contents of your bin are too dry, the process slows down as the materials become harder for the microorganisms to break down.
The lid of a compost bin keeps the rain out so sufficient moisture levels depend on a good balance of greens and browns; greens supplying the moisture, browns soaking up the excess.
In the summer, to combat the high levels of moisture created by greens simply use torn newspaper or card in place of autumnal browns.
In autumn there are larger amounts of drier organic waste. These materials will need additional moisture to be able to compost. Ideally a compost bin should contain 40 - 60% moisture; the material should feel as damp as a wrung out sponge. To keep to this level, simply add water when necessary.
Air
Material needs air to decompose. The amount of oxygen in the bin is reduced by the activity of composting microorganisms, so it is therefore necessary to create air gaps. If this is not done, the waste will decompose anaerobically (without oxygen) - this is a slower process and causes unpleasant smells, like rotten eggs. The solution is to get air back into the bin.
The most effective way to do this is to put a garden fork into the middle of the bin and move it backwards and forwards. Repeat the process by putting the fork around edge of the bin. This is effective as it re-establishes air channels by breaking up the material without totally turning it.
It is better not to totally turn the contents of the bin as this mixes up the layers, which will be at different stages of decomposition.
Material Size
The size of the material put into the compost bin is also important. The smaller the pieces of waste put into the bin, the quicker the microorganisms can process them. This applies to soft vegetables as well as tougher wastes such as cabbage stalks or twiggy material.
For decomposition to start, the tough outer skin or bark has to degrade to such an extent that microorganisms can start eating the softer parts. This process can be speeded up either by chopping or shredding.
Benefits of composting
Homemade compost can be used in many ways and is easy to handle - improving poor soils and maintaining good ones.
Modifies and stabilises pH level
Source of nutrients for plants
Soil structure
Adding compost to soil will result in improvements to the structure of the soil which makes it easier to turn and work with. Your plants will grow more healthily in this environment. The organic matter needed for this occurs naturally in the soil anyway but is broken down slowly over time by soil microorganisms, so it therefore needs to be topped up regularly.
Compost is an excellent source of organic matter and therefore perfect for this.
Moisture management
Conditioning the soil with compost increases its organic matter content and leads to the formation and stabilisation of pore spaces in the soil which are important for soil-water reserves. When soil is changed in this way, it is easier to think of it as a sponge that lets excess water to drain away but keeps good levels of moisture.
Improved organic matter content and structure in your soil means that plants should not need to be watered as often, and for shorter periods. In free-draining sandy soils, improved organic matter content is particularly useful as water drains through less readily.
In contrast, soils such as silts and clays have few large pores spaces which means that water moves slowly through them. They can become waterlogged relatively quickly and the soil structure is easily damaged. Compost, as organic matter, is important for improving its structure and consequently the drainage of excess water
Modifies and stabilises pH level
Ready-to-use composts range in pH from neutral to slightly alkaline according to their raw materials and how long they have been composted for. If added to an acidic soil in great enough quantity, soil pH can be increased towards neutral - and therefore be made suitable for most plants.
Soils have a natural buffering capacity that enables them to maintain a fairly stable pH. This capacity is greater where the organic matter and clay content is higher. Therefore it is easiest to modify and stabilise the pH of a sandy soil that has only low reserves of organic matter.
Source of nutrients for plants
Homemade compost is an excellent source of plant nutrients, especially those that plants need in smaller amounts such as manganese, zinc and iron which are often missing from artificial fertilisers.
Suppresses plant diseases
Research has shown that increased numbers of certain microorganisms can suppress specific plant diseases such as club root and white rot. The microorganisms that cause plant diseases are controlled by beneficial microorganisms, either those already in the soil or those which were added with the compost.
Organic matter also plays a part by improving plant health, directly providing a food source and indirectly by improving the condition of the soil.
How to use your compost
Mulching
Gardeners normally use compost on the surface of the soil to help combat weeds, conserve water and to maintain a loose absorbent soil surface. It also makes the garden look better!
Top-dressing
Top-dressing a lawn replaces the organic matter and nutrients lost through mowing. It is a vital element of managing your lawn. Home-produced compost is ideal for this purpose as its slow release of nutrients helps even growth. Adding compost also means your lawn will hold moisture more easily and will need less watering.
Plant pots can also benefit from top-dressing. Compost will boost the nutrient levels, refresh the plants and they will last for longer.
Soil conditioning
Use compost to enrich your garden soil before planting.
Seed and potting mixes
Prepare your own seed and potting mixes from your home-produced compost by first sieving the compost and then mixing two parts of this with one part sharp sand and one part fine soil. It is then ready to use!
How to use your compost
Mulching
Gardeners normally use compost on the surface of the soil to help combat weeds, conserve water and to maintain a loose absorbent soil surface. It also makes the garden look better!
Top-dressing
Top-dressing a lawn replaces the organic matter and nutrients lost through mowing. It is a vital element of managing your lawn. Home-produced compost is ideal for this purpose as its slow release of nutrients helps even growth. Adding compost also means your lawn will hold moisture more easily and will need less watering.
Plant pots can also benefit from top-dressing. Compost will boost the nutrient levels, refresh the plants and they will last for longer.
Soil conditioning
Use compost to enrich your garden soil before planting.
Seed and potting mixes
Prepare your own seed and potting mixes from your home-produced compost by first sieving the compost and then mixing two parts of this with one part sharp sand and one part fine soil. It is then ready to use!
Composting problems
- Why does my compost bin smell?
- The contents of my compost bin have turned slimy
- My compost bin does not seem to heat up
- Why does my compost bin smell?
- A healthy bin should have a sweet earthy smell.
The solution is to look at each of the three basic elements of the composting process - materials, moisture and air. A compost bin that doesn't have enough oxygen will turn anaerobic. This means that the composting microorganisms stop working and are replaced by another type which work without oxygen.
The by-product of their activity is a smell similar to rotten eggs. The solution is to re-introduce air into the bin to allow the "good" microorganisms to continue their work, and the bad smell to disappear.
If there is too much moisture this can clog up the air spaces in the bin, preventing air from circulating properly. Most of the plastic compost bins have a secure lid, which is ideal for keeping rain out.
High moisture levels are, therefore, generally caused by having too many moisture-rich greens. Mixing in more browns will absorb this moisture.
A strong smell of ammonia is usually a sign that there is too much green material in the bin.
The contents of my compost bin have turned slimy
This is caused by adding too much green material. The microorganisms which carry out the decomposition process wont be as effective if there is not enough brown material to balance the greens.
As a result, the compost bin contents become rotten and closing up valuable air spaces. Brown material that is slower to decompose provides structure to the heap, keeping air spaces open.
This problem is most common during the summer months when there is proportionately more nitrogen-rich green material available. The summer temperatures lead to faster decomposition than at other times of the year so it is important to ensure that materials, moisture and air are balanced - this will stop your bin from smelling or turning slimy.
My compost bin does not seem to heat up
The decomposition process within a compost bin can produce temps of 100 degrees or more. Heat is generated from the microorganisms as they decompose the organic material. As their activity decreases, the material cools down.
The reason for compost bin contents cooling down is that the microorganisms are waiting for something to be added.
If material is being added on a regular basis, the problem is usually that there isn't enough air.
More oxygen = more activity = more heat.
The temperature of the compost bin can also be dependent on the mix of materials added. Green material decomposes a lot more readily because it is softer and contains more nitrogen. You can see this if you put your hand into a pile of freshly cut grass.
You will find that after only five minutes or so it has started to heat up. This is because the microorganisms have already started to decompose the grass and their activity has caused the pile temperature to increase.
This intense activity uses up the available oxygen very quickly. Unless the pile receives more oxygen, the activity stops. Even if you re-introduce air, if there isn't any brown material within the grass pile, the process will eventually stop again.
A compost bin which contains a large amount of brown material is unlikely to become very hot as decomposition is slower. If this is the case, add grass, preferably between layers of brown materials to re-establish the balance and kick-start the decomposition process.
There will also be very little increase in temp if your compost bin has dried out. To cure this, add water over a couple of days to bring it back to life. The compost bin should contain between 40% - 60% moisture and feel as damp as a wrung-out sponge.
Contact a compost advisor
We have teamed up with the London Community Recycling Network (LCRN) to give you access to specialist compost advisors (Master Composters) who will provide support and information on composting, through telephone and email contact, home visits and local events.
If you have a query for a compost advisor please contact:
Charlie Willsmore
Phone: 020 7324 4690
Email: compost@lcrn.org.uk
Website: www.lcrn.org.uk
Want to become a compost advisor?
Training and materials will be provided free of charge. You will be part of a network of fully trained volunteer Master Composters and will provide support and information on composting to other Camden residents.
We are interested in people who either compost at home, or would like to start composting at home. If you live in Camden and would like to be a Master Composter please contact the London Community Recycling Network (LCRN):
Phone: 020 7324 4690
Email: compost@lcrn.org.uk
Website: www.lcrn.org.uk
Set-up a community composting project
The London Community Recycling Network (LCRN) will provide support to existing and developing community composting groups, through basic business support and funding advice, as well as developing a technical resource library.
If you would like further information please contact the LCRN on:
Phone: 020 7324 4690
Email: compost@lcrn.org.uk
Website: www.lcrn.org.uk
Bookmark...