Trench composting

Trench composting  systems are an effective means of  providing compost for  rows of beans, marrow beds etc.  or as a rotation system to compost the whole garden over a period of years. Alternatively,  individual holes can be dug where space allows in the garden. It is also a method of composting which requires no special equipment or expendature, 

At the simplest level a spade or post hole digger can be used to make an hole at least 12" deep (nearer 18" is better if larger creatures might try to dig for the waste) the width of the hole can be varied to suit the volume of waste which should be covered by at least 4" of soil.   If burying meat, dairy or cooked food in a trench  it  needs to be deeper  with the waste being buried under 12" of soil.  The waste material should be moistened before being covered. The soil can be covered with straw or  other  mulch  to provide additional protection.

In-ground trench or pit composting provides a simple  way for composting fruit and vegetable waste including uncooked kitchen scraps. Techniques that involve burying the organic material have the advantage that no special equipment is required and once the material is buried there is no visible evidence that composting is being undertaken. Both trench and pit composting provide a rapid means of converting Bokash pre-compost to soil. Follow the links for more information on  Bokashi Composting   and  Composting Food

 As decomposition in underground composting happens more   slowly than in the more usual bin systems it. is perhaps more important than in normal systems to expose the maximum surface to microbial activity. Cutting the waste to about two inches in  length is recommended. The green and browns can be mixed  in the pit using a fork of spade, but I find it is easier to mix them before adding to the pit.  

One of the concerns expressed by people new to trench or pit composting is that it will attract rats and other animals looking for a free meal particularly if it is left during construction when only some of the waste has been added and it is not yet covered by the  four-inch  layer of organic material. The waste in the pit can be covered with a thinner layer of soil and the whole pit covered by a sheet of plywood. Once  the waste material  reaches the depth of four inches  the pit should be  filled with soil. 

Trench composting can be started at any time of year but if started in Autumn the material will have decomposed and the site reasdy for planting in the spring. 

If the  material  is kept moist (it may need watering) it should  decompose in about a year   after which the area can be planted. 

  Pit composting (see below) is suitable for an area where there is limited space either because the garden is small or is permanently planted areas such as perenial flower beds.

Trench composting is usually used in the vegetable garden so that composting can be started in the late summer or autumn with the trench being filled and ready for spring planting of runner beans, french beans or peas. 

 Trench composting can be started earlier, if space is available on the plot, so that  chopped brassicas stalks can be  included as this offers an easy method of composting the  stems which may be slow to compost in a conventional compost bin. Trenches can also be dug between rows of plants or seeds

A similar method where circular pits are dug, rather than a trench, can be used for courgettes and pumpkins.

The   trench is often dug for convenience about a spade width and depth the length of the required bean row, which might be across the width of an allotment plot. It is worth checking the recommended planting distance for the beans as; if a double row is required the trench will need to be wider.

Place the soil along the side on the trench so that it may be used to cover the composting material as it is placed in the trench. Start added the waste at one end of the trench covering it with the soil as it is added. Some people dig a deeper trench so that a second layer of waste can be added but this will depend on the quantities of waste available and the number of rows of beans to be grown. When the waste has been covered the soil is likely to have made a small mound along the length of the trench but this will settle by the time of planting. I would suggest marking the trench with small sticks so the it can found in the spring when you need to plant in it.

 Some gardeners use trench composting as part of a composting rotational system where the trench is moved across the garden each year.More information can be found at 


Year 1

Compost trench

Access Path



Year 2





Year 3






Post hole, Pit Composting or Chop and Drop composting

Post-hole and  Pit composting are variations  of trench composting and  using a permanent pit or a temporary pit or pits for a single season.  

The “chop and drop” method simply  involves chopping the waste into small pieces with a spade, digging a post-hole  in the garden,  dropping the waste into the hole, giving it a final chop in situ and  covering with  soil. It is sensible to mark the spot when rotating  the sites round the garden. Mark the spot with a small stake and rotate around the garden.  If using fresh green garden waste, it can be covered with  a layer of straw before the soil is replaced to help retain more of the nitrogen.

Usually when making a larger temporary pit a hole is dug to a depth of about twelve inches or for ease of working this may be one spit (the length of the spade blade).The size of the hole may be about three feet wide or be varied depending on the quantity of waste available for composting.  In a temporary pit a 3-4-inch mixed layer of organic material is added to the bottom of the pit. If vegetable gardening in rows it may be helpful to make the pit the same width as the row normally used. 

If a permanent pit is being dug the area chosen should not be close to the house as it might smell. It is best  a sunny part of the garden to keep the  compost pit as warm as possible.

 If a permanent pit is being planned it is usually dug g 2-3 feet deep with the sides of the hole being lined with bricks to avoid  them collapsing  into the pit with use. 

 Whichever method is being used it may be necessary to stockpile  the material so that there is enough to provide a layer in the pit. It is important that the material is cut into small pieces to expose as large a surface area as possible to the action of the composting organisms in the pit  so for ease of cutting I would advise that this is done while the material is still fresh before it is stockpiled even if it is only being kept for a few days. The  Greens and Browns should be kept separate until the time to add them to the pit. However, they should be mixed well either as they are added to the pit or once added to the pit. Some use a spade to mix the materials, but I find a fork easier.

If there is insufficient material to fill the pit it can be left for a week or so provided the waste is covered with a layer of Browns e.g. autumn leaves or shredded paper . The hole should be covered with a board or strong weldmesh  to prevent animals gaining access

 Replace the earth in the pit  and water and continuing the watering to keep the soil (and composting material) moist.

The material may take up to a year to be fully decomposed but if the pit is made in the late summer early autumn it can be used for planting beans in a pyramid, courgettes or pumpkins in the spring.

The mixed Greens and Browns  in the compost pit can be layered with manure  and soil. A layer of the mixed organic materials is added first followed by a layer of chicken, horse, cow or manure followed by a layer of soil.  Another layer of mixed organic material is then added and followed  by manure and soil the pile reaches 1 foot above the ground level.

Some composters using a permanent pit also  add a layer of Blood meal to the organic material to speed the composting process before covering with soil. The compost ingredients should be turned  in the pit weekly to provide proper aeration. Water after turning to  keep the pile moist.




Composting in small or hard landscaped garden

The above information may be read to imply that composting requires a large or medium size garden but in fact composting is practical in a garden of any size even if completely hard landscaped and indeed may be used with household kitchen waste  in an apartment, flat  or patio.

A suitable composting bin, wormery or bokashi bin can be placed on be used as a feature in the garden, painted by the children or grandchildren or  screened by trellis growing plants.

A conventional style plastic bin that would normally be placed on soil can be purchased with a plastic base or stood directly on the concrete or decking with some soil or mature compost being added to the bin as a starter. If too much leachate is produced it might stain the concrete or timber but this can be avoid by standing the bin in a cardboard or wood chip to absorb any liquid and monitoring the contents so that they do not get to wet.

If the bin is cannot to be hidden by trellis wooden beehive bins are  aesthetically pleasing and add an interesting feature to the garden.

Tumble bins are normally mounted off the ground on legs. The original tumbler  where quite large bins and consisted of a single chamber and were most suited  for batch composting but   there are now quite small dual chamber tumblers which allow continuous composting.

Wormeries provide  an interesting alternative to a compost bin and  are normally equipped with legs of stand on a base up off the ground. A commercially available plastic wormery is suitable for kitchen waste supplemented with shred paper and cardboard. There are versions available for use on balconies and even indoors.

Indoor Composting

It is not necessary to have a garden to compost.   In the UK  Bokashi fermentation   and indoor wormeries are frequently used in conjunction with, or as an alternative to, outdoor composting but indoor aerobic composting is also  possible.  Although nor commonly used in the UK indoor aerobic composting  appears to be used more frequently  in the US and features regularly on composting pages of social media.    

Materials suitable for indoor aerobic  composting

In theory any organic waste that can be composted outdoors can be composted indoors  e.g. fruit and vegetable peelings,  coffee grounds, tea bags, shredded paper. In practise items that compost slowly are best avoided, due to limited size  of indoor bins  and lower temperatures reached in  smaller bins.   Fruit and vegetables  with a high-water content, e.g. squash, and strongly smelling waste such as onion  are best avoided unless the composter has a filter fitted. As with outdoor composting if the waste material is cut to lengths of about 2”  or less, it will breakdown more quickly. Meat, dairy, or fats are not suitable for composting aerobically in a conventional  indoor or outdoor bin  but can be treated in a Bokashi bin to produce pre-compost.

Shredded paper or cardboard are good carbon rich browns for use in an indoor bin as they are  easy to store and will not smell. More browns should be added every time greens are added.

Frequent aeration is necessary as the containers are not designed to provide a high level of ventilation, mixing  also breaks up potentially anaerobic lumps and helps provide even moisture distribution. As indoor compost containers are relatively small it difficult to use most types of commercial compost aerators,  but  a long-handled  hand fork makes an effective mixing tool.

Selection of Indoor Compost Bins 

A wide range of waterproof containers may be used for indoor composting with plastic or  metal being the  most popular choice. It is best to have air holes drilled in the lid or around the top of the bin. If the  bins  are  to be stacked to save  storage space the air holes should be drilled in the sides  near the rim rather that in the lid. Drainage van be though holes in the bottom  or a drainage tap can be fitted near the at the base of the bin.  If drainage holes are used the bin will need to be sit on feet to allow drainage in a flowerpot saucer to catch the leachate. This should be emptied regularly to avoid odours. I also fit an inverted flowerpot saucer inside the bin with larger drainage holes to  prevent the compost blocking the drainage holes in the base. Small pebbles can also be used but these are less easily cleaned.

The most used containers are :

Stackable plastic storage bins. These containers have the advantage of being available in a wide range of sizes so it should be relatively easy to get a lidded  bin or a suitable size for the space available. It is better to have a bin that can be filled, sealed, and set aside fairly frequently to avoid smells. A 5 gallon or 20l container is commonly used but larger containers of up to about 40 litres and even dustbins can be used.  However, the larger the bin the heavier it will be to move.

Five-gallon bucket with lids: While any lidded bucket can be used.  “Nappy” buckets with flat lids  are recommended if the bins are to be stacked when full.

To prevent fruit flies   and other flies from escaping from, or getting into, the bin  through the   air holes, they should be kept small or cut close together, and  covered with a piece of nylon screen, fine mesh garden netting  or fine weld mesh. glued to the inside of the container.

I keep my indoor bin and the drainage tray in a small dustbin to contain any escaping critters be they worms or fruit flies. However, in over five years or keeping an indoor bin in the garage I have only had worms escaping once and that was when I failed to refit the lid correctly.

The container can be kept in any suitable room  preferably with an easily cleaned floor and in a position where it will not form a trip hazard.

Filling the bin

 I have loaded my indoor bin in the same way as the outdoor bin but others have used methods divised for indoor composting. 

The bin is either quarter filled with a layer of soil or  a 4” layer of soil or compost used as a base layer. This is covered by a layer of shredded paper or torn up newspaper. Newspaper is more absorbent but can be recycled via most council schemes while shredded  office/computer paper is suitable and cannot be recycled.   

Vegetable waste from the kitchen can be added as it becomes available or can be saved and added weekly or when there is enough to make a layer in the bin. While waiting to be added to the bin waste kitchen  food, and other compostable waste,  can be stored in asealable container such as a kitchen caddy. 

Kitchen waste (Greens)  should be mixed with fresh  browns, such as shredded paper, either before being added to the bin or when being added. A handful of soil or compost should be mixed into the composting material  weekly.  

A layer of shredded paper or finished compost/soil can be used to cover the composting material to reduce the number of fruit flies. The organic materials should be mixed to aerated wekly. Following aeration a layer ofthe contents should be covered with a layer of soil or compost.

It is important that the compost should be mixed and aerated (turned) weekly using the trowel or scoop to mix the layers of compost. Top off the composting material after aeration with a layer of compost/soil.  

When full the bin the contents should be given a final mix and then left for at least a week to allow all the food  to be decomposed.  It can be transferred to another container and left to mature until  it is ready to use.