ARTICLE

Barrel as a composting unit for your garden

By R. Shanthini, EcoEng-Correspondent and K.S. Walgama, Sri Lanka

Contact Shanthini:

Chapter 3 of the booklet "How to compost kitchen waste in your garden", by R.Shanthini and K.S.Walgama (ISBN 955-8916-00-5). The booklet will be published in a series of articles in this newsletter (ordering information).

With the conviction that the major part of the problem of solid waste disposal could best be tackled at the site of generation, Ms. Padmini Batuwitage, Director/ Environment, Ministry of Environment and Natural Resources, Sri Lanka, launched a campaign in 1992 for solid waste disposal through household composting.

Household composting in one's backyard is, of course, an age-old method that has been practiced around the world, including Sri Lanka, from time immemorial. Household composting set-ups, differing from each other in shapes and sizes, can still be found in the rural environment where space is not a major limitation.

In today's urban settlements, however, space available for a typical household is limited. For that reason, Ms. Batuwitage and her team distributed used barrels to willing households to dump their compostable household waste into and monitored the progress.

We, too, were given a barrel to experiment with it in our own garden. And, we have been composting our waste in our garden ever since, thanks to Ms. Batuwitage"s farsighted spirit and efforts.

3.1    Getting a barrel ready for composting waste

If you wish to use a barrel as a composting unit in your garden, start by getting a barrel. You may either purchase it or get hold of a discarded barrel. Cut and remove a rectangular piece from the metal cover on one end of the barrel, as shown in Figure 2. Cut and remove the entire metal cover on the other end of the barrel. You now have a cylinder, which is fully open on one end and partially open on the other. If you wish, you may apply anticorrosive paint on the inside and on the outside of the barrel.

Place the barrel at a suitable place in your garden such that the fully open end of the barrel is in direct contact with the soil, and the partially open end facing upwards, as shown in Figure 2. Take care that your barrel is not positioned at a place where rainwater stagnates. Your composting unit is now ready for use.

3.2    Composting kitchen and garden waste in the barrel

Add to the barrel whatever the compostable solid waste that you get from your kitchen and from your garden. A barrel has enough volume to handle a reasonable amount of garden waste in addition to the kitchen waste. Since kitchen waste is rich in nitrogen, and leaves and dried grass clippings of the garden waste are rich in carbon, combining the kitchen waste and the garden waste in your composting unit may give a better carbon/nitrogen ratio for the composting mass.

It is customary to drill holes on the walls of the barrel in order to let air enter the composting mass. However, when garden waste is added, adequate air remains trapped within the volume of the garden waste added. Therefore, even without the "ventilation" holes, the barrel to which garden waste is added functions well as a composting unit.

It is necessary to cover the opening on the top cover of the barrel with a plank or something else in order to prevent rainwater from entering the composting mass. Excessive water reaching a composting heap containing kitchen waste destroys the optimum conditions needed to maintain a healthy composting unit in your garden.

A lid to the composting unit also helps to discourage rats and other small animals from entering the composting unit from above.

3.3    Taking the compost out of the barrel

Once the composting mass fills three quarters of the volume of the barrel (which, believe us, takes about six months or so from the day you start operating the composting unit), do the following. Place your palm on one side of the barrel, and push it away from you so as to make a small space between the bottom on one side of the barrel and the ground. Into that space, push a brick. Repeat the procedure so as to raise the barrel on bricks as shown in Figure 3.

In this manner, a space is created between the bottom of the barrel and the ground. Through this space, you can now access the composted mass at the bottom of the barrel. Use a garden spade or an iron bar bent on one end to pull the dark soil-like material out of the barrel from the bottom of the barrel.

When you do that, you can observe that the top surface of the composting mass within the barrel goes down. Stop pulling the composted mass out of the barrel from the bottom of the barrel, once the top surface of the composting mass gets to a level such that one third of the height of the barrel is still filled with the composting mass. Onto this top surface, add a generous amount of garden waste or about 15 to 20 cm of sawdust (or dry soil). Now, the barrel is ready to receive another round of kitchen and garden waste.

3.4    Letting the compost mature

If earthworms and other similar life forms can be seen living within the dark soil-like material that you have just removed from the bottom of the barrel, then your compost is matured enough to be applied to your garden soil or to your plants. If not, store the dark soil-like material that you have removed from the bottom of the barrel in a place where it gets good aeration and is protected from the rain, until earthworms and other similar life forms come to live in it. Presence of earthworms in your compost is a clear sign that tells you that your compost is matured enough to be used in your garden.

3.5    Composting a large amount of garden waste using barrels

As mentioned in section 3.2, a barrel has the capacity to handle a reasonable amount of garden waste a day along with the kitchen waste. In case you have a lot more garden waste than what a single barrel could handle, maintain a few more barrels in your garden to add your garden waste into.

If you are worried about the appearance of your garden with a few barrels placed in your garden, you may paint the outside of the barrels with the colour of your choice, and spread the barrels to different locations in your garden where they offer less interference with the appearance of your garden.

When adding only garden waste into a barrel, it is better not to cover the top end of the barrel. Since the garden waste is generally dry, any rainwater getting into the composting mass helps improve the wetness of the composting mass towards the optimum level for best composting. Therefore, the barrel used for composting only garden waste may also be fully open on the top end.

Note that owing to the low nitrogen content of the garden waste, flies, insects, rats and other small animals do not get attracted to the composting mass made up of garden waste alone.

The nitrogen needed to balance the carbon-rich garden waste comes usually from the kitchen waste. Since you are not adding any kitchen waste into these barrels, you must add nitrogen-rich materials, such as fresh grass clippings, nitrogen-rich leaves, cow dung or goat dung, to the barrels in which only the garden waste is being composted.

Nitrogen-rich leaves may be cultivated in your garden itself from the fast growing tress, such as Gliricidia sepium and Erythrina verigeta [1]. Maintaining a goat or cow is certainly another way if you could afford that!

3.6    Limitations in using the barrel as a composting unit

The major problem in using a barrel as a composting unit is in fact finding a barrel itself. The second problem is cutting the ends of the barrel. If you get over both these problems then a barrel is quite useful as a composting unit.

One major point to note with the barrel is that composting action within the barrel is at its best only when adequate amount of garden waste is added to the barrel. If you do not have enough garden waste then a barrel may be too large a unit for your kitchen waste to be composted in, and you may then choose between the units described in Chapters 4 and 5. However, if you have adequate amount of garden waste, then the barrel is the best unit for your waste.

Corrosion destroys the barrel used for composting kitchen waste after about 3 to 4 years of use. But, the oldest barrel in which we have been composting garden waste have been in use for 6 years now, and its condition is such that we expect it to go for another couple of years.

Ordering information:

The booklet can be ordered directly from the publisher. Costs are Sri Lankan Rs 150/= (inclusive of registered postal charges) in Sri Lanka, US$ 3 (inclusive of registered postal charges and airmail fright) for countries in South East Asia, US$ 4.50 (inclusive of registered postal charges and airmail fright) for other countries

Publisher:

Mr. P.A. Gamini De Alwis,
Director/ Engineering Design Centre
Faculty of Engineering
University of Peradeniya
Sri Lanka
Email:
Phone: 94-(0)81-2386429

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Footnote 1: Gliricidia sepium and Erythrina verigeta have the indigenous names "Giniseeriya"/ "Seemaikilluwai" and "Erabadu"/ "Mulmurungai", respectively.