ARTICLE

Frequently asked questions on household composting

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

Contact Prof. R. Shanthini
Head/ Dept of Chemical Engineering
University of Peradeniya
Peradeniya. Sri Lanka

One of the major difficulties that you may face in composting waste in your garden is your lack of experience in maintaining a composting unit. It this chapter, we share our decade-old experience in maintaining many types of composting units in our garden with you, in case you find our experience useful in handling situations that may arise during composting of waste in your garden. 

6.1      Where do I place the composting unit?

Place the composting unit on a levelled ground about 3 to 5 metres away from the kitchen, preferably, where direct or diffused sun light falls. The path leading to the composting unit from the kitchen must be a convenient one to encourage us to take the kitchen waste to the composting unit easily.

Water should not stagnate, after a rain for instance, at the place where the composting unit is placed. The bottom of the composting unit should always be in direct contact with the soil to facilitate removal of excessive moisture via the ground, and also to allow microorganisms, earthworms and other beneficial life forms to have better access to the composting mass within the unit.

6.2      How should I feed the kitchen waste to the composting unit?

Keep a bucket of about 5 litres of volume with its lid in your kitchen to collect the kitchen waste over a day. (The plastic bucket in which laundry detergent or paint is sold is of ideal size.) If you require a larger bucket for a day's kitchen waste, then get the size that you want.

Once a day, at a time that is most convenient for you, take the bucket with the kitchen waste to the composting unit, remove the lid of the composting unit, put the kitchen waste in the bucket into the composting unit, and replace the lid on the composting unit. Wash the bucket, and let the bucket dry until the bucket is needed in the kitchen again.

If you wish to empty your kitchen waste into the composting unit more often than once day, you may also do that. There is absolutely no problem with that.

6.3      What should I do to start the composting process in the composting unit?

Composting process in your composting unit can start on its own. You need not do anything at all to start it. You know that any organic material (say, banana skin) left on the ground exposed to the Nature for a period of time decomposes into a soil-like material on its own. Microorganisms, which are living organisms that cannot be seen by the naked eye, are responsible for the conversion of natural organic matter into compost. The compost making microorganisms live everywhere in the Nature, and therefore the composting process can start on its own in your composting unit.

There are however many products sold in the market to start or to speed up the composting process. Do not add any of these products to the composting mass to start or to speed up the composting action in your unit. Because, it is highly likely that the compost you make in such manner is harmful to your plants, and to the environment.

6.4      What can I put into the composting unit?

• All the unwanted portions of vegetables, fruits and green leaves, and spoiled food.
• Coconut refuse and egg shells.
• Leftover food, which is better be used to feed the birds and other animals that are looking for food to survive. We leave our leftovers on the wide tops of the gateposts, and enjoy watching the birds and squirrels that come in great numbers to feast on our leftovers.
• Fish and meat waste (in moderate amounts).
• Paper without colour, torn into small pieces.
• Garden waste like leaves and grass-clippings (preferably dried).
• An occasional dead rat that your cat brings home to you as a gift.

6.5      What I must not put into the composting unit?

• Coconut shells, wood-apple shells and Ôbeli' shells because they occupy a lot of space within the composting unit, and because they take a very long time to degrade.
• Polythene and plastic items, because they never get composted, even in a million years!
• Tin cans and glass bottles, because they do not get composted.
• Broken glass or ceramic ware, because they do not get composted, and because they could hurt you when you work with compost in your garden.
• Coloured paper, because it contains heavy metals, such as copper, zinc and cadmium. Heavy metals, above certain limits, are toxic to the microorganisms that are helping us, to the plants that would be grown using the compost with heavy metals, and to us who would consume the products from these plants.
• Cardboard, because it contains borates which is toxic over certain limits.
• Batteries, because it contains toxic material, such as mercury.
• Medicine, pesticides and insecticides, because they may kill the microorganisms that are doing the composting.
• Water and very wet items, because excessive wetness makes the composting heap sticky and smelly.
• Waste from cats and dogs, because it may contain parasites.

6.6 What is the most convenient method of taking the compost out of the composting unit?

Sections 3.3, 4.4 and 5.4 explain very clearly how to take the compost out from the barrel, the aluminium composting unit and the ferro-cement composting unit, respectively. In all these cases, the compost is taken out from the bottom of the composting units without stopping the feeding of the composting unit with fresh waste from the top.

The purpose of this method is to maintain a continuous operation of the composting unit. That means, we will be able to feed our composting unit with waste without a break. If the unit is getting filled with the composting mass, then we remove the composted mass from the bottom of the unit to reduce the level of the composting mass within the unit. That would make room for adding fresh waste from the top of the unit. This way we operate the composting unit continuously, without a break. 

If you find the above method of removing the compost from the composting unit inconvenient, then there is an alternative method for you. Maintain two composting units in your garden, instead of one unit. Prepare the first unit, add kitchen waste and suitable amount of garden waste into it for a period of six months, and then stop adding the waste into the first composting unit. Now, prepare the second unit and use it to add the waste into.

Let the composting waste inside the first composting unit continue to transform into mature compost. It would take about another two months or so. Now, you have mature compost to work with. In the remaining four months, take out the quantity of the compost you require from the first unit as and when you want to add compost to your plants or to the soil.

Make sure you use up all the compost contained in the first unit within six months from the day you stopped adding waste into it. Because, aged compost does not possess as much nutrients and soil organisms as the fresh one does.

At the end of six months from the day you start feeding the second unit with fresh waste, stop feeding the second unit. Now, prepare the first unit that has already been emptied of the compost within it, to receive fresh waste. Start feeding the first unit with fresh waste. Let the compost within the second unit mature, add the mature compost to your plants and soil, and prepare the second unit to receive fresh waste. 

Go on repeating the cyclic procedure with the two composting units. In this way, while one composting unit is used for adding the kitchen waste and garden waste for a period of six months, the other composting unit is used as a storehouse for the compost.

This is a very convenient way to carry out household composting. The cost is you need to maintain two composting units. But, in our experience, the convenience of maintaining two composting units in our garden is well worth the cost of two units.

6.7      How do I know that the compost is matured enough to be added to the plants?

Presence of earthworms in the compost indicates that the compost is matured enough to be added to the plants. Earthworms and other similar life forms come to live in the compost only if the temperature of the compost is reasonable, aeration is good, moisture content is balanced, pH is neutral (that means, not too acidic or too alkaline), and toxicity is low or nil.

6.8      Do flies get attracted to the composting unit?

Yes, they do. Flies come to the composting unit to feed on the waste and to lay eggs if the composting mass is wet. When the eggs hatch, a lot of larvae can be seen on the top surface of the composting mass. Presence of larvae in the composting mass is indeed useful in breaking down the fresh waste into smaller pieces, which are suitable for the microorganisms to work on. And what's more, any larva leaving the composting unit gets picked up by birds.

However, if you wish to discourage the flies from being attracted to the composting mass, you can do the following. Soon after you add the kitchen waste to the composting unit, cover the surface of the composting mass by adding a layer of some dried materials. The best materials are dried leaves and other dried garden waste. In the absence of adequate garden waste, add a layer of sawdust or dry soil so as to cover the kitchen waste, which greatly discourage the flies.

If you have ash from your fireplace then that is a best remedy for discouraging flies. Every time you add the kitchen waste to the composting unit, make sure that you cover the top surface of the composting mass with ash.  

6.9      Does the composting mass give off bad smell?

If the composting mass is too wet to prevent air from making contact with the composting mass, then it gives off an unpleasant smell like some of the lakes in the cities of Sri Lanka do. If it ever happens add about 10 to 15 cm of sawdust (or dry soil) onto the top of the composting mass. The smell will cease almost immediately.

When the composting mass is very wet, you shall see black fluid oozing out of the holes on the walls of the unit. Along with that, you also get a bad smell. If it ever happens with your composting unit, do not panic. It is only an indication that you must stop adding kitchen waste, the moisture content of which is very high, to your composting unit, even though you may continue to add dried garden waste to the unit.

To add kitchen waste now, you need to prepare a second composting unit, which is most convenient. You may also consider emptying the content of the existing unit, and preparing it afresh to start adding kitchen waste. We however do not recommend it at all. We have tried it once, and it was such a messy process that we have decided never to do it again.

6.10    Could we compost kitchen waste alone?

The moisture content of kitchen waste is so high that the composting mass containing kitchen waste alone will be very wet. For good composting, the composting mass should be as moist as a wet sponge from which the water is well squeezed out. If the moisture content of the composting mass is more than that then it will attract all sorts of flies to lay eggs on. If the composting mass is very wet and soggy, then it will give out an unbearable stench, like many of our lakes in the heart of our cities in Sri Lanka.

Kitchen waste is in general rich in nitrogen. Therefore, the composting mass containing only the kitchen waste will give out vapours containing compounds rich in nitrogen. The nitrogen-rich vapours give off a very bad smell, and therefore we will be discouraged to maintain a composting heap in our gardens. Besides, the smell of nitrogen-rich vapours sends a welcoming signal to flies, rodents and other creatures, attracting them to the composting heap for their meals.

The final product from composting kitchen waste alone is very sticky and smelly. We will therefore be much discouraged to handle this product originating from composting kitchen waste alone

Therefore, it is not advisable to compost kitchen waste alone. Adding torn off pieces of paper without colour, dried leaves, dried grass clippings, sawdust and other dried, brownish materials to the composting unit in which you are composting kitchen waste helps very much in improving the performance of your composting unit. 

6.11 What can I do with garden waste?

If you collect a small amount (about a 5-litre bucketful) of garden waste from your garden everyday, then let them dry a bit, if you can, and add them to your composting unit, because dried garden waste helps to improve the composting process by balancing the carbon/nitrogen ratio of the composting mass. Since garden waste does not get compacted as easily as the kitchen waste, the presence of garden waste in the composting unit greatly improves the air circulation within the composting mass.

If you collect moderate amount of garden waste a day then it is better to use a barrel to compost them in. See Chapter 3 to know how to use a barrel as a composting unit. In case you have a lot more garden waste than your barrel could handle, maintain a few more barrels to add garden waste into them, as described in section 3.5.

6.12 What can I do with lots and lots of garden waste?

If you have a big land and collect lots and lots of garden waste a day, then it is better to use the composting set-up discussed in Chapter 1, that is Grandmother's composting unit. In a corner of your big land, isolate a rectangular or square area of your choice by planting several of 1 metre long live branches of Giniseeriya, Erabadu , or some other suitable tree. If you insist, even though we do not recommend it, use GI pipes or something similar in place of live branches of trees.

Onto these live branches of trees (or GI pipes), fix thatched leaves (or wire mesh) so as to make a one metre high fence surrounding the isolated area. If you plant the live branches very close together, you will not need thatched leave (or wire mesh) fence. Because the branches which are planted close together, would serve as the fence. This area can be used to decompose all sorts of organic waste including kitchen waste.

6.13 Is it socially acceptable to handle waste in our garden?

Believe us, it is very fashionable today to say that you are an environmentally friendly person, and that you dispose of your waste in an ecologically friendly (eco-friendly) manner. Try it in your social circle to tell others about how you compost your own waste in your own garden, and how you grow your own plants with your own compost, and you will be surprised at the response you receive.  

We have been composting our kitchen and garden waste in our garden using the many different composting units discussed in this book for over a decade now. We take our visitors to these units, explain how the garden waste is turning into compost in these units, show them the compost being made in these units, and tell them how the originally sticky soil in our garden has improved over the years with the constant application of the compost that we have been making in our garden.

Our visitors are simply impressed. And, they tell us they also want to compost their household waste in their gardens, as well. They tell their friends all about it. We have people visiting us to see our composting units and the composting processes. We help them setting up their own composting units in their gardens on request.

We are very proud about not scaring Mother Nature when we could help it. Won't you, too?