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by R. Muhunthan PGIA, University of Peradeniya

In our day to day life major portion of the household waste is coming from the kitchen. But the disposal of the kitchen waste is a big problem for all, in particularly for the metro residents. It has to wait along the roadside till the council refuses to come.

Many unpleasant events happen during this time. First, it brings out unpleasant smell that is hazardous to our health. Secondly, it invites the stray animals and crows to do all the mess up. The direct consequences are, drainage blockades, road accidents and spreading of deadly diseases.

In our real life we rarely realise the value of this kitchen waste. With a little interest we can convert this waste into biofertiliser/compost. Any biodegradable waste could be converted into compost.

Composting is a natural biological process, carried out under aerobic conditions. In this process, various microorganisms, including bacteria and fungi, breakdown organic matter into simpler substances.

The world trend is changing from harmful chemical agricultural practices to ecofriendly organic farming.

The importance of organic farming and its impact on crops yield had been well-addressed in the recently concluded second annual session of National Agricultural Society of Sri Lanka (NASSL) too.

Materials and methods

Bioreactor to process the waste could be made from empty oil barrels. Cut open the lid and bottom of an oil barrel and replace the buttom part with a wire mesh with the pore size of 1-2 inch in diameter or in width. Place the tank on another half size barrel (collection tank), which has a side opening. This opening will be used for the recovery of the biofertiliser.

Few holes of about 1-1.5cm in diameter will be made on the lid of the oil barrel for aeration.

The waste will be converted to compost and that inturn will come down and settle in the lower tank. Whole system should be pre-coated with an anti-corrosive agent. The bioreactor is designed for batch process. On top of the wire mesh put a layer of straw/paper/any similar material to prevent dropping of any small waste particle into the collection tank.

Garden/farm upper soil and lower soil mixture could be used as innoculum.

Cow dung solution and little portion of compost could also be used as inoculum, if available. While putting the kitchen garbage routinely, intermittently we should add the inoculum to the reactor. Composting microorganisms thrive in moist conditions.

For optimum performance, moisture content within the reactor should be maintained at 45 per cent. Excess moisture will lead to anaerobic reaction, which will also bring bad odour.

Bulking agent (straw, dry leaves, paper) could be added to allow proper airflow.

Aerating the compost by turning or regular punching of holes of the compost pile to ensure adequate supply of Oxygen to the microbes. The microbes in compost use C for energy and N for protein synthesis. The proportion of these two elements required by the microbes is 30:1.

Therefore to maintain this ratio an N2 fertiliser such as urea in solution should be sprinkled on the compost intermittently. The composting periods governed by a number of factors including, temperature, moisture, Oxygen, particle size, the C:N ratio and degree of turning involved. The compost from aerobic reaction will be odour free.

Applications

An effective composting program can produce a high quality soil amendment with a variety of end uses. Compost improves soil porosity, drainage and aeration and moisture holding capacity and reduces compaction.

Compost can retain up to ten times its weight of water.

In addition, compost helps buffer soils against extreme chemical imbalances; aids in unlocking soil minerals; releases nutrients over a wide time window; acts as a buffer against the absorption of chemicals and heavy metals; promotes the development of healthy root zones; suppress diseases associated with certain fungi; and helps plants to tolerate drought conditions.

Suggestions

This type of bioreactor is easy to set up, easy to manage, ecofriendly, economical and also make easy to get rid of waste menace.

For an average family 2 or 3 such bioreactors are enough to treat the kitchen waste and also enable to manage a small garden or nursery. This bioreactor is relatively simple to manage, can be carried out on a wide range of scales in almost any indoor or outdoor environment and in almost any geographic location. Also this type of bioreactor could be implemented in rural development programs with the help of NGOs. With the help of such organisations we can increase the efficiency of the system by introducing pure microbial culture inoculum.

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