August 18, 2005 | General


BioCycle August 2005, Vol. 46, No. 8, p. 59
To make recycling more effective, Ibadan officials design a household food waste collection drum with ability to turn materials for efficient composting.
A.O. Coker, M. K. C. Sridhar and J. O. Akinyele

WITH a population estimated at 3.2 million, Ibadan is the capital of Oyo State in the southwestern part of Nigeria north of the equator. The large-scale immigration of ethnic groups into the city have brought a culture, lifestyle and food habits that have influenced the composition of wastes over the years. Along with its population, industrial and development activities have increased beyond limits and today, Nigeria is plagued with waste disposal problems and a vastly changed composition.
In the early years, leaves used in wrapping food formed the major bulk of the refuse in urban and rural areas. Local foods such as “amala” made from yam flour, “lafun” made from cassava flour, “iyan” pounded yam, “eba” and “fufu” made from cassava tuber, “moin moin” made from cow peas, and “ogi” and “eko” made from maize corn were traditionally wrapped in leaves. Upon consumption of the food, leaves were thrown into the garbage. These traditional practices in the old town contributed to 81.3 percent of the waste. A decade later, there have been changes in composition – particularly the leaves have disappeared and plastics have taken over most of the households. More affluent and middle income families still produced more food wastes which entered the garbage dumps. By the 1990s, there had been a drastic change in the attitude of the people who resorted to recycling as a means of conserving resources. Reuse and recycling have become a part of life for middle and low socioeconomic groups. The residuals are 60 to 80 percent organic materials. The five local government areas within the inner city manage the wastes with financial and technical support from the state government. Currently, Ibadan Wastes Management Authority (established in 1997) is responsible for disposal of all solid wastes.
However, on the outskirts, the respective local governments (currently six) are responsible. Large amounts of recycling activities are also going on at the refuse dump sites. One alternative seems to be in the hands of the communities which to be effective, need appropriate technologies at their disposal. With this in mind, a household composting bin was designed and pretested for performance and acceptability.
Before designing a suitable composting bin, a survey was carried out on the weekly generation pattern among selected households in Ibadan. Households were flats, usually with an occupancy of six people in each. Different types of food items commonly processed in the houses were assessed over a period of four weeks to obtain the variety and consistency. A unit measure (as normally sold in markets) of each fresh food item processed and consumed was weighed and the waste resulting from processing was recorded. Wastes from fresh food ranged from 1g for guava to as high as 593g for pineapple.
In addition to the wastes generated during the processing of food, an assessment of the food leftovers after each meal (breakfast, lunch and dinner) was also collected from each family. The results indicated that about 0.63 to 1.6 kg of food is wasted as leftovers on each day amounting to about 3.4 kg per week per family.
A drum – used in collecting food residuals – is employed in the design and construction of the household composting bin. Three key elements – air, humidity, and temperature – were considered in design and construction. The size of the drum chosen was 0.2m3, and the inside was painted to prevent rusting. Before pouring the waste into the barrel, 20 kg of sand and 5 kg of sawdust were poured into the drum as the bottom layer to help maintain moisture levels in the drum which can promote the microbial development when the wastes are introduced. Two sets of three openings of 1 cm diameter were made around the top third and the bottom third of the barrel at a distance of 52 cm from each other. Another opening of 1 cm diameter was made at the bottom of the barrel for drainage. The top is cut by half to provide an opening fitted with a pair of hinges that will allow the top of the barrel to be opened and closed when the bin is in operation.
For stirring, a long rod C plate 1 and 2 were inserted into the inside of the barrel through another hole bored through the half-cut part of the top lid of the barrel. A set of sharp-edged paddles are welded to this rod to facilitate stirring and shredding of the wastes inside the barrel. The stirring and shredding enhances easy access of air into the decomposing waste which is also cut to smaller pieces for easy decomposition. All the openings were closed with pieces of nylon or metal wire mesh to prevent entry of flies. The barrel is placed on a tripod at 25 cm height with a plastic bowl put underneath to collect any leachate that may escape.
Food residuals were collected daily from the surveyed households and were put into the drum. They were stirred at three-day intervals over the 28-day experimental period. Stirring continued for a further period of 45 days to ensure full decomposition of the degraded wastes. Leachate collected from the bottom opening of the bin was continually poured back into the drum. At the end of the test period, about 11 weeks, the household waste was converted to golden brown organic fertilizer. The finished product showed a pH value of 6.4, carbon 6.19 percent, nitrogen 2.22 percent, phosphorus 0.505 percent, and potassium 0.525 percent and was found suitable for backyard gardening.
The drum used in the experiment is easily available in the communities at an affordable cost. It is simple to design and maintain. Once in a while, the contents may be removed, the bin washed and set again for continuation. The time required for compost formation depends on the nature of the waste, the amount, and the ambient temperature. The unit can be conveniently placed in the backyard nearer to the kitchen. Smell and fly nuisance is not a problem if the contents and the process are controlled regularly by one of the family members. More than these benefits, the family can save the cost of engaging private service for its waste disposal. Many households are showing interest in using this device.
A.O. Coker, M.K.C. Sridhar and J. O. Akinyele are in the Departments of Civil Engineering and Environmental Health at the University of Ibadan, Ibadan, Nigeria. E-mail: C. Sridhar and J. O. Akinyele

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