Recycling of organic waste
Practical Action
Usually the design of such a toilet incorporates two chambers, each capable of holding at least one
years deposit of excreta for the proposed site. No water is added to the chamber, but sawdust or ash
can be added to improve the Carbon:Nitrogen ratio. When the first chamber is full it is sealed off
and allowed to aerobically compost. The process produces a rich, pathogen-free compost. When the
second chamber is full, the first chamber is emptied and the cycle begins again. For a single
dwelling, the structure need be no bigger than that of a typical pit latrine. Other methods of home
composting of excreta include co-composting with vegetable matter or anaerobic digestion in a
biogas reactor (see later) or in a septic tank, which yield a rich slurry compost. For more
information on these techniques see Franceys3.
Health, environment, and social aspects of waste reclamation
Waste collection and disposal is often seen as being the responsibility of the government or
municipality. In many cases the municipality is unable to fulfil this role either due to financial
constraints, lack of will or lack of organisational skills. In many cities, collection and separation of
waste by the private or informal sector is seen as being too time consuming because of the content
of the waste, often a mixture of organic and non-organic substances, such as plastic film. For there
to emerge a successful organic waste reclamation process, it has been noted that it is of great help
if the organic and non-organic waste is separated at source. It is here that the responsibility is
thrown back onto the generator of the waste, the public. Many successful schemes are only
successful because of community participation in the activities on a day-to-day basis. Where waste
is separated at source, this lessens the risk of contamination from such items as batteries, means
that the organic waste is cleaner (and will therefore fetch a higher price), it is easier to sort and the
incidence of injury and disease related to sorting is decreased. There are a number of good
examples of community recycling or resource recovery schemes in developing countries. Two such
schemes are outlined below.
Accra, Ghana
In the Ghanaian capital, Accra, small-scale composting of domestic waste has been introduced to
help ease the waste situation. The project has been running since 1985 with 3 collection points in
low-income districts. As soon as it arrives at the collection points (delivered by workers from the
city’s waste management department) the waste is pre-sorted – immediately reusable material is
separated from organic waste. More solid waste is removed after the compost has been turned over
for the first time. The waste is sorted a further two times during the composting process and finally
sieved before being sold by the container-load to local farmers. (GATE Questions and Answers
No3/89).
Mérida, Mexico
In early 1978 a new drainage and recycling system was commissioned as part of a new low-cost
housing project in Mérida, a city in south-eastern Mexico. The system is known as SIRDO (Sistema
Integrada para la Reciclaje de Derecho Organico - Integrated System for Organic Waste Recycling).
Each house is connected to a drainage system that distinguishes between grey (washing) and black
(toilet) water. The grey water is filtered and used for irrigation, and the solids in the black water are
settled out and used in a co-composting process (with household waste) to produce a nutrient rich,
dry-powder fertiliser. The dual chamber system yields compost every 6 months. The treated black
water is also used for irrigation.
The system was designed to be managed by the community. In the early days there was
considerable opposition to the system, not only from the community but also from the local council
and private companies, but this soon dissipated as it became clear that the system improved the
communities sanitation and yielded a good quality saleable compost.
The system is maintained by community members on a voluntary basis and revenue from the sale of
compost (usually to middle class residents for garden use) is reinvested in micro-enterprises or used
to pay for larger maintenance jobs.
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