Sorting & composting of household waste

formation-beiraWaste management is a major challenge in major cities in developing countries, as local authorities have to cope with increasing quantities of waste with limited financial resources. Composting allows to re-use a major portion of the waste and a reduction of quantities sent to landfill. 

Waste from growing cities, very often contains more than 70% of fermentable organic substances, which can be composted.

The composting process gives the opportunity to return organic substances to the soil as fertiliser instead of just burying them in a landfill site. The effects on agriculture are shown here.

Composting process:

An initial sorting process is necessary in order to extract the organic substances from the household waste: the remains of food, rotting fruit and vegetables, as well as green waste, abattoir waste, cardboard boxes or sawdust can be included to a certain degree in the compost. Some of these waste items must be crushed in order to accelerate their decomposition.

The sorting process is carried out manually by workers wearing safety equipment, either on sorting tables or on the ground.  

The windrows, which are fermenting heaps of organic substances, are formed immediately. The fermentation process, which takes 7 to 10 weeks, requires frequent turning-over operations in order to ensure the aeration of the windrows and the aerobic decomposition of the organic substance.  This phase is described as being thermophilic, as the temperature measured inside the windrow increases to more than 70°C. This rise in temperature enables the hygienisation of the compost as it leads to the evaporation of pathogens.

At the end of the fermentation process, the compost is transferred into larger heaps to encourage its maturation, which lasts for about 2 months.

As a result of this process, 100t of household waste enable 25t of compost to be produced, which can enrich approximately one hectare of land.

The On-table sorting process at Lomé (Togo)
The Fork-sorting process at Dschang (Cameroon)
The Compost sifting process at Dschang (Cameroon)

The income emanating from this sale of compost contributes to the financial equilibrium of the investments combined with derived profits coming from the carbon-related finance. 
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