Household waste management in Mahajanga, Madagascar’s third-largest city (located in the north-west of the island, along the Mozambique Channel), with a population of around 200,000 (2004 estimate), growing at 3% per year, is of great concern to the relevant authorities, given the particularly serious public health and hygiene consequences generated by this waste (notably endemic cholera and a particularly virulent plague outbreak in 1999). Local hydrogeological, climatic and social conditions (proximity to the water table, frequent cyclones and flooding, population growth, and significant underemployment) make the city particularly vulnerable to pollution linked to the poorly controlled accumulation of household waste.
This waste is characterised by an exceptionally high organic content, given the local practice of recovering easily marketable valuable components (hollow objects of all kinds, ferrous and non-ferrous metals, certain plastics, etc.).
Agriculture, the leading local economic activity, suffers from soil degradation caused by erosion, and chronically lacks fertilising elements due to insufficient local resources, given the prohibitive cost of imported products.
Compost, however, is a high-quality fertiliser. Comparing its role with that of chemical fertilisers reveals a direct nutrient contribution (likely lower in quantity than conventional chemical fertilisers, for an equivalent weight), but also a contribution to soil restructuring (notably increasing water retention). Compost thus enables fertiliser savings for an equivalent agronomic effect, varying according to crop and soil type.
The city produces 2,200 tonnes of waste per month. Given that one tonne of waste can yield 600 kg of marketable compost, and that 75% of waste could reasonably be collected, the potential compost production can be estimated at 985 tonnes per month, or around 12,000 tonnes per year.
The project’s overall objective is to improve the health and quality of life of Mahajanga’s urban population (250,000 inhabitants), through the management of household waste and its conversion into agricultural soil amendments, compost and crushed horn. Recurring costs will be covered through: a) the sale of soil amendments, b) the sale of carbon credits, c) payment from the Municipality for public service tasks carried out by Tananamadio, and d) potentially, waste disposal fees paid by industrial operators. Sales of soil amendments will target ornamental crops (parks and flower gardens belonging to the municipality, the university, various companies and private individuals) as well as subsistence and export agriculture.
