Approximately 1,5% of the urban organic waste generated in Brazil is recycled ("composted").

On average, compost is composed of 2.5% nitrogen, phosphorous and potassium - NPK. Therefore, by applying ten tonnes per hectare, twelve times that recommended for a mineral fertilizer, the plant will be receiving 250 kg of NPK, the same quantity of essential nutrients found in “chemical” fertilizer, the price of which varies between R$ 300 and R$ 600 per tonne. Organic fertilizer costs from between R$ 40 and R$ 150 per tonne.

Organic solid waste from both domestic and public sources can be used to make the organic fertilizer called compost.

In Brazil, these organic components add up to around 60% of the weight of the garbage collected. In the US, this is 12%, in India 68% and in France 23%.

The reasons for this difference are that the more highly developed the country, or the higher the social class, the smaller the proportion of organic waste suitable for composting and the greater the proportion of recyclable material (paper, cardboard, glass, metals and plastics).

Organic waste has been used as plant fertilizer since the beginnings of agriculture.

In 43 AD, the Roman philosopher Virgil recounted in his book "The Georgics", how plant waste and animal manure, when heaped together, were transformed into material used on cultivated land to increase the harvest. In China and India, composting as an agricultural and sanitary practice goes back thousands of years.

For compost to be an attractive proposition for farmers, certain things must be avoided, such as the presence of large particles, shards of glass, crockery, pieces of plastic, small stones and other contaminants able to be removed after a final sieving. Waste is said to possibly contain heavy metals, and these can be toxic for plants and those who eat them. Heavy metals are frequently found in colored material in urban garbage, such as magazines, labels, rubber and clothes, among others. By using separated waste collection, separating domestic waste into dry and wet garbage, in which latter recipient kitchen waste is included, no significant amounts of heavy metals will be found.

Specifications of Compost:

Brazilian legislation stipulates that organic compost fertilizer must have the following characteristics: minimum 40% organic material; minimum pH 6.0; 1% nitrogen; and have a carbon/nitrogen ratio of 18/1; it must not contain either pathogens or heavy metals above the permitted level.

Reduction at source

There are various ways to reduce waste, by reducing the generation of organic residue, whether in restaurants, industry or at home. In all cases, creativity and efforts at education cannot be used enough.

Incineration

Incineration of domestic organic waste is not recommended, given it’s low heat potential for heat generation and high water content.

Landfill

In landfill sites, sludge resulting from natural degradation of the garbage, when not correctly treated, will contaminate the water table and nearby watercourses.

Back to the origins

Organic material is placed in heaps or beds, and transformed into compost through biological decomposition when in contact with oxygen from the air. Products generated in the decomposition process are compost, carbon gas, heat and water.

The transformation of organic material into carbon gas and water vapor reduces the weight and volume of the heap of material being composted. Correct preparation of the compost means providing the microorganisms responsible for decomposition with favorable conditions for development and reproduction. The compost heap should contain organic remains, moisture and oxygen in sufficient quantities.preparation of the compost means providing the microorganisms responsible for decomposition with favorable conditions for development and reproduction. The compost heap should contain organic remains, moisture and oxygen in sufficient quantities.