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The liquid fertilizer could be used for the agriculture industry in Colombia, which generally imports these kinds of products. Photo: Taken from: www.web.pqp.com.co

Medellín produces approximately 9,000 tons of construction and demolition waste a day. Photo: Taken from: www.reciclajeverde.files.wordpress.com

Waste is taken to a land fill in the municipality of Barbosa. Photo: Taken from: www.descubre.mdeinteligente.co

The youngsters are students of diverse engineering programs.

The process will also produce other byproducts such as citric acid and sodium nitrate which are also marketable. Photo: Taken from: www.agrobeta.com/

The chemical transformation process is carried out in a bioreactor. Photo: Taken from www.//1.bp.blogspot.com/-evNWc2Q6hnw/VSChOo-UJ3I/AAAAAAACG14/cfqJ09dWf2w/s1600/Esquema_biorreactor.png).

“Tomatoes, eggplants and bell peppers need high levels of calcium. Our initiative is hoping to use the product as a fertilizer base and used for many types of crops,” said Petroleum Engineering student Andrés Felipe Aguilar Rendón.

For the proposal the students took into consideration only concretes as they have similar chemical composition to some fertilizers, having nitrogen, potassium, calcium, silicon and magnesium and other micronutrients used in agriculture.

For Geological Engineering student Andrés Bedoya Henao, they are planning on installing a sift near the municipality of Barbosa, where most of the waste of the Valle de Aburrá (Province of Antioquia) is dumped. There they would separate small, mid and large sized particles but they are most interested in particles less than 4 millimeters thick. These particles correspond to 1% of the waste and are generally used as recycled aggregates for new concrete, pavement or fill-ins. The separated material will then sent to a plant in Bello, where after a biochemical process they obtain a mineral concentrate.

“The concentrate has 30% calcium, 15% citric acid, 4% phosphorous and 1% nitrogen; the remaining 48% is water.  This makes it very useful for crops, but it is also a base for other fertilizers which have an average market price of COL $50.000 (US $16.16) and which are generally imported. Other with similar concentrations have an approximate price of COL $30.000 (US $9.70),” added Aguilar.

The idea, which hopes to obtain funding from the industry not only has an economic benefit but is also good for the environment. Using only a small bioreactor for the chemical processing, they can use up to 15 tons of material which generally goes to waste; furthermore the carbon dioxide produced by the energy consumed by the plant is approximately 0.3 Kg. of CO₂ for every kilo on concentrate, while in the regular fertilizer market the same amount would produce 3.5 Kg.

Medellín produces approximately 9,000 tons of construction and demolition waste a day which are not exploited and end up contaminating the environment, demonstrating the relevance of this initiative.

This project is a continuation of the work of doctoral candidate Erika Mejía, a world pioneer in this matter using building waste for agricultural purposes.