Value from waste at Phosphates

As one of the largest producers of phosphate fertilisers in Brazil, we produce around 1.35 million tonnes (Mt) of phosphate concentrate every year to facilitate its production. As a result, the effluent treatment plant associated with the fertiliser production process generates around 7,800 tonnes of phosphate waste annually. The waste comes in the form of a cake rich in P₂O₅ - a powerful desiccant and dehydrating agent.

Despite the potentially beneficial properties of the waste material, only about 20% of this cake was previously available to be re-used, namely in the granulation stage of the phosphate fertiliser production process. The remainder was either sold as a low-value by-product or disposed – raising environmental concerns. However, following a series of lab and industrial scale tests and much persistence from the team at Cubatão, results showed that the phosphate waste could also be used in the acidulation process – the first stage in the fertiliser manufacturing process – reducing the need for new water and creating value from a waste material.

After the success of the tests, the new technique also entered full-scale production at Catalão in March 2012, achieving savings of 48,000 tonnes of phosphate concentrate in 2012 as a result. We also saw a saving of over 13 million litres of water in acid dilution and a reduction of 10 tonnes of CO₂ emissions at the drying plant.

As well as reducing production costs, this research and development is set to have long-term benefits for the environment. Recent figures show that the amount of phosphate waste recovered and re-used has increased to 40% – a figure which could rise to 60% in the future – and the amount of waste disposed of in the environment has decreased accordingly.

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