Anglo American is collaborating with a local Brazilian start-up, turning waste material from its nickel operations at Barro Alto in the State of Goiás, into fertiliser for use by the country’s agricultural industry.
Brazil’s agricultural sector plays a key role in the country’s economy, benefitting from diversified climate conditions, including regular rainfall and abundant sunshine, extensive land area and plenty of natural resources1.
Self-sufficient in the provision of basic produce, Brazil is also one of the largest exporters of a wide range of foodstuffs, including soybeans, corn and orange juice; as well as being the world’s leading producer of coffee2. Brazil’s soil, though, is deficient in magnesium, one of the many essential nutrients that plants need to complete their lifecycle.
That’s where, as Anglo American, we saw an opportunity to draw upon our presence in the country. In particular, at our Barro Alto nickel-producing mine and processing plant we are applying the principles of the circular economy to our own operations, exploring new ways to enhance agricultural productivity and improve crop yields.
The circular economy is a concept centred on minimising all forms of waste and making the most of what we have; re-using, re-designing, sharing, repairing, re-manufacturing and recycling. This approach allows us to rethink traditional business models.
From the electric furnace to the farm
When nickel ore is melted in an electrical furnace, the molten metal – which is more dense – sinks to the bottom before being extracted. The waste product, a type of magnesium silicate (MgSiO) also known as ‘ferronickel slag’, stays on top.
Once the nickel has been extracted from the slag, a water jet is directed at this waste product, cooling it rapidly from around 1600°C to room temperature. This rapid change in temperature causes a thermal shock, granulating the non-metallic elements within the slag and changing its structure from a liquid to a glassy, amorphous product – something more closely resembling sand.
This waste by-product has the potential to be used in the production of a thermo-magnesium fertiliser which, as an input to the agricultural sector, can lead to significant productivity improvements.
Tests designed to validate the efficacy of this slag as a thermo-magnesium fertiliser were conducted on soybean plants by a local Brazilian start-up, in collaboration with Anglo American and a public university. These investigations showed it to be effective at increasing or replenishing the Magnesium (Mg) and Silicon (Si) content of the soil, nutrients proven to improve crop growth and yield potential. Conducted in the field, as well as under greenhouse conditions, the tests revealed several positive outcomes, including an increase in the height and weight of the grains.
There is another advantage to using the waste product in this way. Around 83% of the ore fed into the nickel mining process is converted into slag, before being stored within a designated area of the mine site, as per agreements with the relevant environmental authorities. As a company, Anglo American has long-been exploring opportunities to reduce these volumes at Barro Alto – including by using it in cement and asphalt, as well as to produce bricks for construction.
If successful, this latest collaboration will help to avoid the accumulation of high levels of waste generated by ferronickel production, with the by-product directly re-used as a resource for the fertiliser production process.
1 Agriculture industry in Brazil – Statistics & Facts, Statista, https://www.statista.com/topics/5838/agriculture-in-brazil/
2 Britannica, https://www.britannica.com/place/Brazil/Agriculture