Let’s talk about Red Mud (Bauxite Residue)

Global annual production of red mud (bauxite residue) is about 150 million tonnes. It contains raw materials for the production of iron, silicon and aluminium, and is dumped as waste in spite of the availability of recycling technologies. This is because it is cheaper to dump bauxite residue as waste and continue mining for new ores. Is this sustainable?

 (Obviously not!!)

Inspection of Alunorte Bauxite residue deposit
Photo by Norsk Hydro ASA
CC licenses

What is bauxite residue?

Bauxite residue, or red sludge, appears in the news from time to time. We hear about dams in danger of bursting and disposal sites where bauxite residue is seeping into the environment. But what is bauxite residue? And why do we find such large bauxite residue settling pools scattered around the world?

Let’s answer the first question first. Bauxite residue is a waste product produced by the aluminium industry. To answer the second question – more than twice as much bauxite residue as aluminium metal is produced during a standard production and refinement process.

In a linear economy, valuable raw materials are simply dumped

The annual production of 150 million tonnes of bauxite residue corresponds to about 20 kilos per head of the global population! Only between 1 and 2 per cent is recycled in other industries. The rest is dumped. This creates a major potential for local environmental problems, but it also very poor resource exploitation.

Bauxite residue contains up to 50 per cent iron oxide, and more than ten per cent of components such as aluminium oxide, silica, titanium oxide and other substances. Instead of being used as a raw material in the production of iron, silicon, aluminium, cement, building insulation or other products, it is regarded simply as waste. The raw materials for the production of all these products are instead derived from mining activities, which are associated with their own sustainability issues and local environmental damage.

This is simply a glaring example of the linear economy in which value is measured by short-term cycles of supply and demand without any regard for long-term planning for the conservation of natural resources for future generations. As long as the least expensive short-term solution is dumping, no-one can afford to consider any alternatives.

Linear vs. circular

Is bauxite residue an economic or a technological problem?

Bauxite residue is strongly alkali (high pH values) because it contains high concentrations of lye (NaOH). This is why it cannot simply be discharged into the natural environment. In itself, NaOH is not so difficult to deal with and can be neutralised using substances such as hydrochloric acid (HCl) to produce clean water and table salt.

The high sodium content makes it difficult to use unprocessed bauxite residue in the steel industry as a substitute for iron ore. The European alumina producers are working together to find sustainable solutions, but this is difficult because they are competing in a global market. A great deal of work is being done to identify applications for bauxite residue outside the aluminium industry. It is technically possible to use it in steel manufacture and in the building industry. However, such applications are not yet commercially viable.

However, the really big problem with bauxite residue is that there is so much of it. The enormous volumes of mud produced make the challenges and problems associated with its management, and the space it occupies, equally enormous. And while we surround ourselves with these great volumes, we are fully aware that technological solutions are available.

In other words, we are dealing primarily with a problem of economics. 

Can hydrogen solve the Red Mud problem?

Pilot-scale rotary furnace and bauxite after pre-reduction in hydrogen. @SINTEF

HARARE will demonstrate sustainable pathways to eliminate waste and valorise materials in CO2-emissions free processes by using hydrogen as a reductant.

Substituting carbon with hydrogen is one of the few ways metal production can potentially become truly free of CO2-emissions.

The HARARE-project started June 2021, we will keep you updated on our progress towards our objective to:

to eliminate waste from the metallurgical industry while recovering valuable materials and encouraging the use of hydrogen in the industry