Environmental challenges of alumina production in China
Alumina is the widely recognized industry name for aluminum oxide (Al2O3), the raw material of aluminium production. The alumina industry represents an intermediate stage of aluminium production.
Alumina production process[edit | edit source]
The alumina is mined from bauxite, an ore first discovered in France in 1821. The extracted bauxite ores – gibbsite, böhmite and diaspore – are all elemental variations of aluminium compounds. The aluminium within them is the most common metal in the outer crust of the planet, and is mined directly from the top layers of earth’s soil. Ninety percent of that bauxite ore is found in tropical and subtropical zones along the Earth’s equator, in a belt that includes places like West Africa and India.
Bauxite mines operate on a deceptively simple principle: Wash the soil from the bauxite first. It’s at this stage that much of the water and energy consumption that are the inputs in alumina production appear.
Bayer Process[edit | edit source]
Washing and crushing the bauxite begins the Bayer Process, which remains in use today in almost all alumina production. Lime and caustic soda are added to form a slurry that can be pumped. Following the milling and any removal of silicon, when necessary, the product goes into the digestion stage. A hot caustic soda (NaOH) solution is used to dissolve the aluminium-bearing minerals in the bauxite, with slight variations in concentration or temperature based on which of the three ores is being processed.
This forms an “alumina solution” that is quickly cooled, and then enters a sedimentation process to separate solids – a process that is boosted with more chemicals. After all of the washing and filtering occurs, the partially refined product is sent for the final alumina processing stages to ultimately become the white powder destined for smelters. The remaining liquids, a toxic alkaline mix tainted with heavy metals, are sent to the holding tanks and lagoons. That’s the waste product that is known as red mud, which takes its color from the high iron concentration in the waste by-product. Most of the red mud continues to be stored as liquid, although some companies use a dry storage “stacking” method, a technique that’s emerged across several decades that greatly reduces the danger of red mud leakage.
From the bauxite mine to the finished aluminium product or end user, there are environmental impacts all along the way. Both refining and smelting cause significant greenhouse gas emissions, including carbon dioxide (CO2), nitrogen oxides (NOx), and perfluorocarbons (PFCs). Some atmospheric pollutants like sulfur dioxide (S02) and already mentioned nitrogen oxides (NOx) also mix with water to produce acid rain.
Environmental damages[edit | edit source]
In China, home to roughly half of the world’s alumina capacity, 80% of that production takes place in three provinces: Shandong, Henan and Shanxi, which churned out 53 million tonnes last year. However, as Beijing is grappling with record levels of smog and air pollution, alumina production has become one of the most controversial industrial activities in the country.
After the government announced supply-side reforms and capacity cuts in order to decrease pollution levels, Chinese producers initially heeded the order. Between late 2015 and early 2016, capacity cuts averaged around 7 million tonnes per annum. However, these facilities restarted production during 2016. What’s more, an extra 8.5 million tonnes of new alumina capacities were built by private companies, further compounding the issue.
This additional capacity not only reversed the government’s bid to reduce pollution levels, it actually led to an increase in emissions in 2016 that could have been prevented. Sulfur oxide emissions grew by 28 kilotons, nitrogen oxide by 51 kilotons, dust by 37 kilotons, CO emissions by 23 kilotons, and CO2 by more than 20 million tons. Taking into account the distribution of alumina facilities in China, the most of such increase in emissions occurred in the densely populated provinces of Shandong, Shanxi and Henan. Moreover, the capacity growth of 15.5 million tonnes pa (new and restarted capacities) caused an increase in caustic soda (sodium hydroxide) production by 0.9 million tonnes. The production of this chemical, which is hazardous for people, comes with a long list of health risks. On top of that, chemical production and storage facilities of caustic soda were routinely involved in incidents (explosions in Tianjin and Dongying, Shandong).
The increase in alumina production also translates to an increase in red mud production. In 2012, the global production of red mud was about 120 million tons – with 1.5 ton on average produced for each ton of alumina. The cumulative total amount of red mud stockpiled in the world is estimated at 2.5 billion tons, of which China has a big share: in 2016, in just three Chinese provinces, an additional 35 million tons was stored in Shandong, another 28 million tons in Shanxi, and 18 million tons in Henan; accumulated amount of red mud in these provinces is estimated at 610 million tons.
Red mud, is highly alkaline and tinged throughout with heavy metals. When it leaches into the soil or leaks from a tailing pond, it threatens agriculture and water resources. Some Chinese say they can’t drink the water in their communities because it’s no longer safe, while others avoid locally sourced foods because of soil contamination and heavy metal content. This is especially true in settlements next to Hongqiao plants. The large amount of land required for alumina facilities and red mud containment ponds removes that land from agricultural production as well, especially in Shandong, which is the leading agricultural province in China.
According to sources, Hongqiao, the world’s largest aluminium company, does not allow their personnel to work at its refineries for long periods of time in order to avoid dealing with occupational diseases that appear after 5-10 years of exposure.
Chinese mass media also report emerging “cancer villages,” where clusters of cases of cancer diseases are reported in abnormally high numbers near alumina refineries and red mud disposal areas. It is not unusual in China to see air pollution levels six times above the World Health Organization threshold, resulting in closed schools, canceled flights and other economic impacts. Much of China’s compromised air quality can be traced to the alumina industry and the emissions that are a result, including dust near production facilities that contributes to respiratory disease.