Air emissions

The major air pollutants that occur during the production of steel besides greenhouse gases (in particular CO₂) are sulfur dioxide (SO₂), nitrous oxide (NO_x), and dust. Emissions of all of these pollutants comply with the statutory threshold limits. These parameters are measured regularly and the annual loads recorded; intermittent analyses are also carried out.

voestalpine makes every effort to minimize to the greatest extent possible the air pollutants that occur during production due to purely technical reasons related to the process. On one hand, this is done by way of optimization of the technical process (process integrated (PI) measures) and on the other, through end-of-pipe measures utilizing state-of-the-art technology.

Fundamentally, process-related emissions that result primarily from the raw materials required and from existing production processes cannot be avoided entirely because of technical limitations. Due to the environmental measures that were begun in the mid-1980s and continued since then with significant technical effort and financial expense, emission levels have practically reached the minimum that is currently technically achievable. Therefore, no additional significant reduction is possible with currently available technologies, as illustrated in the following.

For example, the specific emissions for CO₂, SO₂, and NO_x in the last five years are within the production-based fluctuation range. During the last three decades, the specific emissions produced by the voestalpine Group (i.e., based on one ton of crude steel) have been reduced as follows: CO₂ by 20%, SO₂ by 75%, NO_x by 27%, and dust by 95%.

CO₂ emissions

Crude steel production using the LD process, which continues to be the worldwide standard in steel production, creates emissions from unavoidable chemical reactions that are process-related. In the production of pig iron, the raw materials coal and coke are needed in the blast furnace as reducing agents, while carbon is necessary in order to extract oxygen from the iron ore. Subsequently, the carbon still contained in the pig iron is oxidized in the LD converter by blowing in oxygen. Therefore, when carbon and oxygen combine, carbon dioxide (CO₂) is created.

A reduction of these process-related CO₂ emissions can only be achieved by way of partial (or in the case of total decarbonization) complete replacement of carbon, in other words, a completely new production process. (In this regard, see the chapter “Energy and climate policy”.) From today’s perspective, these technological options can only be realized over the long term due to their complexity.

As described above, the required use of carbon and the resulting CO₂ emissions are already very close to the technically possible minimum threshold.

At the Linz and Donawitz locations, whose blast furnaces are among the best compared to other European countries, a total of 11.7 million tons of CO₂ were emitted in 2015. This corresponds to specific CO₂ emissions of 1.67 tons (based on one ton of crude steel); viewed against the comparative figures, the changes are within the production-based fluctuation range.

Specific CO₂ emissions caused by voestalpine, reported in accordance with the Austrian Emissions Allowances Act (EZG)

t/t of crude steel

Figures refer to CO₂ emissions pursuant to the Austrian Emissions Certificate Act at the Linz and Donawitz sites

By way of its applications (such as lightweight construction, improved efficiency in power plants, electric motors, renewable energy), high quality steel makes a significant contribution to the improvement of the energy balance sheet of these products, therefore improving the CO₂ balance sheet as well. According to a study by the Boston Consulting Group, which was carried out on behalf of the German Steel Federation (“Steel’s CO₂ balance sheet: A contribution to climate protection”), these applications save six times the amount of CO₂ than is created during steel production.

Specific SO₂ emissions

kg/t of crude steel

SO₂ emissions

Many raw materials contain sulfur, which is then introduced into the production process. During certain processing steps and when by-products (coke oven gas and blast furnace gas) are used for energy generation, sulfur is released as sulfur dioxide (SO₂).

The specific SO₂ emissions in 2015 were 0.70 kg per ton of crude steel. In recent years, changes were within the production-based fluctuation range.

Specific NO_X emissions

kg/t of crude steel

NO_x emissions

Nitrous oxides (NO_x) are gaseous nitrogen compounds that are generally created during combustion processes; they are also created in the soil through natural microbiological decomposition processes.

In steel production, nitrous oxides are created during the production process in industrial furnaces; they are also created in power plants when utilizing process gases for energy generation.

By deploying denitrification systems and improved combustion technologies, voestalpine has been able to reduce these emissions in a long-term comparison; in 2015, the specific NO_x emissions were 0.58 kg per ton of crude steel.

Emission reduction at Uddeholms AB, Sweden:

Prior to switching to liquid gas, warm-up and heat treatment furnaces were powered mainly by oil. Until 2014, all of the furnaces were converted to burn liquid natural gas. This is based on a modern combustion technology and, combined with additional process improvements during the conversion process, it enabled an overall reduction of energy consumption by 28 GWh per year and a significant reduction of emissions compared to previous technology.

Dust emissions

Dust-laden exhaust gases and emissions that occur during production are captured and routed to a dedusting system by way of state-of-the-art measures and precautions.

The specific dust emissions were 0.042 kg per ton of crude steel in 2015, down slightly compared to the previous year’s figure. After a significant reduction of more than 20% between 2008 and 2009, they have remained at a low level.

Specific captured dust emissions

kg/t of crude steel