It’s about NOX not only CO2

The reason is that NOX is a regional problem that typically requires the flue gas concentration to be continuously maintained below limits. In contrast, CO2 is a global issue and in many countries, there is typically an annually allocated free emission quota after which additional quotas can be bought at market price – if CO2 emissions are limited at all.


“If a cement plant emits too much NOX it will impact the regional ecosystem through acid rain and smog pollution. For instance, high NOX and SO2 emissions from across Europe led to fish dying in Swedish lakes. And, we all remember how London and Los Angeles was troubled by smog pollution years back until politicians started regulating NOX emissions,” explains Lars Skaarup Jensen.

Your license to operate is linked to your NOX emission. If you emit more than allowed CO2 you might buy some additional quotas, but if your NOX emission is too high your cement plant ultimately closes.

LARS SKAARUP JENSENPhD. Chemical Engineering and Project Manager at FLSmidth

Taking NOX out of the equation

NOX occurs in most combustion processes. It is generated from nitrogen in the fuel and can also be generated thermally when air is heated above about 1600°C (degrees Celsius). But, chemistry can be magic, so by adding chemicals (such as ammonia), NOX can be significantly reduced or even removed from the emission.

“As we know from the car industry, a catalytic converter can eliminate most of the NOX emission by combining hydrocarbons with NOX after the combustion process. At a cement factory, we often install low-NOX calciner designs and use ammonia in our SNCR systems to control the NOX emission,” says Lars Skaarup Jensen.

NOx illustration

Harsher regulation expected

Throughout the years, authorities have tightened the NOX regulation as health and environmental issues have arisen. A trend that is expected to continue as world population grows by 2 billion by 2050 and most people will be living in urban areas.

Since the 1970’s, the US and EU, and some other countries have had focus on NOX, e.g. Germany has been a pioneer and today has some of the strictest NOX regulation. India and China are also allocating more resources to handle their NOX related issues, especially smog pollution which is becoming a ticking health bomb in many cities,” adds Lars Skaarup Jensen.


Smog pollution vs sea level rising

Lars Skaarup Jensen calls it imbalanced that world leaders and the public debate primarily talk about CO2. Focus should be on both greenhouse gasses and NOX – as well as reducing other regulated gaseous emission components and waste management.

At the same time as putting great effort into tackling the CO2 challenge to avoid the serious implications of climate change for the world, we must invest in ensuring clean air for everyone on a regional and local scale. We can’t live in cities under a duvet of smog pollution killing people!” ends Lars Skaarup Jensen.

We need to address emissions and climate change holistically, otherwise our solutions won’t be sustainable.



Lars Skaarup Jensen

Lars Skaarup Jensen

PhD. Chemical Engineering and Project Manager at FLSmidth