Nitrogen monoxide, nitrogen dioxide and a number of other nitrogen oxides are collectively known as NOx. They are formed mainly by the oxygen in the air reacting with the nitrogen. This reaction requires high temperatures, which arise during combustion in an engine, for example.
Emissions of nitrogen oxides cause overfertilisation, acidification and contribute to ground-level ozone. The main portion of nitrogen oxide emissions stem from traffic, mainly cars and lorries but also shipping. Emissions in Sweden have been reduced from 314,000 tonnes in 1990 to 145,000 tonnes in 2011, i.e. they have been halved in 20 years. This has been achieved with the help of measures mainly in road traffic, first and foremost through the gradual tightening of exhaust emission requirements on cars and heavy vehicles. Emissions have been addressed in a number of instances and are regulated both inthe Kyoto Protocol and in the Swedish Environment Code, mainly via the Environmental quality standards that were introduced in 1999.
Upcoming emission requirements in the USA and the EU will impose stricter regulations on engines and exhaust emission control than before. In the US, the ULEV requirements and EU 5 and 6 will lower the limit for HC and NOx emissions and the introduction of particle emission limits in the EU.
For diesel engines destined for markets with requirements on very low NOx emissions such as the USA (Tier 2) and in shipping and stationary plants is used today Urea is used as an additive in exhaust fumes. As a result, we can now catalytically reduce nitrogen oxides. The technology is called SCR, Selective Catalytic Reduction, a chemical process where Urea is first hydrolysed to Ammonia which then reacts with nitrogen oxides via catalysis to form nitrogen and water.
At Fred Holmberg & Co AB we work actively with different types of reduction agent to reduce emissions,both for heavy traffic, ships and from other combustion sources (power plants and district heating production). We manufacture the reduction agent AdBlue®, and we also market Ammonia and Urea for NOx reduction.