AdBlue® is an aqueous, colourless and odourless urea solution consisting of 32.5 percent high-purity, crystalline urea and 67.5 percent demineralized water. The urea solution reduces nitrogen oxide (NOx) emissions from diesel engines by up to 90 percent. The water-clear liquid is injected into the exhaust tract and leads to a selective catalytic reaction (SCR). Nitrogen oxides and ammonia are converted into harmless water and nitrogen.