12006 IPCC Guidelines for National Greenhouse Gas InventoriesCO<sub>2</sub> Emissions from Urea-Based Catalytic ConvertersVolume 2, Chapter 3 3.2.1.1`3.2.2`

<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Emissions</mi></mrow></math> = CO<sub>2</sub> Emissions from urea-based additive in catalytic converters (Gg) CO<sub>2</sub>)</p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Activity</mi></mrow></math> = amount of urea-based additive consumed for use in catalytic converters (Gg)</p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Purity</mi></mrow></math> = the mass fraction (= percentage divided by 100) of urea in the urea-based additive</p>It is best practice to use this equation for estimating CO2 emissions from use of urea-based additives in catalytic converters (non-combustive emissions).
The factor (12/60) captures the stochiometric conversion from urea (CO(NH2)2) to carbon, while factor (44/12) converts carbon to CO2. On the average, the activity level is 1 to 3 percent of diesel consumption by the vehicle. Thirty two and half percent can be taken as default purity in case country-specific values are not available (Peckham, 2003). As this is based on the properties of the materials used, there are no tiers for this source.000http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html