Annex 43 Complementary information to source category 5c Diesel Engines

Overview of recent revisions

A new class, Biodiesel vehicles, was introduced in this source category. Additional guidance has been included on classifying sources within this category, estimating activity rates, and on data quality aspects.

Derivation of emission factors

Release to Air

Limited data are available to evaluate PCDD/PCDF emissions from Diesel-fueled vehicles. So far, only passenger cars and trucks have been assessed; there are no data for off-road diesel uses (i.e., construction vehicles, farm vehicles, and stationary equipment). From USA, there are two tailpipe studies where the Californian Air Resources Board reported a relatively high emission factor of 676 pg TEQ/km, corresponding to 3.2 μg TEQ/t of Diesel (assuming a consumption of 1 L Diesel for a 5.5 km distance driven; CARB 1987). Another study tested heavy-duty trucks and determined a range of emission factors from 3.0 to 96.8 pg TEQ/km (mean of 29.0 pg TEQ/km), corresponding to 0.014-0.453 μg TEQ/t of Diesel with a mean of 0.14 μg TEQ/t of Diesel (Gullett and Ryan 1997).

Schwind et al. (1991) and Hutzinger et al. (1992) reported emission factors between 32 and 81 pg TEQ/L (or 6-15 pg TEQ/km assuming a fuel consumption of 5.5 km/L) for a truck engine run under various simulated driving conditions. Hagenmaier et al. (1995) reported no emissions from a bus at a detection limit of 1 pg/L of fuel consumed for individual congeners. For diesel-fueled cars, Hagenmaier et al. (1990) reported an emission factor of 24 pg TEQ/L for one tested car.

Kim et al. (2003) investigated PCDD/PCDF emissions from diesel engines in US D-13 mode at load rates between 25% and 75% at constant speed (2,400 rpm). The mass concentrations for the three different loads of 14.4, 6.9. and 6.4 pg TEQ/m³ convert into the following emissions factors: 2.0, 0.6, and 0.5 pg TEQ/L diesel (corresponding to 0.002 and 0.001 g TEQ/t of Diesel), which are lower than those reported in the studies by CARB, USEPA and the German universities (CARB 1987, Gullett and Ryan 1997, Schwind et al. 1991, Hutzinger et al. 1992).

More recently, Laroo et al. (2011) have tested modern diesel engines with catalyzed after-treatment and found PCDD/PCDF emissions from 0,21pg TEQ/L (0,51 pg TEQ/L for the 95% confidence interval) to 1,28 pg TEQ/L (2,89 pg TEQ/L for the 95% confidence interval), for the 2007 and 2010 emission control configurations respectively. From the above studies, an emission factor for Diesel-fueled vehicles of 0.1 μg TEQ/t of Diesel will be applied. If efficient soot filters are employed, emissions from consumption of Diesel fuel are much lower; currently, only a small proportion of vehicles in use are equipped with this technology.

Lin et al. (2011) have also tested a 1994 Diesel engine with premium diesel fuel (PDF) and several palm-biodiesel-PDF mixtures. The results showed PCDD/PCDF emissions of 1.43 ng TEQ/L, corresponding to 1.7 µg TEQ/t of premium diesel fuel, and 0.904 n TEQ/L, corresponding to 1.08 µg TEQ/t of B20 fuel (20% palm-biodiesel and 80% diesel fuel). A new class and an emission factor of 0.07 μg TEQ/t (70% of regular diesel EF) are thus included for diesel fuel with at least 20% biodiesel.

Release in Residues

Particulate emissions from Diesel engines are likely to contain PCDD/PCDF. Amounts are unknown, thus, more research is needed to determine actual PCDD/PCDF concentrations.