2.4 Quantification of Emissions
Emissions of nickel are influenced by many dynamic factors, including production techniques, different fuel sources, and ranges of pollution controls. The variability of these factors spatially across the EU and over time make it difficult to quantify emissions with accuracy. Emissions are therefore estimated according to the approach described in Text Box 1. The quality of these variables can vary extensively, and quality codes were assigned to each variable according to internationally recognized protocols.
The overall assessment of the method is determined by the lowest quality score, given to the different parameters (activity, emission factor, distribution factor) used in the method. Based on this assessment, sources and quantification methodologies for which a targeted assessment is necessary (because of their importance and/or low quality quantification method) were identified. Ultimately, the quantification method with the highest quality score is selected for each source.
As an example, we can refer to Table 2, in which an overview is given of all methods used for each identified nickel emission source, to quantify the emissions. For the source entitled “residential heating” (located under the “Households” category in Table 2) a mid-tier approach was used based on the equation:
E = A x EF, where
E = Emission
A = Activity (fuel consumption for residential heating)
EF = Emission Factor (e.g., 0.07 g nickel/ton solid fuel used
(1) Indicates that first the emissions are quantified from data from The Netherlands (known region) and are then extrapolated to the EU-15
(2) Full details can be found in background report on the assessment of point and diffuse sources of nickel (compounds) (ECOLAS, 2005)
(3) Additional information is available in a report from RIVM/RIZA (Elzenga et al., 1998)
Table 2: Overview of the emission quantification methods used in the nickel EU RA