EF application of calcium fertilizers
The uncertainties of emissions from application of calcium fertilizers are based on tolerance limits in the composition of fertilizers specified in the Fertilizers Act (Düngemittelverordnung, 2012, pg. 32 ff). The Fertilizers Act tolerates variations of only 2 to 4 %, depending on the type of calcium fertilizer. The total uncertainty (95 % confidence interval) for liming in agriculture varies for the different years since 1990, but has always been lower than 3 %. This value is considerably lower for liming in the forest sector. However, as emissions from agriculture and forest are reported as a total, the calculation of the the total uncertainty of the German GHG inventory is conservatively based on an uncertainty of the emission factor of ±3 %, interpreted as 95 % confidence interval (normal distribution).
In general, some of of the C contained in calcium fertilizers is not converted into CO2, causing additional uncertainties of the emissions. However, this cannot be taken into account due to lack of statistical data on the degree of conversion of C into CO2. Hence, apart from composition tolerance limits, the calculated CO2 emissions represent maximum possible emissions.
EF application of urea
Using the N tolerance for urea in the Fertilizers Act (Düngemittelverordnung, 2012), it is possible to derive an uncertainty of about 1 % of the total urea emission factor. The uncertainty range of ± 1 % is interpreted as 95 % confidence interval (normal distribution).
In general, some of of the C contained in calcium fertilizers is not converted into CO2, causing additional uncertainties of the emissions. However, this cannot be taken into account due to lack of statistical data on the degree of conversion of C into CO2. Hence, apart from composition tolerance limits, the calculated CO2 emissions represent maximum possible emissions.