The Most Accurate Method
To calculate the fraction of biogenic CO2, there are a handful of methods to choose from. Some are based on judgement and estimations.
By using the ratio obtained from the continuous C14 sampling method, and the total CO2 emitted by the plant, the amount of CO2 from biogenic sources can be calculated.
As a result, this method will return the most accurate figures for reporting biogenic CO2 emissions.
How it works
Mixed fuel as used in e.g. Refuse-derived fuel (RDF) or municipal waste incineration (MWI) plants consists of a mixture of biogenic and fossil carbon. The biogenic carbon is included in fuel material which grew recently as e.g. wood, food, plants, paper etc., and the contained CO2 is part of a natural cycle. The fossil carbon is contained in fuel material, which grew millions of years before as e.g. coal, oil, and products derivated from it, such as plastic. These different materials can be identified by a marker of the carbon atoms, as fossil material consists of 12C and biogenic material of 14C.
When the fuel is burned, carbons are emitted to the atmosphere. Biogenic CO2 is thereby defined as CO2 neutral, as the CO2 which is released due to the burning process, was bounded by the material only a short time before. Only the fossil CO2 part of the emission is defined to be a GHG source. By a determination of the 14C fraction of the flue gas it is possible to determine the biogenic part of the fuel.
For the determination of the biogenic fraction, the AMESA B system extracts a part of the flue gas under volume-proportional conditions and the CO2 is sampled in an adsorber cartridge filled with Ascarite or soda lime. After the sampling period of several hours up to one month, the cartridge is sent to a carbon dating laboratory to apply the carbon-14 method and determine the proportion of the 14C and 12C isotopes in the CO2. With the analysis result, and the information of the 14C fraction, it is possible to calculate the emitted fraction of biogenic and fossil CO2 or the amount of green energy.
The used principle is a standardized method and complies with EN ISO 13833 and EN 15440.