There appear to be two main techniques that can be used to determine the quantity of carbon dioxide emitted by a combustion source. These are:
- Direct measurement of the exhaust gases.
- Indirect computation based on the amount of fuel consumed, its calorific value and estimating the efficiency of the combustion process using assigned emissions and oxidation factors.
Direct techniques rely on continuous emissions monitoring (CEM) to measure the amounts of gas passing to the atmosphere. Such systems and their data logging facilities are well proven, but traditionally have been used to monitor the emissions of trace contaminants such as sulphur dioxide, oxides of nitrogen and particulates, rather than the bulk discharge of carbon dioxide. A considerable body of clean air legislation has been drawn up by regulators across the World (both national and regional) and these controls set the performance standards that such equipment is required to meet. For examples, consult the US Code of Federal Regulations (CFR), Title 40 - Protection of the Environment, Chapter 1 Part 60 and Part 75.
Indirect computational techniques are cheaper, less specialist and require less maintenance than CEM equipment. Examples of methodologies that can be used to compute the amount of carbon dioxide emitted from the combustion of a fuel can be located via the following web links:
- Commission of the European Community : guidelines for the monitoring and reporting of greenhouse gas emissions (MRG)
- Australian Dept of Climate Change : National Greenhouse Accounts (NGA) Factors
- Standards and calculation tools on the GHG Protocol Initiative site.
- UK's EEMS. NB: This site directs you to the DTI’s portal and back again !!
A reluctance by industry to change from the current system of manual reporting seems to be based on a perception that CEM type metering must be used. This may be the case for the very largest emitters, but for many smaller installations it should be perfectly reasonable to use the indirect / computational approach.