I-DEV0302: Measurement of methane content of biogas

This request is to allow deviation of measurement of CH4 content of biogas as specified by ID3 in Table D1 of the registered PDD by measuring the CO2 content of biogas and calculating the CH4 content instead of directly measuring the CH4 content.

ID3
The project developer has undergone an extensive evaluation and selection process to find the most reliable and durable equipment for measuring CH4 at its project activities. This process took considerably longer than anticipated by the project developer. At this time, the project developer has identified and begun using this monitoring equipment and, as of February 2009, the direct measurement of CH4 has been implemented in accordance with the monitoring methodology and the monitoring plan and this practice will be used for all subsequent monitoring periods.
Prior to measuring the CH4 content the project developer has monitored the CH4 content of biogas using practices considered to be correct during validation and identical to the monitoring practices at other registered and verified projects by the same project developer applying AM0016 version 02.
Biogas consists of mainly CO2 and CH4. Recent measurements of both the CH4 and CO2 content of biogas taken from sites within this project activity showed that the sum of CO2 and CH4 averaged 98.75% with a 95% confidence level of 96.38%. An earlier analysis of other similar advanced Animal Waste Management Systems (AWMS) in Brazil and Mexico, developed by the same project developer and applying the same project technology showed that the sum of CO2 and CH4 averaged 99.0% with a 95% confidence level of 96.7%. However, in order to be most conservative, the project developer has opted to use the minimum value of the sum of CO2 and CH4 found in its testing as the value to be applied across the all projects of this methodology version. This value is 94% for the sum of CO2 and CH4 with 6% trace or other gas. Hence, if this request for deviation is accepted, the percentage of CH4 in biogas will be calculated as 94% minus the percentage of CO2.
Measurements of the percentage of CO2 in biogas have the same accuracy as measurements of the percentage of CH4. Hence, the monthly measurement of the percentage of CO2 and the calculation of the percentage of CH4 as described above ensures in our opinion the same level of accuracy.

As of February 2009, the direct measurement of CH4 has been implemented in accordance with the monitoring methodology and the monitoring plan and this practice will be used for all subsequent monitoring periods. To use measurements of the CO2 content of biogas to calculate the CH4 content instead of directly measuring the CH4 content is required due to the project participants initially not finding reliable and durable equipment for measuring CH4 at its project activities.

The deviation is expected to result in an underestimation of the emission reductions as it is conservatively assumed that biogas contains 6% trace gases.