I-DEV0422: AWMS Methane Recovery Project MX06-S-50, Puebla, México

This request is to allow deviation of measurement of methane content of biogas as specified by ID 3 in Table D1 of the registered PDD by measuring the CO2 content of biogas and calculating the methane content instead of directly measuring the methane content.

The project developer has undergone an extensive evaluation and selection process to find the most reliable and durable equipment for measuring methane 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 October 2008 (site 32792) and late September 2008 (sites3280047 & 3280074), the direct measurement of methane 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 methane content the project developer has monitored the methane 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 methane. Recent measurements of both the methane and CO2 content of biogas taken from sites within this project activity showed that the sum of CO2 and methane averaged 97.73% with a 95% confidence level of 94.69%. An earlier analysis of other similar advanced Animal Waste Management Systems (AWMS) projects in Brazil and Mexico, developed by the same project developer and applying the same project technology showed that the sum of CO2 and methane averaged 99.0% with a 95% confidence level of 96.7%. For the similar AWMS project in Brazil and Mexico the project developer thus generally applied a value of 94% for the sum of CO2 and methane with 6% trace or other gas unless measurements for specific sites showed that the sum of CO2 and methane is less than 94%.

For the project activity in question, the sum of CO2 and methane was observed to be less than 94% for some instances for sites 3280047 and 3280074. Hence, the project developer has opted to use the minimum value of the sum of CO2 and methane found in its testing as the value to be applied for these sites. This value is 91% for the sum of CO2 and methane with 9% trace or other gas for site 3280047, 93% for the sum of CO2 and methane with 7% trace or other gas for site 3280074. For site 32792 the sumof CO2 and CH4 was never observed to be below 94% and the value of 96% for the sum of CO2 and methane with 4% trace or other gas is thus applied for site 32792. Hence, if this request for deviation is accepted, the percentage of methane in biogas will be calculated as 92% minus the percentage of CO2 for site 3280047, 93% minus the percentage of CO2 for site 3280074, and 94% minus the percentage of CO2 for site 32792.

Measurements of the percentage of CO2 in biogas have the same accuracy as measurements of the percentage of methane. Hence, the monthly measurement of the percentage of CO2 and the calculation of the percentage of methane as described above ensures in our opinion the same level of accuracy.

As of October 2008 (site 32792) and late September 2008 (sites3280047 & 3280074), the direct measurement of methane 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 methane content instead of directly measuring the methane content is required due to the project developers initially not finding reliable and durable equipment for measuring methane at its project activities. Hence, a request for deviation is suitable in accordance with paragraph 212 of the Validation and
Verification Manual (Version 01.2).

A previous deviation request has been submitted for the same purpose for the first monitoring period, which clarified that the request was also covering part of the second monitoring period (I-DEV0231). At that time DNV verified only emission reductions for the period 17 Dec 06 - 31 Aug 08 and as such measurements after 31 August 2008 were not part of the scope of verification. When submitting the previous request for deviation, the project developer indicated that direct measurements of methane would be made as of early September.
The actual verification of the second monitoring period from 01 Sep 2008 - 31 Jan 2011 showed that direct measurements actually started only in late September and mid-October, and thus are in need of a new request for deviation.

The deviation is expected to result in an underestimation of the emission reductions as it is conservatively assumed that biogas contains 9% trace or other gas for site 3280047, 7% trace or other gas for site 3280074,
and 6% trace or other gas for site 32792.