Comment Log Display

June 19th, 2015

California Air Resources Board
Transportation Fuels Branch, SSD
Fuels Evaluation Section
1001 I Street
Sacramento, CA 95814

Re: Comments on Calculating GHG Reduction Credits for the
Displacement of an Open Anaerobic Lagoon with an Anaerobic
Digester
Dear CARB Staff,
We are submitting comments regarding the credits assigned to
methane emissions from an open anaerobic waste treatment lagoons.
The conversion of these operations into anaerobic digestion
facilities represents a significant reduction in methane emissions
from these operations as methane that was emitted to the atmosphere
is captured (with the exception of fugitive emissions). Correctly
accounting the credits these operations receive will have an impact
on whether or not open anaerobic lagoons will be converted and will
divert methane from the atmosphere. 
Methane is a potent greenhouse gas that has 25 times higher global
warming potential than carbon dioxide, and has been generated from
anaerobic waste lagoons and emitted directly to the atmosphere at
many cattle operations across the country. Diverting the manure
created at these facilities to an anaerobic digester avoids
releasing methane emissions to the atmosphere, and reduces the
negative impact of these facilities. Therefore, we believe the
avoided methane emissions should be counted as a credit towards the
biogas produced from anaerobic digesters used to replace these open
lagoons.
The current methodology adopted by CARB  and Argonne National
Laboratory  for the analysis of anaerobic digestion-based renewable
natural gas (RNG) production assumes that CH4 generated is flared,
and that the resulting CO2 emissions and fugitive methane are the
only credits received by the biogas produced by the digester. This
assumed baseline is reasonable because the original destination of
these wastes would be a landfill where the collection and flaring
of biogas is feasible and has already been implemented. 
However, in most current open anaerobic lagoon systems, no biogas
is being collected. Furthermore, once the biogas is collected from
a covered lagoon and/or a bio-digester, the biogas will likely be
sold or used for on-site energy generation. It is highly unlikely
that biogas collected would be flared after the capital and
operational costs have been put into the facility to capture and
use the gas. 
In a report published by US EPA in 2010, of the 157 digester
projects operating on commercial scale livestock facilities, only
15 (or 9.6%) were flaring the biogas full time . Based on this
information, it is at least questionable that the flaring of biogas
should be used as a reference case since it does not reflect actual
operations at a high percentage of digester projects. 
We believe the reference case for calculating the avoided methane
emissions should be that all the biogas generated from the open
anaerobic lagoon is fugitive to the atmosphere.  Consequently, the
CH4 emissions captured by the anaerobic digester should be
accounted for as credits in the GREET model. 
We would like to encourage you to take this into consideration when
finalizing the GREET 2.0 model to allow for reductions based on the
methane emissions that are captured and utilized. This will allow
for better accounting and encourage reducing ghg emissions from
these operations, and from other emerging technologies.
Thank you for the opportunity to submit these comments and to
participate in the re-adoption of the LCFS. Please let us know if
you need any additional information or have any questions on the
above points!

Sincerely,


Dennis M. Langley
President
AltEn, LLC
1344 County Road 10
Mead, NE, 68041