Nevada Greenhouse Gas Inventory and Reference Case Projections

FINAL Nevada GHG Inventory and Reference Case Projection
CCS, July 2007
To obtain the annual disposal needed by SGIT for each landfill, the waste-in-place was divided
by the number of years of operation. This average annual disposal rate for each landfill was
assumed for all years that the landfill was operating. In cases where the estimated annual
disposal rate was much lower than the 2005 disposal rate provided by NDEP, the estimated
disposal rates in recent years were adjusted to reflect the higher emplacement rates.
CCS performed three different runs of SGIT to estimate emissions from MSW landfills: (1)
uncontrolled landfills; (2) landfills with a landfill gas collection system and LFGTE plant
(Apex); and (3) landfills with a landfill gas collection system and flare (Sunrise). Lockwood was
modeled with the other uncontrolled sites (future year emissions were adjusted by assuming a
flare is installed in 2010). SGIT produced annual estimates through 2005 for each of these
landfill categories. CCS then performed some post-processing of the landfill emissions to
account for landfill gas controls (at LFGTE and flared sites) and to project the emissions through
2020. For the controlled landfills, CCS assumed that the overall methane collection and control
efficiency is 75%. 93 Of the methane not captured by a landfill gas collection system, it is further
assumed that 10% is oxidized before being emitted to the atmosphere (consistent with the SGIT
default).
For the uncontrolled LFs and LFGTE LFs, growth rates were estimated by using the waste
emplacement rates (1990-2005) in each category. For uncontrolled LFs, the annual growth rate is
2.9% and for LFGTE LFs it is 5.6%. 94 These growth rates are consistent with the State’s rapid
population growth from 1990-2005 (4.9%/yr), although waste imports also add to the growth in
waste emplacement. The only flared LF is the closed Sunrise LF. The growth rate (-3.4%/yr) of
emissions from this landfill was calculated based on the SGIT-estimated landfill gas generation
rate from 1993-2005 (flaring is assumed to occur beginning in 2007).
CCS adjusted the SGIT default for industrial landfills. The SGIT default is based on national
data indicating that industrial landfills generate methane at approximately 7% of the rate of
MSW landfills. In NV, there is a significant amount of industrial and special wastes emplaced in
the State’s landfills. Based on summary data from NDEP, the amount of industrial waste in 2005
was nearly the same as MSW. Given that a large fraction of industrial/special wastes is likely to
be non-degradable, CCS assumed that landfill gas generation from industrial waste landfilling
was 50% of the rate of MSW generation. A large fraction of this waste is emplaced at Apex and
Lockwood; however, it is not clear whether this waste would be controlled along with the MSW
at Apex (and at Lockwood in the future). Therefore, no controls were assumed for industrial
waste landfilling. For industrial landfills, the overall growth rate in MSW emissions from 1990
to 2005 (4.5%/yr) was used to project emissions to 2010 and 2020.
LF, Battle Mountain LF, Crestline Class II LF, Mesquite Municipal Waste LF, Western Elite LF, Hawthorne LF,
NTS - Area 23 LF, Tonopah LF, Pershing County LF.
93 As per EPA’s AP-42 Section on Municipal Solid Waste Landfills:
http://www.epa.gov/ttn/chief/ap42/ch02/final/c02s04.pdf.
94 The only LFGTE site is Apex, and the growth rate reflects a doubling of the emplacement rate between 1993 and
2005.
Nevada Division of 64 Center for Climate Strategies
Environmental Protection
www.climatestrategies.us