Conclusions

In this chapter, GHG emissions from an uncontrolled landfill site are compared with those from controlled landfill sites in which flaring, conventional electricity generation technologies such as ICE and GT, and SOFC are utilized. It is shown that even with the simplest solution, which is flaring, total GHG emissions in the lifetime of the site can be reduced by 58% compared to the uncontrolled case. Among the different technologies, the SOFC seems to be the best option, as it reduces the GHG emissions by 63%, and has a specific lifetime GHG emission of 2.38 tonnes CO2.eq/MWh when it only produces electricity and 1.12 tonnes CO2.eq/MWh when it is used in a cogeneration application. The latter case has the lowest environmental impact factor, which is equal to 29%. Hence, this study has shown that SOFC is very effective in combating global warming in landfill sites in addition to its other advantages like low emissions and noise and high efficiency. A future study will include an optimization of a SOFC in a landfill site. In this study, operating variables will be optimized to maximize the energetic performance and minimize the greenhouse gas effect.

Acknowledgment

The financial and technical support of an Ontario Premier's Research Excellence Award, the Natural Sciences and Engineering Research Council of Canada, Carleton University, and University of Ontario and Institute of Technology is gratefully acknowledged.

Nomenclature global warming potential specific enthalpy, J/mol higher heating value of landfill gas, MJ/tonnes methane generation rate, year-1 potential methane generation capacity, m3/tonnes lower heating value, J/mol mass, tonnes CO2.eq molar flow rate, mol/s mass of waste accepted in the ith year, tonnes fraction of methane oxidized in the soil annual methane generation, m3/year age of the jth section of waste mass Mt accepted in the ith year, years molar concentration fraction of vented gas in flare

Greek Letters

£lCE specific GHG emission ratio of internal combustion engine, tonnes eq.CO2/MWh p density, g/cm3

G specific lifetime GHG emission, tonnes eq.CO2/MWh nel electrical efficiency 77 collection efficiency nICE electrical efficiency of internal combustion engine

GWP h hhv k Lo

Mi OX

QCH4 *j x vent r greenhouse gas reduction ratio

T Number of days that electricity producing technology operates per year, days

X fuel-air ratio on molar basis Subscripts c,i combustor inlet c,o combustor outlet f fuel

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