LIFE CYCLE ASSESSMENT OF GREENHOUSE GAS EMISSIONS FROM NAM THEUN 2 HYDROELECTRIC PROJECT IN CENTRAL LAOS

Abstract

Conventional energy generation techniques such as coal and oil power plants release large amounts of greenhouse gases (GHGs) due to fossil fuel combustion while renewable energy sources, particularly, hydroelectric generation, are considered as climate-benign since they do not emit fossil carbon to produce energy. However, dams and their associated reservoirs are not entirely GHG-neutral and their emissions need further investigation. In particular, reservoirs contribute to a major source of methane emission owning to the energy and material input in the construction and the decommissioning phase as well as the anaerobic decomposition of flooded biomass in the operation phase. This master’s project evaluates the greenhouse gas (GHG) emissions associated with Nam Theun 2 hydroelectric power plant in central Laos. A life cycle perspective is coupled with two Monte Carlo Simulations and time-specific global warming potential (GWP) for methane, all to predict the statistically most likely 100-yr GWP of Nam Theun 2. The stochastic models indicate GHG emissions of 2.5±0.5 gCO2 eq/kWh GWP in the construction phase, 75±5 gCO2 eq/kWh GWP in the operation phase and 0.60±0.05 gCO2 eq/kWh GWP in the decommissioning phase. The operation phase emission estimation is larger than previously believed (around 10 gCO2 eq/kWh for hydropower) due to the accounting for biomass decomposition. However, the hydropower plant is still significantly lower than the lifetime GWP of a typical coal plant (800-1000 gCO2 eq/kWh). A literature review on the topic of reservoir GHG emissions is conducted, an introduction of the Nam Theun 2 project is presented and GHG mitigation recommendations are provided for various stages of a dam’s life.