Pukhnyuk O. Landfill gas generation and assessment of landfill gas to energy potential at municipal solid waste landfills of Ukraine.

The thesis is focused on investigation and modeling of landfill gas (LFG) generation, and assessment of LFG to energy potential at Ukrainian municipal solid waste landfills. Six Ukrainian landfills of different size were investigated using field tests and laboratory methods for investigation of organic matter stabilization and gas production potential. The observed degree of reactivity and remaining LFG potential is lower than predicted with the IPCC 1st order decay model using decay rate values recommended for the climate of Ukraine. Modeling biological (anaerobic and aerobic), physical and chemical processes in the landfill shows that the factors that are mostly influencing anaerobic decay rate and LFG generation potential (moisture, temperature, aerobic decay) to a large extent depend on the landfill operation practice. Ukrainian landfills, especially old ones, are characterized by poor landfill operation standards, such as low compaction, lack of intermediate cover, low rate of landfill growth, possible leachate accumulation and fires. Therefore, Ukrainian landfills are characterized by intensive aerobic degradation of organic matter and accelerated anaerobic decay during landfill operation, as well as rapid decrease of LFG generation rates after landfill closure. Anaerobic decay rate is higher than values recommended by the IPCC for the conditions of sanitary landfills in similar climatic conditions, and degree of aerobic degradation can reach up to 50%. LFG generation dynamics can be with sufficient accuracy described using two-component 1st order decay model, the ranges of anaerobic decay rates and aerobic decay factors for different landfill characteristics, operational and climatic conditions are suggested. Recommendations on selection of methods for assessment of landfill reactivity and LFG generation potential in the conditions of Ukrainian landfills are presented. The LFG to energy is estimated for Ukraine, recommendations for improvement of landfill operation practice and related increase of LFG generation and collection potential are provided. Alternative methods of decrease of methane emissions are discussed.