Thesis (PhD) - Cyprus International University. Institute of Graduate Studies and Research Energy Systems Engineering Department

Includes bibliography (sheets 131-157)

ABSTRACT
Solid waste has emerged as one of the most pressing environmental issues of our day.
It poses a persistent hazard to both persons and the environment because some types
of trash are toxic and unsafe to be in contact with. Utilizing anaerobic co-digestion
process, which combines waste treatment with the recovery of valuable by-products.
The main objective of this thesis was to analyse experimentally and numerically the
potential of biogas from animal wastes using different experimental conditions like
temperature, and organic loading rates. Co-digestion have also been utilized.
Furthermore, this thesis seeks to numerically investigate the energy and exergy
analysis of utilizing biogas as fuel in power plants for electricity generation. Another
objective of this study is to analyse the biomass production from the Levent farm
(Cyprus international university). The essence of this is being able to quantify the
waste generation, and the energy potential of the wastes. This thesis also seeks to
investigate the anaerobic digestion of microbial biomass as a substrate for
improvement of biogas production was also investigated. This thesis also presents an
energetic and exergetic analysis of a multigeneration system comprising a micro-gas
turbine, an organic Rankine cycle (ORC), an absorption chiller, and a water heater. It
uses energy from biogas combustion produced through anaerobic co-digestion of food
and animal waste. The reported biogas yield from 3 different studies was used in
designing the fuel input for the system. The results showed that substrate combination
of poultry dung and food waste (Biogas-A) needs 35.07 tons of volatile solids (tonsVS/day) of waste compared to 33.11 tons-VS/day for Biogas-B (Cattle dung and food
waste), and 81.87 tons-VS/day for Biogas-C (swine dung and corn straw). For an
increase in the methane content from 40% to 60%, the substrate amounts reduced by
42.3% for Biogas-A, 45.3% for Biogas-B, and 42.7% for Biogas-C. Likewise, for an
increase in recuperator effectiveness from 65% to 95%, the substrate amounts reduced
by 31.6% for Biogas-A, 30.3% for Biogas-B, and 31.4% for Biogas-C. Increasing the
ambient temperature was shown to have an adverse effect on the performance of the
system. The energy efficiency of the system reduces from 47.8% to 39.8% and the
exergy efficiency reduces from 63% to 60% for an increase from 5oC to 40oC. The
total exergy destruction of the system also increased from 1760 kW to 1885 kW.
Keywords: Anaerobic Digestion, Biogas Production, Multigeneration System,
Microbial Biomass, Solid Waste, Organic Rankine Cycle