Investigation and analysis through modelling of the potential for renewable energy production and mitigation of greenhouse gas emissions from anaerobics digestion in Cyprus

Abstract

Biodegradable wastes cause high emissions of greenhouse gases (GHG) if not properly treated. The emissions can be reduced by the development of an effective waste management strategy. Waste-to-energy technologies, such as anaerobic digestion (AD) can be utilised for this purpose. Biomass energy from wastes is of particular interest to Cyprus that has to meet legal commitments for reducing its GHG emissions by 5% compared to 2005 levels and increase the contribution of renewable energy sources to 13% by 2020. This research project is making a significant contribution to this effort. The research considered the quantities and distribution of biodegradable waste in Cyprus and developed the necessary methodologies and tools for their estimation and determination of the potential for energy production through AD. The study identified that the predominant biodegradable wastes in Cyprus are the biodegradable fraction of municipal solid waste (MSW), sewage sludge, solid and liquid agricultural residues and solid and liquid wastes from the food and drinks industries. According to the estimated amount of solid and liquid biomass from these waste streams, at least 4,200 TJ of energy can be produced through AD, which represents 4% of the national energy demand. Livestock production is a very important source of waste due to the high potential of biogas production with the aid of AD. The produced energy can satisfy the needs of a farm, reduce the consumption of fuel and provide renewable energy to the national grid. Simple methodologies were developed and implemented for the estimation of energy consumption of the farm and the respective GHG emissions. It was found that in Cyprus the annual energy consumption per animal is lower than most other countries, due to favourable weather conditions which reduce the energy needs for heating. The emissions from energy use in livestock production contribute 16% to the total agricultural energy emissions. Literature review on AD, confirmed the complexity of the process, due to the many microorganisms involved. To estimate the potential of biogas production from animal waste through AD, three methods were developed based on the accepted relations that exist between Chemical Oxygen Demand (COD), volatile solids (VS), waste digested and biogas production. The results show that livestock production could cover the complete agricultural energy demand and make a considerable contribution to the renewable energy targets of Cyprus. Due to the identified importance that AD could have for Cyprus and to overcome deficiencies of existing models, the software FARMS was developed. The tool can be used by any farmer, consultant or policy maker for the estimation of the potential of biogas production, associated costs, reduction in GHG emissions and comparison of scenarios for waste management. Furthermore, the validation of the tool is presented. This was done through comparison against data collected from existing AD plants and through testing by potential users.