http://hdl.handle.net/10468/194 2017-10-14T04:57:18Z http://hdl.handle.net/10468/4777 Comparison of pre-treatments to reduce salinity and enhance biomethane yields of Laminaria digitata harvested in different seasons Tabassum, Muhammad Rizwan; Xia, Ao; Murphy, Jerry D. Pre-treatment can enhance anaerobic digestion of seaweed; however, seasonal variation in the biochemical composition of seaweed has a significant impact on the pre-treatment effect. In this study, various pre-treatments were employed for the brown seaweed Laminaria digitata harvested in March (with high ash content and low carbon to nitrogen (C:N) ratio) and September (with low ash content and high C:N ratio). Washing of L. digitata harvested in March with hot water (defined as 40 °C) removed 54% of the ash and improved the volatile solids (VS) content by 31% leading to an improved biomethane yield of 282 L CH4 kg VS−1. This pre-treatment affected a 16% increase in biodegradability, reduced salt accumulation in the digestate by 54%, and increased specific methane yield per wet weight by 25%. This level of effect was not noted for seaweed harvested in September, when the biodegradability is higher. 2017-08-16T00:00:00Z http://hdl.handle.net/10468/4638 The potential of power to gas to provide green gas utilising existing CO2 sources from industries, distilleries and wastewater treatment facilities O'Shea, Richard; Wall, David M.; McDonagh, Shane; Murphy, Jerry D. The suitability of existing sources of CO2 in a region (Ireland) for use in power to gas systems was determined using multi criteria decision analysis. The main sources of CO2 were from the combustion of fossil fuels, cement production, alcohol production, and wastewater treatment plants. The criteria used to assess the suitability of CO2 sources were: annual quantity of CO2 emitted; concentration of CO2 in the gas; CO2 source; distance to the electricity network; and distance to the gas network. The most suitable sources of CO2 were found to be distilleries, and wastewater treatment plants with anaerobic digesters. The most suitable source of CO2, a large distillery, could be used to convert 461 GWh/a of electricity into 258 GWh/a of methane. The total electricity requirement of this system is larger than the 348 GWh of renewable electricity dispatched down in Ireland in 2015. This could allow for the conversion of electricity that would be curtailed into a valuable energy vector. The resulting methane could fuel 729 compressed natural gas fuelled buses per annum. Synergies in integrating power to gas at a wastewater treatment plant include use of oxygen in the wastewater treatment process. 2017-07-25T00:00:00Z http://hdl.handle.net/10468/4637 Cascading biomethane energy systems for sustainable green gas production in a circular economy Wall, David M.; McDonagh, Shane; Murphy, Jerry D. Biomethane is a flexible energy vector that can be used as a renewable fuel for both the heat and transport sectors. Recent EU legislation encourages the production and use of advanced, third generation biofuels with improved sustainability for future energy systems. The integration of technologies such as anaerobic digestion, gasification, and power to gas, along with advanced feedstocks such as algae will be at the forefront in meeting future sustainability criteria and achieving a green gas supply for the gas grid. This paper explores the relevant pathways in which an integrated biomethane industry could potentially materialise and identifies and discusses the latest biotechnological advances in the production of renewable gas. Three scenarios of cascading biomethane systems are developed. 2017-07-23T00:00:00Z http://hdl.handle.net/10468/4688 From technology pathways to policy roadmaps to enabling measures – A multi-model approach Mulholland, Eamonn; Rogan, Fionn; Ó Gallachóir, Brian P. Integrating a range of complementary energy models is becoming an increasingly common method for informing low carbon energy pathways at both national and global levels. Multi-modelling approaches facilitate improved understanding of the detailed technology pathways required to meet decarbonisation targets; however, to-date there has been limited attention on the policy roadmaps and enabling measures that might achieve these decarbonisation targets. This paper addresses this gap by developing a multi-model approach using an energy systems optimisation model, a sectoral simulation model together with scrutiny of individual policy measures to explore decarbonisation of the private car sector in the Irish transport system commensurate with an 80% reduction in national carbon emissions by 2050. The results comprise a cost optimal technology pathway for private cars in a future energy system constrained by a maximum level of carbon emissions, a policy roadmap identifying annual changes in energy efficiency, renewable energy and electrification, and a suite of enabling measures including changes to vehicle registration tax, a biofuel obligation on suppliers and a suite of measures to increase the share of electric vehicles in the fleet. The level of confidence in the different enabling measures to achieve the policy goals is compared and discussed. 2017-07-21T00:00:00Z