• Energy Research
• 12. Responsible consumption close

Abstract In the near future, H2 is bound to become an important energy carrier used for surplus power storage and for sustainable transportation. An innovative technology for the production of a H2 rich gas is the Sorption Enhanced Reforming (SER) of hydrocarbons: a solid CaO-based sorbent is used to capture CO2 produced by reforming and water gas shift, enhancing the equilibrium. CaCO3 is decomposed in a fluidized bed oxy-combustion calciner and the sorbent recycled. In this work, the interest is focused on the Calcium Looping (CaL) cycle, more specifically on the combustor/calciner fluidized bed reactor of the pilot scale platform ZECOMIX (ENEA – 5 kmol/h of H2). The feasibility to feed O2 to a bubbling fluidized bed calciner by means of Oxygen Transport Membranes (OTM) is studied using a simulation model. The fluidizing flow rate is made of CO2 and CH4, preliminarily heated up to 700–850 °C by heat exchange with the output gas stream (above 900 °C); overall gas flow rate and methane content are enough to reach vigorous bubbling fluidization (u ≈ 10 umf) and temperature required by calcination, respectively. Cold model experimental tests with a cylindrical bubbling fluidized bed reactor with internals (vertical rods mimicking the OTM system) are carried out to support the design of the calciner unit in the ZECOMIX experimental platform. The hydrodynamic study is performed under ambient conditions to simulate fluidized bed expansion and to evaluate bubbles behavior in the calciner, in presence of vertical, tubular membranes for oxygen transfer.

Abstract Fuel Cells fed with locally produced biogenous primary fuels can convert renewable energy into electricity with high efficiencies, in an environment friendly and CO 2 -neutral manner. The paper analyses different biomass conversion processes, gas conditioning technologies, fuel cells typologies and power plant configurations, focusing on the most suitable gasification and anaerobic digestion processes coupled to high temperature fuel cells. The paper shows that the conversion systems have to be analysed from global perspective including feedstock, processes and plant configurations in order to obtain high reliability and efficiency and low emissions. Indeed, the presence, in the raw produced gas, of particulate, organic and inorganic impurities renders the coupling of biomass-derived gases and Fuel Cells problematic, especially in the case of gasification. However, recently developed hot gas cleaning technologies could improve energy efficiency and lower operational costs for high-temperature utilizations of the biomass-derived gas. Finally, further research and demonstration activities are required in order to improve power plant reliability and reduce global capital cost, especially at the more suitable small scale size.

Abstract The development of renewable energies was impressive in recent years on a global scale. This produced changes regarding production processes, citizens' habits, industrial investments and consumer decisions. In this context, the policy-maker played a crucial role. The subsidies are able to determine the development of a specific market. Biogas market spread globally, while biomethane market concentrated in some territories. Green gas can be used as vehicle fuel or injected into the gas grid but also burnt for co-generation. The present work proposes a techno-economic analysis for an existing biogas plant. In particular, the analysis was focused on the comparison between two possible strategic plans, in order to establish which one was the best in terms of profitability: the first one is the expansion of the plant to upgrade biogas to biomethane, whereas the second one is to continue the production of biogas as planned when the plant was constructed. The Discounted Cash Flow (DCF) method was proposed in this paper, and the Net Present Value (NPV) is the main index used. One 250 m3/h biomethane plant located in Italy using pressure swing adsorption (PSA) technique is analysed. The results demonstrated the positive environmental impact deriving from the use of zeolites synthesized from spent fly ash and the profitability is verified only in some scenarios. However, they are limited only to the construction of new biomethane plants, while the upgrading of existing biogas plants are always unprofitable. A Break-Even Point (BEP) analysis quantifies the value of subsidies of biogas and biomethane by which the profitability could be reached. Biomethane can contribute to the development of circular economy models, while the sustainability targets are achieved only in some scenarios.

The environmental impact of traditional fuels and related greenhouse gas emissions (GHGE) has promoted policies driven towards renewable fuels. This review deals with green diesel, a biofuel obtained by catalytic deoxygenation of edible and non-edible biomasses. Green diesel, biodiesel, and petrodiesel are compared, with green diesel being the best option in terms of physical–chemical properties and reduction in GHGE. The deoxygenation process and the related types of catalysts, feedstocks, and operating conditions are presented. Reactor configurations are also discussed, summarizing the experimental studies. Several process simulations and environmental economic analyses—up to larger scales—are gathered from the literature that analyze the potential of green diesel as a substitute for petrodiesel. In addition, current industrial processes for green diesel production are introduced. Future research and development efforts should concern catalysts and the use of waste biomasses as feedstock, as well as the arrangement of national and international policies.

The reduction of CO2 emissions and solid waste disposal are critical issues with high importance for the environmental protection. Gasification is a promising process for sustainable energy production, because it can produce a versatile gaseous fuel starting from a wide range of organic feedstocks, and with reduced greenhouse gas emissions compared to combustion. Lignite is an abundant carbonaceous resource in Europe and in this work, gasification tests were carried out with lignite and a lignite and Solid Recovered Fuel (SRF) mixture, to evaluate the quality of gas produced from co-gasification of waste materials, in view of the final uses of the gas. Experimental gasification tests were carried out in a bench scale fluidized bed gasifier at different operating temperatures; the results were evaluated in terms of gas composition, tar content and conversion rates. In addition, characterization analyses were carried out on materials before and after the tests, and pressure fluctuation signals were analysed in order to evaluate the fluidization quality of the bed inventory.

This work aims to study the selective catalytic hydrogenation of vegetable oils to maximize oleic acid content and expand the range of non-edible uses. Oleic acid (C18:1) is suitable for use as a biodegradable lubricant and is a building block in producing polymers and plastics from renewable resources. The challenge is the synthesis of heterogeneous catalysts, allowing for a maximum yield of C18:1 and low formation of the corresponding saturated acid (stearic acid). New copper-based catalysts on silica were synthesized via two synthesis methods: hydrolysis precipitation and ammonia-evaporation. Experimental tests were carried out at a lab scale operating in a semi-batch mode. The best conversion reached 90% for C18:3 and 80% for C18:2 HP Cu-silica catalyst results, the best candidate for an industrial case study. Good results were obtained in the selectivities of oleic acid production and cis/trans isomers ratio. The modified return on the investment of the designed hydrogenation plant provides the revenues of the capital costs in less than one year.