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Abstract: The effect of biomass water leaching on H2 production, as well as, prediction of ash thermal behavior and formation of biomass tar during high temperature steam gasification (HTSG) of olive kernel is the main aim of the present work. Within this study raw olive kernel samples (OK1, OK2) and a pre-treated one by water leaching (LOK2) were examined with regard to their ash fouling propensity and tar concentration in the gaseous phase. Two temperatures (T =850 and 950°C) and a constant steam to biomass ratio (S/B =1.28) were chosen in order to perform the steam gasification experiments. Results indicated that considering the samples'' ash thermal behavior, it seemed that water leaching improved the fusibility behavior of olive kernel; however, it proved that water leaching does not favour tar steam reforming, while at the same time decreases the H2 yield in gas product under air gasification conditions, due to possible loss of the catalytic effect of ash with water leaching. [Copyright &y& Elsevier]

Abstract: Air gasification of olive kernels in a 5kW bench scale, bubbling fluidized bed gasifier, aimed at H2 enrichment of the producer gas, was the target of this study. The effects of reactor temperature (T =750–850°C) and equivalence ratio (ER=0.2–0.4), representing the under stoichiometric amount of air inserted into the reactor to that necessary for complete combustion, on producer gas quality were determined. The experimental results revealed that producer gas H2 content increased at the temperature of T =750°C and ER=0.2, resembling the high-temperature pyrolysis conditions that favour H2 and CO production. Further increase in ER deteriorated producer gas quality, decreased H2 content and favoured CO2, thus lowering producer gas heating value. The data obtained from several experiments indicate that olive kernels produced a medium heating value gas (LHV=6.54MJ/Nm3) at 750°C and ER=0.2, while H2 and CO production were maximized at the same conditions (H2: 24%vv, CO: 14.3%vv). [Copyright &y& Elsevier]

A techno-economic assessment of two circular economy scenarios related to fluidized bed gasification-based systems for combined heat and power (CHP) generation, fueled with rice processing wastes, was conducted. In the first scenario, a gasification unit with 42,700 t/y rice husks capacity provided a waste management industrial symbiosis solution for five small rice-processing companies (SMEs), located at the same area. In the second scenario, a unit of 18,300 t/y rice husks capacity provided a waste management solution to only one rice processing company at the place of waste generation, as a custom-made solution. The first scenario of a cooperative industrial symbiosis approach is the most economically viable, with an annual revenue of 168 €/(t×y) of treated rice husks, a very good payout time (POT = 1.05), and return in investment (ROI = 0.72). The techno-economic assessment was based on experiments performed at a laboratory-scale gasification rig, and on technological configurations of the SMARt-CHP system, a decentralized bioenergy generation system developed at Aristotle University, Greece. The experimental proof of concept of rice husks gasification was studied at a temperature range of 700 to 900 °C, under an under-stoichiometric ratio of O2/N2 (10/90 v/v) as the gasification agent. Producer gas's Lower Heating Value (LHV) maximized at 800 °C (10.9 MJ/Nm3), while the char's Brunauer Emmet Teller (BET) surface reached a max of 146 m2/g at 900 °C. Recommendations were provided for a pretreatment of rice husks in order to minimize de-fluidization problems of the gasification system due to Si-rich ash. With the application of this model, simultaneous utilization and processing of waste flows from various rice value chain can be achieved towards improving environmental performance of the companies and producing energy and fertilizer by using waste as a fuel and resource with value. [ABSTRACT FROM AUTHOR]

The nature and airborne dispersion of the underestimated biological agents, monitoring, analysis and transmission among the human occupants into building environment is a major challenge of today. Those agents play a crucial role in ensuring comfortable, healthy and risk-free conditions into indoor working and leaving spaces. It is known that ventilation systems influence strongly the transmission of indoor air pollutants, with scarce information although to have been reported for biological agents until 2019. The biological agents' source release and the trajectory of airborne transmission are both important in terms of optimising the design of the heating, ventilation and air conditioning systems of the future. In addition, modelling via computational fluid dynamics (CFD) will become a more valuable tool in foreseeing risks and tackle hazards when pollutants and biological agents released into closed spaces. Promising results on the prediction of their dispersion routes and concentration levels, as well as the selection of the appropriate ventilation strategy, provide crucial information on risk minimisation of the airborne transmission among humans. Under this context, the present multidisciplinary review considers four interrelated aspects of the dispersion of biological agents in closed spaces, (a) the nature and airborne transmission route of the examined agents, (b) the biological origin and health effects of the major microbial pathogens on the human respiratory system, (c) the role of heating, ventilation and air-conditioning systems in the airborne transmission and (d) the associated computer modelling approaches. This adopted methodology allows the discussion of the existing findings, on-going research, identification of the main research gaps and future directions from a multidisciplinary point of view which will be helpful for substantial innovations in the field., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer Nature B.V. 2022, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)