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A reliable assessment of the availability of bioresources represents the first step to defining local value chains of particular interest. More than 190 and 50 Mt/y of bioresources are currently available in Europe and Italy, respectively, even if they are not fully valorized. The best end use of these feedstocks is strictly dependent on specific territorial/regional peculiarities, that consequently affect the products' final properties. In this work, the Italian web-GIS-based tool “Atlante delle biomasse” was used to determine the availability of many bioresources in Italy at the regional level. A lump classification criterion was used to categorize the available biomasses, and, then, an optimization algorithm based on a process superstructure was applied to find out the available fraction of bioresources, the amount of biofuels potentially obtainable and, consequently, the regional fuel demand coverable by biofuels. In particular, only the energy-self-sufficient technologies with higher TRLs were considered in the mathematical model. The integration between the different selected bioresources led to three biofuels to be considered, evaluating the percentage of biofuel demand that could be covered for each Italian region. The final potential production of biofuels derived from local bioresources in Italy settles down on the range 9 107 – 1.6 108 GJ/y covering about 5, 50, and 100 % of methane, biodiesel and bio-LPG demand respectively. Bio-LPG demand for all regions was to be considered completely satisfied, biodiesel production was also sufficient to cover high demands, on the other hand, low values of biomethane requirements coverable were obtained. [ABSTRACT FROM AUTHOR]

Exhaust gas recirculation is a technique that allows for controlling the combustion chamber temperature and reducing the NOx and particle matter emissions. Moreover, it helps to mitigate soot formation and ash agglomeration in combustion systems. The present study investigated the effect of exhaust gas recirculation on combustion temperatures of a 140 kW underfed stoker biomass boiler. To this purpose, a wide range of operating conditions were used, collecting data regarding flue gas and fixed bed temperatures. It turned out that the recirculating ratio has a significant effect on the temperatures in the primary combustion zone, affecting the thermal gradient and the main thermal zones of the biomass combusting bed. The obtained results can be useful for lumped parameter modeling, or CFD validation purposes. [ABSTRACT FROM AUTHOR]

Nowadays, energy self-sufficiency cannot ignore the environmental sustainability of how it is achieved. On the other hand, one of the largest waste disposal components of a reclamation consortium is represented by residues derived from habitat maintenance. These residues are mainly formed by riparian vegetation that, from an energy point of view, can represent a renewable biomass. Some practical problems arise when passing from a theoretical approach to the development of an effective supply chain, the main of which is the biomass availability. Since the riparian ecosystem is characterized by a wide variety of landforms and biological communities, the functional supply chain must consider seasonal variability, different biomass composition depending on the land, and, hence, a mean biomass feedstock availability. The presented study has been conducted in a reclamation consortium of Northern Tuscany in Italy and examined the main characteristics of the feedstock and estimating its availability. This information has been used to propose different possible supply and utilization chains: a network of small-scale plants, biomass gasification involving external local utilizers or more complex scenarios dedicated to the production of syngas. Among the two final possible supply chains identified, gasification for syngas production and anaerobic digestion for biogas production, the first option resulted to be more profitable. The possible application to the consortium energy balance has been analyzed and commented, evidencing different technical factors that can influence its value. [ABSTRACT FROM AUTHOR]

This work proposes a simple and accurate tool for predicting the main parameters of biomass gasification (syngas composition, heating value, flow rate), suitable for process study and system analysis. A multizonal model based on non-stoichiometric equilibrium models and a repartition factor, simulating the bypass of pyrolysis products through the oxidant zone, was developed. The results of tests with different feedstocks (corn cobs, wood pellets, rice husks and vine pruning) in a demonstrative downdraft gasifier (350 kW) were used for validation. The average discrepancy between model and experimental results was up to 8 times less than the one with the simple equilibrium model. The repartition factor was successfully related to the operating conditions and characteristics of the biomass to simulate different conditions of the gasifier (variation in potentiality, densification and mixing of feedstock) and analyze the model sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: Different thermochemical configurations (gasification, combustion, electrolysis and syngas separation) are studied for producing hydrogen from biomass fuels. The aim is to provide data for the production unit and the following optimization of the “hydrogen chain” (from energy source selection to hydrogen utilization) in the frame of the Italian project “Filiera Idrogeno”. The project focuses on a regional scale (Tuscany, Italy), renewable energies and automotive hydrogen. Decentred and small production plants are required to solve the logistic problems of biomass supply and meet the limited hydrogen infrastructures. Different options (gasification with air, oxygen or steam/oxygen mixtures, combustion, electrolysis) and conditions (varying the ratios of biomass and gas input) are studied by developing process models with uniform hypothesis to compare the results. Results obtained in this work concern the operating parameters, process efficiencies, material and energetic needs and are fundamental to optimize the entire hydrogen chain. [Copyright &y& Elsevier]

The world energy demand growth is more and more supplied by renewable energy sources. In this scenario, biomass has a key role in both heat and power generation. Particularly, biomass combustion can be used in small size micro and distributed generation systems, or in smart grids together with wind and solar energy where a programmable energy source is necessary to keep the electric grid stable. In this paper, a small size 140 kWth biomass fixed bed boiler of the University of Pisa, located at the Biomass to Energy Inter-University Research Centre (CRIBE), was studied experimentally to characterize the biomass combustion process. Emissions of NO x , O 2 , CO 2 and CO, together with the temperature data, were measured in the flue gases. Moreover, the spatial distribution of volatile products from the fixed bed surface, such as H 2 , CO, CO 2 , CH 4 , C 2 H 6 , C 2 H 4 , C 2 H 2 , together with temperature data, was studied in the early combustion stage. The parametric variation of the feed air flow and its effect on the emissions and performances was also investigated. The results indicate that the primary air mainly affects the volatiles distribution on the biomass combustion surface. Therefore, the CO emission was minimized at values of 0.03%vol with an air excess equal to 2 and a 0.06 secondary to primary air mass flow ratio. [ABSTRACT FROM AUTHOR]

The promising properties of torrefied biomass provide a valid co-firing option for large percentage biomass utilization in existing coal-fired boilers. Torrefied biomass is expected to have a better combustion stability than raw biomass and similar to that of coal. The present work will characterizes the oxidation properties of torrefied biomass char and compare with that of raw biomass char. The studied two chars are produced from raw and torrefied biomass in an Isothermal Plug Flow Reactor (IPFR) at high temperature and high heating rate, a sufficient residence time is applied for the completion of the high temperature devolatilization. Char oxidation tests are carried out in the IPFR by varying temperature, oxygen concentration and residence time. The reactivity of two studied chars are analyzed and compared with referenced biomass char and coal char, and the impact of torrefaction on char reactivity is also discussed in this paper. Finally, the char oxidation kinetic parameters are determined using a parameter optimization method, and the obtained kinetics are examined by comparing the experimental and predicted mass conversions. [ABSTRACT FROM AUTHOR]

Abstract: A procedure coupling experimental characterization and computational fluid dynamics (CFD) is developed for providing valuable global kinetic parameters to large applications of biomass fuels (fast pyrolysis, co-combustion and gasification). This is based on an advanced lab-scale apparatus (drop tube reactor), reproducing high heating rates and low residence times at different nominal temperatures (400–800°C) for particle size of practical interest. Although the relative simplicity of the operation, a detailed and accurate evaluation of the particle residence time and effective thermal history is needed to elaborate suitable global devolatilization kinetics, which differ significantly from low heating rate kinetics (for instance in thermogravimetric balance) and also from those obtained assuming strong hypotheses (e.g. constant particle temperature in the reactor). The developed procedure gives kinetic parameters which are not the intrinsic devolatilization kinetics but global kinetics at high heating rates. These global kinetic parameters are useful to simulate practical systems (characterised by high heating rate) with comprehensive codes (CFD), since detailed particle kinetics require additional sub-models (e.g. of external and internal heat transfer) which may be time consuming and need many data, often known only with uncertainty. In this work CFD is used as both diagnostic and predictive tool; its potentials and drawbacks in aiding advanced experimentation on biomass/coal pyrolysis are discussed. [Copyright &y& Elsevier]