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Biomass gasification for energy purposes has several advantages, such as the mitigation of global warming and national energy independency. In the present work, the data from an innovative and intensified steam/oxygen biomass gasification process, integrating a gas filtration step directly inside the reactor, are presented. The produced gas at the outlet of the 1 MWth gasification pilot plant was analysed in terms of its main gaseous products (hydrogen, carbon monoxide, carbon dioxide, and methane) and contaminants. Experimental test sets were carried out at 0.25–0.28 Equivalence Ratio (ER), 0.4–0.5 Steam/Biomass (S/B), and 780–850 °C gasification temperature. Almond shells were selected as biomass feedstock and supplied to the reactor at approximately 120 and 150 kgdry/h. Based on the collected data, the in-vessel filtration system showed a dust removal efficiency higher than 99%-wt. A gas yield of 1.2 Nm3dry/kgdaf and a producer gas with a dry composition of 27–33%v H2, 23–29%v CO, 31–36%v CO2, 9–11%v CH4, and light hydrocarbons lower than 1%v were also observed. Correspondingly, a Low Heating Value (LHV) of 10.3–10.9 MJ/Nm3dry and a cold gas efficiency (CGE) up to 75% were estimated. Overall, the collected data allowed for the assessment of the preliminary performances of the intensified gasification process and provided the data to validate a simulative model developed through Aspen Plus software.

Production of energy or chemicals from biomass and several waste substrates appears a concrete strategy for replacing fossil fuels and reducing carbon dioxide emissions in the atmosphere. In particular, methanol from biomass or bio-waste is considered a reliable energy vector and key intermediate for industrial chemistry. Currently, methanol is industrially produced via syngas conversion using natural gas as the main feedstock. Bio-methane produced via anaerobic digestion (AD) of Organic Fraction Municipal Solid Wastes (OFMSW) may be used as an alternative to natural gas for production of syngas with optimal composition via commercialized reforming processes. In this work, a techno-environmental assessment for methanol production from biogas is presented and discussed. In particular, three case studies were assessed to minimize the environmental impact of bio-methanol production.

An innovative 1000 kWth pilot plant based on a bubbling fluidized bed gasifier with internal recirculation was operated in experimental campaigns of biomass gasification. The evaluations were focused on the gasifier performances and quality of the product gas. To this aim, tests were carried out at atmospheric pressure using almond shells as a feedstock and three defined gasification mediums (i.e. steam/O2 mixture, 35wt.% and 50wt.% O2 enriched air); process temperature was in the range 820-880 °C. The result assessment allowed to evaluate the system flexibility to the gasifying agent and acquire data on the gas producible with this specific configuration. Based on the dry compositions, LHVs in the range 5.9-6.7 MJ/Nm3 dry, 6.3-8.4 MJ/Nm3 dry and 10.9-11.7 MJ/Nm3 dry were respectively calculated for the three product gases. Correspondingly, an increase in the cold gas efficiency from 0.5 up to 0.7 was also estimated. Concerning the contaminant loads, in the case of the tests related to steam/O2 biomass gasification, particle and tar contents were found in the range 6-10 g/Nm3 dry and 12-18 g/Nm3 dry, respectively, while H2S, HCl and NH3 were at concentrations below 100 ppms (v). © 2015 Elsevier B.V. All rights reserved.

Aim of the paper is the analysis of experimental data from digestate from buffalo sewage gasification carried out at high pressure, close water critical condition. Experiments were performed in a semi-continuous reactor, by loading the biomass, continuously feeding the pressurised water and removing the gas product from the reaction vessel. At a fixed value of temperature (310 °C), two pressure levels were investigated across the water critical pressure (110 bar and 320 bar). According to the expectation, from the treatment of this type of biomass a liquid fraction, containing some components that can be used as chemicals for the "green industries", was obtained. Aldehydes and carboxylic acids were the main product obtained and the liquid phase composition was revealed to be sensitive to the pressure level, since a more concentrated product was obtained at lower pressure level. In addition, a reaction pathways is proposed coherently to the observed evolution of the liquid phase composition. © 2014 Elsevier Ltd. All rights reserved.

The paper reports on experiments of glucose gasification with water in supercritical conditions (SCW). The adoption of these process conditions revealed advantages in terms of biomass conversion efficiency as the resulting liquid phase includes some important compounds (Acetic Acid, 5-HFM, furfurals). In addition the high operative pressures allow either to consider the possibility to use this technology inside the steam cycle in order to produce power and liquid/gaseous biofuels such as synthetic natural gas and/or methanol/DME(di methyl ether). In fact, from the experimental tests, it was possible to evaluate that using glucose, that is the main intermedia of SCW gasification from wet biomass, is possible to estimate a syngas production of about 100 lt – 200 lt for each kg of glucose fed, while the global gasification efficiency was of about 10–18%. Syngas product to SCWG has been analysed and the main results shows that, in the range investigated, CO content was 40–50%vol., H2 10–15%, CH4 10–20%, C2+2–8% and at the end CO2 with a volume content of about 20–30% and then with lower calorific value of about 20 MJ/Nm3. Analysis on the liquid phase was carried out and the main results has been an high production of both 5-hydromethil furfural and 2-Furaldehyde that have a great potential as “carbon-neutral” feedstock for fuels and green chemicals.

The paper reports on gasification of almond shells with water at high pressure (above critical value) and temperature. The experimental set up was a semi-continuous reactor, an innovative configuration allowing to continuously remove the gas product from the reaction vessel. The adoption of pressure conditions well above water critical value (30 MPa) and relatively low temperature (300 C) confirmed suitable reaction pathways for biomass conversion with high efficiency leading to a liquid phase rich of some interesting compounds (HMF, furfural). In order to increase the process performances, sodium hydroxide was added as promoter of the gasification reactions. According to an already proposed reaction scheme, results confirmed a positive impact of the additional compound to the liquid yield and quality, while the gaseous phase was enriched in carbon dioxide. © 2013 Elsevier Ltd. All rights reserved.

A modified Olivine, enriched in iron content (10% Fe/Olivine), and a natural bauxite, were tested in the in-bed reduction of tar and alkali halides (NaCl and KCl) released in a process of biomass steam/O 2 gasification. The tests were carried out at an ICBFB bench scale reactor under the operating conditions of: 855–890 °C, atmospheric pressure, 0.5 steam/biomass and 0.33 ER ratios. From the use of the two materials, a reduction in the contaminant contents of the fuel gas produced was found. For the alkali halides, a decrease up to 70% wt was observed for the potassium concentration, while for sodium, the reduction was found to be quite poor. For the organic content, compared to unmodified Olivine, the chromatographically determined total tar quantity showed a removal efficiency of 38% wt . Moreover, regarding the particulate content a rough doubling in the fuel gas revealed a certain brittleness of the new bed material.

The pretreatment step has a key role in the enzymatic conversion of lignocellulosic biomass to bioethanol. Steam pulping of biomass has long been recognized as being effective in producing high biomass fractionation. In this step, the preliminary impregnation of biomass with acid catalysts, including SO2, has been shown to further improve the hydrolytic effect and increase the digestibility of the fibers by enzymes. This work focused on developing an experimental setup for the SO2 impregnation, enabling accurate control of the process variables. The final purpose was the assessment of a method to minimize the quantity of SO2 used, and that could be applicable to continuous operations. Aspen chips were impregnated with the acid catalyst at room temperature in a stainless steel batch reactor, and the influence of the biomass humidity and contact time on SO2 uptake was explored. After the catalyst adsorption, biomass was fed into the steam explosion batch reactor and steamed at 205 °C for 3 and 10 min to obt...

The synergistic effect of pre-impregnation by sulphuric acid and steam explosion has been investigated. Sugar recovery by water extraction and cellulose digestibility by enzymes have been considered. The acid diffusion inside a representative particle, having thickness of 0.7 mm, has been modelled on the basis of available models and diffusion coefficients. The experiments of acid impregnation have pointed out a plateau of the acid uptake after 10 min corresponding to an acid adsorption of 22 g/kg of dry stover. An experiment of acid desorption from the pre-impregnated biomass particles to a new bulk of pure water (reverse diffusion), has confirmed that only a small fraction of the uptaken acid remained free, while most has been consumed by the substrate. Nine conditions have been tested for the steam explosion treatment selecting the temperature of 180, 190, 200 °C and sulphuric acid loadings of 0, 1.5, 3 wt.%. The maximum sugar recovery by water extraction is produced by a SE treatment of 190 °C for 5 min and an acid loading of 1.5 wt.%; at these conditions 25% of the sugars in the feedstock can be recovered as monomers or oligomers. The acid has greatly improved the sugar solubility, e.g. at 180 °C the sugar recovery has been only 1.5% without acid, while by using 3 wt.% of acid the sugar recovery has increased to 16.8%. Also the cellulose digestibility has been improved by the acid pre-impregnation, after 48 h of digestion the yield of glucose reached 93% of the theoretical by using the substrate that was pre-impregnated with 3 wt.% of acid an treated at 190 °C. The high acid loading has also been required to achieve the best recovery of glucose (85% of the initial glucan) as sum of water extraction and 48 h hydrolysis.

The aim of this work is to evaluate the performance of PEEK membrane modules modules membrane with two different configurations plant in order to obtain low pressure biomethane usable directly in the secondary grid injection with a pressure lower than 10 bar. Two configurations were studied: high recovery configuration and high power configuration and for each one an energetical evaluation was carried out. In each one configuration biomethane purity was fixed at 94 vol.% and the experimental tests were carried out fixed a simulated biogas fed at 50 kg/h with a methane content of about 55 vol.%. The experimental tests allowed to establish the feasibility of the biomethane production at low pressure for the secondary grid injection in a polygeneration plant: power, thermal energy and biomethane each one with a productivity that could be regulate by changing parameters of the process. ©2015 Elsevier Ltd. All rights reserved.

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 g(ethanol)/g(initial sugars). This amount of gel entrapped an initial cell concentration of 6 x 1012cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirred-tank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.

This paper investigates the production of ethanol from steam pretreated aspen. The optimal conditions for both the pretreatment and ethanol production were determined. In the former step the parameters investigated were temperature (180−220 °C) and residence time (2−6 min). The most effective combination was 214 °C and 6 min. The exploded substrates were detoxified in three ways, washing with water at 65 °C proving to be the most effective. The substrate was then converted into ethanol via simultaneous saccharification and fermentation. Influences of the reactor type (shaken flasks and stirred bioreactors) and process parameters (solid-to-liquid ratio, enzyme loading, and stirrer speed) have been investigated. The highest ethanol yield obtained from solid-to-liquid ratios of 0.20 g/g was 85% in shaken flasks and 79% in helical stirred bioreactors. In the former case, the ethanol concentration in the broth was 47 g/L. The fermentation unit returns a solid residue with a calorific value of 5612 kcal/kg. The...

The aim of the paper is highly relevant in different countries dealing with some experimental results obtained in a membrane pilot plant designed to upgrade biomethane to such a quality level that it is worth injecting into the methane grid where it is widespread over many territories especially in Italy. The process chosen is able to upgrade biomethane for different inlet conditions assessing the efficiency of this technology in the presence of pollutants typical of a biogas from anaerobic digesters fed by animal waste and biowaste. Specifically, the experimental tests with binary mixtures CH4/CO 2 in the range of typical composition, are carried out tests in order to evaluate the performance of the membrane in the presence of H2S; moreover the results are compared with a prediction model showing a good agreement between experiments and simulation results in terms of biomethane purity and yield. © 2014 Elsevier Ltd. All rights reserved.

It is under development a biomass gasification plant based on a 1 MW th bubbling fluidized bed (BFB) reactor with internal recirculation. Compared to conventional BFB design, the mechanism of internal circulation of solids can give beneficial effect to the process in terms of biomass conversion efficiency into gaseous product and gas quality. A model describing the process of biomass gasification in the two reaction chambers was developed. Expected results were preliminarily validated by experimental results obtained at a bench scale facility working on the same gasification concept. © 2013 The Authors.

The attention regarding bioenergy sources, such as biomass, as an alternative to fossil fuels has increased tremendously over the past few years consequently to the problems related to global warming. For the using of biomass as fuel is very important the basic knowledge of its physical-chemical properties for the using of the sustainable resource. The identification of biomasses in terms of both quantification and characterization of the chemical composition of biomass is a fundamental step for the use of this fuel for energy purposes. There are many differences between the various types of biomass; firstly, the moisture, the chemical composition and in particular that of the ashes, and the content of inorganic substances. The elements mainly present in biomass, in decreasing order of abundance are: carbon, oxygen, hydrogen, nitrogen, calcium, potassium, silicon, magnesium, aluminum, sulfur, iron, potassium, chloride, sodium and manganese. In addition, compared to coal, the chemical composition of biomass is significantly different, in particular the biomasses are highly enriched in hydrogen, manganese, potassium, phosphorus, chlorine, calcium, sodium and magnesium, as well as in terms of moisture and volatile substances compared to coal, while result with a lower ash content, iron, carbon, nitrogen, sulfur, and silicon. The purpose of this work is the quantification and characterization of different types of biomass found in the regions of the southern Italy with similar soil and same climatic conditions, at the end of their use in mixtures in an optical of build several ultrashort bioenergetical chains. Experimental results have shown that the heavy metal content is significantly lower in the fly ash than the bottom ash, and therefore, their mixture may be used as a soil improver to maintain the cycle of nutrients in soils. © 2014 Elsevier Ltd.

This paper deals with the gasification of agricultural residues such as almond shells and wood at high temperature (850 °C) in a small-scale gasification plant coupled with a reciprocated internal combustion engine. Detailed investigation of both organic (tar) and inorganic (NH3, HCN, metals, etc.) products distribution in the process streams are provided. This research aims to assess the existence of certain relations between feedstock composition and the observed products distribution in the steady state. Biomass feedstock is characterized for its elemental composition, its content of metallic species, and lignin, cellulose, and hemicellulose fractions. A different feedstock composition was found to be associated with some important variations in the process monitored parameters such as the gasification rate, the tar content, and the char yield in the flue gas. Also a relation was found between the relative amount of ammonia and cyanide species in the flue gas at the operating conditions of the gasifier (oxygen-to-biomass ratio and activated carbon support). Spectroscopic features of the sludgy condensate formed in the upper part of the gasifier during the early stage of the process together with the characterization of char, fly ash, and acidic species in the flue gas shed light on some mechanistic aspects of the gasification process.

Anaerobic Digestion (AD) is a biological process that takes place naturally when bacteria break down organic matter in environments with or without oxygen. Controlled anaerobic digestion of organic waste in enclosed landfill will generate methane. Almost any organic material can be processed with AD, including waste paper and cardboard (of a grade that is too low to recycle because of food contamination), grass clippings, leftover food, industrial effluents, sewage and animal waste. AD produces biogas which is comprised of around 60% methane (CH4) and 40% carbon dioxide (CO2). This biogas can be used to generate heat or electricity and/or can be used as a vehicular fuel. If the intended use is for power generation the biogas must be scrubbed to remove a number of impurities. After conditioning the biogas can be used for onsite power generation, to heat homes or can be added to the national natural gas grid. In recent years several research groups have shown the possibility of upgrading the biogas for biomethane production [1]. This study will show the feasibility of integrating anaerobic digestion plant with onsite polymeric membrane purification system for conditioned biomethane production. © 2012 Elsevier Ltd. All rights reserved.

A special type of bioreactor was designed and tested in order to improve the bioethanol production from lignocellulosic materials via enzymatic hydrolysis and fermentation. The reactor consists of two chambers kept at different temperatures and separated by a porous medium, through which the solutes can diffuse. The reactor was tested using as substrate wheat straw previously steam exploded and detoxified. The yields of cellulose hydrolysis and glucose fermentation obtained using this reactor were compared to those obtained by simultaneous enzymatic hydrolysis and fermentation (SSF) carried out in only one vessel. The results showed that a significant increase in the ethanol yield (20%) can be achieved by using this bioreactor. An additional advantage of the reactor is the confinement of the solid lignin in one chamber, allowing a simplified separation process between broth and unreacted residue. © 2012 Elsevier Ltd.

Corn stover was treated by steam explosion process at four different temperatures. A fraction of the four exploded matters was extracted by water. The eight samples (four from steam explosion and four from water extraction of exploded matters) were analysed by wet chemical way to quantify the amount of cellulose, hemicellulose and lignin. Thermogravimetric analysis in air atmosphere was executed on the eight samples. A mathematical tool was developed, using TGA data, to determine the composition of corn stover in terms of cellulose, hemicellulose and lignin. It uses the biomass degradation temperature as multiple linear function of the cellulose, hemicellulose and lignin content of the biomass with interactive terms. The mathematical tool predicted cellulose, hemicellulose and lignin contents with average absolute errors of 1.69, 5.59 and 0.74 %, respectively, compared to the wet chemical method.

The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat straw have been investigated. The treatments have been carried out in batch and continuous reactors with capacity of 0.5 Kg/cycle and 150 Kg/h, respectively. The exploded materials have been sequentially extracted with water at 65°C and sodium hydroxide 1.5%. Analytical determinations of liquid fractions and solid residues have led to the fractionation pattern of the carbohydrates as monomers, oligomers, and polymers. Evaluations of total acidity, ash content, and lignin recovery have improved understanding of the process. This part of the work has allowed us to derive: the empiric relationship between the batch and the continuous reactors and the yield and availability of pentoses and hexoses in various phases. Selected samples have been tested in enzymatic-hydrolysis experiments, pointing out the effect of treatment severity and reactor used on the saccharification yield.