• Energy Research

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 e 200 lt for each kg of glucose fed, while the global gasification efficiency was of about 10e18%. Syngas product to SCWG has been analysed and the main results shows that, in the range investigated, CO content was 40e50%vol., H2 10e15%, CH4 10e20%, C2þ2 e8% and at the end CO2 with a volume content of about 20e30% 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.

This chapter is dedicated to an overview of the technological options to produce in an efficient way power from biomass gasification products. This is a very important task as it tries to couple two different aspects: the benefits coming from biomass gasification, in terms of efficiency and environmentally friendly operations, with the new trends of bio syngas energetic valorization. The final goal is to explore all the potential steps for an integrated process able to valorize fully the energy content of biomass in a wide range of potential sustainable energy vectors: from pure hydrogen to electrical energy via-fuel cells or high-performance internal combustion engines. More attention is paid to the effect of processing gas coming out from gasification of biomasses that exhibits some specific characteristics such as a wide variability on hydrocarbon composition or the presence of inorganic undesired compounds.

Abstract Combining anaerobic digestion (AD) and thermochemical/hydrothermal processes is an interesting solution for the treatment and valorisation of agricultural waste. Most of the recent investigations focused on the solid digestate valorisation obtaining syngas and char, the latter for solutions different from land applications. However, there are few investigations based on hydrothermal processes aimed at enhancing the value of liquid digestate. In order to fill this gap, the study aims at verifying the technical feasibility of the combined treatment of AD and supercritical water gasification (SCWG). The experimentation was carried out at a full scale AD plant fed by 110 t/d of buffalo manure (81.8%) and maize silage (18.2%). Methodologically, the study first envisaged a bench-scale experimental phase concerning SCWG and then a theoretical phase aimed at quantifying the mass and energy balances with reference to the AD + SCWG and AD schemes. SCWG was examined using a plug flow reactor working at 550 °C and 250 bar for residence times of 20 min. For feed in the range of 4–14 mL/min, it was possible to produce a syngas with a higher heating value (22 MJ/kg organic content) and with a gas yield of about 13 mol/kg of dry-digestate. Carbon gasification and global gasification efficiency were of 35 and 45%, respectively. Results of the theoretical phase confirmed the energy sustainability of the AD + SCWG scheme although the added value was the production of green chemicals including syringaldehyde (7.6–11.6 kg/d), acetic acid (1.0–6.5 kg/d) and glucose (0.5–5.8 kg/d) with total estimated production in the range 10.2–33.5 kg/d.

Haematococcus pluvialis microalgae is a promising source of astaxanthin, an excellent antioxidant carotenoid. H. pluvialis, as well as other species, could find more extensive applications as healthy food for a variegated carotenoids composition in addition to astaxanthin. Official method has not currently been used for this purpose. The objective of this work was to propose a method to characterize carotenoids in H. pluvialis after the comparison between spectrophotometric and liquid chromatography analysis. In addition, in order to improve the use of astaxanthin in the food industry, thermal stability was investigated. In this context, the effect of temperature at 40–80 °C, over a 16 h storage period was tested on astaxanthin produced by H. pluvialis. A further test was carried out at room temperature (20 °C) for seven days. A decrease in the astaxanthin concentration was observed at all tested temperatures with a decrease >50% of all-trans isomer at 80 °C after 16 h and an increase of 9-cis and 13-cis isomers. In conclusion, the obtained results showed the importance of evaluating the degradation effect of temperature on astaxanthin used as a food additive for a future greater enhancement of this bioproduct in the food field.

In this article, microalgae Nannochloropsis sp. was used for fatty acid (FA) extraction, using a supercritical fluid-carbon dioxide (SF-CO2) extraction method. This study investigated the influence of different pre-treatment conditions by varying the grinding speed (200–600 rpm), pre-treatment time (2.5–10 min), and mixing ratio of diatomaceous earth (DE) and Nannochloropsis sp. biomass (0.5–2.0 DE/biomass) on FAs extraction. In addition, the effect of different operating conditions, such as pressure (100–550 bar), temperature (50–75 °C), and CO2 flow rate (7.24 and 14.48 g/min) on eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) recovery, was analyzed. Experimental data evidenced that, keeping constant the extraction conditions, the pre-treatment step enhanced the FAs extraction yield up to 3.4 fold, thereby the maximum extracted amount of FAs (61.19 mg/g) was attained with the pre-treatment with a ratio of DE/biomass of 1 at 600 rpm for 5 min. Moreover, by increasing both SF-CO2 pressure and temperature, the selectivity towards EPA was enhanced, while intermediate pressure and lower pressure promoted DHA recovery. The highest amount of extracted EPA, i.e., 5.69 mg/g, corresponding to 15.59%, was obtained at 75 °C and 550 bar with a CO2 flow rate of 14.48 g/min, while the maximum amount of extracted DHA, i.e., ~0.12 mg/g, equal to 79.63%, was registered at 50 °C and 400 bar with a CO2 flow rate of 14.48 g/min. Moreover, the increased CO2 flow rate from 7.24 to 14.48 g/min enhanced both EPA and DHA recovery.

Abstract The aim of the paper is based on the experimental tests of Gasification in supercritical water for humid biomass, Scenedesmus dimorphus. In this work, experimental tests were carried out in order to understand the main parameters of the SCWG process and their influence varying the total solids content, GGE and CGE gas yield and energy recovery. Based on experimental test and considering literature data about energy demand for microalgae growth and energy required for SCWG process it was possible to evaluate that with minimum total solid content necessary for setting-up a self-sustainable process considering the only energy recovery from the condensation of the water outlet the process. At the same time these simulation were repeated considering of use the enthalpy of water in SCW condition for turbine expansion instead heat recovery obtained not only syngas production usable for biofuels synthesis but also power production.

Abstract In this paper the lignin gasification by using water in supercritical was studied. The employed lignin was produced via steam explosion of Arundo Donax after alkaline extraction and filtration. The lignin, with a total solid content of about 4 wt% in a solution of sodium hydroxide which confers to the solution a pH of about 11, was fed in a continuous PFR bench scale reactor able to operate at supercritical water conditions. The experiments were carried out at 550 °C and 250 bar by varying the feed flow rate from 10 mL/min to 60 mL/min in order to understand the effect of the residence time on the liquid and solid phases in terms of volume composition, liquid phase composition, carbon and global gasification efficiency. The main results showed that by using lignin after alkaline extraction, syngas with a higher heating value (HHV) greater than 40 MJ/kg without CO2, mainly composed by hydrogen and methane, was obtained. At the same time, in the liquid phase the presence of some compounds, such as glucose, syringaldehyde, formic acid, acetic acid and xylose, was revealed, and all these species are included in the main building block group for the green chemistry or for the development of bioprocess for high added value intermedia production.