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 chemical oxygen demand due to compounds dissolved in the stillage is 28 800 mg of O 2 /L. Test runs were carried out at bench and pilot scales.
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 (NH 3 , 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.
The anaerobic digestion (AD) of organic fraction municipal solid wastes (OFMSW) is a well-known technology for the valorization of wastes with the production of biogas, the latter usually used in power plant. Nevertheless, more and more effort is necessary in order to produce energy and chemicals from renewables as a strategy for replacing fossil fuels and reducing carbon dioxide in the atmosphere. In particular, methanol is considered as a promising energetic vector of the future since it may be produced from renewables and it may be used as a reactant for fuels and chemical production. Currently, methanol is industrially produced via syngas conversion using natural gas as the main feedstock. Biomethane produced in AD unit may be used as an alternative to natural gas for production of syngas that may be used for methanol production. In this work, a techno-environmental assessment for methanol production from biogas is presented and discussed, with focusing on the effect of side-unit, e.g. biomass gasification, carbon dioxide capture and renewable hydrogen production, on the environmental impact. Results show that highest CO2 saving is calculated for the biomass-integrated plant, although more detailed investigations, e.g. cost analysis, need for a proper assessment.
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