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Nowadays, it is urgent to develop new energy production and utilisation routes to achieve sustainable development with low environmental impact. Gasification of biomass wastes followed by biomethane production may contribute to achieve these goals. The objective of this paper is to study hot cleaning and upgrading processes of gasification gas to allow it to be suitable for biomethane production. Gas produced by gasification of eucalyptus wastes at 750 ºC and 850 ºC was used to study the hot gas conditioning process. For this, two sequential fixed bed steps with different catalysts or sorbents and at different temperatures were tested. In Pathway A, a low cost natural mineral, limestone, was used in both steps at temperatures from 500 º to 700 ºC. In Pathway B, limestone was used in the first step and in the second one, a nickel-based catalyst was tested. The effect of temperature was also studied by using temperatures between 500 ºC and 700 ºC. Pathway B showed to be the best option, especially at the highest temperature tested, producing a syngas richer in H2 and CO2, with very low contents of tar and heavier gaseous hydrocarbons. Pathway B was also effective for great NH3 and H2S reductions, around 90 %, leading to final NH3 and H2S concentrations of around 158 and 21 mg/m3, respectively. Further reductions will be studied by testing new multi-functional and more specific catalysts in the next studies, accordingly with new biomethanation catalysts requirements. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) is an energy-efficient technology that converts biomass with high moisture content, such as lignocellulosic material and aquatic biomass, into bio-oil which can be used as a precursor in the production of renewable biofuels. The current state of technology is mostly at a laboratory scale with relatively low Technology Readiness Levels (TRL). Most HTL research takes place in batch reaction systems, but there is growing interest in scaling up the technology through the use of continuous units. The process is influenced by several factors and operational parameters, which affect the performance of the process in terms of production and bio-oil quality. HTL is highly dependent on the type of biomass used. The main advantages in relation to other thermochemical processes is the possibility of using wet biomass, avoiding the high cost of the drying process. In this work several types of biomasses were studied, different types of micro algae (i. e. Spirulina, Chlorella Vulgaris, algae grown in industrial effluents), and grass. Growing microalgae has a significant cost in the production process of liquid biofuels. So, it was also tested algae cultivated in industrial effluents which has advantages from an economic and environmental point of view. Also, the grass wastes, have high moisture content and so its adequate to be process in HTL. In all the tests, four different products were obtained: gases, aqueous and organic (biocrude) products and solids. All these fractions were characterized to suggest their most favourable application. The gases were mainly composed of Hydrogen, Oxygen, Carbon Monoxide, Carbon Dioxide and Hydrocarbons until C4. Bio oil composition was the parameter most affected by biomass type. So, when microalgae were used, it was observed higher content of nitrogenous compounds, like pyrroles, indoles, pyrazines and other nitrogen-containing compounds, probably formed from the protein fraction of the algae. In all the bio-oils it was also detected the presence of oxygenated compounds, such as ketones, esters, phenols, fatty acids, alcohols, that maybe were produced from the lipids and carbohydrates. Hydrocarbons, including alkanes, alkenes, alkynes and aromatics compounds were also present. The composition of the biomass used has a higher effect on the bio-oil composition, so it is important an extensive characterization of the feedstock in order to select the best raw material to be used in HTL process depending on the intended application. This paper analyses the effect of biomass composition in the HTL to assess its viability to be used to produce biofuels or valuable chemicals. [ABSTRACT FROM AUTHOR]

The use of hydrogen (H2) as an energy carrier may have an important role in the near future. Nowadays, H2 is mostly produced from fossil fuels, thus, it is urgent to prove the viability of alternative and sustainable processes to obtain H2. Gasification of renewable sources like biomass that are widely available, inexpensive and carbonneutral is considered a viable technical, economic and environmental alternative for H2 production. The first step of biohydrogen (bio-H2) production through biomass gasification is the production of syngas (gasification gas). Syngas cleaning and upgrading procedures are essential to remove undesirable compounds and to increase bio-H2 content. Steam reforming and water gas shift reactions are also crucial to increase bio-H2 content in syngas. Next, bio-H2 separation from other gaseous compounds is needed to finally obtain bio-H2 at the required purification level. Although some of the mentioned technologies are proven and available on the market for similar applications, some drawbacks and technological challenges for the overall process need to be overcome to improve the overall techno-economic feasibility. This paper aims to analyse and discuss different bio-H2 production routes from biomass gasification to c the most promising ones. [ABSTRACT FROM AUTHOR]

The work was focused on converting plastic mixtures of LDPE (low density polyethylene), PP (polypropylene), and PS (polystyrene) with incorporation of small amounts of organic matter and paper, via catalytic pyrolysis into valuable products. The small incorporation of these materials was due to its low presence in the MPW used in this study. The results were compared with those of thermal pyrolysis. Mixture composition was set to obtain olefins/aromatic ratio of approximately 1 for the success of the next alkylation step. As in thermal pyrolysis, this ratio was difficult to obtain, FCC catalyst was tested. No significant impact in product yields and composition was observed with the incorporation of small amounts of the mentioned materials and with the use of this type of catalysts. The solid seems to contain the incorporated materials in the initial plastic waste mixture. The use of FCC increased the gas and solid content of about 3.7 % and 27.1 %. The liquid-oil decreased 30.8 %. Regarding liquid-oil composition, the use of FCC increased the aromatic compounds. Catalyst increased the quality of the liquid-oils, however it was not observed a significant impact in other products. [ABSTRACT FROM AUTHOR]

Only around 30 % of the 27.1 million tonnes of plastic waste recovered annually in Europe is being recycled efficiently into new products. The most common way to recycle plastics nowadays is through mechanical recycling methods that involve sorting plastics by type, melting them and reprocessing into recycled products. Mechanical recycling requires clean, high-purity mono-material streams, that must be obtained by separation at source (by the citizen or industry) or by manual or automated sorting of mixed waste streams. However, this degree of separation is very difficult or even impossible due to composition or contamination of the plastic waste, such is the case for example of complex materials like composites, made of more than one material that in most cases cannot be separated, and of highly contaminated plastic residues (e.g. food packaging). In economic terms, plastic recycling is not always cost-efficient since many times recycling costs are not covered by the prices of the recycled plastics. As a result, approximately 70 % of European plastic waste is not recycled due to technical or economic reasons, so, they are sent to landfill or to incineration. One of the possible solutions to deal with this type of plastic wastes is the pyrolysis process which allows taking profit of plastics organic matter and tolerates a certain degree of contamination. Pyrolysis products have good quality. Gases have high calorific value and liquids have high energetic content and stability characteristics, including well-defined distillation point, stability of physical properties, low acidity, and high miscibility with conventional fuels. However, products obtained by plastic waste pyrolysis depend on the operational conditions and are strongly affected by the type of plastic waste used. The main purpose of this study is to validate the application of the pyrolysis process for treatment and transformation of plastic mix (essentially derived from MSW and from end-of-life composites) into mainly profitable liquids, together with gases and solid by using thermal (or catalytic) pyrolysis. The raw materials studied were waste streams from municipal solid waste (MSW), containing mainly plastic (i.e. PE, PP, PS, and small amounts of PET and PVC) separated from organic waste pool, as well as end-of-life composites (i.e. packages, electrical wastes, vehicles, etc.). After sorting of these waste materials, plastic fractions of different composition were processed in the pyrolysis reactor. The pyrolysis experiments were carried out in batch 5.5 L reactor using different mixtures, operational conditions and catalysts. All gaseous hydrocarbons produced were measured and collected for direct analysis by gas chromatography (GC), whilst liquid hydrocarbons were distilled and solids were extracted with hexane. Liquid fractions were analysed using a GC-MS (gas chromatography-mass spectrometry) to identify their main compounds, which were quantified by GC. The experimental results obtained showed that, for instance, the use of polystyrene favoured highly the formation of aromatic compounds, mainly toluene, ethylbenzene and xylene, while in presence of polyethylene the hydrocarbons produced are mainly paraffins. Also, the presence of PS, PET and PVC increases the solid content, decreasing the liquid yield. [ABSTRACT FROM AUTHOR]

The need to find alternative liquid fuels more environmental friendly and with a more secure supply, has led to the idea of studying the conversion of carbonaceous wastes, like plastics, used tyres and biomass into liquid products to be used as fuels or as raw materials for several industries. As coal liquefaction is a well-known process to produce liquid products, coal blended with used tyres and plastic wastes was co-liquefied. Coal impregnated with 1% wt. of molybdenum was used in co-liquefaction tests blended with 50% wt. of used tyres or with the main plastics present in municipal solid wastes: PE (polyethylene), PP (polypropylene), PS (polystyrene) and a mixture of these plastics. The results obtained showed that all wastes promoted coal liquefaction. However, liquids yield and quality improved with the presence of plastics, while more solids were obtained when used tyres were used. Coal blends with PS wastes led to the highest liquid yield (74% wt.) and conversion (88% wt.) The presence of PE favoured the formation of linear alkanes, while PS promoted the formation of more aromatic compounds, which is in agreement with these plastics initial molecular structure. Some co-liquefaction tests were done in presence of tetralin, a hydrogen donor solvent that promoted the formation of liquids. Tetralin allowed increasing liquids yields obtained with plastics to values higher than 90% wt., while in co-liquefaction of coal with used tyres led to liquids yields around 77% wt. [ABSTRACT FROM AUTHOR]

Lignin-rich residues are a side stream in advanced ethanol biorefineries and they are usually used for heat and power production. However, an alternative is the lignin valorisation by thermochemical and biochemical processes that might be economically more suitable. In this work lignin-rich residues were firstly thermochemical converted to syngas in a fluidised bed gasifier, using steam and oxygen as gasifying agents. The obtained results so far showed that the rise of steam/lignin-rich residues ratio favoured the release of H2 and CO2 and led to a decrease in CO and hydrocarbons content, as steam reforming reactions were favoured. On the other hand, the rise of the equivalent ratio clearly favoured partial oxidation reactions and thus the release of CO and CO2, while H2 and hydrocarbons contents were reduced, due to their partial combustion. The increase of temperature favoured the formation of H2, at the expenses of hydrocarbons and tar release, as both decreased. However, it is fundamental to control gasification temperature to prevent ash melting and consequent bed agglomeration, due to the high ash content in lignin-rich residues, generally with high content of silica and alkali metals. The results led to the selection of gasification conditions (800 °C, equivalent ratio of about 0.13 and steam/lignin ratio of around 0.4) that headed to the following gas ratio CO/CO2/H2=1:0.7:0.7, which was tested for further bacterial fermentation. Fermentation tests with Butyribacterium methylotrophicum showed that the above syngas composition strongly influenced the production levels of acetic and butyric acids. Marked differences in the CO, H2 and CO2 consumption rates were also observed and were correlated with cell growth and metabolites production. [ABSTRACT FROM AUTHOR]

As an innovation to conventional biomass pyrolysis to produce liquid biofuels, different types of biomass wastes were pre-treated by autohydrolysis, prior to pyrolysis. Eucalyptus forestry waste, corn cobs agricultural residue, and miscanthus (an energy crop) were autohydrolysed. Autohydrolysis led to valuable sugar-rich stream that may be used in fermentation and to solids rich in lignin that were pyrolysed. Pyrolysis of autohydrolysed eucalyptus led to an increase in liquids yields of 24% in relation to untreated eucalyptus, as autohydrolysis weakened initial macromolecular structure and thus helped chemical bonds breakdown during pyrolysis. However, similar pyrolysis liquid yields were obtained by autohydrolysed or untreated corn cobs and miscanthus, thus feedstock composition is an important issue. Nevertheless, the production of added value products by autohydrolysis may still justify this pre-treatment. Otherwise, more severe pre-treatments of these biomasses might improve co-pyrolysis as it happened with eucalyptus. As polyethylene (PE) is easier to pyrolyse than biomass and greatly favours the production of liquid hydrocarbons, autohydrolysed and untreated biomass was mixed with PE wastes to be used in co-pyrolysis. The rise of PE content in the blend clearly favoured the production of liquid products of pre-treated and untreated biomass. 75%wt. of PE in the blend led to liquid yields of 72%wt. for untreated eucalyptus and of 82%wt. for autohydrolysed eucalyptus. [ABSTRACT FROM AUTHOR]