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Abstract The biomass conversion into more valuable fuels represents one of the most viable routes for the exploitation of this material. Hydrothermal liquefaction is currently considered one of the most efficient processes to convert wet biomass into a bio-crude, which however requires expensive upgrading treatments to be used as biofuel. The use of catalysts able to directly improve bio-crude yield and quality during the reaction is of fundamental importance to increase the overall process efficiency. Homogeneous alkaline catalysts are the most studied, but they are not recoverable at the end of the process and so cannot be reused. The use of heterogeneous catalysts allows to overcome this issue making the recovery and reuse possible, maintaining anyway high activity and selectivity in the bio-crude production. The aim of this review is to critically summarize the effect of heterogenous catalyst addition on the hydrothermal liquefaction of lignocellulosic biomass, looking specifically at the improvement in bio-crude yield and quality. On the basis of literature data about the effect of heterogeneous catalyst addition on bio-crude yield and quality in the hydrothermal liquefaction of lignocellulosic biomass, a common catalytic action was identified allowing to group the several catalysts into four classes (alkaline metal oxides, transition metals, lanthanides oxides and zeolites). The hydrodeoxygenation activity of the catalysts, their effect on bio-crude yield and quality and the operating conditions used are highlighted. The highest bio-crude yields are reported using transition metals and lanthanide oxides which are able to guarantee, at the same time, a high-quality bio-crude.

The cleaning of syngas is one of the most important challenges in the development of technologies based on gasification of biomass. Tar is an undesired byproduct because, once condensed, it can cause fouling and plugging and damage the downstream equipment. Thermochemical methods for tar destruction, which include catalytic cracking and thermal cracking, are intrinsically attractive because they are energetically efficient and no movable parts are required nor byproducts are produced. The main difficulty with these methods is the tendency for tar to polymerize at high temperatures. An alternative to tar removal is the complete combustion of the syngas in a porous burner directly as it leaves the particle capture system. In this context, the main aim of this study is to evaluate the destruction of the tar present in the syngas from biomass gasification by combustion in porous media. A gas mixture was used to emulate the syngas, which included toluene as a tar surrogate. Initially, CHEMKIN was used to asses...

Abstract Like ester type biodiesel fuel, green diesel is a next generation transportation fuel emerging due to the need for a renewable replacement of internal combustion engine fuel, which is also fully compatible with existing automotive powertrain systems. Besides other limitations, the main obstacle for wider application of such renewable fuels is their relatively high production cost, depending mainly on the raw material cost and the application of more efficient processing technology. Green diesel and ester type biodiesel can be produced from waste vegetable oil by catalytic hydrogenation, homogeneous alkali catalysed transesterification and supercritical non-catalytic transesterification. Techno-economic analysis and the sensitivity analysis reveal that economics of these production technologies strongly depend on the process unit capacity and the cost of feedstock. Green diesel production by catalytic hydroprocessing located in a petroleum refinery appears to be the most cost effective option for unit capacity close to and above 200,000 tonnes/year. Conventional ester biodiesel process and non-catalytic ester biodiesel process under supercritical conditions are less profitable at specified capacity. Unit capacities of the investigated processes which are below 100,000 tonnes/year are likely to result in negative net present values after 10 years of project lifetime.

Abstract In the last forty years in the “Vinca” Institute, as a result of the operation of two research reactors, named RA and RB, and as a result of the application of radionuclides in medicine, industry and agriculture, radioactive waste materials of different levels of specific activity were generated. As a temporary solution, it is proposed that radioactive waste materials be stored in two interim storages. Radwaste materials that were immobilized in the inactive matrices are to be placed into concrete containers, for further manipulation and disposal. The present paper reports the results on the preliminary removal of sludge from the bottom of the spent fuel storage pool in the RA reactor, mechanical filtration of the pool water and sludge conditioning and storage.

Questions of justice in the transition to a green economy have been raised by various social forces. Very few proposals, however, have been as focused and developed as the “just transition” strategy proposed by global labour unions. Yet, labour unions are remarkably absent from discussions of the transition towards a green economy. This is surprising as labour unions are arguably the largest organizations in the world fighting for basic rights and more just social relations. This paper tries to advance the potential contribution of labour unions in this arena by asking: what is the full scope of “just transition” today and how have labour unions developed and refined it over the years to render the move towards a green economy both environmentally and socially sustainable? The concept of just transition is hotly debated within labour unions and has different interpretations, and hence different strategies. The last section assesses these interpretations by means of a normative framework, which seeks to fuse political economy and political ecology. Empirically, we add to the growing literature on labour environmentalism, as well as transitions more generally. Analytically, our goal is to place the various approaches to a “just transition” within a heuristic framework of environmental justice that is explicit about power relations when demanding justice, two themes central to this special issue.

Introduction: Active modes of transport can be defined as means of travel and transport at reduced speed, which take up little space on public roads and do not emit air pollutants or noise, being seen as an economic, social, and environmental asset, and a real alternative to motorized vehicles. Given its characteristics, the environmental benefits retrieved from active modes of transport should not serve only as a justification for its promotion but as a decisive and active factor in the scope of its actual use, which translates into the provision of pleasant and less polluted routes. Thus, the main objective of this paper is the development of a model for planning and generating urban routes for active modes that have a less negative influence on active users (pedestrians and cyclists) regarding their exposure to air and noise pollution. Methods: Conventional route planners are mostly designed to find the shortest, fastest, or less expensive route. In this research, the model to assign the best route will be presented for pedestrians and cyclists from an environmental point of view, by defining the least polluted, less noisy, and most health-friendly path. Based on the production of noise and air pollution maps, the model proposes the contamination of the network routes, which are used to determine healthoriented routes. The model is carried out through the calculation of the noise and pollution exposure for the routes found, compared to the shortest route. Conclusion: It was possible to conclude that less polluted routes may imply a small increase in the length of routes, but a significant gain in terms of reduction in exposure to PM10 and noise for active modes. Thus, the use of health-friendly routes can be seen as a matter of public health and a way for promoting more sustainable mobility. Available online 12 June 2022 (undefined)

In order to achieve the Paris Agreement goals of keeping the temperature rise well below 2 °C or even 1.5 °C, all countries would need to make fair and ambitious contributions to reducing emissions. A vast majority of countries have adopted reduction targets by 2030 in their Nationally Determined Contributions (NDCs). There are many alternative ways to analyze the fairness of national mitigation contributions. This article uses a model framework based on six equity principles of effort-sharing, to allocate countries’ reduction targets under global emissions scenarios consistent with meeting the Paris climate goals. It further compares these allocations with the NDCs. The analysis shows that most countries need to adopt more ambitious reduction targets by 2030 to meet 2 °C, and even more for 1.5 °C. In the context of 2 °C, the NDCs of the United States of America and the European Union lack ambition with respect to the approaches that emphasize responsibility; China's NDC projection falls short of satisfying any approach in 2030. In the context of 1.5 °C, only India, by implementing its most ambitious efforts by 2030, could be in line with most equity principles. For most countries, the NDCs would use most of their allowed emissions space for the entire 21 st century by 2030, posing a major challenge to transform to a pathway consistent with their fair contributions in the long-term.

This study investigates the environmental improvements associated to the integration of a microalgae unit as a side-stream process within an existing municipal wastewater treatment facility in northern Italy. Microalgae are fed on the centrate from sludge dewatering, rich in nutrients, and on the CO2 in the flue-gas of the combined heat and power unit. The produced biomass is recirculated upflow the water line where it settles and undergoes anaerobic digestion generating extra biogas. A life cycle assessment was performed collecting primary data from an algal pilot-scale plant installed at the facility. Fifteen environmental indicators were evaluated. Compared to the baseline wastewater treatment, the new algal configuration allows an improvement for 7 out of 15 indicators mainly thanks to the electricity savings in the facility. Some recommendations are provided to improve the performance of the algal system in the scaling up.