• Energy Research

The growing increase in world energy consumption favors the search for renewable energy sources. One of the existing options for the growth and sustainable development of such types of sources is through the use of biomass as an input. The employment of biomass as solid fuel is widely studied and is no longer a novelty nor presents any difficulty from the technical point of view. It presents, however, logistic obstacles, thus not allowing their direct dissemination in every organization that is willing to replace it as an energy source. Use of biomass can be rewarding due to the fact that it can bring significant economic gains attained due to the steadiness of the biomass price in Portugal. However, the price may rise as predicted in the coming years, although it will be a gradual rising. The main goal of this study was to analyze whether biomass in the case of the Portuguese textile industry can be a viable alternative that separates the possibility of sustainable growth from the lack of competitiveness due to high energy costs. The study showed that biomass can be a reliable, sustainable and permanent energy alternative to more traditional energy sources such as propane gas, naphtha and natural gas for the textile industry. At the same time, it can bring savings of 35% in energy costs related to steam generation. Also, with new technology systems related to the Internet of Things, a better on-time aware of needs, energy production and logistic chain information will be possible.

The occupation of a territory combines a set of variables which affect the development of the mode by which populations have been organized throughout history. How this occupation takes place demonstrates much of a territory’s past and shows how the populations managed to make the most out of the available resources. The region of Entre-Douro-e-Minho (Northern Portugal), similarly to what happens in other regions, such as Galicia (Northern Spain), Brittany (Northern France), or Ireland, presents a type of dispersed land use, with an alternation of urban, agriculture, and forest areas. On one hand, this proximity allows urban populations to come into contact with a rural environment. On the other hand, this proximity also causes a set of problems, namely those related to rural fires, which are now enhanced by climate change, and associated phenomena, such as heatwaves and the lack of precipitation. The present work analyzes the evolution of rural fires in 1975–2019, in the municipality of Guimarães (Northern Portugal), to understand how these events have been distributed over time and evolved in a climate change scenario. Based on the results and discussion presented, it can be concluded that there is an increasing trend in the occurrence of rural fires in the territory under study, and that this can also be associated to climate change, in the form of a gradual increment in temperature, particularly in the autumn months, and a decrease in rainfall. This situation is responsible for the increment of the risk caused by the proximity of the populations to forest and agricultural areas because rural fires can jeopardize the safety of people and goods.

Recent synergies have increased the use of forest biomass for energy purposes. In addition to high investment costs, low feed-in tariffs, and low operational efficiency, the real potential of forest biomass does not always correspond to the potential that is often claimed in studies. Instead of total forest biomass assessments, it is recommended that sustainable afforestation criteria should be introduced to obtain more reliable and environmentally sustainable scenarios. In this article, the most representative forest species in the Alto Minho region (northern Portugal) are identified, as well as the total forest area available. Based on cartography, forest inventory data, and allometric equations, the annually available usable residual forest biomass (RFB) and corresponding potential energy are estimated. Finally, to promote local forest biomass markets and most efficient thermal use of forest biomass is suggested the creation biomass logistic centres (BLCs) and second-generation biomass logistic centres (2GBLCs) are introduced as well.

One of society’s major current challenges is carbon dioxide emissions and their consequences. In this context, new technologies for carbon dioxide (CO2) capture have attracted much attention. One of these is carbon capture and utilization (CCU). This work focuses on the latest trends in a holistic approach to carbon dioxide capture and utilization. Absorption, adsorption, membranes, and chemical looping are considered for CO2 capture. Each CO2 capture technology is described, and its benefits and drawbacks are discussed. For the use of carbon dioxide, various possible applications of CCU are described, starting with the utilization of carbon dioxide in agriculture and proceeding to the conversion of CO2 into fuels (catalytic processes), chemicals (photocatalytic processes), polymers, and building supplies. For decades, carbon dioxide has been used in industrial processes, such as CO2-enhanced oil recovery, the food industry, organic compound production (such as urea), water treatment, and, therefore, the production of flame retardants and coolants. There also are several new CO2-utilization technologies at various stages of development and exploitation, such as electrochemical conversion to fuels, CO2-enhanced oil recovery, and supercritical CO2. At the end of this review, future opportunities are discussed regarding machine learning (ML) and life cycle assessment (LCA).

This paper aims to make a comparison between the logistics costs of buying Wood Pellets (WP) and Torrefied Biomass Pellets (TBP) produced in Portugal and exported to the major consumer markets of Northern Europe. The starting point was the determination of the value of a shipload of WP and TBP delivered to a North European port and loaded in Aveiro, the main Portuguese WP expeditor port. Torrefaction results in higher energy and bulk density pellets which contribute to increase the logistics costs associated with them. Several studies have shown that the loss of mass is greater than the loss of energy. These changes in bulk and energy densities are an advantage in terms of logistics. More tonnes per unit of volume and more energy per tonne will decrease the transportation cost per energy unit. This analysis determined the energy in gigajoules per tonne and all the comparisons were based on the cost per energy unit. This analysis was supported by data collected in the Argus Biomass Markets report.

The increasing levels of carbon dioxide (CO2) in the atmosphere have become a major environmental challenge due to their contribution to global warming. The primary drivers of the increase in atmospheric CO2 concentrations are the combustion of fossil fuels, deforestation, agricultural practices, or the production of cement, which play a significant role in the increase of CO2 concentration in the atmosphere. However, efforts are being made to mitigate the negative effects of CO2 emissions, including carbon capture and storage (CCS) technologies that aim to capture CO2 from industrial processes and store it in underground geological formations. Methane, another potent greenhouse gas, is another major contributor to climate change and is mainly produced by agricultural activities such as livestock farming and rice cultivation. To address this, sustainable agricultural practices, such as reducing meat consumption and adopting climate-smart farming techniques, are crucial. Ultimately, a sustainable future can be secured for the planet and future generations by implementing effective measures, such as the use of sustainable energy sources, improvements in energy efficiency, responsible land use practices, and reducing the emissions of both CO2 and methane.

The use of biomass as a renewable energy source is currently a reality, mainly due to the role it can play in replacing fossil energy sources. Within this possibility, coal substitution in the production of electric energy presents itself as a strong alternative with high potential, mostly due to the possibility of contributing to the decarbonization of energy production while, at the same time, contributing to the circularization of energy generation processes. This can be achieved through the use of biomass waste forms, which have undergone a process of improving their properties, such as torrefaction. However, for this to be viable, it is necessary that the biomass has a set of characteristics similar to those of coal, such that its use may occur in previously installed systems. In particular, with respect to grindability, which is associated with one of the core equipment technologies of coal-fired power plants—the coal mill. The objective of the present study is to determine the potential of certain residues with agroforestry origins as a replacement for coal in power generation by using empirical methods. Selected materials—namely, almond shells, kiwifruit pruning, vine pruning, olive pomace, pine woodchips, and eucalyptus woodchips—are characterized in this regard. The materials were characterized in the laboratory and submitted to a torrefaction process at 300 °C. Then, the Statistical Grindability Index and the Hardgrove Grindability Index were determined, using empirical methods derived from coal analysis. The results obtained indicate the good potential of the studied biomasses for use in large-scale torrefaction processes and as replacements for coal in the generation of electrical energy. However, further tests are still needed, particularly relating to the definition of the ideal parameters of the torrefaction process, in order to optimize the grindability of the materials.

Agroforestry waste stores a considerable amount of energy that can be used. Portugal has great potential to produce bioenergy. The waste generated during agricultural production and forestry operation processes can be used for energy generation, and it can be used either in the form in which it is collected, or it can be processed using thermochemical conversion technologies, such as torrefaction. This work aimed to characterize the properties of a set of residues from agroforestry activities, namely rice husk, almond husk, kiwi pruning, vine pruning, olive pomace, and pine woodchips. To characterize the different materials, both as-collected and after being subjected to a torrefaction process at 300 °C, thermogravimetric analyses were carried out to determine the moisture content, ash content, fixed carbon content, and the content of volatile substances; elementary analyses were performed to determine the levels of carbon, nitrogen, hydrogen, and oxygen, and the high and low heating values were determined. With these assumptions, it was observed that each form of residual biomass had different characteristics, which are important to know when adapting to conversion technology, and they also had different degrees of efficiency, that is, the amount of energy generated and potentially used when analyzing all factors.

The use of biomass as energy source becomes considered again as a possibility, after a period in which practically felt in disuse, especially in industrial environments. Nowadays it is again an important alternative, mainly due to the increasing prices of fossil fuels, especially oil and natural gas, as well as by the growing environmental and sustainability concerns, since the biomass fuel is considered neutral in terms of CO2 emissions. The use of biomass as solid fuel poses several logistic difficulties that do not allow their straightforward dissemination in all industrial units, which intend to change its fuel source. In this paper, a case study of integration of renewable energy sources provides results obtained based on an experimental setup using biomass technology, posing a major advantage for the Portuguese textile industry, in particular the dyeing textile industry, over the traditional use of fossil fuels.