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Abstract The need to generate thermal and electrical energy, global warming caused by increased emissions of greenhouse gases, rising fossil fuel prices and demand for energy independence, have created a new industry focused on energy production through the use of renewable sources. Among the different options, biomass is the third most important source for obtaining electricity, and is the main source for the production of thermal energy. However, problems related to the low density of the different types of biomass, and the difficulty of transportation and storage, have led to the need to find solid fuels with higher density and greater hardness, known as pellets and briquettes. This paper seeks to develop an analysis of the current situation of the production of pellets, mainly with mixed biomass types, and the possible uses they have, with the main emphasis on the review of different combustion processes.

Abstract The pellet market in Portugal is a developing market where the main producers of wood pellets try to convince the small-scale buyer that wood pellets are a good alternative as a fuel because energy from them is cost-effective in long-term use. For this work, data about production, production capacity and consumption in Portugal were collected. Consumption levels are low since the majority of sales are exports. The different points of pellet production in Portugal have been located, and a price analysis has been made. To obtain data on the production capacity of the plants and get referrals from the market, the database Bioraise has been used in order to complement the information raised through prospecting and inquiries. Although it is noted that the pellet industry in Portugal is a sector in the initial stage of its development, the potential for growth is high, since internal consumption is low compared to the level of exports to other countries in which the pellet industry is booming. We conclude that the pellet industry is an important alternative in the Portuguese energy market due to the competitive price of this fuel compared to traditional fuels.

Abstract There is a growing demand for alternative forms of energy that could firstly replace fossil fuels, with the environmental advantages resulting therefrom, but that could be as well economically more beneficial by allowing companies to obtain competitive advantages from the aforementioned alternative forms of energy. In this sense, the use of waste to produce thermal energy is presented as an alternative worthy of study. In this paper, an analysis is made of the use of waste from the textile industry, more precisely cotton waste, which is used as a renewable resource for the production of thermal energy. After the characterization of the waste, the energetic potential is determined comparatively to other fuels such as woodchips and wood pellets. A comparative economic assessment with other fuels is carried out. The obtained results show that the cotton briquettes have a heating value of 16.80 MJ/kg and a cost of 0.006 €/kWh when used as fuel. This predicts an annual reduction in fuel cost of 80, 75 and 70% when compared with fuel-oil, wood pellets and wood chips, respectively. Thus, the use of cotton waste could be a viable alternative, economically and environmentally, to produce thermal energy.

Short rotation woody coppice (SRWC) cultivations of species like poplar, eucalyptus, or willow are promising options for biomass production, insofar that high biomass productivities, averaging 12–14 Mg ha−1 year−1 are possible, with heating values varying from 16 to 19 MJ kg−1, along with environmental positive effects such as increases in soil fertility or carbon sequestration. SRWC cultivations can last by about 20 years or more, corresponding to 4 to 7 cycles coppice rotation periods of 2 to 5 years, and subjected to intensive management regimes with requirements of herbicides, fertilizers, or irrigation lower than food crops. SRWC cultivations can be installed in marginal lands and, due to positive effects on soil, contribute to upgrade of site quality, including posterior installation of food crops. Overall, these cultivations are considered carbon neutral, with reductions of greenhouse gases of 90% to 99%, comparatively with emissions from coal fired power stations. The biomass production of SRWC cultivations is dependent on factors such management regime, harvesting practices, weed competition, or plant density and rotation time. Biomass from SRWC cultivations along with biomass conversion units shows a decisive potential for contributing to boost economies of rural areas. In this context, this chapter intends to make an integrated evaluation of the cultivation techniques in the field, from the nursery to farm gate, with some focus on topics such as biomass production modeling or genotypic stability along with fuel aptitude of biofuels from SRWC, with a significant focus on information obtained by research carried out by the authors.

Abstract The energy efficiency and the development of environmentally correct policies are current topics, especially when applied to the industrial sector with the objective of increasing the competitiveness of the enterprises. Portuguese textile dyeing sector, being a major consumer sector of primary energy, needs to adopt measures to improve its competitiveness. Biomass appears to be a viable and preferred alternative energy source for the sector, while simultaneously develops an entire forest industry devoted to the supply of forest solid fuels. This work carries out a comprehensive PEST (political, economic, social and technological) analysis, which analyses Political, Economic, Social and Technological aspects of the replacement of the fossil fuels traditionally used in this sector by biomass, providing a framework of environmental factors that influence the strategic management of the companies. The main advantages are the reduction of external dependence on imported fuel due to the use of an endogenous renewable resource, the creation and preservation of jobs, the increased competitiveness of the sector by reducing energy costs, the use of national technology and the reduction of greenhouse gases emissions.

The objective of the present study is, firstly, to identify the types of transaction costs that can be found for a company from the biomass to energy sector. The chosen company has transaction costs in the context of an in-operation company, i.e., a business already in use. A review of the existing relationship between the company and its local biomass suppliers is also explored, being the key factor to evaluate due to its overall importance, as these suppliers ensure the raw material flow to maintain the operation of the production unit. It was found that it is possible to apply the same analysis and business monitoring methodologies to the biomass-to-energy sector, similar to what is already happening with other sectors of industrial activity. Thus, it was verified after the analysis that it is possible for the company to obtain better productivity yields, especially if the assumptions of the transaction cost theory are optimized. By acknowledging the beneficial effects on the environment by replacing fossil fuels with wood pellets, this study aims, in the context of a pellet producer, to analyze the transaction costs of the entire process of biomass transformation in pellets, from raw materials to processing. This study analyses the value chain of the company by applying transaction cost theory to determine if there is a viable application and to identify which are the transaction costs in the company. The results of this study agree with others carried out under the same theme, thereby supporting the viability of vertical integration and the sustainability of the pellet production industry.

Abstract Torrefaction is an option for improving biomass properties for fuel application. Biomass undergoes chemical changes reflected on the upgrading of its properties as a biofuel, such as higher calorific power, lower O/C and H/C ratios, lower higroscopicity or better grindability. Objectives of this experimental study were to analyze the effects of torrefaction, under standart conditions of 265 °C, and residence time of 15 min in a nitrogen atmosphere and during a total 1h45m heating period, on a set of sixteen woody biomasses provenient from poplar short rotation coppice (SRC) and other Portuguese roundwoods. Average mass loss was higher than 40%. The set of poplar clones and common broom provided torrefied products with higher quality than the set of roundwood forest species. The results on other parameters for proximate and ultimate analysis corroborate this global picture. Correlation analysis showed a higher degree of interconnectedness between LHV and proximate analysis results, for poplar clones and common broom, comparatively with roundwood biomasses.

Abstract Biomass as an energy source contributes to a decrease in the dependence on imported fossil fuels, while at the same time, adding value to the countries where biomass fuel sources thrive, in addition to providing a source of renewable energy. Knowledge of the behaviour of fuel is essential in order to design and operate equipment safely and efficiently. In particular, knowledge about mineral content is essential because the ashes play an important role in the dynamics of the generation system. Through knowledge of the chemical composition and physical properties of the ashes, it is possible to predict the tendency to form deposits in the boiler components, as well as their potential to cause corrosion, erosion and abrasion. The behaviour of the ashes in the system is highly dependent on fuel, particularly when it comes from industrial waste or energy crops. These fuels have a higher mineral content, particularly sodium (Na), potassium (K), phosphorous (P) and chloride (Cl). They also have higher ash content with a low melting point and high corrosion potential. This paper focuses on the characteristics of the ashes derived from the combustion of biomass, with particular attention paid to the chemical transformations at high temperatures, as well as its effect on the combustion equipment. Emphasis is placed on the potential problems that occur when biomass-burning technologies are used for energy crops, in order to avoid catastrophic failures. It concludes with recommendations for the management, control and prevention of problems associated with ash.

Abstract Developing an industrial liquid fuel based on charcoal and water was the target of the present work. The relevance of this study is justified by the high energy potential of charcoal, its renewable nature, the easiness of storage and transportation in the liquid form, and by all the associated economic and environmental advantages derived thereof. The ability of a commercially available charcoal to be dispersed in water was evaluated by analysing the rheological behaviour of the resulting charcoal water slurries (ChWS). The charcoal was ground in a conventional ball mill and dispersed in water with the aid of different surfactants. The effects of the most relevant factors influencing the rheological properties of the suspensions were evaluated, including: (i) type of surfactant and its added amount on the fuel viscosity (η) at a given solids fraction; (ii) the charcoal content, which should be as high as possible. The results enabled selecting the most efficient surfactant and its optimal amount required for minimising the fuel viscosity (η) and enhancing the stability of the suspensions. Stable ChWS containing 60 wt.% solids and 1 wt.% surfactant and exhibiting adequate flow properties were successfully obtained.