Biomass Waste for Energy Production

Environmental problems associated with global energy supply systems and the increasing amount of global solid waste production are triggering a shift towards a greater reliance on biomass waste. Waste-to-energy systems have become important for industries and scientists because of the increasing interest in energy production from waste, due to improved efficiency and cost-effective solutions. The shift to biomass is also essential for industries to use their own waste to produce their own energy, which is in line with circular economy concepts. This Special Issue “Biomass Wastes for Energy Production” of Energies comprises ten (10) papers, including one review article, that represent the latest advances of waste-to-energy technologies and contribute to the rethinking of global energy supply systems. The Guest Editor also highlights other relevant topics that fall beyond the coverage of the published articles

Modelling higher heating value of different separated fractions from municipal and construction and demolition wastes

Higher heating value (HHV) is an important property of biomass and wastes used to evaluate their potential conversion to useful thermal or electric energy. Because the measurement of this property requires expensive resources and is somewhat time-consuming, many works focused their attention on the determination of mathematic models relating the HHV with the composition of lignocellulosic biomass or other fuel materials, such as their ultimate and proximate analysis. These models can supply appropriate estimates of HHV but only for analogous materials, so they should not be used to compare samples with marked differences in composition or physical and chemical properties. In this work, 9 different separated fractions of municipal and construction and demolition wastes (wood, paper/card, plastics, sewage sludge and mixtures among them) were used to deduce a mathematical expression relating HHV with their contents of carbon, hydrogen, oxygen, nitrogen, sulphur and ash. For this purpose, HHV's, proximate and ultimate analysis were experimentally obtained and the results used to create three different expressions applying linear regression methods. The best expression was selected and validated by comparing deviations among the calculated results and those retrieved from the literature and from experimental measurements regarding different wastes. It was concluded that the best expression was HHV (MJ/kg db) = 0.3845×C+0.8831×H- 29.1217×S-0.0630×O-1.0063×N+0.3888×ASH-0.2546 (with C, H, S, O, N and ASH in wt% db, considering atomic ratios O/C and H/C within 0.0O/C1.2 and 0.1H/C0.2), giving an average absolute error of 8.5 % and an average bias error of -1.6 %. However, appreciable deviations may be found when estimating the HHV of polyurethane, paper/card, mixtures of paper/plastic and sewage sludge and thus the application of the expression for these materials is questionable.info:eu-repo/semantics/publishedVersio

Pulsating Flow Effects on Hydrodynamics in a Desalination Membrane Filled with Spacers

A previously developed and validated two-dimensional computational fluid dynamics (CFD) model to study the hydrodynamics in a desalination membrane filled with spacers in zig-zag arrangements has been further developed to include the effects of a pulsating flow with the profile of a heartbeat. Numerical solutions were obtained with Fluent for pulsating laminar flows in channels filled with four different spacers and four lengths of cells. Hydrodynamics was investigated for unsteady state, using a characteristic function of a heartbeat, in order to study the influence of temporal variation in the hydrodynamic behavior. The results show the velocities distribution, streamlines, pressure drop and the wall shear stress on the impermeable wall of the membrane, for Reynolds numbers up to 100. The reduction in the distance between the filaments of the spacers, leads to the appearance of more active recirculation zones that can promote mass transfer and decreasing concentrations layers. On the other hand, this reduction increases the pressure drop and consequently the energy expended in the process. Further, the characteristic function of heartbeat demonstrates promising results, with regard to the energy consumption in the process and optimization of the recirculation zones

Advantages of Using a Block Unstructured Grid in a Casting Scenario

Numerical modeling of heat transfer during solidification has become widespread in the foundry industry. This is because it is possible to investigate the effects of adjustment to the casting variables on final casting quality, without having to do costly trial-and-error experiments. After selecting a suitable mathematical model, one has to choose an appropriate discretization method. If the grid is very fine, each type of method yields the same solution. However, some methods are more suitable to some classes of problems than others. The main objective of this paper is to demonstrate the advantages of using a block unstructured grid in combination with a generalized curvilinear formulation in a casting scenario and compare the performance of two discretization methods, finite differences (FD) and finite volume (FV). The validation of the numerical procedure is done by comparison with measurements which experimental set up is also described. A very good agreement of both numerical methods were verified with a slightly advantage for the finite volume method. Block unstructured grids works well with both discretization methods, allows obtain any physical feature in specific positions of the domain and is suitable for parallel computation; in combination with a generalized curvilinear formulation allows avoid geometric complexities and the development of more efficient algorithms.

Evolution of household availability of regional foods in Amazonas

OBJETIVO: Avaliar a evolução da disponibilidade domiciliar de alimentos regionais no Amazonas, sua distribuição segundo características sociodemográficas e potenciais diferenças em relação ao restante do Brasil. MÉTODOS: Foram analisados dados de aquisição de alimentos para consumo domiciliar das Pesquisas de Orçamentos Familiares (POFs) de 2002–2003, 2008–2009 e 2017–2018, que estudaram, respectivamente, 48.470, 55.970 e 57.920 domicílios no Brasil, dos quais 1,075, 1.344 e 1.833 estão no Amazonas. Os alimentos foram reunidos em três grupos: macaxeira e derivados, peixes de água doce, e frutos regionais. A quantidade de alimento regional adquirido, expressa em participação calórica relativa domiciliar, foi analisada para o Amazonas como um todo e segundo variáveis sociodemográficas (diferenças avaliadas pela sobreposição dos intervalos de confiança de 95%). RESULTADOS: A participação calórica domiciliar do total de alimentos regionais no Amazonas foi de 22,54% em 2002-2003, 18,18% em 2008-2009 e 6,49% em 2017-2018. No Brasil, estes percentuais foram bem menores no mesmo período: 3,67%, 3,34% e 1,82%, respectivamente. As mudanças no Amazonas ocorreram, principalmente, pela drástica redução do grupo de macaxeira e derivados (de 14,30% em 2002–2003 para 12,74% em 2008-2009 e 3,09% em 2017–2018) e pelo declínio gradativo da disponibilidade domiciliar de peixes de água doce (de 7,30% em 2002–2003 para 4,85% 2008–2009 e 2,90% em 2017–2018). Domicílios do meio rural e com menor renda per capita tiveram maior participação calórica do total de alimentos regionais, estratos que também tiveram as maiores reduções. CONCLUSÃO: Houve redução significativa da presença de alimentos regionais no Amazonas no período estudado, atingindo principalmente os domicílios da zona rural e com menor renda, cuja pessoa de referência da família era do sexo masculino, mais jovem e com menor escolaridade.OBJECTIVE: To evaluate the evolution of household availability of regional foods in the state of Amazonas, their distribution according to sociodemographic characteristics, and potential differences when compared to the remaining areas of Brazil. METHODS: Data on food acquisition for home consumption from the 2002-2003, 2008-2009, and 2017-2018 Pesquisa de Orçamentos Familiares (POFs – Consumer Expenditure Surveys) were analyzed, covering, respectively, 48,470, 55,970, and 57,920 households in Brazil, of which 1,075, 1,344, and 1,833 are in Amazonas. Foods were categorized into three groups: cassava and its derivatives, freshwater fish, and regional fruits. The study analyzed the amount of regional food purchased, expressed in relative household caloric share, for the entire area of Amazonas. Additionally, the data was stratified and analyzed according to sociodemographic variables, with differences assessed through the overlapping of 95% confidence intervals. FINDINGS: The household caloric share of the total regional foods in Amazonas was 22.54% in 2002-2003, 18.18% in 2008-2009, and 6.49% in 2017-2018. Across Brazil, those percentages were much lower in the same period: 3.67%, 3.34%, and 1.82%, respectively. Changes in Amazonas were primarily attributed to the steep drop in the cassava and derivatives group, which decreased from 14.30% in 2002-2003 to 12.74% in 2008-2009 and further declined to 3.09% in 2017-2018. Additionally, there was a gradual decline in household availability of freshwater fish, decreasing from 7.30% in 2002-2003 to 4.85% in 2008-2009 and reaching 2.90% in 2017-2018. Households in rural areas and with lower per capita income presented a higher proportion of calories from total regional foods; this particular stratum also experienced the most significant reductions in their consumption. CONCLUSION: During the study period, there was a significant decrease in the consumption of regional foods in Amazonas, particularly in lower income households in rural areas. Among them, the family reference person was typically a younger male with a lower educational background

Environmental impact and occupational risk in gasification plants processing residues of sewage sludge and refuse-derived fuel: a review

The authors acknowledge financial support provided by Fundação para a Ciência e Tecnologia from Ministério da Ciência, Tecnologia e Ensino Superior (grant no. SFRH/BD/111956/2015), cofinanced by Programa Operacional Potencial Humano and União Europeia-Fundo Social Europeu.Scope & Goals: This article reviews recent scientific reports on environmental impact, as well as occupational safety and health, of gasification plants using residues of sewage sludge and refuse-derived fuel. Methods: The survey, covering a 10-year time span, was made through a typical systematic review of the literature, retrieved from online databases of scientific publications and by using general search engines; cross-referencing of citations included in documents was also considered. Results: Two tables summarising 38 publications were created, indicating relevant studies on the selected topics and providing a short description on risks, goals and main findings of each study, followed by a general discussion. Conclusions: Overall, gas explosion and inhalation of toxic gases were the most common risks reported in published studies, being considered negligible if safety measures are adopted; however there are fewer studies focusing on occupational safety in gasification plants than those focused on environmental hazards. Release of heavy metals, tar production and toxic gases are the main environmental concerns. From the prevention viewpoint, this review shows that treatment and valorisation of harmful tars is key feature that must be improved in the future to enable a sustainable development of this technology at a commercial scale.publishersversionpublishe

Influence of the Biomass Gasification Processes on the Final Composition of Syngas

AbstractInterest in the technology of gasification has shown a number of ups and downs since its first appearance. It appears that interest in gasification research correlates closely with the relative cost and availability of liquid and gaseous fossil fuels. Gasification is a versatile thermo-chemical conversion process which produces a gas mixture of H2, CO and CH4 the proportions being determined by the use of air, oxygen or steam as oxidizer, with a concomitant range of heat values, low (4–6MJ/Nm3), medium (12–18MJ/Nm3) and high (40MJ/Nm3). A variety of biomass gasifiers have been developed. Differentiation is based on the means of supporting the biomass in the reactor vessel, the direction of flow of both the biomass and oxidant, and the way heat is supplied to the reactor. Gases formed by gasification are contaminated by some constituents such as particles, alkali metals, nitrogen components, tars, sulfurs and chlorides. The level of contamination varies, depending on the gasification process and the feedstock. Gas cleaning must be applied to prevent erosion, corrosion and environmental problems in downstream equipment. In this work, a global perspective about the producer gas final composition dependence, the so-called syngas, from the biomass, oxidizer, reactor type, temperature and pressure is given based on a literature benchmarking. This study shows that there are some discrepancies in the values given by various authors. This highlights the strong dependence of the syngas final composition from the biomass conditions, type of gasifier and pressure and temperature of the process. Thus, in order to make precise studies on the use of syngas it will be necessary to consider that its composition will be rather constant. The development of mathematical models for numerical simulation fully validated experimentally are strongly desirable and may be a very useful tool to determine the final composition of syngas by changes in initial conditions without laborious and expensive experimental tests