Abstract
BackgroundThe need for energy sources with low greenhouse gas emissions and sustainable production encourages the search for alternative biomass sources. However, the use of biomass fuels faces the problem of storage, transport and lower energy densities. Low-density values can negatively affect energy density, leading to an increase in transportation and storage costs. Use of pellets as alternative biomass source is a way to reduce the volume of biomass by densification, which improves their energy quality. They are produced by diverse biomass resources and mainly from wood materials. In all cases, it is important to evaluate the fuel characteristics, to determine their suitability on the heating system and handling properties.MethodsThe present study determines and compares data from proximate analysis, calorific values, physical and mechanical properties of wood pellets produced from the common tropical species Acacia wrightii, Ebenopsis ebano and Havardia pallens. Data were obtained from pellets produced from each species chips collected from an experimental plantation and analyzed through ANOVA and Kruskal–Wallis test at 0.05 significance level.ResultsThe results of diameter, length and length/diameter ratio didn’t show statistical differences (p > 0.05) among species. Acacia wrightii showed the highest density (1.2 g/cm3). Values on weight retained and compression test showed statistical differences (p = 0.05) among species. Havardia pallens was more resistant to compression strength than A. wrightii and Ebenopsis ebano. Statistical differences (p < 0.01) were also observed for the volatile matter and calorific value. E. ebano has the lowest volatile matter (72%), highest calorific value (19.6 MJ/kg) as well as the fixed carbon (21%).DiscussionThe pellets of the species studied have a high energy density, which makes them suitable for both commercial and industrial heating applications.A pellet with low compression resistance tends to disintegrate easily, due to moisture adsorption. The percentages obtained for the resistance index were higher than 97.5%, showing that the pellets studied are high-quality biofuels. Proximate analysis values also indicate good combustion parameters. Pellets of Acacia wrightii and Ebenopsis ebano are the more favorable raw material sources for energy purposes because of their high density, calorific value, low ash content and they also met majority of the international quality parameters.
Highlights
The present society development provides increasing levels of comfort to people, inevitably leading to an increase in energy consumption in all its forms (Van Duren et al, 2015) that requires a constant and permanent supply (Song et al, 2015)
Four trees from each of the species Acacia wrightii, Ebenopsis ebano and Havardia pallens were cut from an experimental plantation established in Northeast Mexico (Ngangyo-Heya et al, 2016)
The density showed two statistical groups: (a) with pellets of Acacia wrightii, which were the denser pellets (1.18 g/cm3), and (b) constituted of pellets obtained from Ebenopsis ebano and Havardia pallens that were statistically similar, with values of 1.10 and 1.12 g/cm3, respectively
Summary
The present society development provides increasing levels of comfort to people, inevitably leading to an increase in energy consumption in all its forms (Van Duren et al, 2015) that requires a constant and permanent supply (Song et al, 2015). Use of pellets as alternative biomass source is a way to reduce the volume of biomass by densification, which improves their energy quality. They are produced by diverse biomass resources and mainly from wood materials. The present study determines and compares data from proximate analysis, calorific values, physical and mechanical properties of wood pellets produced from the common tropical species Acacia wrightii, Ebenopsis ebano and Havardia pallens. Values on weight retained and compression test showed statistical differences (p = 0.05) among species. The pellets of the species studied have a high energy density, which makes them suitable for both commercial and industrial heating applications.
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