Abstract
The current global energy crisis has generated growing interest in looking for alternatives to traditional fossil fuels, presenting lignocellulosic materials as a promising resource for sustainable energy production. In this paper, the calorific values and chemical composition of the trunks, branches, twigs and leaves of five timber species of the semi-arid land of Mexico (Helietta parvifolia (Gray) Benth., Ebenopsis ebano (Berl.) Barneby, Acacia berlandieri (Benth.), Havardia pallens (Benth.) Britton & Rose and Acacia wrightii (Benth.)) were determined according to international standards. The results highlighted the calorific value ranges of 17.56 to 18.61 MJ kg−1 in trunks, 17.15 to 18.45 MJ kg−1 in branches, 17.29 to 17.92 MJ kg−1 in twigs, and 17.35to 19.36 MJ kg−1 in leaves. The pH presented an acidic trend (3.95–5.64). The content of mineral elements varied in trunks (1.09%–2.29%), branches (0.86%–2.75%), twigs (4.26%–6.76%) and leaves (5.77%–11.79%), showing the higher proportion in Ca (57.03%–95.53%), followed by K (0.95%–19.21%) and Mg (0.88%–13.47%). The highest amount of extractives was obtained in the methanolic solvent (3.96%–17.03%). The lignin recorded values of 28.78%–35.84% for trunks, 17.14%–31.39% for branches and 20.61%–29.92% for twigs. Lignin showed a moderately strong correlation (r = 0.66) with calorific value, but the best mathematical model was registered with the calorific value depending on the pH and lignin (R2 = 58.86%).
Highlights
Wood is one of the main commercial product from the forest [1], and one of the energy sources most used before the industrial revolution [2]
Calorific values of trunks and branches representing the main parts used for energy production were in range from 17.15 to 18.61 MJ kg1 with the highest values for trunks of Helietta parvifolia (H. parvifolia): 18.61 MJ kg1 and Ebenopsis ebano (E. ebano): 18.40 MJ kg1
Looking to the values for the different biomass components of each species, H. parvifolia and E. ebano showed the highest differences with values of 17.29 MJ kg1 for twigs of H. parvifolia and 19.36 MJ kg1 for leaves of E. ebano
Summary
Wood is one of the main commercial product from the forest [1], and one of the energy sources most used before the industrial revolution [2]. Facing the current crisis in the global energy model, caused by the excessive use of fossil fuels that cause sometimes irreparable damages to the terrestrial biosphere and the environment [3], the interest in finding substitutes for fossil fuels grows daily, proposing alternatives for strengthening a transition to a more sustainable energy model In this approach, biofuels are the most immediate substitute, since its energy density (energy per unit mass) is similar to that of gasoline (only 20% less) [4]. Forests 2016, 7, 58 are forest, 8.8 million ha of forest with secondary vegetation, 13.1 million ha of rainforests, 21.2 million ha of rainforests with secondary vegetation and 57.6 million ha of arid vegetation In the latter, representing over 50% of the total area [6,7,8], approximately 6000 species of angiosperms, of which between 50%–60% are endemic, are recorded [6,9,10]. This rich and immense diversity of arid and semi-arid areas of Mexico have been, according to Rojas [11], important plant resources suppliers
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