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 (R 2 = 58.86%).

No abstract

No abstract

In many areas of application, the influence of hydrothermal carbonization (HTC) on the composition of organic pollutants is still unexplored. In this study, sewage sludge (SS) was carbonized and the input as well as the hydrochar were examined for the organic pollutants: polychlorinated biphenyls (PCB), polychlorinated dibenzo-dioxins (PCDDs), and polychlorinated dibenzo-furans (PCDFs). The process temperatures of carbonization were 200 • C, 220 • C, and 240 • C and the holding time was 5 h for all tests. The total concentration of PCBs was relatively stable for all temperatures, whereas the toxicity equivalent (WHO-TEQ) at 200 • C and 220 • C increases compared to the input material. The strongest impact on toxicity was observed for PCDDs where concentrations were reduced for higher temperatures, whereas the toxicity increases by more than 16 times for temperatures of 240 • C. The concentrations and toxicity of PCDFs were reduced for all carbonization temperatures. In hydrochar from HTC at 240 • C, the limit values for the application of SS in German agriculture have been exceeded. The results indicate that the process conditions for HTC should be controlled also for SS with average contamination if the hydrochar is to be used as material, especially in agriculture.

No abstract