Abstract
The routine pruning and cutting of fruit trees provides a considerable amount of biowaste each year. This lignocellulosic biomass, mainly in the form of branches, trunks, rootstocks, and leaves, is a potential high-quality fuel, yet often is treated as waste. The results of a feasibility study on biochar production by pyrolysis of residues from orchard pruning were presented. Three types of biomass waste were selected as raw materials and were obtained from the most common fruit trees in Poland: apple (AP), pear (PR), and plum (PL) tree prunings. Two heating rates and three final pyrolysis temperatures were applied. For the slow (SP) and fast pyrolysis (FP) processes, the heating rates were 15 °C/min and 100 °C/min, respectively. The samples were heated from 25 °C up to 400, 500, and 600 °C. Chemical analyses of the raw materials were conducted, and the pyrolysis product yields were determined. A significant rise of higher heating value (HHV) was observed for the solid pyrolysis products, from approximately 23.45 MJ/kg for raw materials up to approximately 29.52 MJ/kg for pyrolysis products at 400 °C, and 30.53 MJ/kg for pyrolysis products at 600 °C. Higher carbon content was observed for materials obtained by fast pyrolysis conducted at higher temperatures.
Highlights
The increase in global energy consumption forces the search for alternative energy sources
The results obtained during this slow pyrolysis process showed that the degradation of the material was initiated above 110 ◦ C by the loss of water
Carbonization of tree pruning residues derived from orchards appears to be a convenient alternative approach to converting biowaste into a high-quality solid fuel with high higher heating value (HHV) and high carbon content
Summary
The increase in global energy consumption forces the search for alternative energy sources. The residual dry biomass from olive annual pruning is about 1.31 t/ha [10], while almond orchards provide 1.34 t/ha [11], and vineyards 4.2 t/ha [12]. Brand et al [22] showed that in comparison with pine wood residues, a higher amount of apple pruning is required for the generation of one unit of energy (MJ) with a simultaneous lower amount of ash. A literature review showed that studies on pyrolysis of orchard wastes were mainly concerned on olive trees [28,29,30,31] and vineyard pruning residues [32,33,34,35].
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