**2. Experimental**

This study focused on thermal treatment temperatures. Selected treatment temperatures were 220, 260, 300, 350, 450 and 550 ◦C. Selection of a wide range of temperatures was used to investigate both torrefaction and low temperature pyrolysis. The torrefaction temperatures of 220, 260, and 300 ◦C were selected to present light (200–235 ◦C), mild (235–275 ◦C), and severe (275–300 ◦C) torrefaction [15] and are considered temperatures reported in most studies [14,15]. The temperatures of pyrolysis were chosen based on reported studies of biochar fuel characteristics for direct combustion and co-firing with coal [10,12,19]. The pyrolysis temperature range is typically considered to be 350 to 650 ◦C [38]. After each of the thermal treatments, the samples were characterized and compared with untreated wood samples to evaluate property changes. The characterizations included biochemical composition/cell wall composition; physical (weight loss, color, dimensions/size, bulk density, and grindability) and chemical properties (proximate analysis and high heating value); and microstructual transformation.
