*2.2. Torrefaction Process*

The torrefaction process was applied to barley straw through a mu ffle furnace. The experimental setup is presented in Figure 1. The mu ffle furnace temperature was in room temperature at zero torrefaction time. The heat increase curve was from 20 ◦C up to 300 ◦C. Each experiment had a different reaction time. The time was increased by 2.5 min from 15 min to 50 min (see Table 1).

**Figure 1.** Experimental setup of the torrefaction process: (**a**) Nuve Muffle Furnace (Internal dimensions: 210W × 300D × 110Hmm) equipped with electric heating and a nitrogen generator that uses molecular sieves and (**b**) barley straw in a ceramic crucible placed in the cold furnace.


**Table 1.** Ranking, time, severity factor and logarithm of severity factor for barley straw torrefaction design of experiments.

Therefore, barley straw was placed in a porcelain capsule and after the process was completed, it was removed from the muffle furnace and finally, it was placed in a dryer for 15 min. Then, the char weight in the capsule was measured. The higher heating value was measured experimentally using an adiabatic bomb calorimeter, which measures the enthalpy change between reagents and products.
