The initial and final ash content, ash removal and biomass loss
percentage after treatment of the six biomass samples with water
and acidic solutions are presented in Fig. 2aec. The data presented
clearly indicate that, in accordance to what was observed in the
preliminary runs (see Section 3.2), washing biomass with acidic
solutions was more efficient in removing ash compared to washing
with pure water. For all six biomass samples, washing with water
managed to remove ash in a range of 17e43% depending on the
sample, whereas acidic washing led to ash removals up to 90%. It is
also evident that between the two acids studied, nitric acid was
much more effective than acetic acid.