Final answer:
In the torrefaction process, biomass loses its moisture but maintains its structure, resulting in a higher energy content per unit mass.
Step-by-step explanation:
In the torrefaction process, biomass undergoes a treatment where it loses moisture but maintains its structure. This is a thermal process typically conducted at temperatures ranging from 200°C to 300°C in the absence of oxygen. During torrefaction, the biomass becomes more homogeneous and partly decomposes, giving off various types of volatiles. The remaining solid product has a higher energy content per unit mass. For the torrefaction process to be successful, it is important that there is a presence of less nonvolatile and more aromatic and highly branched hydrocarbon chain compounds. The key factor is the temperature, which ensures that these desired transformations take place.