Complex sentence: The fibre's extraction and cleaning are expensive, chiefly because several steps--involving scraping, pounding, heating, washing, or exposure to chemicals--are needed to separate the raw fibre from the adhesive gums or resins in which it is ensheathed.
Split into simpler sentences: The fibre's extraction and cleaning are expensive, chiefly because of the several steps--involving scraping, pounding, heating, washing, or exposure to chemicals. Some or all are needed to separate the raw fibre from the adhesive gums or resins in which it is ensheathed.