Viscose and lyocell are both made from wood pulp from trees and plants such as birch, eucalyptus, bamboo, and more. Often, the growing process for these crops is eco-friendly. However, viscose is dissolved using a corrosive solvent (Sodium Hydroxide). So it can never be classified as organic.
Lyocell is a different story. Lyocell is made using an organic solvent that doesn’t create toxic waste. Plus, it doesn’t leave behind traces of harsh chemical residue. That means lyocell can be organic.