Cellulose Tape is metaefficient because it is completely biodegradable. It is difficult to find, especially in the US. Almost all transparent tape sold here is made of acetate. One store, Green Earth Office does offer it.
Sellotape describes their eco-friendly tape making process:
The pulp is made using a process, which is elemental chlorine free and does not harm the environment. At the Sellotape factory, the hot melt coating technology we employ minimises the use of solvents. Any solvents that are used are processed through our Thermal Oxidiser and recycled with the resultant heat being used in our drying ovens.
More information: Sellotape