Out of the given options, the answer is option 2, which is silver foil. Silver foil is not biodegradable because it is made up of metal, specifically silver, which does not break down naturally in the environment. Silver foil is commonly used for food preservation and wrapping purposes.

On the other hand, the other options are biodegradable materials.

Option 1, a woollen mat, is biodegradable because wool is a natural fiber derived from animals such as sheep. Over time, woollen materials will break down naturally in the environment.

Option 3, a leather bag, is also biodegradable. Leather is made from animal hides and will decompose over time. However, the process of decomposition may take longer compared to other biodegradable materials.

Option 4, a jute basket, is biodegradable as well. Jute is a natural fiber obtained from the jute plant, and it is considered to be an environmentally friendly and biodegradable material.

Therefore, the correct answer is option 2, as silver foil is not biodegradable.