What is the fine-grained topic of the following text: The recycling process of any secondary raw material should not be considered as a process chain, but as a closed raw material cycle: from collection and processing, contract sales to a recycling plant and the raw material extraction there, the value creation stages from the production of primary material to the end product and the final repatriation of the secondary raw material to the raw material cycle. Only return the topic.
Closed raw material cycle in recycling process