It's true carbon doesn't "biodegrade," but neither do the others. It's not true that carbon can't be recycled, though it's true enough at consumer level. At an industrial level, the EU requires companies to come up with a recycling plan for their products, and so there are methods where the polymer is baked off or dissolved out, and the carbon strands (somewhat compromised) are chopped and used again. Now some people are working on getting whole fibers out without damaging them. Here's a recent example.

https://www.compositesworld.com/blog...f-carbon-fiber

"Batch" vs "continuous" in this article is an important distinction. In a batch process a lot of the feed stock is put in a pool or mixer or something, and the throughput is very limited by the size of the batch and the time it takes to do the steps. A continuous process can do much more, usually with a much smaller facility, but it has to have enough feed stock and demand for its output to keep it running all the time in order to make financial sense. Basically it means the scale is getting bigger.