Making Carbon

Recycled

So what would you do if natural gas and oil are no longer available as sources of carbon at some point? “In theory, there are three alternative approaches,” said Dr. Ruth Bieringer, lead materials researcher at Freudenberg Sealing Technologies. “One involves the use of recyclates for the production of new plastics.” Recyclates are used materials that have been cleaned and crushed. “Carbon dioxide can also be obtained from biomass or carbon dioxide,” she said. Methods of carbon recycling are the furthest along – in the recycling of PET (polyethylene terephthalate), for example. Fibers for running shoes are salvaged from discarded plastic bottles. Production scrap from certain thermoplastics can be fed back into the production process. Freudenberg already does this, for example, with polyether ketone (PEEK). But in many cases, classic recycling – collecting, crushing, melting down – faces serious limitations, if only because plastics are not fully sorted when collected. In addition, long carbon molecules become shorter during their use, when exposed to ultraviolet radiation or during processing, for instance. In the case of elastomers, the carbon chains are interconnected with molecular bridges – a process that is not reversible. “We would have to use chemical reduction and recycle individual components, not the complete carbon compounds,” Bieringer said. In-depth research is now underway on what is called chemical recycling. The solution would be a crazy professor-style automated system. The old material would go in on top and separate molecular building blocks would come out at the bottom. But that would take some time to develop.

Grown

Biogenic plastics based on plant matter – and not on foodstuffs – could offer a sustainable way to provide a supply of carbon. Here, the problem is not the available volume: About 400 million tons of plastics are currently produced per year, while the global renewable quantity of biomass is more than a thousand times greater. Furthermore, the percentage of water is not included in the calculation. For example, wood is 20 to 30 percent lignin, a substance left as a residue when paper is produced. “Biochemical processes could help us produce high-quality basic materials,” Bieringer said, highlighting a field that is also heavily researched. The situation is similar with the cultivation of algae. It not only can be directly used as biomass. Organic compounds can even be excreted from it by modifying its metabolism.