TECHNOLOGY
outputs as a fuel is not recognised as recycling. Major players in the development of pyrolysis- based technologies include Luxembourg-head- quartered Clariter, Enval, Recycling Technologies, Renew ELP and Plastic Energy in the UK, Fuenix Ecogy in the Netherlands, OMV in Austria, Quanta- fuel in Norway, Brightmark, Encina, Nexus Fuels and Alterra Energy in the US, GreenMantra Tech- nolgies in Canada, and Licella in Australia. Gasification thermal cracking differs from pyrolysis
in that the process takes place in the presence of a controlled but limited amount of oxygen. It can handle almost any organic material — including plastic waste and biomass — and can take on polymers containing oxygen and halogens. The end result is syngas that, depending on its composition and purity, can be used as a production feedstock. The gasification process involves fewer steps than
pyrolysis: pre-treatment of the waste (including water removal); gasification; and cleaning of the gas to remove tars and other contaminants. That final purification step is required to remove impurities such as ammonia, H2
S, alkali metals, NOx and tars.
Gasification is not a new technology. Texaco developed and licensed its TCP (Texaco Gasifica- tion Process) technology back in the 1980s to handle hazardous waste organics. It is a non-cata- lytic, partial oxidation process capable of convert- ing organics to syngas and chars. However, the TCP process does not produce feedstocks suitable for reintroduction into plastic-to-plastic or other value-added chemical synthesis chains. A number of companies are investigating
gasification processes to crack plastic waste to heavy oil and non-condensable gases and conden- sable gases. The non-condensable gases are used as process fuel while condensable gases and heavy oils can be gasified with oxygen and steam. These processes typically involve use of high temperature gasification at more than 900°C, which is energy intensive, followed by additional purification steps. Gasification thermal cracking technologies are under development by a number of companies, including Enerkem in the Netherlands, Eastman in the US, and Showa Denko and Sekisui/Sumitomo in Japan.
Chemical recycling is still a very young technol-
ogy. However, it seems clear from the work carried out to date that hopes that it will solve the chal- lenge of handling mixed waste streams may be misplaced. The reality is that most of the technolo- gies currently under development will need some level of homogeneity in waste feedstock. That means that, initially at least, chemical recycling is likely to draw on the waste sources and supply
Chemical Recycling – Global Insight 2022
infrastructure developed for mechanical recycling. Drawing on the same collection and sorting
infrastructure does not necessarily mean that chemical recycled material will compete directly with mechanical recycled material. Compared to mechanical recycling, all chemical recycling processes are more complex and are likely to be more costly. So, where high quality waste streams are available, mechanical recycled polymer is likely to win out simply on economics. Chemical recycling, on the other hand, begins to look a lot more attractive where waste streams are less homogenous than is preferred for mechanical recycling, or where volumes of recycled material exceed the capacity for reuse in new applications (either for reasons of regulation or for deterioration in material properties). There may be some competition for feedstocks, but even that is likely to be limited. In its most recent Chemical Recycling Global Status report, AMI Consulting says that while the potential exists for competition to develop between the two recycling technologies in some areas — it cites the example of PET bottles and trays — it is also quite conceivable that separate markets may emerge. PET waste with the lowest levels of contamination, for example, could be sought out by mechanical recyclers while PET waste streams with higher contamination levels may be processed by depoly- merisation, the report authors say. Looking at feedstocks for the thermal cracking
processes — either pyrolysis or gasification — that are expected to account for the majority of chemi- cal recycling in volume terms, the AMI consultants say the fact that mechanical recycling can only offer a “downcycling” solution for mixed plastics waste makes it a prime stream for the chemical route. The study authors conclude that the likelihood of feedstock competition “is minimal for the vast majority of chemical recycling.” n
9
Above: BASF’s Andreas Kicherer
holding a jar containing pyrolysis oil
IMAGE: BASF
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