Page 37 - Plastics News February 2023

FEATURE

What Type of Recycling Technology Works the Best? It Depends

Every Plastic Product
More investments are going toward
recycling plastics using a variety of
methods, bringing reactions from lab-
oratory benchtops to industrial scale
facilities. Whether the process is for-
malized in charts like those drafted by
the NREL group or not, these deci-
sions are based on the prioritization
of performance, economic, and envi-
ronmental metrics. The same holds
for public policy.
This approach does not give one an-
swer. I mentioned that mechanical
recycling does well with respect to
REL scientists describe a frame- waste streams if they are recovered all the environmental metrics. But in
Nwork for comparing recycling and returned to production streams. a PET recycling scenario where land
technologies. Much of the momentum around re- use is the critical method, perhaps
cycling stems from this potential to enzymatic hydrolysis should be con-
An article published January 12th in
the ACS journal Sustainable Chemis- reduce the burden on waste manage- sidered (especially if the feedstock
try & Engineering quantifies and com- ment and simply reduce leakage by is contaminated with other plastics).
pares the merits of recycling technolo- reducing volume. But this is one en- Not only is everything dependent on
gies for major commercially produced vironmental impact of production (of the polymer and quality of the feed-
polymers. The strategy, developed by plastic or anything else). The NREL stream, but each technology is likely
a team at the National Renewable study also includes water use, land to mean something different for each
Energy Laboratory, illuminates differ- use, energy use, greenhouse gas emis- manufacturer, policymaker, or citizen
ences in the technical performance of sions, and toxicity. Each process has depending on their priorities.
produced material as well as environ- its strong points, but mechanical recy- Adaption to Future Conditions
mental and economic impacts. cling shines across the board when it
comes to environmental impact. In considering the suitability of tech-
The recycling of HDPE, LDPE, and PP nologies for long-term use, we might
by mechanical means and dissolution In some of the technical merits, me- think about how conditions are likely
were compared with the production chanical recycling lags other process- to change. Greenhouse gas emissions
of virgin resin. For recycling PET, gly- es. For example, it is much less able to data are based on the current US en-
colysis, methanolysis, and enzymatic deal with contaminated PET than any ergy mix, which is changing rapidly.
hydrolysis were also included. No- of the other evaluated technologies. Robustness to contamination is a must
tably, the researchers assessed only The end product also sells for rather today, but could be less so in a world
closed-loop recycling, and concluded less, though the authors point out that with improved sorting, a bottle bill or
that pyrolysis is currently too en- the lower startup costs compensate other enhancement to collection sys-
ergy intensive and too low-yield in a for the price difference. Technologies tems. The recycling processes them-
closed-loop implementation. are also scored for product material selves are likely to change as they are
quality (by melt flow ratio), material
The Multidimensionality of Recy- retention, circularity, and readiness refined, scale up, and are joined by
cling Technologies level (the maturity of the technology). new developments.
Materials are less likely to leak out of The One Recycling Process for

PLASTICS NEWS 39
February 2023