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Carbon footprint of pyrolysis as part of the plastic and electricity mixes for Germany in based on fossil energy carriers. In the lower compared to the virgin poly-
ethylene (PE) production from fossil
second scenario, the energy is substi-
2030. Furthermore, data on the pyroly-
value chain sis technology has been obtained from tuted by electricity from hydropower resources, as indicated by the orange
a commercial manufacturer based on and the thermal energy is substituted by points for the total in the graph. The
his case study, part of a brochure are entirely removed and therefore study was to evaluate the environmen- 2018 data, whereas data for the steam thermal energy from renewable sources; process emissions are indicated by the
of The Renewable Carbon Initia- virgin quality is achieved. tal impacts of pyrolysis as part of the cracker has been used from BASF from this represents a scenario with high grey bar in the fi gure, which are roughly
Ttive (RCI), an interest group of value chain to produce an exemplary 2018. Steam cracking is a technique in shares of renewables in the energy mix, 40% higher compared to the virgin PE
more than 60 well-known companies In July 2020, BASF SE published chemical product with virgin-grade which a gaseous or liquid hydrocarbon e.g., in Scandinavian countries in the production, as can be seen in the grey
founded in September 2020, describes the results of a peer-reviewed LCA, quality and compare it against the pro- like naphtha is diluted with steam and mid-term future (defossilisation). bar on the right. The pyrolysis process
Global Warming Potential (GWP) conducted by Sphera Solutions GmbH duction of an equivalent product via a heated in the absence of oxygen in avoids the incineration of the mixed
impacts of a chemical recycling techno- on the evaluation of pyrolysis in three conventional virgin polymer route. order to obtain smaller hydrocarbons. Assumptions for this summary plastic waste feedstock, resulting in a
logy for mixed plastic waste (MPW). case studies. For simplifi cation purposes, this large differential credit, displayed by
The initiating company, BASF, com- The exemplary chemical product These data have been obtained from short summary only considers the the purple bar.
missioned a peer-reviewed Life Cycle  This summary provides an over- studies are LDPE granulates. The study commercial plants and have been used impact category of GWP and only case
Assessment (LCA) study, according to view of case study number 2 (pro- examines all processes from cradle to as is, which represents a conservative study 2 on the production of LDPE in Finally, the green bar represents the
ISO 14040 and 14044 standards. duct perspective). In this case study, gate, i.e. from feedstock provision up approach as the technologies can be virgin grade quality. green-house gas emissions related to the
mixed plastic waste (MPW) is con- to the factory gate. The environmen- further optimised. The virgin LDPE energy and electricity, which have to be
Although chemical recycling has verted into low-density polyethy- tal impacts are reported per 1 tonne of production is based on crude oil trans- Impact results additionally generated when the MPW is
been introduced to the industry decades lene (LDPE) of virgin polymer LDPE in virgin-grade quality produced formation to ethylene, and the data for The shortened LCA results are visu- not incinerated. The additional emissions
ago, interest in the technologies and its quality and compared with virgin, in 2030 in Germany. In LCA terms, this the production is based on GaBi data- alised in Figure 3. from the energy, which has to be substi-
possibilities has been renewed in the fossil-based production of LDPE. is referred to as functional unit (FU). base (Sphera, 2019). tuted by the German energy and electri-
past couple of years. Chemical recycling LDPE is a widely used plastic and The fi gure shows the GWP per city mix in 2030 (green bar), are substan-
encompasses many different techno- is best known for its usage in plas- MPW is used as a feedstock for The sensitivity of the results to- tonne LDPE in kg CO eq, as well as the tial. 49% of the process emissions in the
2
logies which can for example break down tic bags and fi lms. Its characteristics pyrolysis, which would otherwise be wards the use of the USE approach has contribution of the process emissions, production of chemically recycled LDPE
long-chain polymer molecules of plastic include low temperature fl exibility, burned in waste incineration facilities been investigated by considering two the differential credits and burden from originate from the pyrolysis step in which
waste back into monomers and then sub- toughness and corrosion resistance. generating energy whilst emitting CO . additional scenarios for the energy and the applied USE approach, and the total the main contributor is direct CO emis-
2
2
sequently be converted back into plastics. The MPW feedstock, obtained from In order to account for the multi-func- electricity emissions. First, it considers result when deducting credit from pro- sions. The cracking process is respon-
waste collection and sorting, can be tionality of this process, an approach that the energy from MPW incineration cess emissions and burden. The results sible for 21% of impact, whereas 13%
Pyrolysis describes a technology, (chemically) recycled, thereby dis- called “Upstream System Expansion is substituted by fossil energy carriers, demonstrate that the total greenhouse originate from waste collection, sorting
which can convert MPW into pyroly- placing the alternative waste treat- (USE)” is used (Together for Sustain- which represents a scenario in which gas emissions of LDPE derived from process and transportation, 10% from
sis oil through thermal decomposition ments like incineration. ability, 2022). In this approach, the the energy and electricity mix are still the pyrolysis process are signifi cantly polymerisation and 6% from purifi cation.
in an inert atmosphere. The process energy generated from the MPW incine-
requires additional sorting and purifi -  The other two case studies cover ration has to be substituted by another The sensitivity of the LCA results
cation steps to fi t the specifi cations of the evaluation of pyrolysis from a energy source and the emissions of concerning the emissions of the energy,
the cracker. The purifi ed pyrolysis oil is waste perspective as well as a pro- this energy source are attributed to the which have to be substituted is high, as
then cracked down and further refi ned duct perspective covering plastic pyrolysis processes (this is the upstream is displayed in Figure 4. Using the base-
for new plastics production. products with a lower quality level system expansion burden). On the other line scenario (Germany 2030) the total
than virgin-grade. hand, CO emissions from the MPW emissions are -447-kg CO eq. When the
2
2
One advantage of this pyrolysis and incineration are displaced and credited substituted energy is provided by fossil
subsequent chemical processes is that Goal and scope to the pyrolysis as well (this is the up- sources, the total emissions increase to
plastic additives and contaminations The aim of the peer-reviewed LCA stream system expansion credit). To 3,115-kg CO eq, higher than the 1,894-
2
calculate the displaced impacts, 30% of kg CO eq total emissions from virgin
2
the MPW is assumed to be incinerated PE. When the substituted energy is pro-
in a Municipal Solid Waste Incineration vided by defossilised energy sources
plant (MSWI), whereas the remaining the total pyrolysis emissions decrease
70% is assumed to be incinerated in a to -2,407 kg CO eq, which might rep-
2
Refuse Derived Fuel plant (RDF), after resent the situation e.g. in Scandinavian
waste collection and sorting. countries in the mid-term future. These
results show that the climate change

Fig. 1: Overview of the pyrolysis process As the study is based on forecast- Fig. 2: Simplifi ed production of chemically recycled plastics vs conventional plastic, case study 2 results of the pyrolysis system suffer from
(BASF 2020b) ing, it uses the anticipated future energy (BASF 2020b) use of fossil energy sources, whereas

180 Chemical Weekly January 9, 2024 Chemical Weekly January 9, 2024 181

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