LIFE CYCLE ANALYSIS OF THREE POLYSTYRENE WASTE SCENARIOS - DIVA
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Life Cycle Analysis of three polystyrene waste scenarios Biodegradation by mealworms as an alternative to incineration or recycling of polystyrene waste? Laurens Post Bachelor Thesis Environmental Science 15 ECTS Spring semester 2020 Supervisor: Jenny Zimmerman Examiner: Erik Grönlund
2
List of abbreviations
EU = European Union
FTI = Förpacknings och Tidnings Insamlingen
GWP = Global Warming Potential
ISO = International Standard Organisation
LCA = Life Cycle Analysis
MIUN = Mid Sweden University
PS = Polystyrene
3
Abstract
In this research three waste scenario’s for polystyrene plastic are analysed and compared from an
environmental perspective. Incineration, recycling and biodegradation by mealworms (Tenebrio
Monitor Linnaeus) of polystyrene are to be compared through a gate to grave Life Cycle Analysis.
This LCA is conducted through the International Standard Organisation, 14040 Standard. The
biodegradation facility is non existing and based on assumption backed up by peer reviewed
literature. Incineration and recycling are based on facts and figures from national authorities and
supplemented and peer reviewed literature. All three processes are analysed using IPCC Global
Warming Potential (GWP) 2013 GWP 100a & 1.03 ReCipe 2016 Midpoint (H) 1.02 within SimaPro 9.
Results show that the biodegradation of polystyrene by mealworms is inferior to the two already
existing methods of recycling and incineration from an environmental perspective. The
environmental preference of recycling or incineration cannot be clearly defined. From an energy
perspective (GWP) recycling is highly preferred over incineration. From ReCiPe 2016 methods
incineration is highly favourable compared to most impact categories. However results are not
likely to represent realistic values valid today due to lack of (accurate) data within this LCA. It is
unlikely that without supplemented data results from this research can be used in any form.
Nevertheless this lack of information shows the need for further investigation on biodegradation
by mealworms.
Keywords: Polystyrene, Waste management, Recycling, Incineration, Biodegradation, Mealworms,
Life Cycle Analysis.
4
Table of content
List of abbreviations 3
Abstract 4
Introduction 7
Background 7
Method 10
ISO 14040 Standard 10
Delimitation 11
Scope 11
System boundaries 11
Functional Unit 11
Lifecycle of a mealworm 12
Data collection 12
Databases 12
Inventory analysis 13
Data analysis 13
Impact categories 14
Classification 14
IPCC GWP 2013 GWP 100a 1.03 14
ReCipe 2016 Midpoint (H) 1.02 14
LCA within IMRaD model 15
Results 16
Life cycle of three waste scenarios 16
Incineration 17
Recycling 18
Biodegradation by mealworms 19
Life cycle analysis 21
Global Warming Potential 21
Incineration of polystyrene 22
Recycling of polystyrene 23
Biodegradation of polystyrene by mealworms 24
Environmental impact three waste scenarios 25
Incineration of polystyrene 25
Recycling of polystyrene 26
Biodegradation of polystyrene by mealworms 27
Comparison of Environmental impact Polystyrene waste scenarios 28
Discussion 29
Method 29
Environmental Impact 30
Future perspective 31
Conclusion 32
5
References 33
Appendix 37
Appendix I 37
Appendix II 37
Appendix III 37
Appendix IV 38
Appendix V 38
6
Introduction
Background
In 2015 Yang et al. published a two part research paper investigation the biodegradation of
polystyrene (PS) by mealworms (Tenebrio Monitor Linnaeus). Mealworms are larvae from the
mealworm beetle. Commonly PS is seen as a non biodegradable plastic because of its molecular
weight and stable structure. (Gautam et al. 2007) Yang et al 2015 (I) found that mealworms fed with
a PS diet did not differ in mortality and growth rate from those fed with a normal diet of bran
over a period of one month. Second part of the study by Yang et al. 2015 (II) indicate the
mechanisms behind the biodegradability of mealworms. Inside the gut of the mealworms bacteria
play the essential role which makes it feasible to degrade PS. As a result Yangs papers more
research on biodegradation of PS by mealworms started to be appear. Yang et al. 2017 looked at
factors that effect biodegradation rate such as temperature and feed type. Interestingly this
research concluded that mealworms fed on PS and bran are able to complete their whole life-cycle.
This shows potential for further research in the biodegradation of PS by mealworms.
Creating a product like PS creates a waste stream contribution to the already existing problem of
plastic waste. Virgin plastic made for single use only is made 100% from fossil resources making it
unfavourable for a sustainable future. In 1950 1.5 million tonnes of plastic were produced world
wide whereas in 2015 322 million tonnes of plastic was produced. In the European Union 39% of
plastic waste ends up as energy recovery, 31% ends up in landfill and 30% is recycled. The biggest
attributor to this is plastic packaging, making up 40% of total waste from this sector. (European
Parliament 2018) One of these packaging plastics is PS. This thermoplastic polymer is used in the
food service and protective packaging industry. (Encyclopaedia Britannica n.d.) Commercially
know as styrofoam in USA or frigolit in Sweden.1 This product is allocated for around 6.5% of the
total market for plastic in Europe. (Plastic Europe 2018) Thus an annual production of 21 million
tonnes which has to managed for its waste. With an increasing waste of plastic, managing of this
product in the most sustainable way is of great importance.
Within Sweden (and most European countries) there are four different waste options, material
recycling, biodegradation, energy recovery and landfill, available. Energy recovery (incineration) is
the most likely option in Sweden with around 50% of the total waste being burnt. The percentage
for material recycling is estimated at 40% and for biological treatment around 10%. Landfill
accounts for less than 1% (Avfall Sverige 2018)
1 Polystyrene can be found under the Swedish name of ‘frigolit’. Frigolit would translate back as Expanded Polystyrene
(EPS) to English. However frigolit is also seen as, food packaging made by PS, which in English would be translated to
as EP . For that reason, PS in Sweden would be by using the term frigolit.
7
A mini review published in Waste Management & Research from 2017 looked at the challenges and
opportunities of biodegradable plastics. In this paper PS is categorised once more as non
biodegradable. (Rujnic-Sokele & Philipovic 2017) This literate review from 2017 does not provide
the actual picture present in 2020 research. Implementations of this process are furthermore
missing in society. Take for example Östersund, Sweden. In the guidelines provided by this
municipality there are two ways of sorting PS waste. Smaller products of PS are sorted into
‘Plastförpackningar’, plastic packaging. Which would go to recycling centres. Big plastic packaging
of PS are to be sorted in plastic to be burned, ‘Plast till förbränning’. (Sopsortingsguiden 2018) The
latter is located at the local recycling centres, not directly at the residential areas waste facilities.
(Östersund Kommun n.d.) According to Förpacknings och Tidnings Insamlingen (FTI) all PS should
be disposed of in the container for plastic as provided in residential buildings. (FTI 2020)
Furthermore Avfall Sverige stated in their report that ‘the recycling levels are high for paper and
glass, while material recycling of plastics, is lower.‘ (Avfall Sverige 2018) Directives here are
slightly contradicting and technical feasibility unclear which would mean PS are likely to end up
into two waste scenario streams, incineration or recycling. What currently is missing is an
environmental performance of PS waste scenarios, incinerating (for district heating) and recycling,
in the form of a life cycle analysis (LCA).
Scientific research focussing on mealworms are present, for example in the form of a LCA. This
type of study compares and analyses any implementation of mealworms within the scientific
world on an environmental base. For example, a laboratory study from the Netherlands did a LCA
where greenhouse gas production, energy use and land use of mealworm production was
quantified and compared to traditional sources of animal protein. Results from this assessment
show that traditional sources of protein, milk, chicken, pork or beef results in higher greenhouse
gas emissions and land use but similar amount of energy. (Oonicx & de Boer 2012) Another study
conducted a preliminary LCA focussing on the Global Warming potential (GWP) for the use of
mealworms as feed stock. (Joensuu & Silvenius 2017) What currently is missing in published
scientific writing is a LCA that looks at the implementation of mealworms to biodegrade
polystyrene.
A literature review conducted by Marten & Hicks in 2018 conclude that incineration of PS is the
most common scenario up to date but that recycling has potentially the lowest environmental
impact. The biodegradation of PS by mealworms has not been included in this study. It is however
unsure were to categorise biodegradation by mealworms on an environmental impact scale. This is
due to the lack of information present cause by limited research on the topic. Thus in combination
with the non existence of biodegradation on industrial scale it is expected that the recycling has the
lowest environmental impact compared to incineration and biodegradation by mealworms of a
polystyrene product.
8
In this research the goal is to analyse environmental performance of three different scenarios,
incinerating, recycling and biodegradation, for the waste management of PS. Ultimately through
scientific research it is to find out which scenario is most wanted for the end of life treatment from
an environmental perspective. Improving existing solutions, or finding and testing novel ideas for
our waste is in ever evolving science that eventually decreases pressure we as humanity put on
this planet. We have to ask ourselves what is the environmental impact of these three waste
scenarios, incineration, recycling and biodegradation by mealworms (Tenebrio Monitor Linnaeus) of
polystyrene products so that we can meet the need of many more generations to come.
9
Method
ISO 14040 Standard
This LCA worked within the framework of the International Standard Organisation (ISO). For this
LCA ISO 14040 and related versions are used which up to the presenting of this research is most up
to date. (ISO n.d.) Through Mid Sweden University (MIUN) a license to access this document was
retrieved. On the website of the ISO a licence and/or copy of this document can be purchased.
(ISO n.d.)
Within the standard, four phases of study have to be considered. At first a goal and scope must be
defined. In this part a system boundary and functional unit were defined and level of detail
explained. Your definition of the product on which all impacts are to be weighted.
Second part of an LCA is the life cycle inventory analysis phase. (LCI) Here all the data needed for
the inventory of the life cycle was to be explained and presented. Raw data was presented
separately as life cycle of the product.
Thirdly is the impact assessment phase (LCIA) which provided more information for a better
understanding of the results and its environmental significance. One could read this section to be a
combination of replacement of the results section of a traditional scientific paper, this will be the
approach in this proceedings.
Fourth and last part is the interpretation phase where conclusion and discussion are presented.
The direct link to traditional scientific papers can easily be made and thus is being proceeded so in
this writing.
10Delimitation
Scope
This LCA assessed the environmental impact from gate to grave, the entire life span of a waste
scenario without the raw production. Environmental impact was measured in 17 impact categories
of which one, global warming potential, was highlighted in the results section.
System boundaries
System boundary as you can see in figure 1 below only includes the waste scenario of polystyrene.
Production and usage of polystyrene were not taken into account since is did not affect waste
scenarios. Gate in this research meant the moment an individual decided to throw away a piece of
polystyrene literally standing looking at the alternative scenarios.
FIGURE 1: SYSTEM BOUNDARY
Functional Unit
The functional unit was one kilogram of residential polystyrene waste. Where this waste originates
from and how it looks was not accounted for. PS in whatever form available will be always
referred to as Polystyrene (PS) in this study. This accounts for expanded polystyrene (EPS) or
extruded polystyrene (XPS). A residential perspective was chosen in contrary to an industrial
scope.
11Lifecycle of a mealworm
Within this research mealworms within SimaPro mealworms are seen as a tool to use for the
biodegradation of polystyrene. For simplicity reasons no distinguish is made between the different
lifecycle of this worm within SimaPro but for the understanding of the overall process more
information is needed. Below basic information on the full life cycle of the darkling beetle is
presented.
Mealworm is the larvae of the darkling beetles, which come in around 20 000 different varieties. In
this scenario larvae of the tenebrious monitor Linnaeus is assumed. This beetle has a complete
metamorphosis which means it goes through four stages of life. First life stage is the egg. A female
beetle can lay approximately 500 eggs. Eggs will hatch into larvae after 1-2 weeks. Here they get
there name the yellow mealworm. Average lifespan of larvae stage is around 100 days. After this it
turn into a Pupa where it does have no mouth or anus and does not consume anything. Around 2
weeks of this stage the pupa will turn into a beetle in which it stay 1 to 2 months. (Encylopedia
Britannica, n.d.) (Mealwormscare 2020)
Data collection
Databases
Within this research three databases were constantly used during working with the software
SimaPro 9 to find all the relevant data:
• Ecoinvent 3.4 - allocation at point of substitution - unit
• European Life Cycle Database (ELCD) v3.2
• Methods (default in SimaPro)
To access these databases SimaPro was used primarily through accessing processes. Through
different categories a product/process/use or waste stream can easily be found. It was avoided to
used the search function to find new processes. When a search function was not found it was
implemented manually and added accordingly to the processes. These data bases were chosen
because of the available information. Ecoinvent 3.4 is has most processes/materials available
within the already implemented databases within the software (license) available. At some places
ecoinvent 3.4 was missing data essential for the processes within waste scenarios, here ELCD
database was used. ELCD
12Inventory analysis
Inventory analysis was the collection of data which in this research was presented as the life cycle
of three waste scenarios. All retrieved information was found through searching published data
accessible through databases and websites. Focus was on scientific peer reviewed literature data.
Using the search Primo search engine provided by MIUN and Google Scholar assessable through
MIUN with keywords like, ‘Recycling Sweden’, ’Polystyrene waste scenario’, ‘Biodegradation
Mealworm’, ‘Incineration Sweden’, ‘LCA mealworms’ ‘plastic waste Europe’ etc. For statistics of
Sweden, statistikmyndigheten SCB’s website and databases were used. Statistics about energy
were found by looking through the category energy within their statistics.
To retrieve information as close as possible to reality from literature research starting point of any
research was based on information from Sweden available in English. Information found through
English but accessible in Swedish (e.g. abstract writing in both language) were used. If information
was missing on insufficient search terms broadened to within neighbouring countries and if
needed Europe etc.
Data analysis
In this research SimaPro 9 was used. To access the software a login to MIUN virtual desktop was
used where a shared licence of SimaPro 9 could be utilised.
Basic structure of impact assessment within SimaPro allows 5 different steps. Characterisations,
Damage Assessment, Normalisation, Weighting and Addition. Last four steps are optional within
the ISO standards. (PRé 2019) In this research primary Characterisations, were used.
The use of this method can be seen as a guideline for the overall process of implementing the
analysis. However to present LCA results in traditional scientific papers (in this case student
bachelor thesis) which follows the structured of Introduction, Method, Results and Discussion
(IMRad) are not being defined within this Standard. (Sollaci & Pereira 2004)) In this research a
hybrid form between LCA standard and traditional IMRaD model based scientific work is
proposed. The standard as such can be found and retrieved easily however for readers
comprehensibility a very short introduction of the ISO 14044:2006 was provided.
Traditionally findings of method sections are presented as results. However inventory analysis is a
method from within LCA that cannot be presented as results nor method. Above is describe how
certain data was found then it cannot be presented within the same heading. It is thus chosen to
present finding of this method which contributes to finding results but are not aimed to be the
results in an untraditionally coined heading located between method and results.
13Impact categories
According to Goedkoop et al. 2013 ReCipe method for LCA is most integrative which makes it
possible for both single score product comparison and in-depth analyse within multiple impact
categories. Because of this and in combination with prior knowledge and availability within the
licence system ReCipe method was chosen. Below a list of standard impact categories to this
method is provided. Global warming potential was an additional impact category chosen. A
separate method was chosen, IPCC GWP 2013 GWP 100a 1.03 because of the 100 year scenario.
Classification
Substances that contribute to an impact category listed in table 1 are multiplied by a so called
characterisation factor within SimaPro. This is to show the relative contribution of the substance.
Characterisation number for Carbon dioxide (CO2) is 1 for impact category Climate change.
Methane in this case has a characterisation number of 25 thus 1 kg of methane would have a
similar impact as 25kg of CO2. (PRé 2019) hence the word equivalent behind all the unit presented
in table 1. A very comprehensive document describing more in-depth knowledge is provided by
Huijbregts et al. 2017.
IPCC GWP 2013 GWP 100a 1.03
Global Warming Potential (GWP) or potential climate change in this research was presented in
carbon dioxide equivalents (CO2eq) Chosen time horizon in this method is 100 years. Within this
method characterisation happens in relevance to carbon dioxide. One carbon dioxide equivalent
can potentially refer to 1 unit (kg in this case) of CO2, 25 methane (CH4) and 265 nitrous oxides
(NOx). (Myhre et al. 2013)
ReCipe 2016 Midpoint (H) 1.02
This is a method that calculates all substances used in the lifecycle and attributes them towards the
right impact category with corresponding units. Every process analysed in SimaPro will go
through the impact assessment methods and ReCipe 2016 Midpoint (H). It is chosen to select H as
standard method because hierarchies perspective (H) includes the time frame for most common
policy principles. (PRé 2019)
Part of an LCA is collecting data for an so called The software SimaPro in combination with the
methods used describe above produce graphs and raw data as results which were used to
represent findings of this method. Results are presented according to the two chosen methods,
IPCC and ReCipe describe above.
Global warming potential was presented in-combination of with in-depth analysis of each of the
three waste scenarios in a so called impact flow chart. The 17 other impact categories are analysed
by looking at the biggest contributes within each individual process in collaboration with a
comparison graph of the overall impact.
14LCA within IMRaD model
Emphasise of this study is on finding environmental impact of three waste scenarios using LCA
software. To achieve this data needs to be collected as described above. This so called pre-study
results can be found under the heading life cycle of three waste scenarios. This was not presented as
results because it does not give clarity on the environmental impact of waste scenarios, but simply
information needed for the method chosen. It was not chosen to be presented as method either
because it is representation of method described above. By using peer reviewed literature retrieved
through websites and databases finding can be presented in lifecycle of three waste scenarios that
gave clarity and openness to the process of standard LCA performance.
Impact Category Unit Note
Global Warming Kg CO2-eq Carbon dioxide
Stratospheric Ozone depletion Kg CFC11-eq Trichlorofluoromethane
Ionizing radiation Kg Co-60-eq Cobalt 60
Ozone formation (human) Kg NOx-eq Nitrogen oxides
Fine particle matter formation Kg PM2.5 Particle matter < 2.5 µm
Ozone formation (terrestrial) Kg NOx-eq Nitrogen oxides
Terrestrial acidification Kg SO2-eq Sulfor Dioxide
Freshwater eutrophication Kg P-eq Phosphorus
Marine eutrophication Kg N-eq Nitrogen
Human toxicity (carcinogenic) Kg 1,4-DCB 1,4- dichlorobenzene
Human toxicity Kg 1,4-DCB 1,4- dichlorobenzene
Terrestrial ecotoxicity Kg 1,4-DCB 1,4- dichlorobenzene
Marine ecotoxicity Kg 1,4-DCB 1,4- dichlorobenzene
Land use m2 crop-eq
Mineral resource scarcity Kg Cu-eq Cupper
Fossil reproduce scarcity Kg oil-eq
Water consumption m3
Table 1: Impact categories ReCipe 2016 Midpoint (H) 1.02
15Results
Life cycle of three waste scenarios
FIGURE 2: FLOWCHART OF THREE WASTE SCENARIOS (INCINERATION, RECYCLING, BIODEGRADATION) POLYSTYRENE
16For the duration of the whole project all the waste generated comes from Östersund, Jämtland,
Sweden. According to the local municipality there are two option for PS waste depending on the
size. Big plastic PS is ought to be brought to local recycling station where it can be put in a
container for plastic that will be incinerated. Smaller pieces of plastic are allowed to be put in the
container for plastic meant for recycling. (Östersund n.d.) (Sopsortingsguiden, 2018) Because of
this conflicting scenarios it is assumed that a person, disposing of waste around their houses, can
either put its waste to be burned or specified plastic container.
Incineration
As can be seen in figure 2 above incineration is assumed to be in Sundsvall. First scenario is that an
individual puts the polystyrene product in the bin that is named ‘waste for
incineration’ (brännbar’ in Swedish) All local waste (residential and industrial) gets together at
different locations around Östersund. (Sopsortingsguiden, 2018) No information about the specific
location where the waste would go was found. So in this research it will be assumed that all the
‘waste for incineration’ will be brought to Sundsvall by road and be used for municipal heating
and electricity generation. (Bergkvist n.d.) Through a personal visit with Sundsvall Energy in 2018
information was retrieved that confirms that this scenario is not unthinkable. In the Sundsvall
plant, Korsta, normally waste like; wood, paper, plastic, rubber and textiles is incinerated, thus
very likely that PS from a resident of Östersund could end up there. (Sundsvall energi 2019)
Traveling by road is to be assumed 200 km using google maps for the route Östersund - Sundsvall.
A lorry over 32 tonnes with Euro 4 emissions is assumed to be responsible for this part of the
journey.
Incineration in Europa and Sweden differ slightly. On European level in 2018 around 28% waste
was incinerated while in Sweden this number for the same year was around 50%. (Eurostat 2020)
(AvfallSverige 2018) This results that in Sweden more waste in incinerated thus it is assumed that
waste mixed is different to that in average European incineration facility. Within SimaPro 2 end of
life waste scenarios are used. For the incineration of PS; ‘Waste incineration of plastics (PE, PP, PS,
PB), EU-27’ [ELCD database] is used. This has to be seen as main waste type since it is the only one
specified for the incineration of plastics and thus must be used in every incineration scenario. This
data bases uses the average European waste mixture. For incineration within Sweden ‘Municipal
sold waste (waste scenario {SE}|treatment of municipal solid waste, incineration|APOS, U’ [EcoInvent
database] with waste type allocated to PS is used. Because of this disparity it is assumed in this
research that incineration in Sweden contains 10% of municipal waste incineration from Sweden
and 90% incineration PS Incineration. Incineration of PS is 100% allocated to the incineration in
Germany because German incineration numbers are on average with European Union. (Eurostat
2020)
17Recycling
As can be seen in figure 2 recycling of plastic leads to different waste streams. Second scenario is
that the residential PS waste is placed in the bin that is named ‘plastic waste’. (‘Plastförpackningar’
in Swedish.) (Sopsortingsguiden, 2018) According to Anderson et al. 2015 the market for recyclable
plastic in Sweden is mainly dominated by the sorting plant Swerec. The same source states that
currently many sorting facilities are emerging, however since 2014 not another guideline like
Andersen et al. 2015 has not been published. So assumed is that Swerec handles the plastic for
Östersund. Swerec biggest plastic sorting factilty is located in near Värnemo thus 800km transport
by Lorry Euro 4 on the road has been assumed. (Swerec AB 2017)
A paper sorting factory is the best available scenarios and thus used; ‘Waste paper sorting facility
{RER}|construction|APOS, U’ In a study national experts in the field state that between 10-40% of
incoming to be sorted plastic does not fit and go straight to incineration. Because of this we must
assumer 25%. Side note; the same people suggest that this number is sometimes unto 90% when
mixed with industrial waste for example. (Avfall Sverige 2017) So once the PS arrives on the
sorting facility 25% is assumed to be lost before sorting and thus being incinerated in Sweden.
Local transport to incineration plant is assumed to be 50 km.
Now that the plastic has been sorted is has to be recycled. However in a study by cooperation of
nordic countries it is stated that polymers like LDPE, HDPE, PP and PET are specifically sorted
out. Other polymers, of which PS, are not sorted out and not being subject to recycling in Sweden.
Some of the plastic in Sweden, of which this unsorted part, is currently being sold to Germany.
(Andersen et al 2015 p. 48) (Frane 2014, p. 85)
Thus from Värnemo a 700 km transport by road is assumed to Germany, near Berlin. Here the
plastic is being sorted for the second time using the same facility within SimaPro. Within Sweden
42.17% of all the plastic was recycled in 2018. This is below the European level. The new aim of the
European commission is to have a recycling rate of 55% on plastic packaging. (European Council
2018) The definition of recycling given by FTI: ’The statistics show the amount of material recycled
decided by the amount of packaging and magazines placed on the market by producers affiliated
with FTI’ (FTI 2018) Because of the uncertainty of the plastic recycling definition and rate at
different locations the aim for 2030 of 55% recycling is used. As can be seen in figure 2, 55% PS
waste will be recycled using a process available in EcoInvent Database called ‘PS (waste treatment)
{GLO|} recycling of PS| APOS, U’. This process simply replaced the cost of production of new
polystyrene by adding a factory and energy. The left over PS (20%) will be incinerated in Germany.
18Biodegradation by mealworms
In figure 2 the assumptions made for the life cycle analysis of biodegradation of polystyrene waste
by mealworms are presented. The biodegradation facility is fictional and does not exist. For the
design of such a facility 2 assumption were made. All data must come from processes within
SimaPro and this must be sufficient for the biodegradation of polystyrene of all the inhabitants of
Jämtland, Sweden which is assumed to be 130 000.
Step 1 was similar to the other two scenarios; waste is being sorted by the resident and put in the
according bin, this case a special collecting bin for PS only.
Residential Plastic waste is 217400 tonnes k, of which 6.5% consists of PS divided by the
inhabitants of Sweden 10 000000 accumulates to 1.41 kg Polystyrene waste per year. (SCB 2020)
(PlasticsEurope 2018). Jämtland is estimated to have around 130 000 inhabitants thus meaning the
facility must have a capacity to ‘treat’ 183 703 kg Polystyrene. Biodegradation rate of worms are
dependent on many factors of which feed and temperature are very significant. However it is
assumed that one mealworms can eat on average 160.97 mg/year. Mealworms tested were put in a
container were they had 3.96 cm3 space per worm. (Yang et al. 2017) Thus it can be assumed that a
rough 1 billion mealworms are needed for the biodegradation of mealworms for the inhabitants of
Jämtland. The replicate growing condition from Yang et al. thus a 4120 m3 climate control space is
needed. Here it is wished to be between 20-25 degrees and a humidity of around 80-90% (Yang et
al. 2017)
Within SimaPro a building called, ‘building, hall, wood construction {RoW}|building construction, hall,
wood construction|APOS, U’ has been chosen. The dimension of this fictional building are 50*30*7
meters. Total volume of the building easily fits the space needed for the worms plus potential
office, storage and miscellaneous since the worms can easily be stacked inside boxes for example.
Inside the building worms need to grow in a so called climate room. An industrial climate control
system has been chosen to run for the entire operation. Running cost of such a machine is
estimated to be 0.78 kW (Munters Europe AB 2015) To sort worms, full grown beetles, and frass a
sorting machine is needed. It is to be assumed to be a big shaking device that through several sizes
filter sort out the different entities. Such an industrial machine (1.7 kW) is to be expected to run for
8 hours a day. (Martin Engineering USA n.d.)
Heating of the building is based on an assumption of a report published in 2014 by
‘Boverket’ (Swedish National Board of Housing, Building and Planning.) In part of this report the
average energy costs for housing in three different climate zones is calculated. Number for
Östersund, climate zone 1 is 80 kwh/m2. (Boverket 2015) Another approach was attempted to
come up with heating costs for a fictive building. Through Swedish Energy Agency
(EnergiMyndigheten) annual report of 2018 it could be concluded that average heating for a type
building like factory was 100 kWh/m2. (Swedish Energy Agency 2018) Because of those effects it
can be assumed that the energy use for biodegrading facility in Jämtland is 90 kWh/m2.
19The addition of feed to the mealworms is essential. As much as Yang et al. 2015 claimed that
mealworms are capable of surviving solely on PS reproduction is effected. Yang et al. 2017
suggested that feed is added to the PS to let the worms reproduce. (go through all parts of its life
cycle) In this research it is chosen to add wheat bran as a feed because it only enhances the
consumption rate on polystyrene of the mealworms. (Yang et al. 2017) Bran was not available
within the chosen databases. Traditionally bran is 13-17% of the total weight of the grain. (Onipe et
al. 2015) In this research it is assumed that 10% of the total costs for the production of wheat can be
allocated for bran production.
From such a biodegradation facility three major waste streams can be distinguished. At first
because worms respirate while eating PS 15% of the FU can be located to the raw production of
CO2. (Yang et al. 2015) Furthermore it is assumed that 40% of the FU will be turned into Biomass
and 45% will end up as frass. Frass has to be incinerated because in all cases of worm breeding,
around 35% of the frass contained PS. (Yang et al. 2017) Frass will be incinerated in Sundsvall.
Biomass will end up as chicken feed replacement. There is not one definition of chicken feed thus it
is assumed that protein feed based on wheat grain will be the replaced feed for chicken.
20Life cycle analysis
Global Warming Potential
FIGURE 3: THE RELATIVE DIFFERENCE IN GWP BETWEEN THE THREE SCENARIOS OF WASTE TREATMENT FOR
PS. UNIT FOR GWP IS CALCULATED IN CARBON-DIOXIDE EQUIVALENT (CO2EQ) BUT IN THIS GRAPH
PRESENTED AS PERCENTAGE OF THAT.
Figure 3 showed that biodegradation by worms had the highest relative impact of the three waste
scenarios with a positive global warming potential of 9%. Incineration of polystyrene had a
negative global warming potential, minus 26%. Recycling of PS had the lowest global warming
potential of all three and thus taken as relative reference point (minus 100%).
21Incineration of polystyrene
FIGURE 4: IMPACT FLOWCHART OF GWP OF THE
POLYSTYRENE INCINERATION PROCESS AS WASTE
TREATMENT GIVEN IN CO2EQ
Incineration has the most simplistic life cycle set up of all the three, as you can see in figure 2.
Figure 4 shows a negative global warming impact of minus 0.427 kg CO2eq per functional unit.
Positive GWP is caused by transport and incineration of municipal solid waste in Sweden.
Transport of 200 km from Östersund to Sundsvall in Sweden by Euro 4 lorry has less than 5%
influence of the total impact. Incineration of PS in Sweden is the biggest positive GWP factor in
this process, 0.316 kg CO2eq per FU.
Negative GWP is solely caused by incineration of plastic. Energy production on municipal solid
waste replaces the traditional cost of energy production. The burning of plastics has a negative
effect on GWP creating a net surplus of energy caused by the replacement cost of traditional
energy production in Europe, resulting in a GWP of minus 0.76 kg CO2eq per FU.
However with the chosen parameters the cost of incineration in Sweden and traveling impact are
compensated by the generation of energy of incineration of Polystyrene and thus give a negative
GWP.
22Recycling of polystyrene
FIGURE 5: IMPACT FLOWCHART GWP RECYCLING OF 1KG OF
POLYSTYRENE AS WASTE TREATMENT GIVEN IN CO2EQ
Figure 5 shows a positive GWP for recycling that is mainly caused by transport and the waste
facility. Transport contributes to 0.116kg CO2eq in this scenario. This is due to the transport from
Östersund to Germany by road, 1340 km. Impact due to transport is round 5%. This seems similar
to that of incineration but the actual number is 10 fold the total. The sorting of the plastic in two
places (Sweden and Germany) has almost double the impact compared to transport, 0.219 kg
CO2eq.
Negative GWP is caused by the actual recycling of PS, the replacement costs for the production of
raw polystyrene that adds to minus 1.89 kg CO2eq. In combination with incineration of processes
lost this adds up to minus 2.17 CO2eq.
Thus adding energy in the form of transport, facilities and electricity (e.g. inside the recycling
process and sorting facility) creates a negative GWP of 1.84 CO2eq for 55% recycling rate of PS.
23Biodegradation of polystyrene by mealworms
FIGURE 6: IMPACT FLOWCHART GWP BIODEGRADATION BY MEALWORMS OF 1 KG
POLYSTYRENE AS WASTE TREATMENT GIVEN IN CO2EQ
Figure 6 shows that a positive GWP in this process is caused by CO2 production of respiration of
worms, actual facility and its costs where the worms degrade and transport. The highest positive
contribution is the addition of bran to the system. Impact of the production of wheat grain has the
highest effect in this process, 0.176 CO2eq GWP which is only produced by 0.045kg of wheat. This
shows relative high importance and costs of wheat production. Transport (100 km) influence is 5%
of that total impact with an actual impact of 0.009 kg CO2eq. Creating and running a location for
the mealworms has an impact of 0.0464 kg CO2eq per FU which is mainly due to the electricity
usage in the process. The costs for the facility is around 20% of the plastic sorting facility including
relative higher electricity usage. Electricity usage is due to the fact that a climate room is needed to
control temperature and humidity. Manufacturing of the facility with a life expectancy of 50 years
and construction material wood has an impact less than 1%. Due to respiration of the worms, 15%
of input is being polluted as CO2eq in this assessment.
Highest negative contribution is the production of worms which replaces the production cost of
chicken feed elsewhere, minus 0.146 kg CO2eq. The production of worms almost account for a
balance in wheat production (net production being 0.045kg) 40% of the input is accounted for as
frass which has to be incinerated since the presence of PS in fractions. Here the incineration process
is the same as accounted for in scenarios incineration and recycling resulting in an overall negative
GWP for frass, 0.0595 CO2eq.
The introduction of the biodegradation facility, worm feed, electricity usage and transport
accumulates to an overall positive GWP for de biodegradation of 1 kg of PS by mealworms mainly
caused by the environmental costs of wheat production in Germany.
24Environmental impact three waste scenarios
Incineration of polystyrene
FIGURE 7: RECIPE 2016 MIDPOINT (H) INCINERATION OF 1 KG POLYSTYRENE WASTE ON 17 IMPACT CATEGORIES
Figure 7 shows that most of the impact is originated from the actual incineration of the
polystyrene. Transport and incineration share significant impact on categories, ozone formation,
freshwater eutrophication, terrestrial ecotoxicity. Land use impact is only related to transport of the
waste. Water consumption is the only category that has a negative impact which is solely due to
incineration process of polystyrene.
25Recycling of polystyrene
FIGURE 8: RECIPE 2016 MIDPOINT (H) RECYCLING OF 1 KG POLYSTYRENE WASTE (BLUE IS RECYCLING) ON 17
IMPACT CATEGORIES
Figure 8 shows that recycling process of the actual plastic and the facility where plastic is sorted
show most significant impact overall. Sorting facility shows only positive impact namely on,
ecotoxicity (terrestrial, freshwater, human and marine), land use and mineral resource scarcity for
which it is solely responsible in this analysis. Recycling of PS has a positive impact on stratospheric
ozone depletion, ionising radiation, fine particle matter, terrestrial acidification and eutrophication.
On ozone formation, human toxicity, fossil resource scarcity and water consumption recycling of
PS has a negative impact. Recycling of PS involves a recycling part and incineration thus below a
further analysis is given. Transport does not have a significant impact on most categories except
terrestrial ecotoxicity and land use. Impact from terrestrial ecotoxicity can directly be related to
transport and its brake wear emissions. (Appendix I) Impact from other freshwater and marine
ecotoxicity is related to the chose of building which involves sulfidid tailing in the process which is
directly related to the construction of the specific building used. (Appendix II & III)
FIGURE 9: RECIPE MIDPOINT (H) ANALYSIS OF RECYCLING PROCESS OF 1 KG POLYSTYRENE ON 17 IMPACT CATEGORIES
Figure 9 shows that all negative impact is caused by the recycling of PS due to the avoided impact
of producing raw polystyrene. However this direct recycling causes negative impacts on land use,
eutrophication, ozone depletion and ionising radiation. Apart from avoided products electricity is
added to contribute to the success of this process. Part of the overall process of recycling PS causes
the incineration of PS due to technical issues of sorting plastic.
26Biodegradation of polystyrene by mealworms
FIGURE 10: RECIPE 2016 MIDPOINT (H) BIODEGRADATION OF 1KG POLYSTYRENE WASTE ON 17 IMPACT CATEGORIES
Figure 10 shows that positive impacts are caused by worm-feed and the facility. Worm-feed is
directly related to the production of wheat. Whereas impact of the facility of biodegradation of
worms is mainly due to the electricity usage. [see figure 11] Negative impact is caused by
SortingWorm. These are directly related to the avoided production of wheat which is called in this
process the production of chicken feed. [see figure 2]
FIGURE 11: RECIPE 2016 MIDPOINT (H) ANALYSIS OF BIODEGRADATION FACILITY
27Comparison of Environmental impact Polystyrene waste scenarios
FIGURE 12: RECIPE 2016 MIDPOINT (H) ANALYSIS OF TREE 1 KG POLYSTYRENE WASTE SCENARIOS; RELATIVE
COMPARISON ON 17 IMPACT CATEGORIES
Figure 12 shows that most processes have a positive environmental impact in most categories.
However five process in four categories have a negative environmental impact. The recycling
process has a negative impact on ozone formation, fossil resource scarcity and water consumption.
The incineration of polystyrene has a negative impact on water consumption impact category too.
Recycling of PS prevent the production of raw material for PS thus is able to have a negative
environmental impact.
For the incineration process relatively high impact is present in 3 impact categories. Fine particle
matter, fossil resource scarcity and terrestrial acidification. All three process are directly linked to
the incineration of municipal solid waste.
Recycling of polystyrene causes the highest impact in 7 categories. Most significant difference can
be found in freshwater eutrophication, terrestrial ecotoxicity, human toxicity and mineral resource
scarcity.
As a relative comparison 7 impact categories are highest for the biodegradation by mealworms.
Most significant difference can be found in marine eutrophication, land-use, water consumption
and ionising radiation. Ionising radiation is mainly caused by processes involved in the uranium
mine which is directly related to the electricity net of Sweden which is dependent on Nuclear
energy and thus implemented in SimaPro this way. (see Appendix IV) Marine eutrophication
shows highest impact for biodegradation followed by recycling. Land and water use impact on the
environment are highest in the biodegradation scenario furthermore.
In Appendix V the real numbers for all the impacts compared figures 7 to 12 are given.
28Discussion
Method
A level of detail in this research was hard to quantify. In this study no case study was used so
majority of information came through literature research. Meaning that average numbers found
through databases for example were used as numbers in this analysis. Data used aimed to be as
accurate to the location, Östersund, Sweden as possible. Furthermore only general processes found
through literature and/or online were included in this analysis. e.g. machines that was used
internality inside a plastic sorting factory (beside the machinery included in the sorting process)
will not be accounted for since no information was retrieved for this. e.g. no interviews take part of
this method. In depth processes like how many factory workers and social impact was not the
scope of this LCA. This LCA was primarily an analysis of the technical process.
A residential perspective is taken already in the method section in contrary to an industrial. This is
chosen due to simplicity reasoning, gathering less data creates less space for error. It can be
assumed however that this choice does seem to effect findings. Through literature found in this
research waste is gathered on a municipal scale meaning waste is treated the same. However from
a practical side point of view might change. Potentially a case study is conducted, where collected
material is written down more actually. When this material is of bigger quantities and thus more
uniform it could be easier calculating impact but because this was not taken into account results
did not seem to alter.
Lacking information in LCA in general is partly due to its complexity. Within this given time frame
it is impossible to conduct in-depth on all the sections looked by in this research. Collaborating
with institution that provide more raw data would be a step in the right direction. Within LCA
processes are always limited but conducted with the best available information method. One
example that could have been improved was the impact from recycling on ecotoxicity. Major
impact was caused by a process called sulfidic tanning. This was due to specifics of the building
process chosen. The conclusion that recycling causes most harm into impact categories ecotoxicity
can thus not be made. An update method could solve this problem. Input information in this
study, presented in the chapter life cycle of three waste scenarios, was retrieved from data that not per
definition represents reality but is an estimation. Once the input scenarios for all three waste
scenarios are documented better, e.g through collaboration with the waste industry or three
specific study cases, results potentially will be closer to reality.
It could be concluded that biodegradation of PS by mealworms is the least favourable environment
option by looking at different impact categories. However a more weighted answer on its actual
impact comparing to other processes would have been given by an Endpoint analysis. This ReCiPe
Endpoint analysis weights data and accumulates this into three categories. (Huijbrechts et al. 2017)
However due to the in accuracy of the data this type of analysis and further analysis of the
different impact categories seem unwanted.
29Environmental Impact
From a GWP perspective biodegradation of polystyrene by mealworms seem highly inferior to the
already existing methods of waste management, incineration and recycling, based on the results
found in this LCA research. However great uncertainties are present in the data selection and thus
alter trustworthiness of all the results.
The use of municipal waste incineration in Sweden within the EcoInvent Database has caused
several problems. In a recent article Singh & Singh (2020) compare different waste types to its
renewability on energy recovery. Different values were found for different waste types e.g. plastics,
wood, textiles. Thus as part of a life cycle analysis these need to be allocated accordingly to its
waste type. This has been attempted by using incineration of PS on European scale in combination
with incineration of municipal waste for Sweden. However difference municipal solid waste
incineration in Sweden accounts for roughly 30% of results of which only 10% functional unit is
allocated to of which later even smaller part would be incinerated due to losses in the process. The
incineration of municipal waste in Sweden only result in positive GWP whereas incineration of
plastics in Europe shows negative GWP. The incineration plant used in this case, energy recovery
plant of Sundsvall energy, produces approximately 120,000 MW electricity and 300,000 MW district
heating. (Bergkvist n.d.) However within the framework used in the software and databases this
research is not reflective for reality thus results do not fully represent incineration of polystyrene
residential waste from Östersund.
Bran has shown to be a high impact on GWP and several impact categories for the biodegradation
of polystyrene by mealworms. The use of bran is optional and specifically chosen in this research.
However worm feed can be replaced by many other products depending on different factors. A
LCA conducted by Oonincx & de Boer (2012) stated that worms where fed a mix of carrots, mix of
grains and egg cartons. Every producer of mealworms is likely to have its preference of worm feed
linked to the availability of local resources. No local research into the potential of worm feed has
been included in this research. More specific number of additional food (that would be available in
the available databases within SimaPro) to worms would increase accuracy of this LCA. A
percentage of frass from the mealworms unfortunately has still parts PS present. Through selective
breeding of mealworms this percentage could alter. (Yang et al. 2017) This same study suggested
the potential of the frass that could be used as fertiliser. To improve this more knowledge has to be
built in this section. Lifecycle analysis of poultry feed has been published in 2012. This research
focused on finding the lowest environmental impact poultry feed. (Nguyen et al. 2012) A study like
this but focussing on mealworm feed in combination with the potential of selling frass as fertiliser
in a local area would be of high interest. Many studies show the potential of mealworms. (Huis et
al. 2013) (Joensuu & Silvenius 2017) (Oonincx et al. 2015) (Wilkinson 2011) (Smetana et al. 2015)
(Smetana et al. 2016)
30Recycling scored the best in GWP and similar to biodegradation on overall environmental impact.
However we have to take into account that recycling rate in this research is 55%. This number has
not been achieved yet in Sweden and most European countries. (Plastic Europe 2018) Plus different
techniques for recycling of this polymer are present. (Maharana et al. 2007) No environmental
impact assessment comparing these methods as of today has been published. This would suggest
potential of different impacts that have not been included in this paper.
Future perspective
Within this study the aim was to find environmental impact of three waste scenarios by using LCA
framework. Through the results presented lessons can be learned that all togheter can contribute to
a better understanding of the problem which hopefully will potentially lead to better policy
making. This study on its own does not achieve that but contributes to it. New findings has been
found and discussed that will point future research into the right direction. The potential of
biodegradation has proven to be significantly better or worse been. This study shows the weakness
of chosen method and findings which lead to better understanding of the necessary future
research.
Furthermore for future research several aspects has been highlighted but one specifically could be
interesting. For the future the EU ‘has a will to make its economy and environment sustainable for
the benefit of future generations. This action planned is coined ‘European Green deal’. One priority
in achieving this is implementing a clean circular economy. (European Commission n.d.) ‘In a
circular economy, the value of products and materials is maintained for as long as possible. Waste
and resource use are minimised, and when a product reaches the end of its life, it is used again to
create further value’ (European Commission 2015) Meaning we must see ‘waste’ as a new resource
to maintain it longer in the system. Recycling seems to be the most logical way but as this research
has shows specific environmental problems can occur because of this process. Biodegradation of
mealworms in general can be an interesting approach from a circular perspective since it separates
‘waste’ into two products that will not leave this circle, frass for fertilisers and worms itself for less
environmental harmful animal or human consumption. Thus analysing the biodegradation of
waste by mealworms or similar from a circular perspective would be of great interest.
31Conclusion
In the results of IPCC 2013 100 year scenario and SimaPro software for a lifecycle analysis show
that recycling off polystyrene is the most wanted waste scenario from a global warming potential
perspective. Incineration show a negative GWP too but is inferior to recycling because of the high
GWP of production of new PS. Biodegradation of 1 kg of polystyrene by mealworms has as only
waste scenario a positive GWP and is the most unwanted waste scenario from that perspective.
From an environmental perspective 17 impact categories were analysed. Of these 17 impact
categories incineration of polystyrene is shows to have the least impact with relative highest
impact on only 3. Both recycling and biodegradation of polystyrene score worse respectively 7
relative highest impact each. Overall transport has a negative impact, below 5% in all three waste
scenarios suggesting that local waste treatment always needs to be re-evaluated against
alternatives.
Overall the biodegradation of polystyrene by mealworms as a novel waste scenario does not seem
to be environmental beneficial compared to the two existing methods, incineration and recycling.
However findings stated above do not represent reality due to inaccuracy of the available data and
thus these results cannot be taken into decision making as of today. Because this research shows
the lack of information available on biodegradation by mealworms and thus expresses the need
for further research.
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