Research on Environmental and Scientific Issues
in Carbon Fiber-Reinforced Plastics (CFRP)
Recycling
メタデータ

言語: English
出版者:
公開日: 2023-06-26
キーワード (Ja):
キーワード (En):作成者: 上田, 裕之
メールアドレス:所属:

URL

http://hdl.handle.net/20.500.12099/00101283

Research on Environmental and Scientific Issues in
Carbon Fiber-Reinforced Plastics (CFRP) Recycling(Ⅳ⣲⧄⥔ᙉ໬ࣉࣛࢫࢳࢵࢡ(CFRP)ࡢࣜࢧ࢖ࢡࣝ࡟࠾ࡅࡿ
⎔ቃ⛉Ꮫⓗㄢ㢟࡟㛵ࡍࡿ◊✲)2022

The United Graduate School of Agricultural Science,
Gifu University
Science of Biological Resources(Gifu University)

UEDA, Hiroyuki

Research on Environmental and Scientific Issues in
Carbon Fiber-Reinforced Plastics (CFRP) Recycling(Ⅳ⣲⧄⥔ᙉ໬ࣉࣛࢫࢳࢵࢡ(CFRP)ࡢࣜࢧ࢖ࢡࣝ࡟࠾ࡅࡿ
⎔ቃ⛉Ꮫⓗㄢ㢟࡟㛵ࡍࡿ◊✲)UEDA, Hiroyuki

Contents
1. OVERVIEW ........................................................................................................................ 1
2. REVIEW AND EXPERIMENT ........................................................................................... 2
2-1 Organizing current issues in CFRP recycling ................................................................. 2
2-1-1 Organizational issues for disseminating recycling technologies of CFRP in theJapanese industrial landscape .......................................................................................... 2
2-2 Assessment of the impact and toxicity on aquatic organisms caused by carbon fibers
generated during CFRP recycling ...................................................................................... 16
2-2-1 Assessment of biological effects and harm to Japanese medaka due to carbonized CFs
generated by a pyrolysis carbon fiber recycling process ................................................. 16
2-3. Measurement of airborne carbon fibers at SME’s site where CFRPs are handled ....... 33
2-4. Study on risk management approach for recycled CFRP manufacturing/handling sites
using control banding method ............................................................................................ 34
3. FUTURE PROSPECTS IN CFRP RECYCLING .............................................................. 44
4. CONCLUSION.................................................................................................................. 51
5. ACKNOWLEDGEMENTS................................................................................................ 52
6. REFERENCES .................................................................................................................. 53

1. OVERVIEW
Carbon fiber-reinforced plastics (CFRP) are used for structural materials in the aircraft
and automotive industries due to their lightweight and high strength characteristics.
CFRP is a very hard and chemically stable material and therefore the disposal of waste
CFRP has been a big issue over the last few years.
In the U.S., it is widely known that retired aircrafts made of CFRP have been left on thedesert due to a lack of proper disposal method. At present, there are still no suitabledisposal methods in terms of price and environmental impact (energy consumption, LCAetc) and as a result, landfill disposal, which is relatively inexpensive, is the preferred
method.
As for the world movement, in Japan, the "Circular Economy Vision 2020" (issued by
the Ministry of Economy, Trade and Industry, Japan on 22 May 2020) designates CFRP
as one of the five areas (Plastics, Textiles, CFRP, Batteries, and Solar panels) that are inurgent need of consideration for recycling systems.
In Germany, landfilling of untreated CFRP waste is prohibited since 2005.
For such a situation, the establishment of recycle/reuse system is being urged around theworld.
In this study, firstly I organized the issues for disseminating recycling technologies of
CFRP, especially in light of Japan. As a result, it was clarified that CFRP recycling
process inevitably generates carbon fiber (CF) fine particles (dust/milled) as a byproduct,
and while there is an urgent need to establish recycling technology, only the technicalaspects of the recycling process have been paying attention and little has been known
about how CFs including not only the recycled CFs but also the secondary dust affect theecosystem.
There also exist reports that CF is nanoscaling and finally become NOAA (Nano-objects,
and their aggregates and agglomerates greater than 100 nm). With regard to NOAA, there
is concern about its health effects.
In this background, secondly I delved into the effects of milled CFs or CF dust generated
during a CFRP recycling process on the environment and living organisms when CFs are
released into the water environment as a by-product unintentionally.
Specifically, the toxicity evaluation of CFs was conducted by using Japanese medaka
fish (O. latipes, orange-red variety or himedaka).
This study will help us to predict how CF fine particles generated from the recycling
process and unintentionally contained in industrial wastewater will affect aquaticorganisms in rivers, lakes and marshes etc.
It is also helpful to formulate countermeasures in the future when CFRP recycling isprevailed and large amounts of recycled CFs are used in our daily lives.
1Finally, an occupational health risk assessment study by using Control Banding
approach for CF dust which includes NOAA was conducted on a pilot basis for the aimof future implementation on SMEs (small and medium-sized enterprises) work site.

2. REVIEW AND EXPERIMENT
2-1 Organizing current issues in CFRP recycling
2-1-1 Organizational issues for disseminating recycling technologies of
CFRP in the Japanese industrial landscape2-1-1-1 Introduction
Carbon-fiber-reinforced plastics (CFRP) are used for structural materials in the aircraft
and automotive industries due to their lightweight and high strength characteristics.
Global CFRP market demand was 92,900 tons in 2015 and is expected to reach 269,500
tons by 2024 [1]. As an alternative to metals, they are expected to expand their application
into many fields. However, the recycling businesses/technology of waste CFRP is stillvirtually unestablished especially in Japan and waste CFRP has been mostly landfilled
across the globe. The main reason for landfill disposal of CFRP is that it is incombustible
and thus requires a large amount of fuel to burn [2]. In addition, in aircraft applications,in-plant waste such as trimming offcuts are often regarded as “strategic supplies” because
carbon fiber lamination and knitting are areas of corporate technology expertise.
Therefore, small- and medium-sized companies that have been commissioned by aircraft
manufacturers run the risk of being penalized by the outsourcing companies if the waste
is mishandled and consequently leaks outside. To prevent such risks, landfill disposal has
been prevalent so far. Consequently, landfill is still preferred in many countries as themost cost-effective disposal option in monetary terms.
For reference information, in the UK, the landfill cost of waste CFRP is reported to beapproximately £82.60 per tonne [3] and there is also an article stating that in 2015 some
18,000 tonnes of CF waste was produced from manufacturing operations globally, of
which only around 1,600 tonnes (8.8%) was recycled [4]. In Germany, landfilling ofuntreated waste is prohibited since 2005. Under such circumstances, to further spread andexpand the use of CFRP in the future, it is highly desirable to reduce the environmentalload of the entire value chain from production to recycling through the development ofrecycling and reuse technology. As a remarkable movement within the EU, there is areport that the European Union is aiming for zero landfill disposal by 2025 [5]. There isalso a report that the market size of CFRP recycling will reach approximately 100 billion
2yen in 2030 [6]. In anticipation of the growth of waste that is derived from the growth ofdemand for CFRP in the future, it is necessary to create a waste material treatment system.
Therefore, the establishment of CFRP recycling technology and the development ofapplications for recycled products are an urgent requirement. However, up until now,there have been almost no cases where reclaimed CFs have been used for mass production,
only prototypes, such as aircraft seat arm rests, have been produced, except for the caseof BMW. Ahead of the rest of the world, BMW started to use recycled CF in the roof andrear seat shells of their electric i3 and the hybrid i8 vehicles [7, 8]. More recently, especiallyin Japan, it has become desirable to expand applications by utilizing functional
characteristics such as low thermal expansion rate, thermal conductivity, corrosion
resistance, and rustlessness, besides the more conventional mechanical properties such as
lightness, strength, and hardness. New businesses have been developed by utilizing these
additional benefits of CF other than lightness and strength. Concretely, a number ofJapanese companies are developing its use in new fields, such as medical field, byutilizing virgin/reclaimed CF as electromagnetic shielding materials [9, 10]. To conclude
this section, the flow of collecting and recycling CFs from waste CFRP consists ofmaterial recycling and thermal recycling as shown in Fig.1. CFRP waste comes in many
forms, such as dry fiber, prepreg (intermediate feedstock that is impregnated with resin
in lined CF) scraps, cured parts and currently, regarding CF waste from the aircraft
manufacturing process, prepreg, preform (pre-molded CF that fits the product shape), andmolded waste are mainly discharged. However, in the future, a large amount of end of life
CFRP waste materials are expected to be discharged.

Fig.1 Flow chart of collecting and recycling CFs from waste CFRP

3

2-1-1-2 CFRP recycling technology
Categorizing crudely, there are two types of recycling technologies [8].
As shown in Fig.2, the first one is a direct reuse (mechanical recycling) technology thatcan use waste CFRP as it is for the purpose of filler, reinforcement, and so on. Uhlmann
and Meier [11] have studied the application of CFRP milling dust as a filler material. They
regard the approach to consider milling dust as an additive for reinforcement purposes as
one of many possibilities to close the material cycle of used CFs.
The second one is a full recycling process technology. It can be divided into fiber
reclamation (recovery of the fiber from the matrix) and remanufacturing into a valuable
material (the production of a new feedstock or component).
In terms of fiber reclamation, techniques can be categorized in two intersecting groups:
the thermal processes (pyrolysis, fluidized bed pyrolysis, microwave-assisted pyrolysis)
and the chemical processes (solvolysis, super-critical fluid solvolysis). In terms of
remanufacturing, it is possible to use the recycled CFs (rCFs) as reinforcement in direct
molding techniques (injection molding, bulk compound molding, extrusion molding) or
to create non-woven or chop strand mats for injection molding [12, 13].
In a full recycling process technology, technique that can recycle both resin and fiber isideal and research into processes such as the effective separation of resin and fiber isunder way by AIST, Japan etc [14]. With regard to recycling technology aimed atrecovering CF threads, many companies and research institutions in Japan and overseas
are involved, as shown in Tables. 1, 2, and 3. Wet methods such as solvolysis [15, 16] havea better separation accuracy than dry methods from an academic perspective. However,
it is expensive and necessary to conduct cumbersome waste liquid disposal and therefore
many companies, especially overseas recyclers, adopt pyrolysis (thermic treatment)
technology [17]. Generically, the pyrolysis method is energy intensive and can leave charresidue on the surface of CFs which is hampering further processing though it depends
on process conditions.

4Fig.2 Two concepts for CFRP recycling
Table 1. Example of major recycling companies in the world classified by major
recycling method
Solvent Method

CA TACKH (South Korea), Vartega (USA), Ai-Carbon Co., Ltd. (Japan)(Electrolysis), ACA Co., Ltd. (Japan) (Technology to strike CFRP with an air
flow close to sound speed and finalize up to 1 μm in diameter) (1),
SANWAYUKA INDUSTRY CORPORATION (Japan) (Solvolysis - wet andlow temperature (100-150 ℃) CFRP recycling technology by using sulfuricacid), Earth Recycle Co., Ltd. (Japan)(Wet depolymerization method)

Pyrolysis

Karborek (Italy), ELG Carbon Fibre (UK)(2), CarboNXT GmbH - CFK Valley
Stade Recycling GmbH & Co. KG (Germany), Composites United (formerly
CFK Valley) (3) (Germany), Carbon conversion (United States), GEM Co.,Ltd(China) (details are unknown)(4), Shinryo Corporation (Japan), KUREHA
CORPORATION (Japan), Fuji design co.,ltd - Re-Tem Corporation (Japan),
Teijin Limited (Japan)(1) ACA CO.,LTD. website http://www.ss-aca.jp/english/reuse/ Accessed 21 August 2020
(2) Holmes M (2018) Recycled carbon ﬁber composites become a reality. Reinforced Plastics, Volume 62,
Number 3, May/June 2018. doi: https://doi.org/10.1016/j.repl.2017.11.012(3) JEC GROUP NEWS (2019) CFK Valley and Carbon Composites to merge into Composites United.
http://www.jeccomposites.com/knowledge/international-composites-news/cfk-valley-and-carboncomposites-merge-composites-united Accessed 21 August 2020
(4) GEM (2014) Mitsui & Co. to expand its car recycling business in China, establishing a joint venturewith GEM Co.,Ltd. (2014.05.26) (in Chinese) http://www.gemchina.com/gongsidongtai/2014/0526/599.html Accessed 21 August 20205

Table 2. Comparison of Japanese recycling technology
Technology

Two-step pyrolysis

Pyrolysisclassification

Research InstituteType of resin

Thermal activation

Depolymerization ofof semiconductors

Epoxy Resin under(TASC)

Ordinary Pressure(6)CarbonFiber

The Japan Carbon

JinTech Corporation

Hitachi

ChemicalRecycleIndustry

Fiber Manufacturers(5)Company, Ltd

co.ltd.

Association(withdrawal(CFRI)(JCMA),

the business)

All resins that do not

All resins that do not

generate toxic gas

generate toxic gas

during pyrolysis

during pyrolysis

Unknown

Long CF,fiber type

Resin pyrolysis gas

Temperaturest

500℃(1 step)

Milled CF

Shizuoka University

fluid method (6)Kumamoto

from

Ester

Long CF

fluid method

Subcritical(6)

University

Ester

Ester

Methanol

Benzyl alcoholLong CF,CF, Resin oligomer

CF,

Resin degradation(Dissolved

Resin degradation

product

in alcohol)

product

Type of solvent
Recoverable

Supercritical

500-700℃

400℃

200℃

250-350℃

300-400℃

440℃(2nd step)
Pressure

ordinary pressure

ordinary pressure

ordinary pressure

ordinary pressure

5-10MPa

1-4MPaTime(minute)

30

120

10

90-180Unknown

Unknown

Preliminary process

unnecessarysmashunnecessary

unnecessarysmashunnecessary

Scale(ton/year)

2,000

1,000

Unknown

12

Laboratory level

Laboratory level

6

(5)

JinTech (2013) Outline of the TASC technology in English http://jintech.org/?page_id=342 Accessed 21 August 2020

(6)

Tanaka K, Yoshimura T, Ijiri M, Nakagawa D (2019) Approach from cavitation processing for new recycling technology development of carbon fiber reinforced

plastics. The Japan Society of Mechanical Engineers Vol.85, No.874.
doi: 10.1299/transjsme.18-00342https://www.jstage.jst.go.jp/article/transjsme/85/874/85_18-00342/_pdf/-char/ja Accessed 21 August 2020

Table 3. Comparison of recycling technology other than JapanCountry

the United Kingdom

Italy

Germany

Swiss

FranceSpain

the United States

China

Research

ELG

Impe

Universit

Karb

RYM

FraunhCarboNX

SGL

V-

I2M

FormosoCarbonAdheren

UHT

FuyuanInstitute

Carbon

rial

y

of

orek

YC

ofer

T

Automoti

CARBO

Laboratory

Technolo

Converst

Unitechnew

Fibre Ltd (2)Colle

Nottingha

Recy

IGCV

GmbH,

ve

N

(engineering

gies

ions,

Technol,Trans.

material

ge

m

cling

CFK

Carbon

and

Group

Inc.

ogies,

Com

technolog

Lond

Carb

ValleyFibersmechanics

(7)

on

on

Stade

institute,

Fibre

Recyclin

University ofsg GmbH

Bordeaux)& Co. KG

7

Inc

y

(8)

LTD

Co.

(FUY) (9)Technolo

Pyrolysisgy type

Scale

2,000

Unkn

Microwa

Unkn

Non-

Pyrolys

Pyrolysis

Solvolysis

ThermalPyrolysi

Wet

Microwa

own

ve

own

chemi

is

and

(10)

decomposchemicavepyrolysiscal

N2, O2,chemicalsitionlpyrolysis

flow,

proce

(oxidati

reaction(recovery

degradat

Moving

ss,

on

of

oil

ion

layer,

likelypossiblfrom thethethermic

Super

e)),

resins andpolymer

fluid

heate

max.

fibres)matrixtreatment

d

temp:

Steam

800℃

300

Under

1,000

Pyrolysis

Pyrolysis

(Ar,

Labo

Laborator(ton/year

rator

y level)yresearc

level

h

3,500

Unknown

Unknown

joint

Laboratory

Pilot

2,000

Pilot

level

plant

plant

level

level

Pyrolysis

of

88

1,500

with

companies(7) Oliveux Géraldine, Luke O Dandy, Gary A Leeke (2015) Current status of recycling of fibre reinforced polymers: Review of technologies, reuse and resulting properties. Progress inMaterials Science 72, 61–99. doi: http://dx.doi.org/10.1016/j.pmatsci.2015.01.004(8)Adherent Technologies (2020) Recycling Technologies. https://www.adherent-tech.com/recycling_technologies/carbon_fiber_reclamation_faqs Accessed 21 August 2020

(9)

Fuyuan new material technology Co. LTD (FUY) website http://www.rcffy.com/, http://www.rcffy.com/news/info.aspx?itemid=74. Accessed 21 August 2020 Recently, threeassociation standards associated with CF recycling were drafted under their lead and had been released.
(10)

Matthieu Ayfre, Olivier Mantaux (2019) Innovative semi-products made of recycled carbon fibres. JEC COMPOSITES MAGAZINE 2019, N°131, November-December 2019.

8

2-1-1-3 Issues in commercializing CFRP recycling technology
The high important issues of commercializing CFRP recycling technology are as
follows:(a) Quality assurance and standards for the fiber properties of reclaimed CFs do not exist.
Catalog values for reclaimed fibers do not exist and very few recyclers such as ELG
Carbon Fibre specify their properties on their homepage. Therefore, users cannot choose
reclaimed fibers with confidence.
As a background for the above, with regard to CFRP recycling, the quality and physicalproperties of in-plant waste and other waste materials used as raw (input) materials are
not uniform. It is therefore difficult to maintain the quality of recycled products within acertain range. As Longana et al. [13] state, it is necessary to develop new quality control
and characterization techniques able to provide reliable mechanical properties in a
production-compatible timescale to promote the industrial application of recycled
composite materials. Furthermore, the need for ad hoc characterization and quality
control techniques for recycled composite materials is further justified by the fact that thewaste, and consequently the rCFs, can come from multiple, and potentially unknown or
scarcely documented, sources. Regarding the issues related to remanufacturing, needlessto say, the quality assurance and standardization will be also applied to theremanufactured feedstock. While there are efficient industrial scale setups for fiber
reclamation, remanufacturing methods capable of producing high performance recycled
composites are still rare. The most immediate way to remanufacturer CF is to use indirect
molding techniques, such as injection molding, bulk molding compound (BMC), andSheet Molding Compound (SMC) compression [12].
(b) Lack of a reliable supply chain and established market outlet.
For the input, CFRP scrap materials are not continuously available. Furthermore, for the
output, the application development of reclaimed CFs has not yet been established andtherefore customers and applications of recycled products have not been secured. If thenumber of lots on the input side cannot be secured, the recycling business itself will not
become established.
(c) With regard to the effects on humans and ecosystems caused by CF (dust/milled),enough studies on their bio-toxicity and environmental toxicity have not been conducted.
The impact of microplastics on ecosystems has been noted in recent years and selectedreports are as follows. Though CFRP is a variation of the same kind of plastic andattracting attention as an environmentally friendly product, there are few reports on its
9environmental impact, especially regarding the effects on living organisms, compared tomicroplastics [18, 25].
࣭Intake of harmful substances, such as adsorbed microplastics, carries a risk of causing
health damage to the ecology [19, 20].
࣭Low-density polyethylene plastic (LDPE) causes liver dysfunction in Oryzias latipes. Note that human and oryzias latipes share 70% of the same genes.

[21]

࣭The accumulation of 14 plastic particles in the intestines of sea turtles leads to 50%
mortality [22].
࣭The rate of infection to coral diseases under the influence of plastics increases from 4
to 89% [23].
Considering and summarizing the above, Fig.3 shows the whole issue related to each
recycling process.

Fig.3 Issues in each step of CF recycling process
In addition to the above (a) to (c), there are other aspects regarding the impact of CFRP
recycling both in terms of process and in terms of LCA impact categories. Needless tosay, the aspect of economic and environmental assessment is important. [18, 24-26]
The choice of technology route of CFRP recycling and cost/profit consideration are alsohigh important issues since there are many technology routs for CFRP recycling.
10Moreover, the choice of technology itself is a key factor for the commercial operation
since it is highly related to the cost and discharge type of CFRP recycling process. [7, 27]

2-1-1-4 Solutions and prospects for CF recycling business
The solutions and prospects for CF recycling business are as follows:(1) Quality assurance and standardization
For virgin CF, the test methods and standards have been established to some extent inJapan etc [28]. Conversely, with regard to reclaimed CF, there are still no established test
methods and standards and therefore each batch of reclaimed CF products is shipped ina specified quality range according to user demand. In addition, it is expected that
CFRP waste from unknown sources will be found in the future. The quality assurance
and standardization will be applied to both the reclaimed fibers and the remanufactured
feedstock. Longana et al. [13] describe issue of collection and sorting of the waste andreclamation-induced alterations to fiber geometry, architecture, mechanical and physicalproperties. Moreover, they describe a study of quality control and property assurance
methodology based on the HiPerDiF (High Performance Discontinuous Fibre) method
aimed at blending of different fiber lengths. The HiPerDiF method has been used toremanufacture rCFs to obtain high mechanical properties in intermingled hybrids with
virgin fibers and interlaminated hybrids with continuous glass fibers and to demonstrate
the possibility to maintain high performance after multiple closed loop recycling
processes. In the future, it will be necessary for Japan to standardize resin type,
formulation ratio, shape, fiber length and so on, and propose a standard measurement
method or at the very least a guideline in cooperation with the European norm etc sothat sellers and buyers can trade with confidence. Currently, in Japan, a study on thereclaimed CF testing and evaluation method (method to quantitatively evaluate thestrength [29], length, orientation (fiber alignment), residue and so on for reclaimed CFs)
has been conducted mainly at the AIST and Kyoto University. Such standardizations arealso required overseas (such as Airbus). We would therefore like to suggest the launchof a global standard from Japan. It is also expected to proceed with a collaborative study
for the establishment of a test and evaluation method in cooperation with Fraunhofer
IGCV and the Brightlands Materials Center in the Netherlands, among others.
11(2) Lack of a reliable supply chain and established market outlet
There is an urgent need for establishing a waste supply chain. As mentioned so far,there are still no predominant applications and this is the most challenging issue
especially for Japan. Reclaimed CF is a cut fiber and it is therefore difficult to apply to
structural materials requiring strength. However, reclaimed CF is adequate if users seeka weight reduction equivalent to those of general reinforced plastics. Through further
improvement of the existing remanufacturing techniques (carding [30, 31], wet laying [32],HiPerDiF [12, 13, 33, 34], TuFF (the Tailorable Feedstock for Forming) [35, 36], rotating drum
[37]etc), new remanufacturing methods capable of producing high performance recycled

composites are expected to be developed. This conceivably contributes significantly tothe expansion of application. In the future, it is expected to expand its application into
automotive parts, civil engineering and construction materials, medical components,
and daily necessities. For civil engineering and construction materials, for example, by
replacing steel (iron) in bridges with lightweight CF, the burden of repair work can be
reduced and maintenance-free is potentially possible. This will have a significant impact
on the aging society and participation of women in society. This effort has already been
made by a number of Japanese companies by combining virgin CF with glass fiber andthe use of CFRP as a reinforcement for the pillars of houses is also under consideration[38]. Conversely, in automotive component applications, if automatic operation

progresses in the future, it is expected that the material strength for personnel protection
will no longer be required and robust composites such as CFRP will become overspecification with general types of plastic being good enough. As a solution toapplication development especially in Japan, we would like to suggest listening to theopinions of downstream users (end product manufacturers) as to which type ofintermediate feedstock are better among drylaid nonwoven and wetlaid nonwoven.
Specifically, the exchange of opinions involving all stakeholders across upstream(recyclers), midstream (intermediate feedstock manufacturers), and downstream (endproduct manufacturers) is considered effective as shown in Fig.4. Moreover, it isbelieved that collaborative market development will be effective through mutual
cooperation among intermediate feedstock manufacturers, resin manufacturers, andprocessing manufacturers beyond the watershed area.
12Fig.4 Example of application development solution– exchange of opinions involving
all manufacturers involved in CF recycling(3) Effect of CF on humans and ecosystems
Generally, carbonized CF (after partial firing treatment) recovered from the pyrolysis
method contains many impurities such as tar and char [39]. Therefore, its users are more
likely to be anxious about its impact on workers and ecosystems than with virgin CF. In
particular, reclaimed CF recovered from CFRP retains more tar, char etc than thatrecovered from CFRTP due to the difference in matrix resin decomposition properties.
In addition, unintended impurities such as glass fiber, metal foil, and dust can becontaining on the surface of reclaimed CF [40]. When wet treatment method is used as
the production of intermediate feedstock or water jet cutting is used, the transfer of CF
dust to the water system through discharged water is a significant concern. Even when
scrubber systems are used, a risk remains that, if mishandled, the CF dust-tainted water
recovered from the atmosphere transfers to external water bodies. If robotic automation
systems [41] are not installed for mass production, comfortable working environments
will need to be established. For not only in the intermediate feedstock manufacturing
process but also in subsequent processes, the safety of workers continues to be a13

concern because CF dust will always be generated when the CF is cut, smashed, and soon.
As for the impact on humans and ecosystems, the following are clarified:First, the impact on human health;-Carbon is considered to be biocompatible and CF and its composite materials are also
used in artificial biomaterials [42].
-The diameter of original CF on the market is 5 μm or more, and its particle size differsfrom “black carbon (2.5 μm or less in diameter)” contained in PM2.5 and “carbon
nanotubes (CNTs) (0.4–50 nm in diameter),” which have associated concerns withregard to health effects on the respiratory system. Particularly, it is elucidated that CNTs
pose serious health risks similar to those of asbestos and carry a high risk of inducing
lung cancer [43-48].
-Unlike asbestos, dust aspiration does not affect red blood cells, alveolar macrophages,
and so on, or is considered to have a small effect. [49]-Waritz RS et al. conducted histopathological evaluations by exposing rats to CFs in theatmosphere. CFs used in their study were made from polyacrylonitrile fiber and 3.5 μm
in diameter and 72% were 10–60 μm long. Rats were exposed for 6 h /day, 5 days
/week, for 16 weeks to an atmosphere of 20 mg /m3 of CFs (25 × 106 fibers /m3).
As a result, no effects due to the exposure were seen, as judged by clinical signs, bodyweight, organ weight, organ-body weight ratios, organ-brain weight ratios etc. There
was also no indication of fibrosis. [50]-Judging from the particle size of original CF, it is unlikely to cause serious damage tohuman health through inhalation. However, fine particles such as those of milled shortfiber (fiber diameter less than 3 μm, fiber length less than 80 μm) treated by industrial
processes have a likelihood of reaching the human alveoli by inhalation. Therefore,
Nakano et al. of Keio University have recommended that a reassessment of their
toxicity should be conducted using those small/fine fibers. In addition, they haverecommended that a re-evaluation of special CFs, such as those treated with a chemical
surface coating, should be conducted. [51]-Moriyama and his team, of Gifu University, have studied and analyzed the toxicity andhealth effects on workers of CF dust, which is generated during a pyrolysis recycling
process at the molecular level, by using live mice. They suggested the inherent
14impurities, such as dioxins, attached to the CF rather than the physical state of the fiber(such as fiber length) may impart toxicity to CF dust. They also found that the toxicity
and potential hazard to human health changes depending on the degree of firing
treatment, has no severe impact on human health as a consequence. [52]Secondly, the effect on aquatic organisms;
Although CF has characteristics that do not affect the ecological environment of theorganism as a biocompatible material [53], there are very few formal reports, such as
papers and articles, with scientific evidence [54]. Regarding other types of plastics, likemicroplastics as mentioned in Subsection (c) of Section 3, the ecological effects havebeen analyzed to some extent. However, the effects of CF migrated to water sources,
such as rivers and lakes, remain unclear and those effects have yet to be investigated. In
addition, there is concern over the transfer of CF to groundwater and surrounding sea
areas from the final disposal area. Regarding CF, the yarn itself is treated as a stable
final disposal site, however, in the form of CFRP, it is treated as a managed final
disposal site in Japan. [55] In the event that the capacity of the landfill site is full,
although it is unknown whether CF will separate from CF containing products inseawater over the years, it is feared that waste CF products will be dumped into theocean illegally. Since the announcement of Professor Kojima of National Institute ofTechnology, Gunma College, Japan in 1994 [56], it has been confirmed that CF canpurify water by attaching to microorganisms and sludge in water. In 2012, Professor
Hori of Nagoya University, Japan along with TEIJIN LIMITED succeeded inscientifically elucidating the mechanism regarding the ease of adherence between
microorganisms and CFs from an energy perspective as follows [57]:
1. The repulsion between negative charges acting between microorganisms and fibers
is small when using CFs compared to other fibers.
2. The attractive force, “intermolecular force,” between the fibers and microorganisms
is strong when using CFs compared to other fibers.
As mentioned above, mainly for pitch-derived CFs, the study on CF use in water
purification materials has already been conducted in Japan [53, 58] and the product has
been sold [59]. It is believed that from this good image of “biocompatible materials,
water purification materials,” the environmental and ecological toxicity of CF may have15

been overlooked so far. As for technical solutions to prevent dust from scattering,wrapping with paper, surface coating, and slivers (cotton strips) are considered to beeffective. In addition, we would like to propose the development of a dedicated captureand dust collection technology for CF dust/milled and the introduction of downdraft
equipment that drains water to the ground. It is also effective to develop an excellent
filter system that can recover floating CF dust/milled from water.

2-2 Assessment of the impact and toxicity on aquatic organisms caused by carbon
fibers generated during CFRP recycling
2-2-1 Assessment of biological effects and harm to Japanese medaka due tocarbonized CFs generated by a pyrolysis carbon fiber recycling process
2-2-1-1 Introduction
Carbon-fiber-reinforced plastics (CFRPs) are used as structural materials in the aircraft
and automotive industries owing to their light weight and high strength. The global
demand for CFRPs tripled between 2010 and 2020 and is expected to exceed 190 kt by
2050 [60]. Their application as an alternative to metals is expected to expand into many
fields. Carbon fiber (CF) has unique functionalities, such as electromagnetic shielding [9,10], depending on the composite resin that is combined. Thus, CF products, such as CFRPs,
have attracted substantial attention and are used worldwide. However, it was recently
reported that there is little scientific information on the safety of CFs [61].
In recent years, the environmental impact of microplastics has become a major issue
worldwide. Specifically, the effects of the accumulation of plastics in living bodies andelution of chemical substances attached to the plastics are thought to be issues of concern.
Therefore, the impact of microplastics on ecosystems has attracted attention in recent
years [62], and the following risks have been reported. The intake of harmful substances
adsorbed by microplastics may cause ecological damage [19, 20].
Low-density polyethylene plastics cause liver dysfunction in Japanese medaka (Oryzias
latipes) [21]. The accumulation of 14 plastic particles in the intestines of sea turtles resultsin 50% mortality [22]. The rate of infectious diseases in coral species increased from 4%
to 89% in the presence of plastics [23].
In contrast, there are few reports on the toxicity of CFs to ecosystems compared to thatof microplastics; however, two remarkable reports should be noted by those planning for16

a circular economy, which is an industrial system in which products are reused,remanufactured, and recycled at the end-of-life stage.
According to Nakano et al. [51], the inhalation of CFs with diameters of 5 μm or more isunlikely to seriously affect human health. However, fine particles such as milled shortfibers with diameters of less than 3 μm and lengths of less than 80 μm after treatment byindustrial processes are likely to reach the human alveoli after inhalation.
According to Moriyama [52], when mice were fed CFs, the CFs were not acutely toxic,in contrast to carbon nanotubes and asbestos. However, the results of a gene expression
study suggested that carbonized CFs with residual carbons, etc., on the surface may bemutagenic in the long term; this possibility was not confirmed in mice injected withrecycled CFs having a clean surface and few impurities. Another report indicates that thetransfer of milled CFs or CF dust to external water sources during manufacturing,processing, and recycling of CF-related products may be of concern [61].
The selection of sample organisms is an important first step in the observation of theeffects of chemical substances on aquatic organisms. As a standard strain for theassessment of ecological toxicity, the Japanese medaka is an important species, especiallyin Japan [63]. Medaka (O. latipes, orange-red variety or himedaka) is a freshwater teleostfish that is widely distributed in the Japanese freshwater environment. Its habitat is
typically near the water surface, where they are commonly seen during spring in Japan.
Medaka is registered as an index organism for the assessment of the ecological toxicityof newly synthesized chemicals of which more than 10 ton/year are produced in Japan. A
recently published medaka draft genome showed that humans and medaka share 70% of
their genes.
Therefore, it is highly probable milled CFs or CF dust will ultimately result in the sameproblems as microplastics if they are released into the aquatic environment. Therefore,
referring to studies on microplastics, we tested the ecotoxicity of CFs using Japanese
medaka.

2-2-1-2 Materials and methods
2-2-1-2-1 Medaka culture conditions
Medaka were purchased by mail order over the internet from FOCUS (Kumamoto,Japan) and CHARM (Gunma, Japan) as a standard strain for the assessment of ecological
toxicity. They were bred in tap water dechlorinated by a water conditioner. The fish were
fed Tetra KilliMin from Spectrum Brands Japan, Inc. (Yokohama).

17

The purchased medaka were held for one week in a place other than the test aquarium(fish tank) for acclimatization. Medaka with deformities (such as backbone deformities)
were eliminated, and finally 10 medaka per beaker were selected for the ecological
toxicity test.
2-2-1-2-2 Ecological toxicity experiments
Ecological toxicity experiments were performed under two conditions. The semistatic
experiment was performed according to the OECD TG 204 guideline: Fish, Prolonged
Toxicity Test: 14-day Study [64] under CF inputs of 0 mg/L (the control), 5 mg/L, and 50
mg/L. Table 4 shows the detailed test conditions.

Table 4 Conditions for semistatic ecotoxicity experiment
Item

Experimental methodology and condition

Organism species

Japanese medaka, Oryzias latipes(orange-red variety or "Himedaka")

Test medium

De-chlorinated (chlorine removed) tap water

Test period

4 weeks (28 days)

Number of organisms

10

Test method

Semi-static test in accordance with OECD TG
204: Fish, Prolonged Toxicity Test: 14-day
Study [64](water is renewed continuously in the test
chambers)

Test temperature

21–25 °C

Feeding frequency

Once a day

Number of tests

3

Measurement item

Number of deaths, abnormal shape, behavioral
inhibition, food intake, water temperature andpH

For the static experiment, we set our own test conditions, referring to the OECD TG204
guideline, and used the same CF inputs as in the semistatic experiment. Table 5 shows thedetailed test conditions.

18

Table 5 Conditions for static ecotoxicity experiment
Item

Experimental methodology and condition

Organism species

Japanese medaka, Oryzias latipes(orange-red variety or "Himedaka")

Test medium

De-chlorinated (chlorine removed) tap water

Test period

4 weeks (28 days)

Number of organisms

10

Test method

Static test
(water is not renewed in the test chambers)

Test temperature

21–25 °C

Feeding frequency

Once a day

Number of tests

4

Measurement item

Number of deaths, abnormal shape, behavioral
inhibition, food intake, water temperature andpH

The CFs placed in the aquarium consisted of primary heated product samples (carbonized
CFs after partial firing treatment, where the fiber length was 0.2–3.0 mm) were obtained
from Carbon Fiber Recycle Industry Co. Ltd. (Gifu, Japan).

2-2-1-2-3 Microscopic observation of medaka
After the death of the medaka, the epidermis and internal organs were observed with aphase-contrast microscope to check for the presence of CFs. Further, the internal organsof the medaka were excised, crushed, and examined for the presence of CFs.

2-2-1-2-4 Medaka transparency experiment
To observe the effects of the CFs more clearly, pigments were removed from theepidermis of the medaka using trypsin and alkaline procedures according to Yoshioka etal. [65]. Note that to stop the action of the trypsin, the trypsin was removed from the sample
bottle, and the medaka were washed with water several times. Then the medaka were
soaked in a liquid containing 0.5% KOH and glycerin.

192-2-1-2-5 Determining the number of colonies in aquarium water onstandard agar medium
The water in an aquarium with surviving medaka was diluted 100-fold with phosphatebuffered saline (PBS) and applied to a standard agar medium. The medium was preparedby growing Saccharomyces cerevisiae for two days at 30 ℃ in a yeast extract-peptone
dextrose medium (15.0 g of agar, 2.5 g of yeast extract, 5.0 g of peptone, and 1.0 g of
glucose) [66].
2-2-1-2-6 DNA extraction
The DNA of microorganisms in the water was extracted using an Extrap Soil DNA Kit
Plus, Ver. 2 (Nippon Steel Eco-Tech Corporation, Kisarazu, Japan) according to themanual [67, 68]. Water (1,000 mL) was collected from a beaker in which medaka were living
and filtered through a membrane filter (pore size, 0.1 μm) manufactured by Advantec
Toyo Kaisha, Ltd. (Tokyo, Japan).
2-2-1-2-7 Gene amplification
Gene amplification was performed by the polymerase chain reaction (PCR) using
universal primers. The designed sequence of primers is shown in Table 6. The reagentswere prepared using a KAPA kit (Kapa Biosystems, Inc., Wilmington, DE, US) according
to the manufacturer’s instructions [69]. The 16S rRNA gene V3-V4 region was amplified
by PCR using 2X KAPA HiFi HotStart ReadyMix.

Table 6 Entire primer sequence
Area Species

16S

BacteriaSequence of the entire primer (Illumina adapter | index (for forward
primer only) | Region-specific sequence) [70]Forward primer

Reverse primer

TCGTCGGCAGCGTCAGATGTGTATAAGAGACAG| index |GTCTCGTGGGCTCGGAGATGTGTATAAGAGACAG|GACTACHVGGGTATCTAATCC

CCTACGGGNGGCWGCAG
As a primer, an adapter manufactured by Illumina, Inc. (San Diego, CA, US) was added20

to 341fF805R (S-D-Bact-0341-b-S-17/S-D-Bact-0785-a-A-21) [70]. As the forward
primer, a six-base index sequence [71] for sample separation was added between theadapter manufactured by Illumina, Inc. and each specific sequence.

2-2-1-2-8 Next-generation sequencer data analysis
The PCR amplification products were submitted to the next-generation sequencer
service at Gifu University, which employs Illumina MiSeq (San Diego, CA, US).
First, using the obtained FASTQ sequence files, each sample was separated on the basisof the index sequence, and the primer and index sequences were removed. Next, forsequencing after separation, the forward and reverse sequences were combined, andquality filtering was performed using a Q value of 30 as the cutoff. Then, operationaltaxonomic units (OTUs) were formed by clustering based on 97% sequence similarity.
Finally, chimeric sequences and low-frequency OTUs (less than four sequences in total)
were removed.
The above series of operations was performed using the software package Claident
v0.2.2017.05.22 (https://www.claident.org/). Representative OTU sequences wereclassified using RDP Naive Bayesian rRNA Classifier, version 2.11 [72].
During the classification, RDP 16S rRNA training set 16 was used as a reference database,and the 80% confidence threshold was used.

2-2-1-3 Results
2-2-1-3-1 Medaka survival rate
2-2-1-3-1-1 Survival rate of medaka under semistatic conditions
To examine the effect of CFs on ecosystems, we determined the effect of CFs in water
on medaka. Therefore, on the basis of the standard ecotoxicity test OECD TG 204: Fish,
Prolonged Toxicity Test: 14-day Study, we conducted an ecotoxicity experiment in which
medaka were exposed to CFs for 4 weeks (28 days) under semistatic conditions. Under
these test conditions, we continuously renewed the water in the aquarium.
The graph in Fig. 5 shows the survival rate of the medaka for 28 days and that in Fig. 6
shows the results of the Log-rank test [73, 74] for all samples under semistatic conditions.
The p-values of the Log-rank test were all greater than 0.05, and the test results showedthat there was no significant difference between the survival curve of medaka at CF inputsof 5 and 50 mg/L and the control samples.
21

Although there is some dispersion, the three experimental results under semistatic
conditions do not differ significantly. Therefore, exposure to CFs is unlikely to affectmedaka under such conditions.

(A)

(B)

22

(C)

Fig. 5 Survival rate of medaka under semistatic conditions(A) First experiment: after approximately two weeks, the number of surviving individuals
decreased. Ultimately, there was no significant difference in the number of surviving
individuals under both CF inputs.
(B) Second experiment: the number of surviving individuals began to change on day 17,
and the number of surviving individuals was ultimately the same under all conditions.
(C) Third experiment: there were no significant differences in the number of surviving
individuals.

Fig. 6 Results of the Log-rank test of all samples under semistatic conditions
Treatment 1: control, Treatment 2: CF input of 5 mg/L, Treatment 3: CF input of 50 mg/L
Log-rank p-values for comparison between: CF inputs of 5 and 50 mg/L and control
samples = 0.2,
23

CF input of 5 mg/L and control samples = 0.5,
CF input of 50 mg/L and control samples = 0.08, andCF input of 5 mg/L and CF input of 50 mg/L = 0.3.
Note: In general, p = 0.05 or less indicates a significant difference.

2-2-1-3-1-2 Survival rate of medaka under static conditions
CFs are reportedly able to purify water [53, 56], which might be relevant for theexperimental results obtained under semistatic conditions. If CFs have a purifying effect,
it is thought that raising medaka under static conditions for a long period (4 weeks ormore) may result in improved water quality and thus extend the life of the medaka. Thus,
we conducted an additional experiment under static conditions.
Under static conditions, the survival rates of medaka at CF inputs of 50 and 500 mg/L
were significantly lower than that of the control sample, as shown in Fig. 7. The survival
rate of medaka at a CF input of 50 mg/L was lower than that under semistatic conditions,
except for the first experiment.
The Log-rank test p-values were less than 0.05, except for the comparison between CF
inputs of 50 and 500 mg/L, as shown in Fig. 8.
The results of the survival time analysis (Log-rank test) of all samples showed that there
was a significant difference between the survival curve of medaka at CF inputs of 50 and
500 mg/L and that of the control samples.

(A)

24

(B)

(C)

(D)

Fig. 7 Survival rate of medaka under static conditions(A) First experiment: after approximately three weeks, the number of surviving
25

individuals changed; ultimately, the number of surviving individuals was lowest at a CF
input of 500 mg/L.
(B) Second experiment: after approximately two weeks, the number of surviving
individuals at a CF input of 500 mg/L decreased sharply.
(C) Third experiment: after approximately one week, the number of surviving individuals
decreased sharply at CF inputs of 50 and 500 mg/L.
(D) Fourth experiment: after approximately 10 days, the number of surviving individuals
decreased sharply at CF inputs of 50 and 500 mg/L.

Fig. 8 Results of the Log-rank test of all samples under static conditions
Treatment 1: control, Treatment 2: CF input of 50 mg/L, Treatment 3: CF input of 500
mg/L
Log-rank test p-values of comparison between: CF inputs of 50 and 500 mg/L and control
samples= 2e-05,
CF input of 50 mg/L and control samples = 0.004,
CF input of 500 mg/L and control samples = 2e-06, andCF input of 50 mg/L and CF input of 500 mg/L = 0.06.
Note: In general, p = 0.05 or less indicates a significant differenceThis result suggests that CF exposure is lethal to medaka under static conditions.
Moreover, for the control samples, the survival rate under static conditions was evidently
lower than that under semistatic conditions. This possibly occurred due to thecontamination of the growing environment (i.e., changes in the microbiota) under static
26

conditions and in the CF input conditions the degree of the contamination was not lower
than that of CF free conditions. Therefore, the medaka mortality under static conditionsis attributed in part to the CFs.

2-2-1-3-2 Presence of CFs in medaka epidermis, viscera, and feces
CF exposure is lethal to medaka under static conditions. Thus, the CFs must come into
contact with the medaka. We observed the CFs in or on medaka. To observe how CFs
penetrate the medaka, CFs were placed in a medaka aquarium. The results demonstrated
that needle-like CFs had adhered to the entire skin of the medaka, as shown in Fig. 9. The
attached CFs may have direct physical effects or systemic effects on the medaka.
CFs were observed in the viscera of the medakas at CF inputs of 50 and 500 mg/L. This
result indicates that the medaka ingested CFs with food or mistakenly ate CFs as food; itis thought that some of the ingested CFs remained in the body, and the rest were excreted
as feces. As expected, CFs were not present in either the viscera or the feces of the control
samples, as shown in Fig. 9.
Oshima et al. [75] investigated the pharmacokinetics of medaka using virgin microplastic(polystyrene, 2–200 μm) and reported that the microplastic that entered the body was
excreted in approximately 1 day. However, our experiment demonstrated that CFs are lesslikely to be discharged from the body.

27

Semi-static conditions in accordance with OECD TG 204
Control

CF 5mg/L input

Static conditions
CF 50mg/L input

CF 500mg/L input

epidermisviscerafeces

Fig. 9 Observations of CFs Arrows indicate examples of CFs adhering to or penetrating the medaka.
28

2-2-1-3-3 Medaka transparency experiment
To observe the CFs on the medaka epidermis more clearly, a medaka from theexperiment with a CF input of 50 mg/L was transparentized according to a general
preparation procedure [65]. Consequently, the appearance of CFs adhering to the skin of
the medaka became clearer, as shown in Fig. 10.
The results in sections 3.2 and 3.3 indicate that CFs adhere to the body surface of the
medaka and that the medaka take CFs into their bodies. We assume that over the longterm, injuries would appear, followed by infections at the wound site, and finally the
medaka would die.

Fig. 10 Observations of medaka epidermis (caudal fin) after transparency processing(50 mg/L CF input under static conditions)
Arrows indicate examples of CFs adhering to or penetrating the epidermis.
2-2-1-3-4 Contamination of medaka aquarium by bacteria
An apparent difference between the semistatic and static conditions is the water quality.
The static water appeared to be contaminated by microbes. To examine the contaminationof the medaka aquarium, we measured the number of colony-forming unit (CFUs) on astandard agar medium.
Water (100 μL) from the medaka aquarium was applied directly to a standard agar
medium. Except on day 0, the samples were diluted 100-fold with PBS, and the CFUs
were counted after two days of incubation at 30 ℃.
Fig. 11 shows the number of viable bacteria under static conditions. Compared to thaton day 0, the number of viable bacteria increased for 7 days and then remained constant;
all three samples showed similar behavior over time.

29

Number of colonies (CFU/mL)

160000Control
8000
CF 50 mg/L input
400
CF 500 mg/L input
20

1
㻜

㻣

㻝㻠

㻞㻝

Day

Fig. 11 Number of viable bacteria under static conditions.

2-2-1-3-5 16S rRNA gene analysis
The medaka aquarium under static conditions is clearly contaminated with bacteria. We
analyzed the bacterial flora. Fig. 12 shows the structures of the bacterial community at
the genus level for each experiment. The genus names of each bacterium are given on theright side of the figure. Colors indicate different genera of bacteria.
To elucidate the effect of CFs attached to the body surface and inside the body of the
medaka, water was sampled from each medaka aquarium with CF inputs of 0, 50, and
500 mg/L under static conditions, and the 16S rRNA gene was analyzed.
The results revealed changes in the microbiota of all the samples, and the flora were
found to become more complex over time. That is, the water was initially a single
ecosystem, but over time, the numbers of various microorganisms increased. This result
indicates that there was a risk of infection.

30

Relative abundanceControl

CF 50mg/L input

CF 500mg/L input

Fig. 12 Microbiota analysis results under static conditions.
Bar plots of the taxonomic profiles of each sample at the genus level.
Colors show the relative abundance of each genus.

2-2-1-4 Discussion
The carbonized CFs used in this experiment were 0.2–3.0 mm in length; thus, they werelonger than those used by Nakano et al. [51], which were less than 80 μm in length.
However, adverse effects on some medaka were observed.
Under semistatic conditions, none of the obtained data indicated that the CFs affected
the survival of medaka. We may conclude that the mortality was low under these
conditions.
By contrast, under static conditions, the number of surviving medaka decreased
remarkably. The number of surviving medaka at a CF input of 50 mg/L was much lower
than that under semistatic conditions. This result shows that the suspension of CFs in thewater is not always environmentally safe. As the CFs had little effect under semistatic
conditions, the water quality of the samples may affect the medaka health.
31

We observed dead medaka and confirmed that CFs were attached not only to theepidermis and viscera but also to the feces of the medaka, and the CFs were needle-likeand easily adsorbed. This result indicates that the medaka ingested CFs along with foodor mistakenly ate CFs as food; it is thought that some of the ingested CFs remained in thebody, and the rest were excreted as feces. The CFs in the bodies and gastrointestinalorgans were similar in shape to the CFs before exposure, and they could penetrate themedaka body and organs.
Bacterial infections can occur where CFs enter the body, and these may be fatal. The
microbial number increased for 7 days under static conditions, and the microbiota became
diverse. These results support an increase in bacterial infections. Therefore, they suggestthat in environments where the water is stagnant, CFs can be considered to be actively
toxic to medaka.
It is not uncommon for fish to be injured by objects in the water in a real environment.
Therefore, depending on the growth environment, wounds are assumed to be fatal.
Further studies are needed to determine whether and to what extent CFs that are released
into the environment will increase the number of wounds to fish.
Herein, we apply our experimental results to natural environments. It can be assumed
that semistatic conditions occur in rivers, whereas static conditions occur in areas of
enclosed water, such as enclosed gulfs, lakes, and reservoir. Rivers are typically in flux
and the water is changing; however, enclosed water shows little change, and the water isstable.
In rivers, it is possible that CFs accumulate near the banks and in deep pools where thewater is calm; however, most CFs are expected to flow easily. By contrast, in lakes andreservoirs, because there is almost no flow, CFs are likely to accumulate.
Furthermore, in terms of hygienic analysis, the relationship between the survival rate of
medaka and the CF input was analyzed using the difference in the microbiota of the waterin the medaka aquarium.
Flavobacterium is a pathogen of freshwater fish, and Flavobacterium columnare causes
infectious diseases such as tail diseases (for example, frayed and ragged fins), which is
known as columnaris disease in warm-water fish such as medaka. In this experiment, theproportion of Flavobacterium was low except on day 0. This result suggests that taildisease is not likely to be the main cause of medaka fatality.
Mycobacterium, which causes swimming disease, was also found at CF inputs of 50 and
500 mg/L, but not in the control samples. During the observation of the medaka in theaquarium, swimming disease was confirmed several times. It is therefore highly likelythat Mycobacterium is one of the causes of medaka mortality.
In summary, it is highly probable that the reduction in the number of living medaka
under static conditions resulted from the presence of CFs, which increased the occurrenceof infections. However, we do not expect a CF concentration of 50 mg/L in our actual
environment under normal circumstances, and in practical situations, injured fish accountfor a small proportion of all medaka.
In addition, as medaka mortality can be affected by various factors including bacteria,
parasites, and physical effects, we conclude that it is difficult to clarify a specific causeof death in terms of infectious disease.

32

2-3. Measurement of airborne carbon fibers at SME’s site where CFRPs are handled
2-3-1 Methods of air sampling࣭Location: Laboratory, Moritomi Environmental Engineering
Laboratory at Gifu prefecture, Japan
࣭Measurement date: 2021.3.29, 30
࣭Equipment: Particle counter (Lafil400)
࣭Flow rate: 23 L/min (60 Hz)
Photo of airborne CFs
࣭Measurement hours:12 H
࣭Carbon fiber was collected on a membrane filter(4.5 cm in diameter, 1 μm in mesh)
࣭Work in the laboratory: Cutting, rubbing, bending, and twisting ofrecycled carbon fibers to make twisted yarn.
࣭Room environment: Windows basically closed, four commercial air
purifiers running all day.
Lafil400
࣭Equipment location: on the floor
2-3-2 Results of data analysis
Analysis conducted by AIST Chubu Center
Table 7. Results of the measurement of the number of airborne carbon fibers in thelaboratory atmosphere
Measurement date:
Measurement date:afternoon of 2021/03/29
afternoon of 2021/03/30
Carbon fiber related work was not Carbon fiber related work was
conducted in the morning of the conducted in the morning of the
day.
day.
Photo ofmembranefilter after
image
correction

0.3μm
0.5μm
1.0μm
2.0μm
5.0μm
10.0μm

1504792239544
13245
1084
644
215

1599565265169
15296
2109
2054
893

33

㻝㻜㻜

㻤㻜

⧄⥔ᮏᩘ

Number of fibers

㻢㻜

㻠㻜

㻞㻜

㻜

㻜

㻝㻜㻜

㻞㻜㻜

㻟㻜㻜

㻠㻜㻜

㻡㻜㻜

⧄⥔㛗䛥㻔P㼙㻕

Fiber length (μm)

Fig.13 Measurement result of the number of carbon fibers on the membrane filter usedon 30 March 2021 (automatically analyzed by software)
The membrane filters measured on 30 March 2021, just after the carbon fiber related work
was done, were observed by a stereo microscope, and after image correction, the fiber
length was identified.
As a result, carbon fibers (long and thin needles) were recognized.
Most of the carbon fibers were 20 to 60 μm in length, and the maximum length was about
0.5 mm (500 μm) as shown in Fig. 13.
However, there were also many dust particles other than carbon fiber, such as dust anddirt.

2-4. Study on risk management approach for
manufacturing/handling sites using control banding method

recycled

CFRP

2-4-1 Introduction
CFRP is mainly used for structural materials in the aircraft and automotive industries
due to its light weight, high strength, and other properties. As an alternative to metal andglass fiber composite materials, CFRP is expected to be used in many future applications
such as wind power generation [76] and flying cars, and the amount of CFRP used is
expected to increase year by year, with demand exceeding 190,000 tons/year by 2050. [2]However, the recycling of CFRP is currently not progressing well, especially in Japan,
and almost all of the waste CFRP is disposed of in landfills, which is considered to be a
problem.
34

In addition, in response to the recent trend toward decarbonization, some shareholders
and others are questioning the existence itself of the CFRP manufacturing industry, whichemits a large amount of CO2 during production. [77]Given these circumstances, in order to further expand the use of CFRP in the future, it
is strongly desired to reduce the environmental impact of the entire value chain fromproduction to recycling by converting CFRP into recycled products. [78]
Carbon fiber (CF) (primary heated product) extracted from the pyrolysis process, which
is currently the leading technology for CFRP recycling, contains a large amount of
impurities such as tar, and there are concerns about its impact on workers and theecosystem compared to virgin products. The possibility of unintentional containment of
impurities such as glass fiber, metal foil, and dust has also been pointed out in research
reports by AIST [40], [79].
Ueda et al.[ 61] summarized the issues to be addressed to increase social acceptability andpromote CFRP recycling and stated that it is necessary to resolve concerns about thebiological and ecological effects of CF dust released from recycling-related operations at
workplaces and other sites in the future.
Moreover, Moriyama et al.[52] had conducted cell tests using recycled CF artificially finely
ground in a ball mill and reported that CF can be finely ground down to several 10 nm byprolonged grinding in a ball mill.
Through measuring by dynamic light scattering (DLS), they reported that with proper
fractionation and centrifugation, it is quite possible to refine CFs to 100-300 nm indiameter, some of which are several 10 nm in diameter.
Given the fact that CF can be made into nanoscale materials under artificial conditions,
it can be said that if recycling technology is further advanced in the future [81] and CF isused and utilized over and over again, it may eventually be micronized to the nano-level.
Therefore, in recycled CFRP, it is desirable to conduct control measures at the nanoscalelevel, rather than at the microscale level normally found in virgin products.
In recent years, studies in Europe and the United States have reported the formation of
NOAAs (nano-objects, and their aggregates and agglomerates greater than 100 nm).
The composition of NOAA is shown in Figure 14 [82].

Fig. 14 Composition of NOAA[82]35For example, with regard to occupational exposure to NOAA, studies have been
conducted on the occupational exposure risk of airborne NOAA [83]-[87] and measurementsof NOAA suspended in actual factories [88]-[92]. The results of actual sampling show thatNOAA was present in more than 70% of the samples [89]. It has also been reported thatNOAA is formed not only in air but also in liquids such as cell culture medium [93].
Moreover, with regard to industrial products, the effects of TiO2 nano bjects and NOAA
on microorganisms under UV irradiation [94], the dermal exposure of NOAA transferredto humans via sweat from antimicrobial textiles containing silver nanoparticles and UV
absorbing textiles containing TiO2 nanoparticles [95], and the dermal exposure of NOAA
transferred from TiO2 nanoparticles. A wide range of studies have been conducted,
including an evaluation of the release potential of NOAA from paints containing NOAA
[96]
and a study of the release potential of NOAA from wood products treated with coatings
containing nano-objects [97].
However, these studies do not include studies on the conversion of CF, including CFRP,
to NOAA.
As a noteworthy Japanese move, the Labor Standards Bureau of the Ministry of Health,
Labor and Welfare issued a notice "Preventive Measures to Prevent Exposure to
Nanomatearials" in 2009 [98].
In this notice, it is clearly stated that exposure control measures should be taken for dust
generated during operations involving the handling of nanomaterials.
CF is inherently a brittle material, susceptible to breakage and frying (dust).
These characteristics are more represented in recycled products, which are inferior instrength to virgin products.
Since agents such as sizing agents that modify the surface have been removed, it has thenegative characteristics of fiber breakage and frequent flyings during processing.
Therefore, dust control measures in workplaces related to recycled CFRP should be
more stringent than the current measures for virgin products because of concerns about
the impact aspects on people and the environment.

2-4-2 Current worker safety management measuresFigure 15 [99] shows a diagram that systematically organizes the manufacture, use, anddisposal of recycled CFRP from the perspective of the entire life cycle.
In the life cycle of recycled CFRP, some relevant studies have been conducted on theeffects of particulate CF on humans (workers) and the environment, including gene
expression analysis [52] using animals. However, there are still many unknowns andconcerns [100].
Although different from CF, there have been relatively few studies in the evaluation of
toxicity related to nano carbon materials.
For example, Coyle et al. [101] evaluated the cytotoxicity of products incorporating
carbon nanotubes as fillers or additives into thermoplastics for potential pathologicaleffects due to particulates released upon recycling or disposal, especially incineration.
The results show endocytosis, but no acute cytotoxicity, and that further investigation isneeded.
At CFRP handling sites, dust dispersion is a major bottleneck with respect to the impact
on people (workers).
For reference, Figure 16 shows a photograph of dust control measures at a publicresearch institute that conducts trial production and press working tests of recycled CF
36

nonwoven fabrics.
In particular, in the trial manufacture of non-woven fabrics using recycled CF, a large
amount of CF dust is generated by carding (combing) and other processes, so the workers
always wear personal protective equipment (PPE) that covers their entire body.
In a past METI-Chubu project, survey about recycling CF-related work sites of domestic
companies was conducted. As a result, it was found that countermeasure methods against
CF dust vary depending on the size of the company and other factors. [102]In many cases, large companies, such as materials manufacturers and aircraft
manufacturers, have completely isolated workers from direct contact with CF dust.
On the other hand, in small and medium-sized companies, including venture companies,
the measures taken varied greatly from company to company, and in many cases,
measures such as natural ventilation with open windows and doors were found to bepassive measures with minimal capital investment.
In particular, during the summer, there were many sites where CF-related processing
work, such as grinding and cutting, was performed with windows and doors fully opened.
Considering the above situation, it is important to develop product technology such as
dust prevention technology by surface coating treatment of materials in consideration of
the expected increase in recycled CFRP-related businesses.
However, it would be desirable to have guidance that can be used as a reference whensmall, medium, and micro enterprises implement dust control measures onsite.
Fig. 15 Production, use, and disposal of recycled CFRP from the perspective of theentire life cycle (red arrows indicate areas of concern) [99]

37























Fig. 16 Photograph of dust control measures at a public research institute
2-4-3 Proposal for a worker safety management method using control bandingIn a nutshell, control banding is a risk management (=control) method based onclassification (=banding).
Originally, COHSS Essentials was developed by the Health and Safety Executive (HSE)[103]
in the UK in 1998 for SMEs, and later the International Labor Organization (ILO)
arranged it as a toolkit for SMEs in developing countries. The main advantage is that it
enables a simple risk assessment of the health hazards of chemicals without specializedchemical knowledge.
This method has been used previously for aerosols containing ultrafine particles(welding fumes, carbon black, viruses, etc.).
The target is occupational exposure to unknown hazardous substances whose toxicity is
unknown or uncertain and for which quantitative exposure estimates are not available.
The main feature of this method is that highly skilled measurement of exposure
concentrations of chemical substances is not required.
However, it should be noted that this is only a guideline-level risk management method
and is not legally binding, that it only covers inhalation exposure of workers, and that it
assumes normal on-site work such as maintenance and cleaning, and does not consider
accidental incidents and accidents.
Controlled banding of nanomaterials (NOAA) in industrial working environments is
specified internationally in ISO/TS 12901-2 (2014) [104].
It covers NOAAs that can be unintentionally released throughout their life cycle.
This control banding approach for NOAA, like the case for common chemicals, uses
Hazard Bands (HB) and Exposure Bands (EB) to identify the level of risk to workers at38

the nanomaterials handling site and presents appropriate control measures.
With regard to research trends in control banding, Kuijpers et al. [105] and Bekker [106]have conducted studies for further development of control banding tools, including
validation of existing NOAA exposure assessment models, which tend to be conservative.
Bekker [107] discusses advanced modeling approaches for quantitative exposure
estimation, the second step after applying control banding.They also evaluate theeffectiveness and applicability of the "Advanced REACH Tool-ART" software.
The banding procedure for NOAA is shown in Figure 17.

Fig. 17 Banding Procedure
Note that in the hazard banding in (2), various factors such as in vivo persistence, easeof particles reaching the airways, ease of deposition in the airways, and biologicalresponse, as well as toxicity, are taken into account in assigning hazard levels for the
NOAA in question. The bands will be classified based on the toxicity of basic, similar
known chemicals.
In the exposure banding of (3), the exposure potential to humans shall be assigned,
taking into account the ease of airborne release of the target NOAA.
Based on recent research results on dust generated in various recycled CFRP-related
operations, such as the firing process, paper making process, cutting, polishing, andmachining of recycled CF, it is undeniable that the dust may change from micro-scale tonano-scale.
The possibility of formation of NOAA by nano scaling cannot be denied at the sametime.
NOAA is currently being discussed in international forums.
For example, ISO/TC229 (Nanotechnology)/WG3 (Environment and Safety
Subcommittee) is engaged in activities related to standardization and standardization of
methods for measuring airborne NOAA amounts, etc. In this activity, it is also stated thatNOAA will become a target for control in the workplace and environment [108].
39

In spite of the above situation, at present, no consideration has been given to thenanoscaling of CF dust in the process of recycling and other industrial processes, and tothe conversion of CF dust to NOAA.
Therefore, the application of NOAA's controlled banding approach in an industrial work
environment to recycled CFRP-related work sites is useful in terms of improving worker
safety management aspects.

2-4-4 Examples and results of control banding applications in the fieldIn this study, we attempted to apply NOAA's control banding to the CFRP recycling
operations of Company A, a SME located in Gifu Prefecture.
Company A is mainly engaged in removing CFRP from waste CFRP products using thecalcination method, and has 10 primary pyrolysis furnaces and one secondary
carbonization furnace in its plant. In addition, the removed CF is bagged into flexible
container bags by hand.
The banding procedure is shown in Figures 18 [104],19[104] and Table 8.
Table 9 shows the results of the comparison with the current management measures.
For reference, Figure 20 shows the measurement results of particle size and particle size
distribution of CF dust in the laboratory of a SME that actually conducts processing
operations such as fiber opening using recycled CF manufactured by Company A.
In this case, a particle counter Lafil 400-LF30 (Rocker Scientific) was used to measurefor 12 hours.
Figure 20 shows that although the data is not from the actual Company A work site,
there are some particulates below 0-20 μm that could be categorized as NOAA. In the
future, it would be desirable to further improve the sampling accuracy to cover thenanoscale and further investigate the presence or absence of NOAA.
As a result, there is a difference between the content of the control measures
recommended from the application of control banding (CB-5) and the content of thecontrol measures of the current Company A (CB-2), which has already obtained ISO
14001 (environmental management system) and ISO 9001 (quality management system)in 2020.
Currently, Company A is conducting measures ranging from general ventilation to theinstallation of local exhaust ventilation, however the control measures recommended by
the banding this time present complete containment (total isolation) so that workers do
not come into contact with any CF dust. This result was consistent with the real situationof the work environment in which workers are exposed to CF dust every time when they
remove recycled CF from the furnace and pack it in bags.
Therefore, the results of the application of NOAA's control banding to a CFRP
recycling-related work site indicate that further studies are needed for other sites, and thatit does not present an ideal control method when considered in total, including costeffectiveness, etc. However, considering its advantages, such as the fact that measures
can be easily studied without measurement, control banding is a useful risk management
method.
40

Fig. 18 Hazard Band (HB) assignment [104]The term "fiber paradigm" refers to the physiopathological mechanisms that cause
asbestos-like mesothelioma.CF is not an asbestos-like WHO fiber (inhalant fiber (WHOfiber definition): "a fiber that is at least 5 μm long, less than 3 μm in diameter, and withan aspect ratio (length to diameter ratio) of at least 3:1"), so the answer is "No"Fig. 19 Exposure band (EB) assignment [104]





41

Table 8. Control band (CB) fitting
















Table 9. Results of applying NOAA-covered control banding to Company A(Comparison with current management measures)

















Fig. 20 Results of air sampling in the laboratory where processing work is performed
using recycled CF manufactured by Company A.
42

2-4-5 Discussion and Conclusion
In response to the recent trend toward decarbonization, it is important to recycle CFRP,
which emits a large amount of CO2 during manufacturing process in virgin products, inorder to exist as a material.
The current recycling technology [109] is basically a down-cycle, and the fiber length of
CF gradually shortens with each repeated recycling.
And eventually, it may be micronized to nanoscale particles to form NOAA, based on a
discussion of recent research results.
However, toxicity derived from the nanosize of some nanomaterials has been reported
in recent years, raising concerns about their impact on human health and the environment,
and methods for evaluating their safety remain unestablished [110].
Through studies by the Health and Safety Executive (HSE) [103] in the UK and the
National Centre for Occupational and Environmental Research [111] in Denmark, it has
become clear in recent years that nanoscale particles do not exist on their own but
polymerize to form NOAA, and their properties, including toxicity, are still poorly
understood.
In such a worrisome situation, proactive implementation approach before exposure ismore important than retroactive implementation approach.
Currently, not enough research has been done on CF, including CFRP, to evaluate
toxicity, including human and animal studies.
In this controlled banding, the lack of toxicity data led to a risk assessment on the safe
side and the most conservative control measures, which resulted in the recommendationof complete isolation. The full isolation measure is difficult to implement in practice for
SMEs due to the high capital investment, and as a result, they tend to wear PPE that covers
the entire body.
As everybody can easily imagine, PPE that covers the entire body is cumbersome towear and makes work difficult, especially in the summer.
Therefore, further research on toxicity assessment of CF, including CFRP, will be needed
to improve the accuracy of recommended control measures when applying control
banding.
The application of control banding to the work site where recycled CFRP is handled, as
described in this report, has several advantages, including the fact that sampling(measurement) of exposure concentrations, which requires advanced technology, is notnecessary, and the study of countermeasures is easy to perform.
The simplicity and accuracy of the method make it useful for SMEs to consider control
measures, and we recommend its application to SMEs.
Finally, it is believed that the application of this control banding to SMEs will contributeto the achievement of the UN Sustainable Development Goals (SDGs) "8: Decent Workand Economic Growth" and "12: Responsible Consumption and Production".

43

3. FUTURE PROSPECTS IN CFRP RECYCLING
3-5-1 Movement of further reducing of environmental impact
Table 10 summarizes the products in which recycled carbon fibers have actually been
adopted. All of these cases are from Europe and the United States, not Japan. In
particular, in Japan, although the recycling technology of carbon fiber materials has
been established in some areas, it is difficult to obtain added values due to its material
characteristics, and the use of recycled materials has not progressed smoothly. The
development of technology to recycle carbon fiber-based materials with high added
values is still underway.
Table 10. List of major applications of recycled carbon fibers
Product area
Electronic
products

Examples of recycled carbon fiber applications
Laptop bodyIn the U.S., recycled carbon fiber products have been adopted mainly
by DELL for notebook PC cases, and some other brands have also
started to adopt them. DELL has teamed up with Carbon Conversions
Inc. of the U.S., a supplier of recycled carbon fiber, and is working
with aircraft manufacturers to collect off-spec, surplus, and scrap CFs
and cut them into small pieces and pelletize them, and then compoundthem with resins for use in notebook PC covers.
For example, in the Latitude 7300, launched in 2019, by using rCF(18.8% content) for the lid of the notebook, the weight has been
reduced by 24g compared to the previous model.
IC chip tray

Energy field

Wind power generation-related products (wind turbine nacellecovers, etc.)
In Europe, where wind power generation has been developed as anenergy source, recycled carbon fibers have been adopted for windturbine nacelle covers. Compared to glass fibers, the use of carbon
fibers can reduce the deflection of wind turbine blades.

44Automotiveparts

Roof coverBrake rotors
Hood
Trunk partitions
A-pillarC pillar
For automotive applications, the amount of use is increasing inEurope and US for OEMs. In addition to C-pillars, which attracted
attention in BMW's 7 series, recycled carbon fibers are also used inroof covers and other applications.

Aircraft field

Side panel
Recycled carbon fibers have also been used in airplane side panels
and access doors.
In December 2014, Boeing issued a press release stating that theaccess doors on the underside of the wings of the Boeing 787
Dreamliner are manufactured by using recycled CFRPs made from
scrap materials from the Boeing 787 manufacturing process.
This is the first time that carbon fibers which were recycled fromaerospace components had been used as a component in commercial
aircrafts. Boeing is working with Rolls Royce, a global engine
manufacturer, and other companies to promote carbon fiber recycling
business.

Space fieldAC power supply components
Recycled carbon fibers have also been used for AC powercomponents in spacecraft. However, the hurdles to entry in theaerospace industry are high due to their high specifications formaterial properties and performance.

Other products
Sports playground equipment, Molding materials related to 3D printing materials,
Medical equipment (X-ray diagnostic beds, X-ray equipment for medical use, etc.)
It has been shown that a weight reduction of 100 kg in an automobile vehicle is worth
a reduction of 20 g/km in CO2 emissions, and the wide use of recycled CFRPs in
vehicles is expected [112]. The National Composites Center (NCC) at Nagoya University
has successfully fabricated a 100% thermoplastic CFRP automobile chassis by using the45

Long Fiber Thermoplastics Direct (LFT-D) method, which mixes thermoplastic resinand virgin carbon fiber. Under these circumstances, in recent years, there has been ashift in thinking in terms of reducing environmental impact, aiming for "plastic-free"composites with paper (pulp) (so to speak, "Carbon fiber-reinforced paper"), rather thanconventional composites with petroleum-based plastics. As an advanced example,
SANKEN CORPORATION is mixing carbon fiber with paper to make carbon fiber
sheets (paper), which they are aiming to use as heating elements (components that
dissolve ink in inkjet printers). Although traditionally, keeping affinity with matrix
resins has been a challenge in composite materials, there has been a changing of the wayof thinking by focusing on the concept of ”reuse”, in which recycled CFs (rCFs) are not
returned to the composite, but are used as a nonwoven fabric as they are, such as sputter
sheets (sheets for catching welding sparks). When considering the reuse of CFRPs, it isalso a good point that they can be manufactured directly by recyclers themselves
without going through a compounder, a company that processes materials into pellets
etc and sells them to molding and processing manufacturers.
Moreover, the introduction of less environmentally damaging recycling methods isalso highly required, and there is a movement to devise ways to make the products
easier to recycle from the production design stage. It is known that separating the resin
matrix from waste CFRP at the end-of-life stage is very difficult. In order to dissolve
current thermoset resins, aggressive chemical or high-temperature reaction conditions
are required, which can cause damage to the recovered CFs. Therefore, it is a good idea
to use biodegradable resins in the manufacturing stage of new products [60]. Lastly, I
regard it is effective to aim for alternative applications of “activated carbon” (utilizing
the performance of carbon itself), in addition to the reuse of non-woven fabrics such as
sputter sheet. For example, it is a way to look for applications in environmental fields
such as exhaust gas treatment, water quality, and soil improvement.
3-5-2 Advantages of recycled compared to virgin CFs and its utilization
Regarding energy consumption (CO2 emissions), the following has been elucidated [60].
-vCFs: 198–595MJ/Kg (about 10 times higher energy consumption than glass fibers)-

rCFs: 38.4MJ/Kg (when using fluidized bed method)46

-Regarding cost, for automotive applications, if the plant's production capacity is
500–6,000 tons per year, it is expected to be less than $5 per kilogram ($5/Kg),
which is about 15% of vCFs. However, at the production capacity of 100 tons per
year, the cost will be about $15/Kg.
In summary, the advantages of rCF products over virgin products are mainly

environmental and price aspect. In recent years, when evaluating upstream recycling
technologies, downstream automakers have been asking how much their recycling
technologies can contribute to achieving the SDGs and decarbonization. Not only ifthey have the ability to recover clean rCF from waste CFRP, but also the ability torecover them with a low LCA values is becoming an important factor.
Here, we further pursued the superiority of rCFs and reorganized the other advantages.
It is often said that vCFs are strong, but have weak elongation and cannot be bent well,whereas rCFs have less strength than virgin ones, however rCFs are easier to form whencreating a three-dimensional structures. In terms of compensating for the shortcomingsof vCFs as mentioned above, twisted yarn is a very viable option. The reason is thattwisting can change the elongation and shrinkage, and also can change the formability.
The low performance of ordinary rCF short fibers makes it difficult to apply them tostructural components such as automobiles, however, by making them into continuous
yarns like twisted yarns, the performance can be improved. By establishing the twisted
yarn technology, it is highly likely to meet the needs of all users. By mixing rCF milled
fibers during 3D printing and using rCF powder as a reinforcement material in thepolymer, it is expected to make the created objects less distorted. Therefore, if 3D
printers are used widely in the future, rCFs can be expected to be used more [113]. It is
generally believed that milled carbon fiber with a length of less than 200 μm (0.2 mm)
does not have sufficient strength. This has been an issue in the development ofapplications for recycled carbon fibers. In these circumstances, Chubu Center of AIST
has developed a new technology to improve oxidation resistance (heat resistance) andadd insulating properties of milled carbon fibers with a length of about 200 μm (0.2mm) by coating its surface with silicon carbide or silicon nitride (ceramic coating) [114].
This technology is so-called "upcycling", which means a recycle that improves physicalproperties and increases added value and makes it possible to improve thedecomposition temperature to 600–700℃, which is higher than that of ordinary carbon
47

fibers (around 500℃). rCFs have different surface properties compared to vCFs. Theinterfacial adhesion between CFs and matrix resin when using rCFs is higher and at thesame time the number of functional groups on the surface is lower than when using
vCFs [115]. CFRP products using rCFs have different surface treatment characteristics
from those using vCFs. It is therefore hoped that applications will be developed that canmake good use of this difference in characteristics. Research on the superheated steam(SHS) method [116], in which high temperature steam, nitrogen, carbon dioxide, etc. areused at the firing stage in order to increase the surface activity, is also being conductedunder the support of the Japan Fine Ceramics Center (JFCC). By using this technology,
it can be possible to modify the fiber surface (improvement of the adhesion to resin).
Technically, SHS method is expected to improve the adhesion between fibers and resinin addition to fiber recovery. As a result, post-treatment processes such as sizing
treatment for recovered fibers can be deleted, and the manufacturing cost of CFRP canbe reduced. Moreover, surface pre-treatment technology of CFRP to activate and clean
the surface of carbon fiber prior to resin bonding by using a dry process atmosphericpressure plasma has already been developed. The research on the evaluation of theinterface properties of rCFs and the quantitative measurement of carbon residue andanalysis of impurity elements on the surface of rCFs which are both simple/efficient andaccurate has been conducted by AIST as part of the "Innovative Structural Materials
R&D" project from FY2013 -2022. They have been working on the development of asimple analytical method for impurity elements using microwave acid digestion(pretreatment) and flow injection ICP-MS
3-5-3 Organizing the unique functionalities of CFRP (irrespective of virgin or recycled)
At The Japan Carbon Fiber Manufacturers Association's 32nd Composite Material
Seminar in February 2019, Airbus executive expert said "one of the key areas wheremore effort is being made is the development of next generation multifunctional CFRP
which includes anti-contamination, self-cleaning." The key will be how much we canpromote the use of rCF and gain citizenship by taking advantage of its uniquefunctionalities (vibration damping, electromagnetic shielding, etc.) other than its lightweight and high strength. The functionalities of CFRP are listed below Table 11.
48

Although not related to functionality, there are also some products (motorcycles,
racing cars, etc.) that use CFRP because of the attractive appearance of its crease
pattern.
Table 11. Functionalities of CFRP
Functionalities

Major factor that
produces functionality

Lightweight, high strength, high elasticity (high rigidity)

CF

Excellent radio wave transmissivity

CF

Excellent x-ray permeability

CF

Excellent vibrational damping

Matrix resin

Excellent dimensional stability

CF(very low coefficient of thermal expansion)
High thermal conductivity

CFElectromagnetic shielding

CF

High radiation resistanceCF [117]Microwave absorption

CF [114]High sliding properties (high wear resistance, self-CFlubrication)
Anti-static performance

CF

Sound absorption properties (soundproofing, sound

CF and Matrix resin

absorption, sound modulation)
Impact energy absorption properties

CF and Matrix resin

Chemical resistance (acid and alkali resistance), corrosion CF, Adhesive (binder)
resistance (rust and salt damage resistance), heat

and Matrix resin

resistance (insulation), fire resistanceNon-magnetic properties

CF

Water purification characteristics

CF

Please note that above properties vary depending on the type and grade of used CFs, thematrix resin, and the laminate structure etc. The properties and rigidity of CFRP vary
greatly depending on the material used and the molding method.

49

3-5-4 Future prospects in CFRP recycling
Companies on the user side, such as automobile manufacturers, have been hoping tofurther reduce the price of rCFs. However, there is a limit to the approach to lowering
the price of rCFs. In particular, rCFs come from discarded CFRPs are finally recovered
after a series of work processes including collection, dismantling, separation, andtreatment of used products. Hence, it is very time-consuming. Though of course,
manufacturers who sell recycled carbon fibers must continue to make efforts to reduce
their costs, it is factual that there is very little room for recycled carbon fiber
manufacturers to reduce the costs. At the same time, however, it is also necessary tohave an attitude to appeal the merits of using rCFs to users.
For example, the use of recycled materials can contribute to the SDGs and the circular
economy, and therefore efforts to promote a branding for recycled materials, so-called"eco-branding" are effective. In the future, it will be necessary to create a social systemthat can generate a demand even in such a high price range. Circular economy (CE)aims at using renewable energy, eliminating toxic chemicals, and eliminating waste bybetter design of materials, products, systems and business models. As the concept of CE
is accelerated in Japan as well, it is safe to say that it will become more and more
important to evaluate the ecological impact of milled CFs or CF dust generated during
the recycling process [118].
Understandably, with repeated recycling, the length of the fiber shortens andeventually becomes milled. Therefore, the issue of the health effects of milled CFs or
CF dust on humans and other living things, as discussed in this study, is the last issue
that must be addressed when promoting a resource circulation, including a recycling.
Therefore, we consider the issue of the health effects of milled CFs or CF dust on
humans and other living things is an important theme that cannot be avoided and where
we end up eventually.

50

4. CONCLUSION
The use of recycled CF is expected to expand in the future and it is also expected that
not only in-plant waste and scrap materials but also waste materials associated with endof life machines and vehicles will be discharged in the future.
Most of the CFRP matrix resins used worldwide are thermosetting resins such as epoxy
resin. The main issue in recycling CFRP is that it is difficult to reuse by remolding becauseof the nature of the thermosetting resins. That means thermosetting resins have highmechanical properties and account for a large part of the market but are not easy to recycle.
Epoxy resins have a three-dimensional cross-linked structure, thus the complete thermal
decomposition in CFRP requires treatment in an oxidizing environment, making a certain
amount of damage to CF inevitable [119].
In this study, we organized the issues in the Japanese industrial landscape as to why
CFRP recycling businesses and technology have not yet been established.
In consequence, Environmental, health, and safety (EHS) issues still exist in promoting
CFRP recycling and among the presence of various issues, such as quality assurance andstandardization of the evaluation methods of reclaimed CF, we noticed that,conspicuously, information with scientific evidence on the toxicity of CF itself is poor
and CF is seemingly treated as a non-toxic substance without adequate verification
especially in Japan.
Despite that situation, two journal articles [51, 52] indicate that fine particles such as milledshort CF treated by industrial processes have a likelihood of reaching the human alveoli
by inhalation and CF may possibly exhibit toxicity depending on the method of treatment
and management such as firing treatment during the pyrolysis recycling process because
the inherent impurities such as dioxins attached to CF may impart toxicity to CF dust.
The conclusions that emerged from organizing the issues are we should regard theimprovement of CFRP recycling and processing methods as an important issue, because
they have a correlation with biological and health effects as well as environmental andenergy issues.
We therefore suggest that further analysis focused on elucidating the anxiety of theeffects of CF (dust/milled) itself on people and ecosystems be conducted in order to gain
a true understanding of the impact on citizens at the time of using CFRP recycled products
on an industrial scale.
Through distributing appropriate information, confirmed on a scientific basis, that will
not disrupt society, it will be possible to obtain safety and relief from anxiety for ordinary
citizens. By doing so, it will also be possible to develop a socially receptive recycling
business implementation system to make it easy for new recyclers to start a business.

51

In order to elucidate above issue, I delved into the effects of milled CFs or CF dust
generated during a CFRP recycling process on the environment and living organisms
when CFs are released into the water environment as a by-product unintentionally.
Specifically, the effect of CFs on Japanese medaka fish (O. latipes, orange-red variety
or himedaka) in the coexistence of rCFs was confirmed by experiments in a water tank.
As a result, no remarkable toxicity was observed in the CFs. However, the CFs clearly
injured the medaka. The wounds would be expected to heal in a prepared environment
such as an artificial experimental model. However, in an actual environment, especiallyin one with high biochemical oxygen demand or chemical oxygen demand, the rate of
infection of wounds by microorganisms is expected to increase.
Although only small amounts of milled CFs or CF dust are entering the aquatic
environment, the amount is expected to increase in the future as disposal and recycling
increase. If large amounts of milled CFs or CF dust are discharged in the future, the effects
on aquatic organisms such as fish will be a major concern.
We recommend formulating a solution such as preventing the transfer of milled CFs and
CF dust generated during various industrial processes to natural aquatic areas before
recycled CFs are used to replace virgin CFs for the purpose of resource circulation.
Actual air sampling in the laboratory of a SME showed that CF remained in the indoor
air for some time after the CF-related work was completed. In addition, particulates in the
0-20 μm range were also found to be present. This is a fact that should be of concern.
Obviously, with each repeated recycling, the fiber length of CF gradually shortens.
Eventually, there is concern that they will become nanoscale fine particles (NOAA).
Therefore, as part of the evaluation of occupational exposure to recycled CF minute dust,
an occupational risk assessment using a controlled banding (CB) approach was also
piloted.
The results showed that the CB method is useful for small and micro enterprises toconsider control measures as a first step.
Finally, we hope that our efforts will contribute to the achievement of sustainable
development goals such as Goal 14 of the United Nations, which covers life below waterand Goal 8: Decent Work and Economic Growth and 12: Responsible Consumption and
Production.

5. ACKNOWLEDGEMENTS
I would like to thank Dr. Hitoshi IWAHASHI and Dr. Hiroshi MORITOMI of Gifu
University for giving me an opportunity to study in his laboratory. I must thank for his
valuable suggestions and guidance. I’m also thankful to Dr. Masanori HORIE, Dr.
52

Takehiro HIMAKI and Dr. Akihiro MORIYAMA for sharing their technical and scientificknowledge to conduct this research. I also express thank to all students in Applied
Microbiology Laboratory of Gifu University for their earnest help.

6. REFERENCES
1) Grand View Research. (2016). Carbon Fiber Reinforced Plastic Market Size, Share &Trends Analysis Report By Raw Material, By Product (Thermosetting, Thermoplastic),
By Application, And Segment Forecasts, 2018 - 2024. Published Date: Sep, 2016.
https://www.grandviewresearch.com/industry-analysis/carbon-fiber-market
2) Ishino Y, Tabata M, Toyama R. (2017). Study on CFRP (Carbon Fiber Rainforced
Plastic) Combustion for Incineration:(Detail Observations of Combustion Processes of
CFRP). The Proceedings of the Symposium on Environmental Engineering 2017.27:303.
3) Keith M, Géraldine O, Gary A.L (2016). Optimisation of solvolysis for recycling
carbon fibre reinforced composites. ECCM 17 -17th European Conference on Composite
MaterialsMunich, Germany, 26-30th June 2016.
4) ams. (2016). Automotive Manufacturing Solutions Recycle route for carbon fibre. (1stOctober 2016) https://www.automotivemanufacturingsolutions.com/recycle-route-forcarbon-fibre/35335.article5) PlasticsEurope report. (2018). https://plasticseurope.org/knowledge-hub/plastics-thefacts-2018/6) Aoki C, Morita Y. (2018). The EU Plastic Strategy and Relevant Policy Trends andInitiatives for a Circular Economy. Journal of Waste Resource Circulation, Vol. 29, No.
4, pp. 286-293.
7) Meng F, Pickering S.J, McKechnie J. (2018). An Environmental Comparison of
Carbon Fibre Composite Waste End-of-life Options. SAMPE Europe Conference 2018
Southampton,UK.
8) Pimenta S, Pinho S.T. (2011). Recycling carbon ﬁbre reinforced polymers for structural
applications: technology review and market outlook. Waste Management 31, 378–392.
9) Fan W, Li D.D, Li J.L, Li H. (2017). Electromagnetic properties of three-dimensional
woven carbon fiber fabric/epoxy composite. Textile Research Journal
88(20):004051751772302.
10) Mitsubishi Paper Mills Limited (2020) Carbon fiber nonwoven fabric & recycled
carbon fiber nonwoven fabric "Carboplus & Carboplus Repro".
https://www.mpm.co.jp/products/pdf/carboplus_cellulomix_ja.pdf
11) Uhlmann E, Meier P. (2017). Carbon fibre recycling from milling dust for theapplication in short fibre reinforced thermoplastics. 1st Cirp Conference on Composite
53

Materials Parts Manufacturing, cirp-ccmpm 2017, Procedia CIRP 66, 277–282.
12) Parthasarathi Aravindan et al. (2020). Remanufacturing of Woven Carbon Fibre
Fabric Production Waste into High Performance Aligned Discontinuous Fibre
Composites. J. Compos. Sci. 2020, 4(2), 68.
13) Longana M.L, Yu H, Hamerton I, Potter K.D. (2018). Development and applicationof a quality control and property assurance methodology for reclaimed carbon fibers
based on the HiPerDiF (High Performance Discontinuous Fibre) method andinterlaminated hybrid specimens. Advanced Manufacturing: Polymer & composites
science, 2018 vol. 4, no. 2, 48–55.
14) Kai Y, Shi Q, Dunn ML, Wang T, Qi H.J. (2016). Carbon Fiber Reinforced Thermoset
Composite with Near 100% Recyclability. Advanced Functional Materials 26(33), 60986106.
15) Oliveux G, Bailleul J.L, Gillet A, Mantaux O, Leeke G. (2017). Recovery and reuseof discontinuous carbon fibres by solvolysis: Realignment and properties ofremanufactured materials. Composites Science and Technology, Vol.139, No.8, pp.99108.
16) Knappich F, Magdalena K, Schlummer M, Wölling J, Mäurer A. (2019). Recycling
process for carbon fiber reinforced plastics with polyamide 6, polyurethane and epoxy
matrix by gentle solvent treatment. Waste Management Volume 85, 73-81.
17) Naia G, Lopez-Urionabarrenechea A, Solar J, Acha E, Caballero B.M, Félix A.L,
Isabel D.M. (2018). Thermo-Catalytic Treatment of Vapors in the Recycling Process ofCarbon Fiber-Poly (Benzoxazine) Composite Waste by Pyrolysis Catalysts, 8(11), 523.
18) Khalil YF. (2018). Comparative environmental and human health evaluations ofthermolysis and solvolysis recycling technologies of carbon fiber reinforced polymer
waste. Waste Management 76:767-778.
19) Kooi M., J. Reisser et al. (2016). The effect of particle properties on the depth profile
of buoyant plastics in the ocean. Scientific Reports volume 6, Article number: 33882.
20) Yamashita R, Tanaka K and Takada H. (2016). Marine Plastic Pollution: Dynamics
of plastic debris in marine ecosystem and effect on marine organisms (in Japanese).
Journal of the Ecological Society of Japan 66, 51-68.
21) Rochman C. M, Hoh E, Kurobe T, Teh S. J. (2013). Ingested plastic transfers
hazardous chemicals to fish and induces hepatic stress. Scientific Reports volume 3,
Article number: 3263.
22) Wilcox C, Puckridge M, Schuyler Q.A, Townsend K, Hardesty B.D. (2018). A
quantitative analysis linking sea turtle mortality and plastic debris ingestion. Scientific
Reports volume 8, Article number: 12536.
23) Lamb J. B, Willis B.L, Fiorenza E.A, Couch C.S, Howard R, D et al. (2018). Plastic
54waste associated with disease on coral reefs. Science 26 Jan 2018: Vol.359, Issue 6374,
pp. 460-462.
24) Lefeuvre A et al. (2017). Modelling pyrolysis process for CFRP recycling in a closedloop supply chain approach. Computer Aided Chemical Engineering,Volume 40, 2017,
Pages 2029-2034.
25) Phuong Anh Vo Dong, Azzaro-Pantel C, Cadene A.L. (2018). Economic andenvironmental assessment of recovery and disposal pathways for CFRP waste
management. Resources, Conservation and Recycling, Volume 133, Pages 63-75.
26) Howarth J, Sada S.R. Mareddy, Paul T. Mativenga. (2014). Energy intensity andenvironmental analysis of mechanical recycling of carbonfibre composite. Journal of
Cleaner Production,Volume 81, 15 October 2014, Pages 46-50.
27) Xiang Li, Ruibin B, McKechnie J. (2016). Environmental and financial performanceof mechanical recycling of carbon fibre reinforced polymers and comparison withconventional disposal routes. Journal of Cleaner Production, 127 . pp. 451-460.
28) Iwahori Y. (2009). Strength test method for carbon fiber reinforced plastic laminates(in Japanese). Journal of the Adhesion Society of Japan Vol.45 No.3.
29) Sugimoto Y, Shimamoto D, Imai Y, Hotta Y. (2020). Simultaneous evaluation oftensile strength and interfacial shear strength of short length carbon fibers using
fragmentation test. Carbon 161, 83-88.
30) Shah, D.U., Schubel, P.J. (2016). On recycled carbon fibre composites manufactured
through a liquid composite moulding process. J. Reinf. Plast. Comp. 2016, 35, 533–540.
31) Longana, M.L. et al. (2018). Reclaimed carbon and flax fibre composites:
Manufacturing and mechanical properties. Recycling 2018, 3(4), 52.
32) Wong, K.H., Pickering, S.J., Rudd, C.D. (2010). Recycled carbon fibre reinforced
polymer composite for electromagnetic interference shielding. Compos. Part A Appl. Sci.
Manuf. 2010, 41, 693–702.
33) Thomas R. Pozegic et al. (2020). Improving Dispersion of Recycled Discontinuous
Carbon Fibres to Increase Fibre Throughput in the HiPerDiF Process. Materials 2020,13(7), 1544.
34) M. L. Longana et al. (2019). Quasi-Isotropic and Pseudo-Ductile Highly Aligned
Discontinuous Fibre Composites Manufactured with the HiPerDiF (High Performance
Discontinuous Fibre) Technology.Materials 2019, 12(11), 1794.
35) Nathalie Antunes, John T. Dardis-II, Thomas Grandine, Brittan Farmer and Gail Hahn.
(2020). Design Optimization of Short Fiber Composite Parts. AIAA Scitech 2020 Forum,
6-10 January 2020, Orlando, FL.
36) Heider, D. et al. (2019). Closed Loop Recycling of CFRP Into Highly Aligned High
Performance Short Fiber Composites Using the TUFF Process. In Proceedings of the55

SAMPE, Charlotte, NC, USA, 20–23 May 2019.
37) Turner, T.A., Warrior, N.A., Pickering, S.J. (2010). Development of high value
moulding compounds from recycled carbon fibres. Plast. Rubber Compos. 2010, 39, 151–
156.
38) Tanigaki M, Ibe H. (2015). Introduction of repair and reinforcement of concrete
structures with continuous fiber reinforcement (in Japanese). Vol.53, No.4, 358-363.
39) Limburg M, Stockschläder J, Quicker P. (2019). Thermal treatment of carbon fibre
reinforced polymers (Part 1: Recycling). Waste Management & Research, 37(1) 73-82.
40) Kamo T. (2018). Current status and issues of carbon fiber reinforced plastic (CFRP)
recycling (in Japanese). Japan Society for Waste Resource Recycling, Volume 29 Issue 2
p. 133-141.
41) KADO Co., Ltd website http://www.kado-corporation.com/english.html
42) The Japan Carbon Fiber Manufacturers Association website (in Japanese).
https://www.carbonfiber.gr.jp/tech/faq.html#q1443) Cavallo D, Fanizza C, Ursini C L, Casciardi S, Paba E, Ciervo A et al. (2012). Multiwalled carbon nanotubes induce cytotoxicity and genotoxicity in human lung epithelial
cells. J. Appl. Toxicol. 32, 454-464.
44) Hirano S, Fujitani Y, Furuyama A, Kanno S. (2010). Uptake and cytotoxic effects ofmulti-walled carbon nanotubes in human bronchial epithelial cells. Toxicol, Appl.
Pharmacol, 249, 8-15.
45) Craig A Poland et al. (2008). Carbon nanotubes induced into the abdominal cavity ofmice show asbestos-like pathogenicity in a pilot study. Nature Nanotechnology. 3, 423428.
46) Donaldson K, Murphy F.A, Duffin R, Poland C.A.(2020). Asbestos, carbon nanotubes
and the pleural mesothelium: a review of the hypothesis regarding the role of long fiber
retention in the parietal pleura, inflammation and mesothelioma. Part. Fibre Toxicol 7, 5.
47) Dong J, Ma Q. (2015). Advances in mechanisms and signaling pathways of carbon
nanotube toxicity. Nanotoxicology 9 (5), 658-676.
48) Johnston H J, G.R Hutchison, F M Christensen, S Peters, S Hankin, K Aschberger, V
Stone. (2010). A critical review of the biological mechanisms underlying the in vivo andin vitro toxicity of carbon nanotubes: the contribution of physicochemical characteristics.
Nanotoxicology 4, 207-246.
49) Central Industrial Accident Prevention Association. (2001). Asbestos substitute fiberand its ecological effects survey report (in Japanese).
https://www.jstage.jst.go.jp/article/tanso1949/2001/200/2001_200_271/_pdf50) Waritz RS, Ballantyne B, Clary JJ. (1998). Subchronic inhalation toxicity of 3.5-μm
diameter carbon fibers in rats. Journal of Applied Toxicology 18:215-223.
5651) Nakano M, Nagataki Y and Omae K.(2008). Carbon fiber toxicity (in Japanese).
Literature introduction regarding industrial health in Japan and overseas. Industrial
Health Journal Vol 31.
52) Moriyama A, Hasegawa T, Nagaya C, Hamada K, Himaki T, Murakami M, Horie M,
Takahashi J, Iwahashi H, Moritomi H. (2019). Assessment of harmfulness and biologicaleffect of carbon fiber dust generated during new carbon fiber recycling method. Journalof Hazardous Materials, 378 1-6.
53) Tanaka T. (2008). Lake Water Treatment System using a Carbon Fiber Artificial Algal
Bed (in Japanese). Environmental Information Science Proceedings 22. P499-504.
54) Chester NA, Haley MV, Kurnas CW, Checkai RT. (2004). Assessing Toxicity of
Obscurant Grade Pan-Based Carbon Fiber Aquatic Species Chronic Tests. U.S. Army
Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD 21010-5424.
55) Fiber Repair and Strengthening Newsletter Vol.36/2017.7. (in Japanese)
http://www.fir-st.com/pdf/gijutu/Vol36-gijutu.pdf56) Kojima A. (2003). Recent Advancement of Water Purification and Artificial Alga
Bed Formation using Carbon Fiber. Journal of Fiber Science and Technology. Vol.59,
No.6.
57) Matusmoto S, Ohtaki A, Hori K. (2012). Carbon fiber as an excellent support material
for wastewater treatment biofilms. Environ. Sci. Technol. 2012, 46, 18, 10175-10181.
58) Kubota T. (2009). Basic research on water purification system using carbon fiber (inJapanese). Civil Engineering Society 64th Annual Academic Lecture (Sept 2009).
59) SO-EN CO., LTD website https://so-en.net/shurui-e.html
60) J. Zhang, V.S. Chevali, H. Wang, C.H. Wang. (2020). Current status of carbon fibreand carbon fibre composites recycling. Composits,Part B 193,108053.
61) Ueda, H., Moriyama, A., Iwahashi, H. et al.(2020). Organizational issues fordisseminating recycling technologies of carbon fiber-reinforced plastics in the Japaneseindustrial landscape. J Mater Cycles Waste Manag, 23(2),505-515.
62) Mizuho Information & Research Institute, Inc. (2020). Research report on generalpurpose plastic substitute materials and recycled materials market etc for the purpose ofpromoting the circulation of plastic resources (in Japanese).
Available at: https://www.meti.go.jp/meti_lib/report/2019FY/000053.pdf63) Iwahashi H, Kitagawa E, Kishi K. (2007). Medaka (Oryzias latipes) of Freshwater
Teleost Fish, Challenging to the Deep Sea. High Pressure Bioscience and Biotechnology,
Volume 1 Issue 1 Pages 153-156.
64) OECD GUIDELINE FOR TESTING OF CHEMICALS "Fish, Prolonged Toxicity
Test: 14-day Study" (Adopted 4 April 1984).
65) Yoshioka E. (1995). An Improved Procedure for Clearing and Staining Fish Bone
57

Specimens (in Japanese). Kobe Yamate Women's Junior College annual report, No.38,
P157-164.
66) Fujita K, Matsuyama A, Kobayashi Y, Iwahashi H. (2004). Comprehensive gene
expression analysis of the response to straight̺chain alcohols in Saccharomyces
cerevisiae using cDNA microarray. Journal of Applied Microbiology 2004, 97, 57–67.
67) Environmental DNA Sampling and Experiment Manual (ver. 2.1) (published April
25, 2019)eDNA Methods Standardization Committee, The eDNA Society.
Available at: http://ednasociety.org/manual68) NIPPON STEEL Eco-Tech Corporation Extrap Soil DNA kit Plus Ver.2 instruction
manua (in Japanese). Available at:https://manualzz.com/doc/4815454/%E5%8F%96%E6%89%B1%E8%AA%AC%E6%
98%8E%E6%9B%B8---extrap-soil-dna-kit-plus-ver.2--pdf-356kb69) KAPA Library Quantification Technical Guide, KAPA Library Quantification Kits forIllumina® platforms v2.19. Available at:https://www.n-genetics.com/products/1104/1024/17225.pdf70) Klindworth A, Pruesse E, Schweer T, et al. (2013). Evaluation of general 16S
ribosomal RNA gene PCR primers for classical and next-generation sequencing-based
diversity studies. Nucleic Acids Res. 2013;41(1):e1.
71) Mizuno T, Iwahashi H, Horie M. (2020). Identification of microbial flora associatedwith fermentation of Ishizuchi-Kurocha (in Japanese). Japanese Society of Taste
Technology. Vol. 19, No. 1.
72) Wang Q, Garrity G.M, Tiedje J.M, Cole J.R. (2007). Naïve Bayesian Classifier for
Rapid Assignment of rRNA Sequences into the New Bacterial Taxonomy. Appl Environ
Microbiol. 73(16):5261-7.
73) Nagai H et al. (2011). Diameter and rigidity of multiwalled carbon nanotubes are
critical factors in mesothelial injury and carcinogenesis. PNAS December 6, 2011, 108(49), E1330-E1338.
74) Edmund A. Gehan. (1965). A Generalized Wilcoxon Test for Comparing Arbitrarily
Singly-Censored Samples. Biometrika Vol. 52, No. 1/2, pp. 203-223.
75) Oshima Y. (2020). Micro-plastic risk assessment (in Japanese), CERI
(Chemicals Evaluation and Research Institute, Japan) News. No.89 2020 April.
Available at: https://www.cerij.or.jp/cerinews/cn_backnumber.html
76) Masao Anzai: Mitsubishi Chemical Corporation"Current Status and Future of PANbased Carbon Fibers" Carbon Fibers Association Committee, Japan Chemical Fibers
Association 35th Composites Seminar Carbon Fibers Contributing to a Carbon-Neutral
Society (2022.2).
77) Sugino et al. (2021). Mass Production of New CFRP Recycling Technology and58

Market Development of rCF - Realization of Circular Economy of Carbon Fiber andSDGs -. Plastics Age 9 Vol.67 2021 Sep.pp77-85.
78) Mr. Ueno, Toyota Motor Corporation: Monozukuri in 2030 to Create a Chain of"Happiness": Toward a Sustainable Circular Economy Society. Special Lecture at Web
Seminar hosted by ANC Technology Research Association (2022.2).
79)Yano Research Institute Ltd.: FY2020 Research Commission for Measures to Copewith Global Warming and Resource Recycling International Trend Survey on Utilizationand Evaluation Methods of Recycled Carbon Fiber (2021.3).
https://www.meti.go.jp/meti_lib/report/2020FY/000308.pdf80) Grant-in-Aid for Scientific Research: "Safety Verification and Establishment of
Evaluation Criteria for Carbon Fibers Focusing on Sustained Inflammation - Toward
International Standards -" Report of Achievements (2020).
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-20J11212/
81) Teijin Limited: Toward the Commercialization of Recycled Carbon Fiber: Business
Alliance with Fuji Kashiko Co.News release (2022.2).
https://www.teijin.co.jp/news/2022/02/24/20220224_01.pdf82) ISO/TS 80004-2 㸸 2015(E) Annex B Agglomerates, aggregates, and constituent
particles (2015).
83) Derk, H. Brouwer et al. (2014). Monitoring and Sampling Strategy for(Manufactured) Nano Objects, Agglomerates and Aggregates (NOAA): Potential Added
Value of the NANODEVICE Project. Handbook of Nanosafety: Measurement, Exposure
and Toxicology, 173-206.
84) Boccuni, F. (2017). Measurement techniques of exposure to nanomaterials in theworkplace for low- and medium-income countries: A systematic review. International
Journal of Hygiene and Environmental Health, Volume 220, Issue 7, October 2017, Pages
1089-1097.
85) Boccuni, F. et al. (2018). Workers’ Exposure to Nano-Objects with Different
Dimensionalities in R&D Laboratories: Measurement Strategy and Field Studies. Int. J.
Mol. Sci. 2018, 19(2),349.
86) Francesca Larese Filon et al (2016).Occupational dermal exposure to nanoparticles
and nano-enabled products: Part I—Factors affecting skin absorption. International
Journal of Hygiene and Environmental Health, Volume 219, Issue 6, Pages 536-544.
87) Derk, H. Brouwer. (2016). Occupational dermal exposure to nanoparticles and nanoenabled products: Part 2, exploration of exposure processes and methods of assessment.
International Journal of Hygiene and Environmental Health, Volume 219, Issue 6, August
2016, Pages 503-512.
88) Brouwer, D.H. (2013). Workplace air measurements and likelihood of exposure to59manufactured nano-objects, agglomerates, and aggregates. J Nanopart Res 15, 2090.
89) Brouwer, D.H. et al. (2013). 187 Monitoring and modelling of exposure to
manufactured nano objects, agglomerates & aggregates (NOAA) for epidemiologic
studies. Session: Mini sympsoium I: Nanomaterials and health: Sponsored by NanonextNL.
90) Bressot, C. (2018). Exposure assessment of Nanomaterials at production sites by a
Short Time Sampling (STS) approach: Strategy and first results of measurement
campaigns. Process Safety and Environmental Protection, Volume 116, May 2018, Pages
324-332.
91) Hedmer, M. et al. (2015). Detection of Multi-walled Carbon Nanotubes and Carbon
Nanodiscs on Workplace Surfaces at a Small-Scale Producer. The Annals of Occupational
Hygiene, Volume 59, Issue 7, August 2015, Pages 836–852.
92) Oberbek, P. et al. (2019). Inhalation exposure to various nanoparticles in work
environment—contextual information and results of measurements. Journal of
Nanoparticle Research, volume 21, Article number: 222.
93) 2021 Gifu Technology Innovation Center Management Council (2021). The 1st
Technical Seminar "Sustainable Society and Composite Materials "Lecture 2: Evaluationof Biological and Ecological Effects of Recycled Carbon Fibers Hitoshi Iwahashi".
94) Yamada, I., Nomura, K., Iwahashi, H., Horie, M. (2016).The effect of titanium
dioxide (TiO2) nano-objects, and their aggregates and agglomerates greater than 100 nm(NOAA) on microbes under UV irradiation. Chemosphere, Volume 143, Pages 123-127.
95) N. von Goetz, et al. (2013). Migration of Ag- and TiO2-(Nano) particles from Textiles
into Artificial Sweat under Physical Stress: Experiments and Exposure Modeling.
Environ. Sci. Technol. 2013, 47, 17, 9979–9987.
96) Morgeneyer, M. (2018). STEM imaging to characterize nanoparticle emissions andhelp to design nanosafer paints.Chemical Engineering Research and Design, Volume 136,
August 2018, Pages 663-674.
97) Fransman, W. et al. (2016). Potential Release of Manufactured Nano Objects During
Sanding of Nano-Coated Wood Surfaces. The Annals of Occupational Hygiene, Volume
60, Issue 7, August 2016, Pages 875–884.
98) Director, Labor Standards Bureau, Ministry of Health, Labor and Welfare:
Precautionary Measures to Prevent Exposure to Nanomaterials (2009.3).
https://www.jaish.gr.jp/anzen/hor/hombun/hor1-50/hor1-50-8-1-0.htm
99) Based on the website of Chemicals Evaluation and Research Institute (CERI):
Exposure and Risk Assessment.
https://www.cerij.or.jp/service/10_risk_evaluation/hazard_assessment_03.html
100) Ueda, H. et al. (2021). Assessment of biological effects and harm to Japanese60medaka due to carbonized carbon fibers generated by a pyrolysis carbon fiber recycling
process. J Mater Cycles Waste Manag 23, 1071–1080.
101) Coyle Jayme, P. et al. (2020). Carbon nanotube filler enhances incinerated
thermoplastics-induced cytotoxicity and metabolic disruption in vitro. Particle and Fibre
Toxicology, volume 17, Article number: 40.
102) FY 2020 Regional Enterprise Innovation Support Project "Support Project for
Creation of New Supply Chain for Promotion of Resource Recycling of Carbon Fiber
Reinforced Plastics (CFRP)" Activity Overview Slide (2020).
https://www.meti.go.jp/policy/sme_chiiki/localinnovation/project/2020project/200409.p
df103) Health and Safety Executive (HSE): Nanotechnology introduction website
https://www.hse.gov.uk/nanotechnology/104) ISO/TS 12901-2㸸2014 Nanotechnologie―Occupational risk management applied
to engineered nanomaterials―Part 2㸸Use of the control banding approach (2014).
105) Kuijpers, E. et al. (2017). Understanding workers' exposure: Systematic review anddata-analysis of emission potential for NOAA. Journal of Occupational andEnvironmental Hygiene, Volume 14, 2017 - Issue 5.
106) Bekker, C. (2017). Assessment of Determinants of Emission Potentially Affecting
the Concentration of Airborne Nano-Objects and Their Agglomerates and Aggregates.
Annals of Work Exposures and Health, Volume 61, Issue 1, Pages 98–109.
107) Bekker, C. (2016). The Validity and Applicability of Using a Generic Exposure
Assessment Model for Occupational Exposure to Nano-Objects and Their Aggregatesand Agglomerates. The Annals of Occupational Hygiene, Volume 60, Issue 9, 14
November 2016, Pages 1039–1048.
108)
Nanotechnology
Standardization
National
Deliberative
Committee:
Nanotechnology International Standardization Circular (NTSC No. 48) Special Issue on
Nanotechnology International Standardization Workshop 2022 (2022.1).
https://unit.aist.go.jp/spc/tc229/files/20220208/NTSC48_Jan_2022.pdf
109) Irisawa, T. et al.(2021). Elucidation of damage factors to recycled carbon fibers
recovered from CFRPs by pyrolysis for finding optimal recovery conditions. Composites
Part B 218.
110) Endo et al. (2014). Importance of Toxicity Assessment of Carbon Nanotubes andNanomaterials - Toward Design of Safe Nanostructures. 41st Annual Meeting of theJapanese Society of Toxicology.
111) Danish National Research Center for the Working Environment: NanoSafer website
http://www.nanosafer.org/?msclkid=7d5f9d74a81011eca45a37c01205db05
112) Ishikawa T. (2015). Overview of Carbon Fiber Reinforced Composites (CFRP)
61

Applications to Automotive Structural Parts,-Focused on Thermoplastic CFRP-, Journalof the Japan Society for Precision Engineering, Vol 81, No. 6.
113) Liua W, Huanga H, Zhua L, Liua Z (2021). Integrating carbon fiber reclamation andadditive manufacturing for recycling CFRP waste, Composites Part B: Engineering
Volume 215, 15 June 2021, 108808.
114) Sugimoto Y, Sato K, Hotta Y (2019). Protection of carbon ﬁber surfaces with siliconbased ceramic coating. Journal of the Ceramic Society of Japan 127 [5] 331-334 2019.
115) Irisawa T. et al. (2018). The influence of oxygen containing functional groups on
carbon fibers for mechanical properties and recyclability of CFRTPs made with in-situ
polymerizable polyamide 6. Composites Part A: Applied Science and Manufacturing,
Volume 112, Pages 91-99.
116) Wada M, Kawai K, Suzuki T, Hira H, Kitaoka S. (2016). Effect of superheatedsteam treatment of carbon fiber on interfacial adhesion to epoxy resin. Composites Part
A: Applied Science and Manufacturing, Volume 85, Pages 156-162.
117) Udagawa A. (1992). Influence of fiber upon the radiation degradation of fiberreinforced plastics (in Japanese). Kobunshi Ronbunshu, 49(6), 551-553.
118) Rhys J. Tapper et al. (2019). A closed-loop recycling process for discontinuous
carbon fibre polyamide 6 composites. Composites Part B: Engineering Volume 179.
119) Irisawa T., Aratake R.,Hanai M., Sugimoto Y., Tanabe Y. (2021). Elucidation ofdamage factors to recycled carbon fibers recovered from CFRPs by pyrolysis forfinding optimal recovery conditions. Composites Part B: Engineering Volume 218.

62