POLYMERS TO POLLUTION: AN EXAMINATION OF POLYURETHANE FOAM

AND SOLUTIONS FOR ITS DEVASTATING EFFECTS ON THE ENVIRONMENT

by

Erin Straw

BS, University of Pittsburgh, 2014

Submitted to the Graduate Faculty of

Environmental and Occupational Health

Graduate School of Public Health in partial fulfillment

of the requirements for the degree of

Master of Public Health

University of Pittsburgh

2017

ii

UNIVERSITY OF PITTSBURGH

GRADUATE SCHOOL OF PUBLIC HEALTH

This essay is submitted

by

Erin Straw

on

April 28, 2017

and approved by

Essay Advisor:Jim (James) Peterson, PhD ____________________________________Department of Environmental and

Occupational HealthGraduate School of Public HealthUniversity of Pittsburgh

Essay Reader:George C. Bandik, PhD ____________________________________Department of ChemistryDietrich School of Arts and SciencesUniversity of Pittsburgh

iii

Copyright © by Erin Straw

2017

ABSTRACT

Contrary to what many still believe, global warming is a serious issue that demands answers

now. One effective, and rather simple, method to combat climate change is to recycle.

Recycling reduces greenhouse gas emissions as well as the total amount of waste disposed.

Unfortunately, the amount of waste being thrown away is increasing, but recycling is not. Due

to new political circumstances, one being that the new head of Environmental Protection Agency

is a climate change denialist, environmental responsibilities will shift to local governments and

communities. An area of recycling innovation revolves around polyurethane foam, a low

density, high volume material that makes its way into landfills and oceans around the world.

This essay takes a comprehensive look at public health significance of polyurethane foam, its

effects on the environment and promising mitigations.

iv

James Peterson, PhD

[POLYMERS TO POLLUTION: AN EXAMINATION OF POLYURETHANE

FOAM AND SOLUTIONS FOR ITS DEVASTATING EFFECTS ON THE

ENVIRONMENT

Erin Straw, MPH

University of Pittsburgh, 2017

TABLE OF CONTENTS

1.0 INTRODUCTION.........................................................................................................1

2.0 REVIEW: BACKGROUND OF POLYURETHANE FOAM..................................3

2.1 PROPERTIES, USES AND POLYURETHANE FOAM WASTE.................3

2.2 SYNTHESIS AND PRODUCTION OF POLYURETHANE FOAM.............5

3.0 ANALYSIS: ENVIRONMENTAL SOLUTIONS TO POLYURETHANE FOAM

POLLUTION.................................................................................................................................9

3.1 DISPOSAL AND RECYCLING METHODS....................................................9

3.2 ENVIRONMENTALLY FRIENDLY POLYURETHANE FOAM FOR

IMPROVED DEGRADATION.........................................................................................16

4.0 CONCLUSION...........................................................................................................18

BIBLIOGRAPHY........................................................................................................................21

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LIST OF FIGURES

Figure 1. Polyurethane Synthesis Reaction.....................................................................................6

Figure 2. Polyether vs. Polyester Structures....................................................................................7

Figure 3. Cyclical Incorporation of Hydrogen Cyanide................................................................11

Figure 4. Glycolysis of Polyurethane Foam..................................................................................15

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1.0 INTRODUCTION

One field where simple changes can be made to improve environmental health is

recycling. Recycling waste can recover not only reusable materials, but also energy which can

then be used to provide power and electricity. Recycling materials has benefits including

reducing the amount of greenhouse gas emissions as well as the total amount of waste disposed.

Unfortunately, the amount of waste thrown away is increasing, but recycling is not keeping pace;

for instance, 254 million tons of trash was produced by Americans in 2013, but only a 34.3%

recycling rate was obtained [18]. It has been estimated that more than five trillion plastic pieces

are currently polluting the world’s oceans, the most visible being foamed materials [8].

One of the most desirable qualities of plastics and foams is their high durability, which

unfortunately, pairs with poor environmental degradation [13]. In 2000, Japan enacted the “The

Basic Law for Establishing the Recycling Based Society” which included reduction of pollution

through restrictions in the generation of waste, reuse of materials, recycling and appropriate

disposal of waste; feasible steps that can be applied to any society [9]. Since so many novel

materials are present in the world today, some of them produced in vast quantities, improvement

in overall waste reduction of any one of them would likely be beneficial to the environment and

the organisms that rely on it.

Political side note: Following the 2016 presidential election, the United States of America

was faced with new policies and regulations that many individuals have deemed as controversial.

1

The newly elected, 45th president has promised to increase factories and manufacturing here in

the US, as well as the utilization of US resources including coal and natural gas [14].

Unfortunately, an increase in these practices means an increase in burning of fossil fuels,

consequent pollution and, ultimately, an increase in climate change and its results. Previously,

these factors have not been as much of a concern, as branches of government exist, like the

Environmental Protection Agency, that uphold the standards and regulations in place to protect

the environment and provide clean air and water for the people and other resident organisms.

However, the newly appointed Head of the Environmental Protection Agency is on record a

denialist of climate change [15,16]. Since the inauguration, resources like the White House

climate change web site have been removed, reducing climate change information to the public

[17]. Without the support of the federal government, protecting the environment is placed in the

hands of individuals and local governments requiring effort at new levels across the nation in

order to reduce the inevitable effects of global warming and increased pollution.

This essay is an in-depth examination of an everyday material, polyurethane foam,

especially its properties and characteristics that have led to its nuisance value for the

environmental world. A review of available literature has provided insight into several recycling

and environmentally friendly production options for polyurethane foam, that will ultimately

reduce the amount present in landfills and oceans. Targeted readers include concerned citizens

of the United States as well as anyone interested in improving the quality and health of the

environment as the future of the environment now currently resides in the hands of the people.

2

2.0 REVIEW: BACKGROUND OF POLYURETHANE FOAM

2.1 PROPERTIES, USES AND POLYURETHANE FOAM WASTE

Polyurethane foam is a subset of synthetic plastics. The main properties of polyurethane

foam include the ability to be easily molded into various shapes and the capacity to return to its

original shape. Polyurethane foam comes in three types: flexible, rigid and viscoelastic (i.e.

memory) foam. These foams are typically either polyether or polyester based polyols, that are

not considered to be biodegradable compounds and are obtained from petroleum based resources

[7,23,26]. In general, polyether is softer, less scratchy and more cost effective than polyester

[23]. Due to its various formations, polyurethane foam is present in a wide array of applications

including cushions found in furniture and car seating, packaging, footwear, mattresses and

bedding, insulation for refrigerators, freezers and buildings, sports equipment, carpet padding

and many others [6,11,12,19,20]. A more novel use for polyurethane foam has been

demonstrated in the medical field where was studied as a topical hemostatic agent comparable to

collagen or gelatin to control local bleeding [2]. Polyurethane foam has incorporated itself into

the daily lives of individuals around the world and new applications are continually being

developed.

Considering the versatility of polyurethane foam, it is understandable that demand is

going to continue to increase with increased usage and application. At the global level,

3

polyurethane foam utilization reached 8 million tons and was expected to reach 9.6 million tons

by 2016 [1]. In 2010, the top consumers included North America, Asia-Pacific and Europe, with

95% of the global demand [12]. Also in 2010, polyurethanes reached number six on the top

most produced chart with polyurethane foams accounting for about half [11]. Of all

polyurethane foam produced, reaching over three quarts of global production, an estimated 28%

accounts for furniture materials and 25% for construction materials [12]. There is no doubt that

polyurethane foam is of high demand of the global level and with the increase in demand and

production, there ultimately will be an increase in the amount of polyurethane foam waste

present throughout the environment.

The next question to consider is where all of this polyurethane foam ultimately ends up

after it has served its purpose and is no longer of use to the consumer. The answer, in general, is

either a landfill or the ocean. An analysis conducted by Marcus Erikson and colleagues to

estimate the amount of plastic pollution currently residing in the world’s oceans found that

92.3% of all samples collected contained plastic materials and of the visual surveys conducted,

they identified that the most frequently observed larger plastics were synthetic polymer foams.

The group discovered plastics in all ocean regions, including those with low coastal populations.

This evidence suggests that the ocean pollution is dispersing, leading some to consider synthetic

polymers as hazardous waste [8]. In 2011, approximately 675,000 tons of polyurethane foam

was discarded with as much as 15% occurring during the foam production in China alone [3].

To help put this in perspective, Wenqing Yang and colleagues identified appliance, furniture and

consumer goods as the main components of foam waste. In China, they estimated 14.66 million

refrigerators to be thrown away each which would result in an estimated 93,200 tons of wasted

4

polyurethane foam each year from a single household item [3]. One can imagine the global

amount to be significantly more.

Another study, conducted by Lee Mahoney in 1974, examined the amount of

polyurethane foam present in discarded vehicles. Their analysis concluded that, on average,

approximately 23.4 lbs of polyurethane foam would be recovered from each junked vehicle by

1981 [5]. The European Diisocyanate and Polyol Producers Association estimates about 120 to

150 kg of plastic material per car. Ten to 15% (12-22.5 lbs) of the plastic material is

polyurethane foam, which is fairly consistent with Mahoney’s estimation from 1974 [21]. In

total, millions of tons of polymeric material will be thrown away each year [10]. Before one can

begin to identify potential methods and technologies to more efficiently discard this polymeric

material, specifically polyurethane foam, one must first gain an understanding of how this foam

is produced, and the chemical properties that contribute to its versatility and environmental

persistence.

2.2 SYNTHESIS AND PRODUCTION OF POLYURETHANE FOAM

By definition, a polymer is a macromolecule (i.e large molecule) made up of basic

repeating structural units otherwise known as monomers. The general synthetic reaction for

polyurethane-type polymers includes the condensation reaction between an alcohol with more

than two reactive hydroxyl groups, known as a polyol with difunctional iisocyante or a

polymeric isocyante. The reaction is conducted in the presence of a catalyst to decrease the

overall activation energy. The polyols are usually obtained from ethelyne gas, a product from

crude oil refining; a controversial field in the current feud between the environmental and

5

political worlds. The diisocyantes or polymeric isocyanates are generally MDI (Methylene

diphenyl diisocyante) or TDI (Tolulene diisocyanate) [1,23,24]. Figure 1 depicts the synthesis

reaction below.

6

Figure 1. Polyurethane Synthesis Reaction

Polyurethane synthesis reaction of an isocyanate and diol depicting characteristic urethane linkage in final polyurethane product. (The figure was created using Chem Draw.)

In the above reaction, the 4,4’-MDI provides the isocyanate group and the ethane-1,2-diol

is the necessary polyol. Initially, there is no distinct urethane monomer present in the reaction; it

is the reaction that occurs between the two reagents that creates the urethane linkage,

contributing to the polyurethane polymer [25]. The polymerization/depolymerization between

the polyols and isocyanate groups contribute to the overall stability of the urethane linkages

present in the resulting polyurethane foam [26].

In order to turn the polyurethane polymer into a polyurethane foam, some additional

reagents must be included in the reaction process. Depending on the type of foam desired for

production, either polyether or polyester polyols may be used for the creation of a co-polymer

[7,23]. The polyether/polyester co-polymer ultimately provides the structural chemical backbone

for the final foamed product. As mentioned in the introduction, polyether polyurethanes will

produce a softer, more flexible foam product, whereas polyester will produce a more rigid foam

[23]. These products are a result of the structural properties of the polyether and polyester

polyols, which are depicted below in Figure 2. It is important to understand the role that the

starting materials play in the qualities and characteristics of the final polyurethane foam

products.

7

Figure 2. Polyether vs. Polyester Structures

Structural depiction of differences between polyethers and polyesters.The figure was created using Chem Draw.)By comparing the shape and size of the ester and ether functional groups and resulting

polyester and polyether chains, one can better understand how differences in the two functional

groups result in a difference of foam structure. Due to the smaller, more compact nature of the

polyether, the resulting foam will be made of smaller cells with more compact air flow, which

ultimately results in a more rigid foam. The larger size of the polyester chains, do not allow for

the such tight air flow and cell formation, resulting in a more flexible, less rigid foam. The

functional groups present in the reaction’s reagents will ultimately determine any linearity or

crosslinking present in the final foam product [7,23]. Furthermore, the addition of water to the

polyurethane reaction mixture results in the production of CO2 gas. As the reaction proceeds, the

mixture becomes heavier and more viscous, trapping the CO2 gas and ultimately producing the

air cells present in a polyurethane foam [25,32].

Production of polyurethane foam has been described by several scientists as a “one-shot”

method. In simple terms, this means that all of the raw materials or reagents needed (i.e. the

8

polyols, isocyanates, catalysts, water, methylene chloride and any desired additives) are mixed

together in a single reaction container, poured into a mold then left to cure until the product foam

is complete [6,7]. As demonstrated with the comparison of polyester and polyether polyols, the

raw materials (i.e. the reagents of the polymerization reaction) are what determine the ultimate

properties of the polyurethane foam. Various additives to the initial reaction mixture produce

different properties of the resulting foam such as color, fungal and UV protection, varying

densities and others to the desired foams [23,24]. Additives may also include agents that

promote stabilization and cross-linking, fillers, and chain extenders [7]. Understanding how

polyurethane foam is synthesized enables analysis of how it can be broken down to reduce its

hazardous accumulation it the environment.

9

3.0 ANALYSIS: ENVIRONMENTAL SOLUTIONS TO POLYURETHANE

FOAM POLLUTION

3.1 DISPOSAL AND RECYCLING METHODS

Landfill, incineration, or recycling are the three potential fates for any item or material

that has been deemed to have no more potential value to the consumer or manufacturer [3]. This

ideology holds true for polyurethane foam as well. Being a high volume, low-density, non-

biodegradable material is a hazard to the environment, so it is important to examine each of these

disposal methods to identify the most reasonable solution to reducing the high volume of

polyurethane foam pollution.

Landfill disposal of polyurethane foam is one of the most convenient methods of

disposal, but also the most ineffective. Items are placed in the trash by consumers and

manufacturers and relocated to landfills across the nation. A negative consequence of landfills is

the production of methane gas, a detrimental greenhouse gas, that results from the degradation of

organic materials present in the landfills [30]. Polyurethane foam is a low-density material that

often occupies large volumes, like those in couch cushions and car seats [3,5,11,12]. Once

polyurethane foam has entered a landfill (or elsewhere in the environment), it will continue to

persist and resist degradation due to its structural stability. Several countries, mostly in Europe,

have even banned landfill disposal of polyurethane foam as a result of these unfavorable

10

environmental qualities [3]. A study by Ferdinand Broekema examined the biodegradation and

persistence of polyurethane foam in vivo and found the foam still present after three years, and

that was for a much smaller amount of foam compared to that ending up in landfills and the

environment [2].

The next option aside from landfill disposal, is incineration, or burning, of polyurethane

foam. Unlike landfill disposal, in terms of reducing the overall amount of waste volume, this

method is extremely effective. Incineration reduces the waste by almost 100% of its initial

volume and can reduce overall landfill volumes by 90% [31]. Incineration is also a convenient

method, as materials do not have to be sorted or purified prior to burning and the resulting heat

energy produced can also beneficial if utilized appropriately. As a result of overall landfill

reduction, the accompanying methane gas produced will also be reduced [29]. It has been

estimated that recovered energy from the combustion of waste will prevent millions of tons of

carbon dioxide from entering the atmosphere each year and is considered a renewable, low

emission power source [31].

Thermal energy obtainable by incineration of synthetic polymers, is equivalent to that

generated by coal. Approximately 1kg of both polyurethane foam and coal generate around

7000 kcal/kg each [3]. To obtain the same amount of energy from natural gas, 1.00 m3 of natural

gas is equivalent to 1.35 kg of coal. This indicates more natural gas would be required to recover

an equal amount of energy compared to coal and polyurethanes [28]. Upon full utilization of

energy recovering facilities across the nation, enough electricity could be generated to power

upwards of 14 million homes from the energy recovered from combustion [31]. As with any

combustion of materials, potentially adverse environmental pollutants are generated, some of

which can be toxic [3]. For instance, hydrogen cyanide (HCN) is a known product of

11

polyurethane combustion and is therefore released into the atmosphere [27]. However, Malone

and colleagues demonstrated that the HCN released from polyurethane combustion is

incorporated into both nitrogen cycle and carbon cycle on a global level. A visual representation

is depicted in Figure 3 below. As a result of incorporation of HCN into these global cycles, the

amount of HCN released from polyurethane incineration would not be of sufficient quantities to

invoke environmental concern [27].

Figure 3. Cyclical Incorporation of Hydrogen Cyanide

Incorporation of hydrogen cyanide into both the global carbon and nitrogen cycles.(The figure is an adapted version of a figure published in Toxicology of Cyanides and Cyanogens: Experimental, Applied and Clinical Aspects, 2015 and was kindly provided by Jim Peterson, PhD.)

Recycling, of any material, is generally deemed the most “green” method of disposal

available. Under perfect conditions, the recycling process would be sustainable, limiting both

energy use and production of further environmental hazards with no compromises in terms of

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quality of manufactured items produced from recycled materials compared to non-recycled

materials [10]. Polyurethane recycling generally consists of two types: mechanical, also

referred to as physical, and chemical.

Mechanical recycling is the simpler method of the two as it simply involves changes to

the final shape(s) of the foam. By mechanical processes like grinding, crushing and pulverizing,

the foam cushion from old car seats can be physically transformed into fine flakes and powders

[3,10,12]. The finer flake and powder formation allows for easier use and purification. The

mechanical recycling method is a practical way for polyurethane foam manufacturers to directly

reuse any foam waste they produce [10]. Once the discarded foam has been physically

transformed into a flake or powder, the options for its reuse have greatly increased. The

polyurethane flakes or powders still have the same chemical properties as their high-volume

counterparts and can, therefore, be directly reincorporated into the production of new

polyurethane foam. Fabrizio Quadrini and colleagues found that the polyurethane flakes can be

compressed into a mold without the use of any adhesives or binding agents, which in turn results

in a product foam with a much higher density and good stability [12].

Often, adhesives are added to the flakes, which are then placed into a desired mold. With

the accompaniment of high temperature water vapor and high pressure, a new foam with as high

as 90% recycled polyurethane flakes is produced. Unfortunately, the direct use of recycled

polyurethane flakes and powders alone do not typically produce high quality product foams

[3,10]. As a solution to combat poor stability in recycled products, stabilizing agents may be

added to the flaked foam, improving the quality of the resulting foam [10]. The polyurethane

flakes and foams may also be used as a filler and added in smaller amounts, generally up to 20%,

to accompany and reduce the amount of raw materials that are used for production of new

13

polyurethane foam [3,12]. Direct reuse of waste for new products thus offers economic benefits

as well as environmental ones.

One of the challenges to polymer recycling is the high strength and durability of the

polymer products, resulting in relatively poor recovery of the constituent monomers as well as

increased expenses to the recycler [7,9]. A unique characteristic of polyurethane polymers, is

that the polymerization of polyurethane is reversible, which allows for recovery of the monomer

subunits [3]. Chemical recycling is a more involved process than mechanical recycling but offers

promising results for both the polyurethane manufacturers and the environment. Chemical

recycling breaks down the polymer foam into various starting materials that can either be utilized

as fuels for purposes unrelated to polyurethane foam production or as starting materials for new

polyurethane foam synthesis. Due to the strong nature of polyurethane foam, degradation is not

observed until the reaction reaches a temperature greater than 200C. Subsequently, the urethane

functional groups begin to breakdown around 230C followed by degradation of the ether

linkages around 320C, indicating the two general steps of polyurethane degradation [7]. Once

the reaction reaches a temperature greater than 200C, different chemical recycling process will

yield different products. Processes of chemical recycling for polyurethane foam include

alcoholysis, hydrolysis and glycolysis. [3,5,9,10,11, 12].

Alcoholysis involves the reaction of the polyurethane foam with an alcohol and catalyst

at a temperature around 170C, which results in what is basically a low weight polyurethane

liquid. After distillation of the liquid, the main recycled products obtained from alcoholysis are

polyols and amines. These products are of good quality can then be reincorporated as starting

material for new polyurethane foam [3].

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Instead of reacting the polyurethane foam with an alcohol, another option is to react it

with high temperature water for hydrolysis, eliminating the use of additional organic chemicals.

Hydrolysis is very efficient in terms of volume reduction. A study by Lee Mahoney found that

hydrolysis reduced the volume of the initial starting foam product by a factor of 30 at 200C [5].

Like alcoholysis, a liquid is produced containing the primary products, polyols and amines, that

can be distilled and reused for the same purposes [3,5,10]. Following distillation, amine recovery

has been demonstrated to reach as high as 80% [5].

Hydrolysis often falls under a general category of recycling known as feedstock

recycling. Feedstock recycling means that the chains that make up polyurethane foam are

broken down into their monomers, like polyols and amines, and used as a stock solution for other

products [9,10]. However due to the nature of water, the reaction temperature is closer to 300 C.

Recycled product recovery only reaches up to 30% and is accompanied by high energy

consumption due to the high temperature of the reaction and secondary environmental problems

like emissions and toxins associated with hydrolysis and feedstock recycling [10].

The most well recognized chemical recycling method associated with polyurethane

materials, including foam, is glycolysis. Glycolysis is the reaction of polyurethane foam and

diols (i.e. glycol) with heat at approximately 200C yielding primarily polyols. The polyol

products of the glycolysis are primarily used as raw material for further polyurethane foam

production [10,11]. The glycolysis reaction is depicted below in Figure 4.

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Figure 4. Glycolysis of Polyurethane Foam

Glycolysis recycling reaction of polyurethane foam.(The figure was created using Chem Draw.)

The ester/ether group attached to the urethane group is exchanged with the hydroxyl

group of the diol to yield at least 61% polyols [11]. With the glycolysis process, the above

reaction is not always the reaction that takes place. Several other reactions may occur including

glycolysis of the urea groups, reaction of the urethane group with water or general degradation of

the urethane group due to the high reaction temperature [11]. An increase of subsequent

reactions leads to a decrease in polyol recovery. With the help of purification processes, the

polyol quality is not compromised. The quality of product generated with polyols comprising

20% weight was high [3]. This finding demonstrates the benefits of glycolytic recycling

including reduction in raw materials and integrity of products.

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3.2 ENVIRONMENTALLY FRIENDLY POLYURETHANE FOAM FOR

IMPROVED DEGRADATION

One final solution for reducing the accumulation of polyurethane foam in the

environment is not a recycling method, but instead a production method. By incorporating more

environmentally friendly raw materials into the production method of polyurethane foam, natural

degradation and decomposition will be more feasible should the foam make its way into landfills

or the oceans in its post-consumer life.

Several methods have been examined that ultimately increase the degradation abilities of

polyurethane foam. The most notable is to incorporate environmentally friendly polyols, bio-

polyols, into the production process. Bio-polyols utilize the natural polymer characteristics of

starch and cellulose [7]. These bio-polyols can reduce the amount of non-biodegradable

polyether and polyester polyols typically used in polyurethane foam production. Similar to the

incorporation of polyethelene oxide, addition of starting materials with hydroxyl groups can be

used as additives or fillers for polyurethane foam. Potential fillers and additives include

celluloses, starches, soy, tree bark and natural oils [7]. A study by Jan David and colleagues at

the Brno University of Technology substituted carboxyl-methyl cellulose sodium salt, acetylated

potato starch, 2-hydroxyethyl cellulose, and wheat/protein gluten for the typical polyether polyol,

with weight ranging from 1-30% and found the resulting foam products to be comparable to their

non-environmentally friendly counterparts as well as little ecotoxicity.

Another proposed method of promoting degradation is to incorporate the addition of

Polyethelene oxide as a reagent. Polyethelene oxide (also known as polyethelene glycol) is a

hydrophilic compound and therefore will allow for an increased amount of water present in the

resulting foam, increasing the potential and rate for hydrolysis and degradation [2].

17

As one of the potential natural additives mentioned above, tree bark, which largely

consists of cellulose, is the focus of examination for Jason D’Souza at the University of Toronto.

D’Souza and colleagues liquefied bark at various temperatures below 200C, which as mentioned

in the recycling section is the minimum value for most polyurethane recycling, making bark

liquidation more economical and energy efficient in comparison. The liquefied bark extracts can

then be mixed with polyols for polyurethane foam production. By performing the reaction at a

lower temperature, the sugars present in the bark are better preserved contributing to foaming

behaviors consistent with polyurethane foam produced with the normal polyether or polyester

polyols. The final findings indicated that the foam produced from bark extracts obtained similar

characteristics and properties to typical polyurethane foams but in general were not as stable or

flexible [26].

The final potential solution for remediation of polyurethane foam waste involves natural

degradation processes of synthetic polyurethane materials, instead of degradation of natural

materials found in polyurethane. This is referring to the use of microbial degradation of

polyurethane foam as an environmentally friendly disposal method. The bacterial organisms

Pseudomonas putida, Alicycliphilus and fungi Pestalotiopsis microspora were found to degrade

polyurethane foam with enzymatic activity. P. putida was the most efficient and utilized

polyurethane foam as a sole carbon source [1]. Enzymatic properties that allow microorganism

like P. putida to break down polyurethane foam can be identified and carried out on a larger

scale. Utilizing microorganisms for disposal of polyurethane foam eliminates some of the

secondary environmental concerns that occurring during chemical recycling processes and

provides an economical option for a degradation process.

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4.0 CONCLUSION

This essay examined polyurethane foam at a chemical level in order to identify the

characteristics that have contributed to polyurethane foam’s negative environmental

consequences based on available literature and resources. The desirable properties of

polyurethane foam that allow it to be a strong and versatile material inadvertently allow it to be a

persistent environmental pollutant. The low-density, high volume material resists biodegradation

in the environment and requires mechanical and chemical recycling, or incineration, in order to

reduce its volume and overall waste present.

In summary, the options for disposal of polyurethane foam include landfill, incineration

or recycling. Recycling is the most desirable in terms of product recovery, but also the most

challenging of the three. Landfill disposal is good for convenience, but bad in terms of resource

waste (i.e. polyurethane foam taking up space in the landfill). Incineration is another rather

convenient disposal method that can allow for the use of energy production from the heat

produced by burning polyurethane foam but is may have some negative consequences if carried

out irresponsibly.

Each recycling method has its own pros and cons. Mechanical recycling eliminates the

need for additional chemicals and reduces the amount of raw materials needed for new foam

production, but the new foam may not uphold the qualities that consumers desire in traditional

polyurethane foam. Alcoholysis, hydrolysis and glycolysis all allow for the regeneration of

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reagents for new polyurethane foam production. If the desired recycled product is amines, then

hydrolysis the most suitable method of amine recovery and recycling. If polyols are the desired

recycled product of interest, then glycolysis is the most efficient method of the three chemical

processes examined and also requires lower energy expenditure than both alcoholysis and

hydrolysis.

Production of polyurethane foam with more eco-friendly and biodegradable starting

materials reduces the need for post-consumer recycling techniques. Should this environmentally

friendly foam make its way to a landfill or ocean, which it still probably will, the environmental

burden will be reduced due to its improved ability to degrade on its own. If it can’t degrade on

its own, the assistance of microorganisms that break down polyurethane foam may be utilized as

another environmentally friendly disposal method, however it may not be as rapid as the other

techniques mentioned.

Utilizing any one of these methods will lead to an improvement in the environmental

accumulation of polyurethane foam for the future, especially when considering the versatility

and the impending increased production at a global level. Considering the pros and cons of each

method however, a combination might be the best option for faster results. Convenience is large

factor of whether or not anything gets accomplished. Therefore, despite environmental

consequences, polyurethane foam will continue to be disposed in landfills after consumer use.

The incorporation of bio-degradable starting materials into the foam will provide the most

benefit so that under the inevitable circumstances that the foam that does not end up recycled, it

can more efficiently degrade on its own. When polyurethane foam does manage to make it to the

point of recycling, incineration should be considered as the next best option of polyurethane

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waste reduction. Large amount of energy would be able to be recovered from the non-recycled

plastic materials, as well as large reduction in landfill volume, with little hazardous emissions.

Nonetheless, with the increasing demand for polyurethane foam products and

manufacturing, novel recycling methods and improvements to existing methods should continue

to be examined. Through the use of environmentally friendly materials, energy recovery

techniques and various recycling methods, individuals and organizations can begin to counteract

the negative effects of polyurethane foam pollution.

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BIBLIOGRAPHY

1. Peng, Y., Shih, Y., Lai, Y., Liu, Y., Liu, Y., & Lin, N. (2014). Degradation of polyurethane by bacterium isolated from soil and assessment of polyurethanolytic activity of a Pseudomonas putida strain. Environmental Science and Pollution Research,21(16), 9529-9537. doi:10.1007/s11356-014-2647-8

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