Enhancing the Biodegradation of Waste Rubber a Novel Approach to Sustainable Management of Discarded Rubber Materials

INTERNATIONAL LATEX CONFERENCE 2015

Enhancing the Biodegradation of Waste Rubber A novel approach to sustainable management of discarded rubber materials

Teresa Clark 8/12/2015

Rubber items are a critical part of modern society and a focus on the waste management of rubber is becoming more critical. Advancements have been made in recycling rubber waste, but a vast majority of rubber products are discarded into landfills. Sustainability efforts must include self-remediation through biodegradation of rubber (pre- consumer and post-consumer) in these waste sites. Current advancements provide insight into alternative methods of utilizing bio-mimicry to these return waste products to the natural carbon cycle, produce “green” energy and expand the scope of “Zero Waste”. Included are an assessment of the unique environment within landfills and the energy impact of utilizing these methods. Additionally, a brief update to the current progress in validating the biodegradation of rubber waste is included. Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

Contents Introduction ...... 2 Waste disposal of rubber materials ...... 2 Composting of Rubber ...... 5 Recycling Non-Tire Rubber Waste ...... 5 Recycling Waste through Biodegradation ...... 7 Carbon Recycling of Landfilled Rubber ...... 8 Biodegradation of Rubber ...... 8 Bioremediation within Landfills ...... 9 Modern Landfill Design ...... 10 Biodegradation Process in Modern Landfills ...... 10 Microbial Biodegradation In Landfills ...... 11 The Value of LFG from Modern Landfills ...... 12 Biodegradation Rates and GHG ...... 14 Energy Conversion of Landfilled Rubber ...... 15 Testing methods and results ...... 16 Importance of Microbial Diversity in Testing ...... 19 A Novel Approach to Rubber Waste ...... 20 Works Cited ...... 22

Figure 1 – Conversion of complex materials to ...... 12 Figure 2 (Barlaz, Landfill Gas Modeling, 2010) ...... 15 Figure 3 – ASTM D5511 performed for 195 days...... 17 Figure 4- ASTM D5511 performed for 305 days...... 17 Figure 5- ASTM D5526 performed for 200 days ...... 17 Figure 6 – BMP performed for 110 days ...... 18 Figure 7 – BMP performed for 105 days ...... 18 Figure 8 – BMP performed for 175 days ...... 18 Figure 9 – BMP performed for 30 days ...... 19

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

Introduction

Rubber products are everywhere to be found, though most people don’t recognize rubber in all of its applications. Since 1920, the demand for rubber in manufacturing was primarily dependent on the automobile industry, the biggest consumer of rubber products. Today, rubber is used in a wide variety of other applications such as, radio and T.V sets and in telephones. Electric wires are made safe and more effective by rubber insulation. Rubber forms a part of many mechanical devices in the kitchen. It helps to exclude draughts and to insulate against noise. Sofas and chairs may be upholstered with foam rubber cushions, and beds may have natural rubber pillows and mattresses. Clothing and footwear may contain rubber: e.g. elasticized threads in undergarments or shoe soles and protective gloves. Most sports equipment, virtually all balls, and many mechanical toys contain rubber in some or all of their parts. Still other applications have been developed due to special properties of certain types of synthetic rubber, and there are now more than 100,000 types of articles using rubber as a raw material. (Eldho Abraham, 2011) While the production of rubber articles continues to increase, the waste of disposed rubber must be considered. Ideally, waste rubber should integrate seamlessly into the natural carbon cycle without any residual toxicity. A novel concept is to produce self-remediating rubber articles that take advantage of our existing waste disposal methods to create the most valuable end of life scenario.

Waste disposal of rubber materials

Rubber items are a critical part of modern society and as the use of rubber continues to increase, a focus on the waste management of rubber is paramount. The waste rubber formed in latex-based industries is around 10–15% of the rubber consumed (Eldho Abraham, 2011). While this is a significant amount of industrial waste, the post- consumer rubber waste is far greater. In the US alone the waste disposal of rubber and leather is 15,060,000,000lbs - an increase of over 250% in the last 40 years (See Table 1). Recovery for recycling of these materials is at 17.9%. In 1960 the recovery rate for rubber and leather was also at 17.9%, however it dropped drastically in 1980 to 3.1% and has been slowly recovering over the past 30 years (Table 2). Interestingly, as is seen in Table 3, virtually all the recovery is for durable tires, with no reportable amounts of rubber in other durables and non-durables being collected for recovery. So while advancements have been made in recycling rubber waste from tires, virtually all of non-tire rubber products are discarded into landfills. This is an increasingly concerning issue as the disposal of rubber articles can cause negative environmental impacts.

An effective integrated waste management system includes waste collection and sorting, followed by one or more of the following options: recycling, biological treatment of organic materials, thermal treatment, and landfilling. Composition of solid waste varies among communities or regions; as such, there can be no single acceptable solution to solid waste management (SWM). The waste management options implemented, however, must both be environmentally sustainable and economically viable for all sectors of the community. (Caraban, 2008) In the US, the primary method of disposal is landfilling, with the remaining portions sent for recycling, composting and incineration. This is reflected in the number of facilities. In the US there are approximately 1908 operating landfills, 633 material reclamation facilities recycling) and 86 incineration sites. (EPA, Municipal Solid Waste Generation, Recycling, and Disposal in the United States, Tables and Figures for 2012) Other countries have higher landfill diversion, however this is typically limited to plastics, metals and paper and does not significantly impact the landfilling of rubber based disposable items, resulting in the disposal of most rubber waste in landfills as well.

While landfilling is the primary disposal method for most all rubber products, with exception of approximately 40% in rubber tires, there can be serious detrimental aspects to disposing of rubber in this manner. Rubber materials are not inherently biodegradable within landfills, which leaves the material stagnant for hundreds of years.

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

Additionally, different ingredients such as stabilizers, flame retardants, colorants, plasticizers and other additives that are mixed with rubber during compounding are of concern. After discarding the materials for landfilling there is a probability of leaching small molecular weight additives from bulk to the surface and from surface to the environment. These small molecular weight additives are not eco-friendly and may kill advantageous bacteria of soil. In this way landfill causes serious environmental problem. (Eldho Abraham, 2011). To resolve these issues, one must understand the conditions within a typical modern landfill, scientific advancements in rubber remediation, the beneficial potential of remediation within the landfill and then use the concept of bio-mimicry to address landfilled rubber in a way that provides maximum value.

Table 1 - US EPA Waste Generation (Thousands of Tons) Materials 1960 1970 1980 1990 2000 2005 2008 2010 2011 2012 Paper and Paperboard 29,990 44,310 55,16 72,73 87,74 84,840 77,42 71,31 70,02 68,62 Glass 6,720 12,740 0 0 0 12,540 0 0 0 0 Metals 10,300 12,360 15,13 13,10 12,77 15,210 12,15 11,53 11,47 11,57 Ferrous Aluminum 340 800 0 0 0 3,330 0 0 0 0 Other Nonferrous 180 670 12,62 12,64 14,15 1,860 15,95 16,83 16,54 16,80 Total Metals 10,820 13,830 0 0 0 20,400 0 0 0 0 Plastics 390 2,900 1,730 2,810 3,190 29,380 3,410 3,500 3,510 3,580 Rubber and Leather 1,840 2,970 1,160 1,100 1,600 7,290 1,940 2,020 2,000 2,000 Textiles 1,760 2,040 15,51 16,55 18,94 11,510 21,30 22,35 22,05 22,38 Wood 3,030 3,720 0 0 0 14,790 0 0 0 0 Other ** 70 770 6,830 17,13 25,55 4,290 30,26 31,29 31,84 31,75 4,200 0 0 0 0 0 0 2,530 5,790 6,670 7,570 7,440 7,580 7,530 7,010 5,810 9,480 12,70 13,11 13,12 14,33 2,520 12,21 13,57 0 0 0 0 0 0 15,45 15,71 15,78 15,82 3,190 4,000 0 0 0 0 4,650 4,700 4,630 4,600

(EPA, Municipal Solid Waste Generation, Recycling, and Disposal in the United States, Tables and Figures for 2012)

Table 2 - RECOVERY* OF MUNICIPAL SOLID WASTE (In thousands of tons and percent of generation of each material) Materials 1960 1970 1980 1990 2000 2005 2008 2010 2011 2012 Paper and Paperboard 5,08 6,77 11,74 20,23 37,56 41,96 42,940 44,57 45,90 44,36 Glass 0 0 0 750 0 0 0 2,810 0 0 0 Metals 100 160 370 2,630 2,880 2,590 5,330 3,130 3,170 3,200 Ferrous Aluminum 50 150 310 2,230 4,680 5,020 720 5,770 5,460 5,550 Other Nonferrous Neg. 10 540 1,010 860 690 1,340 680 720 710 Total Metals Neg. 320 1,220 730 1,060 1,280 7,390 1,400 1,370 1,360 Plastics 50 480 20 3,970 6,600 6,990 2,140 7,850 7,550 7,620 Rubber and Leather Neg. Neg. 130 370 1,480 1,780 1,270 2,500 2,660 2,800 Textiles 330 250 160 370 820 1,050 1,950 1,320 1,350 1,350 Wood 50 60 Neg. 660 1,320 1,830 2,120 2,010 2,020 2,250 Other ** Neg. Neg. 500 130 1,370 1,830 1,280 2,280 2,350 2,410 © 2015 ENSO Plastics 3

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

Neg. 300 680 980 1,210 1,330 1,310 1,300

Total Materials in 5,61 8,02 14,52 29,04 53,01 59,24 61,900 64,99 66,31 65,29 Products 0 0 0 0 0 0 0 0 0 Percent of Generation of Each Material Materials 1960 1970 1980 1990 2000 2005 2008 2010 2011 2012 Paper and 16.9% 15.3% 21.3% 27.8% 42.8% 49.5% 55.5% 62.5% 65.6% 64.6% Paperboard Glass 1.5% 1.3% 5.0% 20.1% 22.6% 20.7% 23.1% 27.1% 27.6% 27.7% Metals 0.5% 1.2% 2.9% 17.6% 33.1% 33.0% 33.4% 34.3% 33.0% 33.0% Ferrous Aluminum Neg. 1.3% 17.9% 35.9% 27.0% 20.7% 21.1% 19.4% 20.5% 19.8% Other Nonferrous Neg. 47.8% 46.6% 66.4% 66.3% 68.8% 69.1% 69.3% 68.5% 68.0% Total Metals 0.5% 3.5% 7.9% 24.0% 34.8% 34.3% 34.7% 35.1% 34.2% 34.0% Plastics Neg. Neg. 0.3% 2.2% 5.8% 6.1% 7.1% 8.0% 8.4% 8.8% Rubber and Leather 17.9% 8.4% 3.1% 6.4% 12.3% 14.4% 16.8% 17.7% 17.8% 17.9% Textiles 2.8% 2.9% 6.3% 11.4% 13.9% 15.9% 15.4% 15.3% 15.4% 15.7% Wood Neg. Neg. Neg. 1.1% 10.1% 12.4% 13.7% 14.5% 14.9% 15.2% Other ** Neg. 39.0% 19.8% 21.3% 24.5% 28.2% 27.5% 28.3% 28.3% 28.3% Total Materials in 10.3% 9.6% 13.3% 19.8% 29.7% 32.0% 34.1% 36.6% 37.6% 37.0 Products

(EPA, Municipal Solid Waste Generation, Recycling, and Disposal in the United States, Tables and Figures for 2012)

Table 3 - RUBBER AND LEATHER PRODUCTS IN MSW, 2012 (In thousands of tons and percent of generation) Product Category Generation Recovery Discards (Thousand (Thousand tons) (Percent of (Thousand tons) generation) tons) Durable Goods Rubber in Tires* 3,020 1,350 44.7% 1,670 Other Durables** 3,500 Neg. Neg. 3,500 Total Rubber & Leather Durable Goods 6,520 1,350 20.7% 5,170 Nondurable Goods Clothing and Footwear 770 Neg. Neg. 770 Other Nondurables 240 Neg. Neg. 240 Total Rubber & Leather Nondurable 1,010 Neg. Neg. 1,010 Goods Total Rubber & Leather 7,530 1,350 17.9% 6,180

(EPA, Municipal Solid Waste Generation, Recycling, and Disposal in the United States, Tables and Figures for 2012)

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

It is apparent that our global method of waste management is at best ineffective and to achieve a sustainable approach it is important to make a fundamental change in the approach and handling of our "waste" materials. The first key concept that is that, to the extent practical and environmentally beneficial, materials must be removed from the waste stream through programmed recovery and reuse of materials or through recycling the materials. To do this, it is necessary to develop an entire infrastructure and markets to handle, process, sell and use the recovered materials. All aspects of this sub-industry must be developed in concert. It is not productive or useful to recover materials for which there is no market or demand. (Associates) To achieve the maximum value, both economically and environmentally, in the recycling of materials we must take a scientific approach as opposed to an emotional response. This approach brings to question the validity of the modern popularity of “zero landfill’ initiatives.

Composting of Rubber

Composting is a landfill diversion scenario primarily for food discards and yard trimmings. However, a thorough assessment of rubber waste management should include study to determine the feasibility of landfill diversion into composting as an effective method Studies indicate the net GHG emissions from composting are lower than landfilling for food discards and higher than landfilling for yard trimmings. (EPA, Solid Waste Management and Greenhouse Gases, 2006) This is primarily due to the rapid degradation of food waste in landfills and the high percent of food waste that decomposes slowly in compost - leaving carbon in the soil (humus). 10 percent of the carbon in compost can be considered “fast” (i.e., readily degradable). The remaining 90 percent can be classified as either slow or passive, passive carbon represents approximately 52 percent of carbon in compost (EPA, Solid Waste Management and Greenhouse Gases, 2006). Unfortunately, compost standards for synthetic materials require 90% conversion to CO2 within 180 days (ASTM D6400), which negates out the value of potential slower degrading portions of carbon remaining as humus. The value proposition for these synthetic materials is not the same as it is for food waste because less than 10% of the carbon can remain in the soil. But, how does composting compare with modern landfilling from an environmental perspective, and which is the most beneficial route for rubber disposal?

There have been a number of studies conducted to compare the environmental impact of professional composting vs. landfill bioreactors. In these studies, the potential environmental impacts associated with aerobic composting and bioreactor landfills were assessed using the life cycle inventory (LCI) tool. The results are fairly the same across the studies performed. These studies concluded that the emissions to air and water that contribute to human toxicity are greater for the composting option than for the landfill option and the landfill option yields greater energy savings due to the conversion of the landfill gas (LFG) to electrical energy.

One such study was conducted at the Michigan State University under the Fulbright Research Grant by Maria Theresa I. Cabaraban, Milind V. Khire and Evangelyn C. Alocilja and was later published in November 2007. Their study looked at the potential environmental impacts associated with aerobic in-vessel composting vs. bioreactor landfilling. The results using the LCI model showed that the estimated energy recovery from bioreactor landfilling was approximately 9.6 MJ per kg of waste. The air emissions from in-vessel composting contributed to a GWP of 0.86 kg of CO2, compared to 1.54 kg of CO2 from the bioreactor landfill. Emissions to air and water that contribute to human toxicity were greater for the composting option that for the landfill. In addition, costs associated with in- vessel composting were about 6 times greater than that for the landfilling alternative. In conclusion, bioreactor landfill was a favorable option over in-vessel composting in regards to cost, overall energy use, and airborne and waterborne emissions. (Clark D. , 2009)

Recycling Non-Tire Rubber Waste

In a recent Perspective article, Bill Sheehan and David Kirkpatrick asked, “Is zero waste, which means recycling

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark nearly everything, achievable?” The answer provided by Winston Porter the originating father of our current recycling craze is:

“No. Not only is 100 percent recycling not reachable, but it is not even good for the environment. Georgia and the nation are recycling more than 25 percent of their trash, thus meeting the national goal I set in 1988 while an assistant administrator at the U.S. Environmental Protection Agency. However, most areas are not going much higher than 30 percent to 35 percent recycling for several reasons. First, at least one- fourth of trash—including such items as kitty litter, paper towels, dirt and broken toys—is virtually non- recyclable because it is hard to collect and has almost no value. So to reach even 50 percent recycling, about two-thirds of every “recyclable” item would need to be recovered. Second, only a few of the 50 or so identifiable items in garbage are present in significant percentages: cardboard boxes (13 percent of trash) and newspapers (6 percent), to name two. Those items are already recycled at high rates. To increase overall recycling dramatically, we would have to go after dozens of “one-percenters,” at great cost and inconvenience to consumer. How about 15-20 recycling bins at your curb?

There’s more. It is often difficult and expensive to recycle in rural areas. And much of our recycling is voluntary—we can’t force everyone to do it. Finally, we have to sell our recyclables, which is not easy when prices for these commodities soften, as they do periodically. The zero-waste notion begins with the false assumption that reuse or recycling is always best for the environment. In March 1996, I conducted a study of reusable vs. disposable food service packaging, analyzing more than 30 European and American environmental investigations. The basic result was that a disposable package or container (e.g., a foam coffee cup) is preferable to a reusable one (e.g., a porcelain cup) from the standpoint of water supply and water pollution, since washing the reusable cup creates hot, soapy wastewater. Disposables are also safer from a public health viewpoint. The reusables are better from air and solid waste standpoints, but only if reused several hundred times.

It is apparent that the zero-waste advocates are talking about zero solid wastes. But what about air and water pollution or energy usage? Not to mention the negative economic impacts of pursuing such a pie-in- the-sky venture. Also, modern landfills, demonized by Sheehan and Kirkpatrick, have to meet very stringent federal and state regulations and pose very small environmental risks.

Finally, the zero-waste concept ignores the law of diminishing returns. We already recycle the items that make the most environmental and economic sense. As we force ourselves to go after less valuable wastes in more difficult locations—say, hotdog wrappers at ballparks or leftover napkins at the airport—the costs will skyrocket. Recovered items will be trucked greater distances, or more resources will be used to clean and process dirty recyclables.

Our goal should be to minimize the overall environmental impact of our products, not simply to shut the door in one area—solid wastes. And every dollar spent on zero waste is a dollar taken away from other environmental problems or from such areas as education, health care, or transportation.” (Porter, 1997)

In terms of making an environmental difference, that's getting close to what cities should aim for, says J. Winston Porter, who, as former assistant administrator for America's Environmental Protection Agency, was the first to establish nationwide recycling targets in the United States in the 1980s. His target then was 25%, and it's a number he largely sticks by. Diverting 35% of waste into recycling is about as a high as any city can justify, he says. Trying to recycle more can be wasteful, if not harmful, he says, even though many major cities are setting targets at 70% or higher. "People say you can't recycle too much. It turns out you can," says Mr. Porter, president of the environmental consulting firm, the Waste Policy Center, near Washington, D.C. "If you spend enough money, you can recycle anything. That doesn't mean you should." (Libin, 2009)

As case in point, San Francisco's Department of Waste recently calculated it paid $4,000 a tonne to recycle plastic

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark bags. Its resale price for the recycled product? $32. Often the effects of aggressive residential recycling programs harm environmental goals. Citywide blue box programs typically mean a whole new fleet of trucks: Calgary added 64 more diesel-burning rigs retracing the same tracks its garbage trucks did just a few days before implementing their curbside recycling program, roughly doubling carbon dioxide emissions and other pollutants. A 2000 study by the London-based environmental group Friends of the Earth found that collecting yard waste for recycling (i.e., making mulch) emitted 264 more pounds of CO2 than burying it in a landfill. In 2002, two of Sweden's leading environmental authorities argued that recycling's benefits were usually undone by the resources required to collect and process it. The promise of environmentalists of a "flourishing recycling market" where reused goods would find ready buyers "was already a dream 40 years ago and is, unfortunately, still a dream," (Libin, 2009)

This is not to mean that recycling of materials is inherently detrimental, only to point to the fact that the decision as to what materials are collected for recycling can determine if the program is beneficial. Too often it is assumed that if recycling aluminum, copper, paper and select other materials is beneficial, that same benefit will be realized with all materials. It is also assumed that recycling is limited to the collection, separation and reprocessing of materials into similar products. This limited perspective blinds to the possibilities available relative to the recycling of materials through novel methods.

Recycling Waste through Biodegradation

In nature, there is no waste because everything gets recycled. This recycling is much different than the crude processing and attempts to re-use materials as we see in plastics and polymers. In nature, the waste products from one organism become the food for others, providing nutrients and energy while breaking down the waste organic matter in a process called biodegradation. Biodegradation is nature's way of recycling wastes, or breaking down organic matter into nutrients that can be used by other organisms. "Degradation" means decay, and the "bio-" prefix means that the decay is carried out by a huge assortment of bacteria, fungi, insects, worms, and other organisms that eat dead material and recycle it into new forms. Some organic materials will break down much faster than others, but all will eventually decay. The products of this biodegradation become the building blocks for other life processes, similar to the recycling of plastics by de-polymerization and reconstruction of polymers (although this process in plastics is seldom used as it is very resource intensive and inefficient). During composting when organic material is decomposed, it is often referred to as organic recycling.

Biodegradation is the biological breakdown of organic compounds by microorganisms into cell biomass and less complex compounds, and ultimately to water, and either carbon dioxide (aerobically) or methane (anaerobically). The extent and rate of this natural process depend on interactions between the environment, the number and type of microorganisms present and the chemical structure of the compound(s) being degraded. (Board, 1999) Oxygen, moisture, nutrients and microorganisms are very often the limiting factors in soils. To biodegrade complex and synthetic materials, microorganisms must also secrete enzymes that catalyze the degradation and break the material into more simple components such as organic acids. These organic acids are then further degraded by microorganisms in to the basic building blocks of nature; air, soil and water.

While microorganisms can degrade most natural compounds, they lack the appropriate enzymes to degrade many synthetics. Compounds having a molecular structure to which microorganisms have not been exposed to (i.e. xenobiotic compounds) are usually resistant (recalcitrant) to biodegradation. They pose threats to the ecosystems they contaminate. These may sometimes undergo biotransformation where small structural changes occur that affects the toxicity and mobility of the original compound with no loss of molecular complexity. Bio-degradative activities in natural material and energy cycling constitute one of the most important processes in water, sediment, soil and other ecosystems. An issue of concern for professionals and the public at large is the accumulation of recalcitrant organic compounds in the environment, sufficiently long (persistence) that they have undesirable effects. (Board, 1999)

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

By harnessing these natural forces of biodegradation, it is possible to reduce the environmental contaminants within our waste materials (bio-remediation). This can be accomplished through enhanced bioremediation (increasing the rate of biodegradation by supplying required nutrients to an indigenous microbial population (bio- stimulation) or by inoculating the site with microorganisms capable of degrading the target pollutant (bio- augmentation). Biodegradation is currently used within waste management for organic waste, sewage, landfills and other human produced contaminants. Through composting, natural biodegradation is accelerated to convert organic wastes to soil amendments. Wastewater treatment also accelerates natural forces of biodegradation to break down organic matter so that it will not cause pollution problems when the water is released into the environment. Landfills harness biodegradation to convert organic matter into energy and eliminate contaminants that could otherwise leach into groundwater and soil. Through bioremediation, microorganisms are used to clean up oil spills and other types of organic pollution. Bioremediation is used as a method to decrease human pollutants within the environment. This is not limited to aerobic soils and industrial sites; bio-remediation is also used within landfill sites.

Carbon Recycling of Landfilled Rubber

It is well understood that biodegradation is the most fundamental and beneficial method to remove waste products. Since 1914 there have been efforts to investigate microbial rubber degradation (Rose & Steinbuchel, 2005) in efforts to create more effective methods of remediating waste rubber. As most of our rubber waste is disposed of within landfills, sustainability efforts must include self-remediation through biodegradation of rubber (pre-consumer and post-consumer) in these waste sites while considering optimal decay rates.

Specifically related to disposable gloves; domestic and contaminated industrial gloves that do not require specific handling are disposed along with other household wastes as non-hazardous municipal solid wastes into domestic landfills. In a landfill, residual chemicals e.g. accelerators, will leach out as the rubber biodegrades. Under standard landfill conditions, vinyl is not biodegradable but the plasticizers (esters of phthalic acid) will leach out from the material when in contact with non-aqueous solvents. Nitrile itself is not biodegradable and the chemical by- products leaching out will be similar to those produced by natural rubber gloves (Board, 1999)

Biodegradation is the ultimate form of recycling and is the process we see has been successful in nature for millions of years. Within the landfill, biodegradation allows for carbon recycling as well as energy production. Additionally, during anaerobic biodegradation studies have shown no evidence for leachate toxicity associated with the decomposition of any component except food waste. (Barlaz & William Eleazer, Biodegradability of Municipal Solid Waste Components in Laboratory-Scale Landfills, 1997) Thus we should consider the options for waste management of rubber through biodegradation within the landfill.

Biodegradation of Rubber

Microbial degradation is a natural process by which organic compounds, including rubber polymers are converted by the action of bacteria to simpler compounds, mineralized and redistributed through the elemental cycles. Unlike natural polymers, many synthetic polymers are not biodegraded because they have not been available for a long-enough time in natural evolution for microorganisms to develop degradative enzymes that will utilize the compounds. Microorganisms will have to evolve new genes and genetic functions which encode catabolic enzymes to degrade new chemicals generated by the chemical industry. Various molecular mechanisms exist to enable microbes to recruit genes from pre-existing genes of related catabolic pathways and to modify the nucleotide sequences in the structural and regulatory genes to enhance expression and to use synthetic compounds as substrates. Thus microbes have occasionally responded to synthetic chemicals by producing degradative enzymes although the pathways may not be optimally regulated. (Board, 1999) However, this process is not controlled and utilizes an evolutionary factor that could theoretically require decades or longer to appear. Thus the need remains

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark to understand the microbial degradation pathways and provide more optimal methods of degradation in waste environments.

Over the years, there have been concerted efforts to investigate microbial rubber degradation. It became obvious that bacteria as well as fungi, are capable of degrading rubber, that rubber biodegradation is a slow process and it was assumed that degradation of the rubber backbone is initiated by oxidative cleavage of the double bond (G. N. Onyeagoro, 2012). These studies also used isolated strains of bacteria and found that specific bacteria were able to secrete extracellular enzymes capable of degrading rubber. However, in the landfill environment synthetic rubber seemed to be resistant to biodegradation. More recent research identified the primary degradation pathway of rubber has been mechanical oxidization which does not occur in the anaerobic conditions of a landfill. (Clark T. , 2013)

In the past few years, methods have been developed to optimize the production of rubber degrading extracellular enzymes in naturally occurring anaerobic microorganisms. ENSO RESTORE™ RL is one such method which employs a unique material designed to not only attract specific naturally occurring microorganisms, but to induce rapid microbial acclimatization to synthetic rubbers and resulting biodegradation. The method of biodegradation caused is strictly enzymatic and is designed to utilize naturally occurring microorganisms within waste environments, including landfills. (Clark T. , 2013) In this study, the mechanism of biodegradation is not studied but instead the commercial and environmental implications are considered. Details on these novel methods can be obtained through the published study1. However, an updated review of more recent test studies is included in this report for informational purposes.

Biodegradation testing has been completed on various rubber based materials including, nitrile, polyisoprene, polychloroprene, polyvinyl chloride, styrene butadiene rubber, thermoplastic elastomers, natural latex rubber, rubber based adhesive and polyurethane. While the rates of biodegradation vary dependent upon the chemical structure, it appears that all the samples tested show significant acceleration in the rate of complete biodegradation as measured by conversion to gaseous carbon.

Bioremediation within Landfills

For most, the term “landfill” conjures images of garbage, pollution and excessive waste. We imagine landfills filling at an enormous rate and the eventuality of the world as one large garbage dump. We consider billions of tons of trash mummified in tombs that will never go away. What we don’t envision is these sites as a source for clean inexpensive energy, a process for detoxifying materials or a resource recovery facility.

With increasing amounts of waste generation, decreased amount of landfill space, increased landfilling costs and environmental concerns associated with landfills, there has been a push to operate landfills with a process based vs. a storage/containment approach. This process based strategy for municipal solid waste (MSW) includes landfills that accelerate biodegradation to enhance gas generation, improve leachate quality, and reduce leachate treatment costs. Methane generated during waste decomposition is captured to prevent atmospheric pollution, and is used as a valuable source of clean-burning alternative energy (Wisconsin-Madison, 2011). Ultimately, the use of bioremediation tactics within landfills has proven an effective method to detoxify waste and create value.

In 2014 more than 1.8 billion tons of wastes are landfilled across the globe each year with most of this waste being deposited in municipal solid waste landfills. (EPA, A Landfill Gas To Energy Project Development Handbook). Understanding the design and processes in modern landfills will provide a guide to the determining the impact and

1 http://www.rubbernews.com/article/20131202/TECNOTEBOOKS/131209995/key-advancements-in-rubber- disposal?utm_campaign=&utm_medium=%09email&utm_source=20131211&utm_content=article3 © 2015 ENSO Plastics 9

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark performance of discarded products in these environments. It will also facilitate the development of materials that provide maximum value in the unique environment of a modern landfill.

Modern Landfill Design

Conventional sanitary landfills as practiced in North America in the 1970s and 1980s are generally referred to as "dry tombs" because the approach taken in designing them was to minimize water contacting the waste with a view toward minimizing excursions of the resulting leachate into the groundwater. (Associates). Modern research and technology has created a transition in the landfill industry from the conventional landfill, where municipal solid waste (MSW) biodegradation is minimized due to limited moisture addition, to the bioreactor landfill and hybrid landfill energy site, where MSW biodegradation is a primary objective. Waste decomposition is optimized through the increase in moisture content, and also through increase in temperature, and/or nutrient/microbial seed addition to the refuse. The most widely used approach is to increase the moisture content through recirculation of leachate or addition of supplemental liquids (e.g., sewage or industrial wastewater). (Wisconsin- Madison, 2011) The aim of operating landfills in this way is to accelerate the degradation of municipal waste and increase methane production in the short term during landfill gas (LFG) harvesting. This reduces fugitive methane release into the atmosphere after closure. The increased moisture/temperature conditions induce the waste to settle. This permits a larger volume of waste to be disposed in a given area. This aspect of the design also allows for landfill operators to benefit economically from the energy potential of the methane gas, allowing most of the methane generated to be captured during active energy recovery vs. after closure.

The design of modern landfills utilizes the understanding of the biological processes occurring within the landfill. These modern landfills focus on biodegradation for the purpose of generating methane, the primary component in LFG, and the value of converting the resulting methane to energy. While some of these landfills are built more recently and designed from inception for maximum capture of LFG, others are retrofitted conventional landfills. Internationally there are 1937 LFG energy projects registered with the Global Methane Initiative program, In the US there are 967 projects producing 1044 million cubic feet per day of LFG that is actively converted to energy) (Initiative, 2015). The U.S. Environmental Protection Agency (EPA) estimates that more waste is placed in landfills that capture methane to energy than landfills that allow the methane to escape into the atmosphere. 35 percent of municipal solid waste goes to landfills that capture methane for energy use, 34 percent of landfills capture methane and burn it off on-site, while 31 percent allow the methane to escape (Shipman, 2011)

Biodegradation Process in Modern Landfills

Biodegradation is the process by which organic substances are broken down into smaller compounds using the enzymes produced by living microbial organisms. The microbial organisms transform the substance through metabolic or enzymatic processes. Although biodegradation processes vary greatly, the final product of the degradation is most often carbon dioxide and/or methane. Biodegradable matter is generally organic material such as plant and animal matter and other substances originating from living organisms, or artificial materials that are similar enough to plant and animal matter to be put to use by microbes. While some microorganisms have the astonishing, naturally occurring, microbial catabolic diversity to degrade, transform or accumulate a huge range of compounds including hydrocarbons (e.g. oil), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pharmaceutical substances, radionuclides and metals, many synthetic materials remain resistant to microbial biodegradation.

Organic material can be degraded aerobically, with oxygen, or anaerobically, without oxygen. Biodegradable waste in landfill degrades in the absence of oxygen through the process of anaerobic digestion. Anaerobic digestion is a series of processes in which microbes break down biodegradable material in the absence of oxygen. It is widely used to treat wastewater sludge and biodegradable waste because it provides volume and mass

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark reduction of the input material. Anaerobic digestion also produces biogas, an energy rich blend of methane and carbon dioxide. While methane which has approximately 21 times the global warming potential of carbon dioxide if released directly into the atmosphere, in a cradle to cradle approach, this biogas is collected and converted into eco-friendly inexpensive power generation and carbon dioxide.

There are a number of bacteria that are involved in the process of anaerobic digestion including acetic acid- forming bacteria and methane-forming bacteria. These bacteria feed upon the initial feedstock, which undergoes a number of different processes converting it to intermediate molecules including sugars, hydrogen & acetic acid before finally being converted to biogas. The process begins with bacterial hydrolysis of the input materials in order to break down insoluble organic polymers such as carbohydrates and make them available for other bacteria. Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia , and organic acid. Acetogenic bacteria then convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Methanogenic bacteria finally are able to convert these products to methane and carbon dioxide.

Landfill Decomposition Cycle

Aerobic Phase – A very short period, often limited to just a few days, when aerobic microbes are becoming established and moisture is building up in the refuse. Aerobic decomposition is at its maximum and the oxygen is replaced with CO2 as the waste decomposes. During the final stages of this phase the anaerobic microbial populations increase by a factor of 100.

Anaerobic Acid Phase - After O2 concentrations have declined sufficiently, the anaerobic processes begin. During the initial stage (hydrolysis), the microbe colonies eat the particulates, and through an enzymatic process, solubilize large polymers down into simpler monomers. A rapid accumulation of carboxylic acids and organic intermediaries as well as decreased in pH occurs during this stage. CO2 production occurs rapidly at this stage and then progresses to CH4 toward the final stages.

Accelerated Methane Production Phase – During this phase there is a rapid increase in methane production to maximum concentrations of 70% CH4. During this phase, carboxylic acids and organic intermediaries are consumed faster than they are produced. This results in an increase in the pH and decrease in the carboxylic acid content. Microbial populations remain steady during this phase.

Decelerated Methane Production Phase - The final stage of decomposition involves a decrease in the CH4 production although the CO2 and CH4 ratios remain steady at 60/40 relative. This decrease results from a decrease in carboxylic acids. Polymer hydrolysis is maximized during this phase, however the resulting carboxylic acids are decomposed at a similar rate to their production due to a balance of microbial population. Humic material is produced during this stage, similar to the humic matter produced during composting. (Barlaz, Microbiology of Solid Waste, 1996)

The decomposition process in landfills demonstrated above is a microbial mediated process that requires a coordinated effort between several groups of micro-organisms. The decomposition products from one group of bacteria become the food source for another group of bacteria until the complete decomposition is finalized.

Microbial Biodegradation In Landfills

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

Anaerobic digestion occurs when the anaerobic microbes are dominant over the aerobic microbes. The anaerobic biodegradation process begins with bacterial hydrolysis and fermentation of complex organic structures to smaller low-molecular-weight insoluble organic acids, such as carbohydrates (e.g. acetate). These smaller compounds can be used by some bacteria to be directly mineralized to CO2. Acetogenic bacteria then convert the low-molecular- weight organic acids (sugars and amino acids) into carbon dioxide, hydrogen , ammonia, and acetic acids. Methanogens finally are able to convert these products to methane and utilize hydrogen as an energy source.

There are four key biological and chemical stages of anaerobic digestion; hydrolysis, acidogenesis, acetogenesis and methanogenesis. In most cases biomass is made up of large organic polymers. In order for the bacteria to access the energy potential of the material, these chains must first be broken down into their smaller constituent parts. These constituent parts or monomers Figure 1 – Conversion of complex materials to CH4 by anaerobic microbes such as sugars are readily available by other bacteria. The process of breaking these chains and dissolving the smaller molecules into solution is called hydrolysis. Therefore hydrolysis of these high molecular weight polymeric components is the necessary first step in anaerobic digestion. Through Hydrolysis the complex organic molecules are broken down into simple sugars, amino acids, and fatty acids.

Acetate and hydrogen produced in the first stages can be used directly by methanogens. Other molecules such as volatile fatty acids (VFA’s) with a chain length that is greater than acetate must first be catabolized into compounds that can be directly utilized by methanogens.

The biological process of acidogenesis is where there is further breakdown of the remaining components by acidogenic fermentative) bacteria. Here VFAs are created along with ammonia, carbon dioxide and Hydrogen sulfide as well as other by-products. The process of acidogenesis is similar to the way that milk sours.

The third stage anaerobic digestion is acetogenesis . Here simple molecules created through the acidogenesis phase are further digested by acetogens to produce largely acetic acid as well as carbon dioxide and hydrogen. The terminal stage of anaerobic digestion is the biological process of Methanogenesis. Here methanogens utilize the intermediate products of the preceding stages and convert them into methane, carbon dioxide and water. It is these components that makes up the majority of the biogas emitted from the system.

The process ultimately produces CH4 as the final biogas as illustrated in diagram 1. However it is a complex process that involves hydrolysis, fermentation, acetogenesis and methanogenesis. It is the concentric effort of various methanogenic bacteria, acetogens, protozoa and flagellate. Landfills are a thriving ecosystem of biological diversity and modern landfills optimize this process.

The Value of LFG from Modern Landfills

Landfill gas (LFG) is created when organic waste in a municipal solid waste landfill decomposes in the landfill as

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark demonstrated above. This gas consists of about 50-70 percent methane (the primary component of natural gas), about 30-50 percent carbon dioxide (CO2), and a small amount of non-methane organic compounds (NMOCs). Instead of being allowed to escape into the air, LFG is captured, converted, and used as an energy source. Since the late 1970s, LFG has been captured and used to provide a renewable energy resource in the form of electricity and fuel to citizens, communities and industry.

In 2014, the US had 636 operational LFG energy projects in 49 states/territories that supplied approximately: 16 billion kilowatt hours of electricity, and 100 billion cubic feet of LFG to end users. Annually, LFG energy projects produce enough energy to power nearly 1.2 million homes for a year and heat more than 731,000 homes. (EPA, Green Power from Landfill Gas, 2015) LFG energy projects help curtail global climate change, because they reduce emissions of methane, a greenhouse gas more potent than CO2. Reducing LFG emissions by converting them to energy reduces local ozone levels and smog formation, diminishes explosion threats and unpleasant odors created by the landfill, and improves overall landfill management. Even the United Nations Development Program has recognized anaerobic digestion facilities as one of the most useful decentralized sources of energy supply. (Clark D. , 2009)

LFG is used in a variety of ways, as liquid fuel, gaseous fuel and direct conversion to electricity and almost any entity can use LFG for a variety of purposes. One option is for utilities and power providers to purchase the electricity generated from the recovered LFG. Purchasing electricity from LFG enables utilities and power providers to add a renewable energy component to their energy portfolios. LFG can be piped directly to a nearby facility for use as either a boiler or industrial process fuel. Direct use of LFG is reliable and requires minimal processing and modifications to existing combustion equipment.

The benefits of LFG energy in terms of greenhouse gas emission reductions are substantial. For example, a 3 megawatt LFG energy facility requires approximately 1,075 standard cubic feet per minute (scfm) of LFG to operate. Not only does the combustion of this quantity of methane in an LFG energy facility result in direct methane emission reductions, but also in indirect CO2 emission reductions of about 11,950 metric tons per year, depending on the type of fuel that was used to generate the displaced electricity. The indirect environmental benefits of fossil fuel displacement through LFG energy can amount to nearly 10 percent of the direct greenhouse gas emission reduction benefits from methane combustion. The direct and indirect CO2 equivalent (CO2e) emission reductions from a direct–use project utilizing 1,000 scfm of LFG are approximately 126,000 and 12,440 metric tons per year, respectively. 22 states and the District of Columbia have renewable portfolio standards (RPS), requiring that electricity producers obtain a certain amount of their power from renewable sources. In most of these states, waste-to-energy facilities and landfill gas are permitted energy sources. (EPA, Solid Waste Management and Greenhouse Gases, 2006) The annual environmental benefits from current landfill gas-to-energy project are equivalent to; planting over 20.5 million acres of forest per year, preventing the use of over 177 million barrels of oil, removing the carbon dioxide emission equivalents of over 14.5 million cars, or offsetting the use of 370,000 railcars of coal (ENSO Plastics, 2011)

Landfill and LFG collection operations in the United States are well established and more than 90 percent recovery can be achieved at cells with final cover and an efficient gas extraction system. (EPA, LFG Energy Projects) However this efficiency is dependent on the design of the landfill as well as the length of time the waste has been within the waste environment. The first three phases, aerobic decomposition, non-methanogenic phase and the unsteady methanogenic phase produce primarily carbon dioxide and smaller amounts of methane. The majority of the methane will be produced during the fourth phase when methane is generated at between 40 and 70 percent of total volume. (Associates) Typically, the waste in most landfill sites will reach the stable methanogenic phase within less than 2 years after the waste has been placed. Depending on the depth of the waste lifts, and the moisture content of the waste, the methanogenic phase might be reached as early as six months after placement. LFG may be produced at a site for a number of decades with emissions continuing at declining levels for up to 100 years from the date of placement. (Associates)

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

LFG energy projects provide significant cost savings and long-term, sustainable energy to LFG end users. Some recent examples include:

o Coca-Cola’s Atlanta Syrup Branch facility gets nearly all of its energy in the form of electricity, steam and chilled water from green power generated at a nearby landfill, providing Coca-Cola with real energy savings. The landfill annually generates 48 million kilowatt-hours of on-site green power. o The U.S. Navy saves approximately $1.1 million annually in utility costs at the Marine Corps Logistics Base located in Albany, Georgia, since its first LFG cogeneration plant was completed in 2011. This facility is made up of a dual-engine generator, a heat recovery steam generator and two dual-fuel boilers. o In 2012, Gundersen Health System’s Onalaska Campus became the first energy-independent medical campus in the United States by using LFG piped from the local landfill in La Crosse County, Wisconsin. The LFG is used to power a generator that supplies 100 percent of campus energy needs. o The U.S. Department of Justice obtains 80 percent of its Federal Bureau of Prisons’ Allenwood Correctional Complex’s electricity from the combustion of LFG at the nearby landfill in Lycoming County, Pennsylvania. (EPA, Green Power from Landfill Gas, 2015)

The benefits of LFG energy are also well recognized and include:

o LFG is recognized by energy certification programs as a renewable energy resource. o LFG serves as the “baseload renewable” for many green power programs, providing online availability exceeding 90 percent. o Most states have landfills that can support LFG projects. o Energy produced from LFG is one of the more cost-competitive forms of renewable energy. o Several financial incentives exist in the form of federal tax credits and state grants. (EPA, Green Power from Landfill Gas, 2015) o Landfill gas comes from one local source, and it usually costs less than conventional fuels. o Landfill gas energy recovery is a proven technology. Operators and equipment manufacturers have gained experience with the conversion technologies used in landfill gas recovery operations. o Landfill gas recovery projects provide a net environmental benefit by reducing methane and volatile organic compounds emissions, conserving fossil fuels, reducing explosive hazards, and reducing odor. In addition these benefits ease the permitting process, may be shared with the utility, or used as a bargaining chip. o Most landfill gas projects are situated at a landfill site, which may ease or eliminate local permitting and zoning requirements. o The price of fuel and equipment is fixed at the project outset; there is only minimal price escalation. o Landfill gas projects can serve on-site electrical loads at dispersed locations, thus reducing the need for new generating plants and transmission facilities. o Landfill gas projects offer a way for utilities to attain Climate Challenge voluntary greenhouse gas emission reduction targets. o Title IV of the Clean Air Act (Acid Rain Program) creates a quantifiable value for avoided SO2 emissions. (EPA, A Landfill Gas To Energy Project Development Handbook)

Biodegradation Rates and GHG

It may initially appear that rapid movement into the fourth phase and the resulting methane production would be

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark most beneficial. However, studies show that more rapid degradation may actually be environmentally harmful, because federal regulations do not require landfills that collect methane to install gas collection systems for at least two years after the waste is buried. If materials break down and release methane quickly, much of that methane will likely be emitted before the collection technology is installed. This means less potential fuel for energy use, and more greenhouse gas emissions. (Shipman, 2011)

As a result, the researchers find that a slower rate of biodegradation is actually more environmentally friendly, because the bulk of the methane production will occur after the methane collection system is in place. (Shipman, 2011) Ideally, the majority of biodegradation, and the resulting methane, should take place after the collection system is in place and biodegradation should complete during actively managed post closure (50 years). In this scenario, the collection of methane is most likely to reach the 90% efficiency.

Most food and garden waste is shown to have a half-life between 6 months to 1.5 years, whereas paper and moderately degradable materials have a half –life of 5-25 years. (Associates). This indicates there may be a benefit to diversion of food waste from landfills as the methane production from these materials would most likely be released directly into the atmosphere. So, although 75.8% of all MSW is placed in landfills managing biogas (Dr Morton Barlaz, NC State), the management can be limited if the waste biodegrades too quickly, as demonstrated in Figure 2. Thus it is important from an environmental perspective to encourage the use of biodegradable materials with a moderate rate of biodegradation as opposed to a rapid rate (years instead of months).

Figure 2 (Barlaz, Landfill Gas Modeling, 2010)

Energy Conversion of Landfilled Rubber

Understanding that virtually all rubber waste is disposed of within landfills, and also that the current trend worldwide is the capture and use of methane to produce power, it is a logical conclusion that converting this landfilled rubber to methane is an optimal energy strategy. While much has been studied regarding the value of LFG energy, less has been done to calculate the energy impact of discarded rubber. To calculate the energy value one must know the actual carbon content and methane conversion ratio of each discarded material, as this is unavailable calculations in this report are performed on an average of natural rubber and styrene-butadiene rubber. The results are very encouraging!

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

If the waste rubber in the US alone was to biodegrade within landfills converting methane to energy, the 12,364,260,000lbs landfilled annually would produce upwards of 8,009,567 million Btu. 2 This is a significant amount of energy without requiring any additional infrastructure, collection vehicles, separation or government subsidies.

This amount of energy and methane is:

Equivalent to 1,412,978 barrels of oil! The energy required to power the annual usage of 104,898 cars3 194,496 homes could be powered each year from the energy4

The energy values calculated are directly from the methane energy. If one were to calculate the overall energy/carbon savings considering the offsetting of coal produced energy, the reduced transportation cost by remaining integrated with municipal waste, and the avoided energy of handling/reprocessing in alternative methods, the actual realized benefit would be far greater.

Testing methods and results

There are several methods employed to study the biodegradation rates of materials in landfill conditions. While some tests utilize physical weight loss, disintegration or molecular weight loss; the most effective measurement of biodegradation is the measurement of gas production. Gas production measures the conversion of carbon in the test sample to gaseous carbon, the by-product of complete biodegradation of organic materials, whereas the other methods employ measurements of degradation or fragmentation of a material. ASTM publishes two tests that utilize gas measurement to determine biodegradation, ASTM D5511 and ASTM D5526. Additionally, universities and researchers utilize a test referred to as a bio-chemical methane potential that measures gas in a similar manner.

Recent testing of rubber materials treated with ENSO RESTORE show significant increase in the biodegradation of rubber based materials. Test duration ranged from 30 days to 305 days to demonstrate continued effectiveness over long term residence. For most all materials tested, the untreated material indicated little to no biodegradation during the test period, with some samples confirming the concerns of soil toxicity. Once treated with ENSO RESTORE, all samples tested provided positive results. Testing conducted using all three test methods mentioned above indicate that the use of ENSO RESTORE is an effective means for bioremediation of waste rubber in landfills.

The rate of biodegradation fluctuates within the test as it would in a natural environment. This is normal and is expected. There are also periods of more and less rapid biodegradation during a test as microorganisms go through standard periods of activity and transition however the charts provided provide only the final calculation of total biodegradation during the test period. All treated tests samples were produced using ENSO RESTORE at

2 To calculate how much energy can be created from the biodegradation of landfilled rubber waste we take the total weight of rubber waste (15,060,000,000lbs), remove the 17.9% recovered for recycling and we are left with 12,364,260,000 lbs landfilled annually. We then multiply it by % carbon (approximately 90%), multiply by 1.33 (molecular weight of CH4 16 / molecular weight of carbon 12 – this converts the carbon to methane), then multiply by 22.4 (L/g – ideal gas law). This will provide the volume of methane potential, which we then convert to cubic meters (331,520,430.528m3 or 11,707,533,508ft3). Assuming that the gas production is approximately 70% methane and 30% carbon dioxide, we then multiply by .7 to achieve the actual methane potential value. The energy value is calculated using an average of 7 barrels per TOE and the 1TOE energy equivalent of 39.68 million Btu as defined by the US EIA.

3 1 barrel of oil = 42 gallons: driving 1400 km (840 miles) in average car, the average vehicle miles traveled in 2011 was 11,318 miles per year, equivalent is 13.47 barrels/vehicle/year - US EPA 4 Average home electricity use in US (2013) - 12,069Kwh © 2015 ENSO Plastics 16

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

1% by weight unless notated otherwise. Additionally, the treated and untreated samples were produced at the same facility and biodegradation was tested simultaneously to avoid misinterpretation due to the natural variations in microbial content of inoculum.

ASTM D5511 – Tests performed in accordance with ASTM D5511 standardized test method. This testing provides reliable results in an anaerobic environment. This test is used to validate if a material is biodegradable in anaerobic environments by replicating the conditions found in an anaerobic digester. 195 days 305 Days 18 20 16 14 18 12 16 10

8 14 6 12

Biodegradation % Biodegradation 4 2 10 0 8

Biodegradation% 6 4

2 0 5511 - Nitrile - 5511 - Nitrile Treated Untreated

Figure 3 – ASTM D5511 performed for 195 days. Figure 4- ASTM D5511 performed for 305 days.

ASTM D5526 – Testing was performed in accordance with ASTM 200 Days D5526 standardized test method. This test is used to provide realistic 50 results of biodegradation rates of the 40 material in modern landfills. This is a long term test that replicates the 30 landfill environment through low temperatures, limited moisture, 20 anaerobic, and under pressure. Interestingly, this testing shows an 10 inhibitory effect of the rubber 0 materials on the natural respiration Biodegradation% 5526 - 5526 - 5526 - 5526 - 5526 - PVC 5526 - PVC occurring in the inoculum. This -10 Latex - Latex - Nitrile - Nitrile - - Treated - Untreated indicates that the material, unless Treated Untreated Treated Untreated treated with ENSO RESTORE may -20 become toxic to the environment. Biochemical methane potential Figure 5- ASTM D5526 performed for 200 days

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

(BMP) – These tests were performed under anaerobic laboratory conditions using high moisture and heat to facilitate an optimal biodegradation environment. This test utilizes landfill leachate to obtain microbial flora similar to that found within municipal landfills. This test is an important parameter that is used in landfill research to determine MSW stability. The BMP of a sample is the amount of methanogenic degradation still possible for a sample. A high BMP indicated that the waste is still active, containing an easily available carbon source while a low BMP indicates inertness and low carbon availability.

110 Days 105 Days 5 25

3 15 2 10 1 Biodegradation% 5

Biodegradation % Biodegradation 0 BMP - Hot Melt BMP - Hot Melt 0 -1 Adhesive - Treated Adhesive - Untreated 2% BMP - PU Foam - BMP - PU Foam - -2 Treated Untreated Figure 6 – BMP performed for 110 days Figure 7 – BMP performed for 105 days

175 Days 25

Biodegradation% 5

0 BMP - Nitrile - Treated BMP - Nitrile - Treated BMP - Nitrile - Untreated

Figure 8 – BMP performed for 175 days

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

30 days 40

10 Biodegradation % Biodegradation

-5

-10

Figure 9 – BMP performed for 30 days

Importance of Microbial Diversity in Testing

Methane is generated as a result of physical, chemical, and microbial processes occurring within the refuse. Due to the organic nature of most waste, it is the microbial processes that govern the gas generation process (Associates). Within landfills, many types of microorganisms have been identified that contribute to the biodegradation of materials and resulting methane production. It is also well recognized that only a fraction of these microorganisms have been identified and even fewer are cultivable in the laboratory. Thus many laboratories struggle with biodegradation testing related to landfill conditions due to a lack of expertise in microbiology.

Though not presented in this paper, it is recognized that laboratories who source inoculum from in-house processes very likely have limited diversity in microorganisms leading to inaccurate test results as it is problematic to attempt to simulate the organic/inorganic matrix within a landfill. Hence, in these scenarios it is far more common to observe false negatives due to inadequate microbial diversity as opposed to false positives. It is often mistaken that microbial flora within native soil and/or compost are adequate for landfill biodegradation testing. Compost and soil contain significant colony forming units and have a wide variety of bacteria and fungi that are

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark optimized within aerobic environments, but not in anaerobic ones. Laboratories undertaking biodegradation testing of landfills will find repeatable results by obtaining microbial flora from landfill leachate. This leachate is most often used as a seed for test inoculum.

Another limitation to be considered is the use of commercially produced cellulose as a test sample to measure microbial activity. It has been found that commercially produced cellulose can have up to 10X greater activity than the level indicated by the vendor. There are methods to address this issue. (Barlaz, Microbiology of Solid Waste, 1996)

A Novel Approach to Rubber Waste

There is significant benefit to adjusting our waste management strategy for rubber to include biodegradation within landfills. While this approach may seem contrary to the public perception of “zero waste”, it is in fact part of the same directive. By utilizing technologies, such as ENSO RESTORE, to achieve controlled biodegradation it is possible to implement biomimicry and achieve zero waste through full biodegradation. This complete biodegradation integrates in the natural carbon cycle while also creating clean energy to offset fossil fuel use.

The common approach to waste management is focused on diversion from landfills. Studies show that while diversion of some materials from landfills creates a beneficial footprint, other materials such as rubber, mixed plastics and other waste (approx. 65% off all waste) is most beneficial to discard within landfills. Often this is due to the additional routes required for separated collection. Around 91–95% of the total energy use in waste management scenarios is due to collection activities. When separate routes are created for the collection of yard waste, recyclables, and residuals, and their subsequent transportation to waste treatment facilities such as, respectively, windrow composting, and MRF, waste diversion from the landfill doubles gaseous emissions contributing to global warming arising from the burning of diesel fuel used by vehicles for collection and transportation. Interestingly the energy consumed in collection is at least 60% less than the energy generated by the recovery and use of the LFG (Caraban, 2008) indicating that LFG energy can not only offset the energy requirements in waste collection but in single source collection can be a net positive.

LFG is a critical part of the overall energy profile for municipalities as LFG is a local, renewable energy resource. Because landfill gas is generated continuously, it provides a reliable fuel for a range of energy applications, including power generation and direct use. (EPA, A Landfill Gas To Energy Project Development Handbook) Landfill gas is one of the few renewable energy resources that, when used, actually removes pollution from the air. In addition to these environmental benefits, using landfill gas is cost-effective and generates economic opportunities. (EPA) This is recognized by UCLA who meets 20% of its energy needs from LFG (Hisey) and other communities who see the valuable resource as a way to reduce greenhouse gas emissions. (Ballard) Carbon credits can be created both directly or as a result of fuel offsetting. LFG energy projects may generate supplementary offset credits that represent the emissions avoided through the use of the LFG fuel in lieu of other fuel sources. For example, the offset fuel could be natural gas or coal. (Associates). And, LFG projects are considered less expensive than many of the other options for emission reductions (Associates)

Some of the primary values in landfill biodegradation as opposed to compost/recycling are the ease of implementation (we are already landfilling these materials), reduced transportation emissions (no need for separate collection), reduced toxicity, and valuable energy. With composting we take carbon based materials and by ASTM D6400 convert 90% directly to greenhouse gas with no option for capture or value. Less than 10% is retained as carbon storage or soil so the value of the compost is negated. With incineration, the majority of the carbon is converted to N2O and CO2, however we get an energy value from it. The remaining carbon is sent to a landfill as ash. With landfill biodegradation, we convert the carbon material into approximately 40% CO2 and 60% CH4, which is captured and utilized for energy (the same total amount of carbon is released as composting, but we get added value of energy). Additionally, we remove the synthetic material and return it to the natural carbon

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark cycle without the requirement of separation or additional transportation. Overall this presents a more beneficial method for rubber disposal.

Integrating biodegradable rubber waste into LFG projects creates an innovative method to increase the energy potential of landfills, decrease the toxicity of the leachate, support the financial viability of LFG projects and return the carbon within the rubber article to the natural carbon cycle. It also avoids the increased emissions required to divert rubber from the landfill. Overall, it appears that utilizing landfill biodegradation as the waste management for rubber is the most beneficial option in today’s integrated waste management strategy.

Landfill biodegradable materials also provide a unique opportunity for brands and manufacturers looking to improve their sustainability profile. Most often once a material leaves the factory there is no method for the producer to control the disposal or end of life scenario of that product. Utilizing landfill biodegradable materials is one of the few methods available that address the sustainability of materials in the customary disposal method, creating a means for companies to implement extended producer responsibility by ensuring that the end of life scenario is beneficial even when the producer no longer has possession of the product.

Enhancing the Biodegradation of Waste Rubber International Latex Conference 2015 - Teresa Clark

Works Cited 2014, 3. G. (n.d.). Associates, C.-R. &. (n.d.). Handbook for the preparation of LGE projects in Latin America. Ballard, R. (n.d.). Facilities Design & Management Administrator City of Tucson. Barlaz, M. (1996). Microbiology of Solid Waste. Bob Stern. Barlaz, M. (2010). Landfill Gas Modeling. Barlaz, M., & William Eleazer, W. O.-S. (1997). Biodegradability of Municipal Solid Waste Components in Laboratory-Scale Landfills. Environ. Sci. Technol. Board, M. R. (1999). Environmentally Friendly Natural Rubber Gloves. Caraban, M. T. (2008). Aerobic in-vessel composting vs bioreactor landfilling using life cycle inventory models. Springer. Clark, D. (2009). Landfill Biodegradation. Clark, T. (2013). Advancements in Rubber and Latex Disposal. RUbber News Technical Notebooks. Cliff Chen, N. G. (2003). Is landfill gas green energy. Natural Resources Defence Council. Eldho Abraham, B. M. (2011). Recent advances in the recycling of rubber waste. ENSO Plastics. (2009). MSW Landfill Gas Collection. ENSO Plastics. (2011). Aerobic Anaerobic Biodegradation. EPA, U. (n.d.). US EPA. EPA, U. (2006). Solid Waste Management and Greenhouse Gases. EPA, U. (2015). Green Power from Landfill Gas. EPA, U. (n.d.). A Landfill Gas To Energy Project Development Handbook. EPA, U. (n.d.). LFG Energy Projects. Retrieved from www.epa.gov EPA, U. (n.d.). Municipal Solid Waste Generation, Recycling, and Disposal in the United States, Tables and Figures for 2012. EPA, U. (n.d.). MUnicipal Solid Waste Generation, Recycling, and disposal in the United States: Facts and Figures for 2012. G. N. Onyeagoro, E. G. (2012). Studies on Microbial Degradation of Natural Rubber Using Dilute Solution Viscosity Measurement and Weight Loss Techniques. Hisey, D. (n.d.). Energy Facility Manager UCLA. Ikram, A., & Amir Hashim, M. Y. (2002). Natural rubber biodegradation in soil in relation to the waste disposal of used latex products. Initiative, G. M. (2015). Landfill Gas Energy Sites. Lassaux, S. (n.d.). Integrated scenarios of household waste managment. Libin, K. (2009). The Recycling Conundrum: How your blue bin hurts the environment. Canwest News Service. Millman, O. (2015). We are destroying the earth in ways even worse than climate change. Mother Jones. Porter, W. (1997). Too much recycling can be a waste of resources. Atlanta Journal-Constitution. Publishing, V. (2009). Biodegradable over recyclable. Natural Products Insider. Rose, K., & Steinbuchel, A. (2005). Biodegradation of Natural Rubber and Related Copounds: Recent Insights into a Hardly Understood Catabolic Capability of MIcroorganisms. Applied and Environmental Microbiology. Shipman, M. (2011). Study: Biodegradable Products May Be Bad For The Environment. Wisconsin-Madison, N. M.-D.-U. (2011). Biochemical Methane Potential of Municipal Solid Waste and Biosolids.