#wastewednesday

Waste Management

Waste is subjective - one person's trash is someone else's treasure, after all. But the fact remains that the management of waste is something that needs to be considered when designing, manufacturing, using, or disposing of any material object. Waste can be industrial waste created during the manufacturing process, or it can be a product intentionally designed for single use, or an item can be thrown away at the end of a long life cycle.

Waste can be the gases and air pollution that fill the air, either during production or the incineration of materials. What may be waste by-products to one industry could be useful raw materials to another. In this increasingly connected world, people are paying more attention to waste than ever, designing new recycling methods, creating products that can be reused, or downcycled, and reducing the waste generated in the first place. Waste can carry with it a variety of hazards, from chemical to biological to radioactive.

In the field of materials science, just as it is can be said that everything falls within our realm (every thing is made of something), everything generates waste, in one way or another, and this waste cannot and should not be neglected or ignored.

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Concrete Recycling

One effort to increase sustainability in the construction and architecture industries is the recycling of concrete, typically from demolished structures. One of the most common ways to recycle concrete is by crushing the waste/destroyed material, either into powder or aggregate, both of which can be added to future concrete production. However, contaminants can make their way into waste concrete, particularly from demolished buildings, such as steel, wood, and even plastics, which can make recycling challenging.

Hazardous Waste Disposal Failures

Proper disposal of all waste is important for health, human safety, environmental safety, and a host of other factors - but hazardous and toxic waste especially need to be treated with care. Throughout history, there are numerous examples of improper disposal of toxic wastes, many of which such examples were legal at the time and led to changing atmospheres - or governmental policies - on the disposal and treatment of similar wastes.

Two such examples of improper hazardous waste disposal include what happened in Love Canal, New York, in the United States, and in Minamata Bay in Kumamoto Prefecture, Japan.

In Love Canal, over decades, the chemical byproducts of industrial manufacturing were dumped by Hooker Chemical Company. In 1953, the dumping stopped and the land was sold for a single dollar. It wasn't until the late 1970s that residents concerns about health issues, odors, and chemicals oozing from the ground finally began to be addressed.

In Minamata Bay, the dumping was largely of one specific chemical: methylmercury. The dumping occurred into the bay during the 1950s and 1960s, with the company responsible, the Chisso Corporation, initially denying any dumping. Because of the high seafood diet of local residents, the resulting mercury poisoning was prevalent enough to get its own name, Minamata disease.

Hazardous Waste Storage Failures: Coal Slurry

Even more specific examples of improper storage of waste than what was discussed last week can be found in four examples from the coal industry specifically:

In October of 1966, a spoil tip (waste byproducts from coal mining) in Aberfan, Wales, in the United Kingdom, failed after heavy rain. The resulting slurry of waste and rain water ran down the mountainside into the town, engulfing buildings. Twenty-eight adults were killed - and 116 children at a local junior school.

In February of 1972, in Logan County, West Virginia, in the United States, a coal slurry dam burst in similar conditions (following heavy rain). The resulting spill killed 125 people and injured over a thousand more, destroying hundreds of homes in the process. It also ran into Buffalo Creek, damaging the local aquatic environment for the decades that followed.

In October of 2000, a coal slurry in Martin County, Kentucky, in the United States failed. In this instance, it was the bottom of the waste storage which broke, spilling the waste into the mine below it. The mine was abandoned, and no deaths were directly attributed to the initial spill, but the waste spilled out of the mine openings, killing everything in the nearby waterways and contaminating the water source of thousands of residents. The spill was an estimated 306 million US gallons.

Finally, in December of 2008, a coal ash pond at the Kingston Fossil Plant in Tennessee, in the United States, failed. Over a billion US gallons of slurry were released, the largest industrial spill in the country's history. Again, no deaths were associated with the initial spill beyond wildlife, but dozens of workers involved in the cleanup suffered negative health consequences as a result of poor management and safety regulations, including an estimated thirty deaths.

Polyethylene Recycling

Polyethylene - either in the form of high density polyethylene (HDPE), low density polyethylene (LDPE), or another - is considered to be the mostly widely used plastic in the world. It is used to make plastic bags, food containers, cutting boards, etc. However, rates of plastic recycling as a whole are considered relatively low compared to other materials like paper or some metals and polyethylene is no exception to this. This is partially because most plastics, polyethylene included, cannot be infinitely recycled in the way of most metals. Recycling of polyethylene typically results in a decrease in strength of the resulting product, especially after repeated recycling.

Polypropylene Recycling

Polypropylene (PP) is a widely used plastic with a steadily growing production - and growing recycling rates. It is considered to be one of three plastics, by US standards, that is 'widely recyclable' (the other two are polyethylene terephthalate and high density polyethylene). This, however, refers to the capability of recycling the plastic, not the actual recycling rates. In the US, the recycling rate of PP was estimated to be around 8% annually (for consumer household items, PP is known as plastic #5). PP is often mechanically recycled, with the recycled (or downcycled) product used for items such as carpets, fibers, car parts, etc. Chemical recycling of PP, while possible, is not often done on large scales, still in the early stages of development.

Glass Recycling

Much like most metals, glass is considered to be a fully recyclable material. For the production of new glass it has been estimated that up to 95% of the materials used can be substituted with old glass, or cullet, saving raw resources and lowering energy consumption and the carbon emissions involved in the process. Glass recycling is often present on both industrial and consumer scales, however, the rate at which glass materials are recycled varies widely by region/country. In the United States, for example, glass recycling has hovered at just over 30% (of glass packaging materials) for decades (within the country, however, glass recycling again varies widely by region depending on local glass recycling and collection capabilities; California, for example, has reached around an 80% recycling rate for glass bottles in more recent years). In the EU these rates tend to be much higher with increasing progress over time with many countries now recycling 70-90% of glass packaging (it should be noted that in 1994 the EU set a glass recycling target of 60%).

Not all glass can be easily recycled. Bottle glass and packaging glass is usually sorted into color for recycling (green, clear, brown, etc.), but other glasses are often not a part of the recycling stream. Ceramic glasses and borosilicate glasses, such as Pyrex and those used in cooking, should not be mixed with packaging glass. Mirrors, windows, and light bulbs should also, generally speaking, be kept to separate waste streams.

Fiberglass Recycling

Fiberglass is a type of composite that consists of a polymer material reinforced with glass fibers. Because of the nature of many composites, and the separation that recycling would entail, fiberglass is not often recycled and is considered to be difficult to recycle. This is particularly the case if thermoset polymers are used (as opposed to thermoplastic polymers), which cannot currently be recycled. Typically, when fiberglass is recycled, it is ground down before separation occurs between the plastic and glass components, and only the glass is often recycled. It should be noted that fiberglass is often made from recycled glass as a raw material to begin with. As the demand to recycle fiberglass increases, interest also grows in developing the infrastructure and policies needed to do so.