Waste Types
The initial step in studying waste management and its impacts in urban settings should be to develop an understanding of the various sources and types. Overall, municipal solid waste is made up of a combination of potential materials and products. Many of these decompose at different rates based on makeup and content. Communities of all sizes can learn much about their waste disposal habits and trends simply by analyzing their waste stream. This section aims to detail the various types of sources of municipal solid waste as well as the most common methods of disposal for such materials.
First off, organic waste includes yard waste and food waste sources. These products have a high carbon content and as a result emit gases such as carbon dioxide and methane as they break down. Paper products include cardboard, newspapers, magazines, computer or notebook paper, and many more. Plastics commonly found are plastic bottles, cups, and plates; plastic bags usually found in grocery stores, and other types of containers. Although these are all part of the same overall category, they differ in their chemical makeup which determines how quickly they break down or persist in the environment. Some common chemicals in varying types of plastics include polypropylene, polyethylene, polyvinyl chloride, and polystyrene (also known as Styrofoam) (1). Glass products may include glass jars and bottles, or any other similar type product. Metal waste materials usually contain copper, aluminum, lead, steel, or zinc. Similarly, a major waste category that has accumulated tremendously within the last 15 to 20 years is known as “E-waste”. These sources are older electronics products which may be no longer useful or are simply discarded for newer models, such as televisions, computers, and cell phones to name a few. Finally, the last waste category generally includes rubber, leather, and textiles.
Municipal Solid Waste Stream Trends in the United States
In observing 2013 data on total municipal solid waste generation in the United States, the largest waste type came from paper products at approximately 27%. The next three highest types were food waste (14.6%), yard waste (13.5%), and plastic products (27%). Before accounting for recycling, total generation of municipal solid waste in 2013 equated to 254 million tons (2).
Waste Management Techniques
Landfills: By far the most common method of waste disposal, landfills typically offer communities and municipalities an affordable and feasible option for waste management. Although relatively simple in its concept of using land and soil as a cover for disposed waste, specific strategies are put in place to provide for more accountability. Typical security and safety measures include the use of synthetic and compacted clay liners to prevent the leaking of leachate (the liquid residue remaining from waste product), gas monitoring and collection techniques, and regular soil cover to deter the spread of waste product and bacteria.
Incineration: This management strategy involves the direct combustion or burning of garbage or waste material at approximately 1000°C to produce either heat, electricity, or fuel (2). Any remaining ash (usually around 10% of the original volume) is then sent to a landfill for disposal. While certain obstacles and health concerns (which will be discussed in the next section) are associated with the process, it does offer cities a space-friendly option to deal with trash. The energy recovery works as facilities burn some form of biomass to produce steam which eventually turns a turbine to create electricity (3).
Composting: Similar to landfill disposal, this technique requires direct collection of waste product, specifically organic materials such as yard and food waste. With the proper storage and handling, the composting procedure encourages the breakdown of the food or yard waste material by small microorganisms. The final output can then be used as fertilizer for local gardens or agriculture (2).
Recycling: One of the more well-known alternative disposal methods, this approach involves the collection of recyclable materials (mainly plastics, paper, glass, and metals) to reprocess them for future use. While certain capital and processing time is required, this technique is beneficial as it diverts material from landfill disposal and saves on natural resources (4).
Sources:
1) Liboiron, M. 2016. Redefining pollution and action: The matter of plastics. Journal of Material Culture. 2(1): 87-110
2) United States Environmental Protection Agency. (2016) “Municipal Solid Waste” Retrieved from https://archive.epa.gov/epawaste/nonhaz/municipal/web/html/
3) United States Environmental Protection Agency. (2016) “Energy Recovery from Waste” Retrieved from https://archive.epa.gov/epawaste/nonhaz/municipal/web/html/index-11.html
4) United States Environmental Protection Agency. (2016) “Recycling Basics” Retrieved from https://www.epa.gov/recycle/recycling-basics