Solid Waste Management
Written by Steve Hudgik February 2013
Nearly everything we do leaves behind waste. That waste needs to be managed such that it is handled and disposed of safely and in an manner that does not cause health or environmental problems. Accomplishing this is known as solid waste management.
Solid waste management involves planning and managing the collection, transport, processing, recycling or disposal, and monitoring of waste materials.
The term "solid waste" most often is used to refer to municipal solid waste, a type of waste that predominantly includes household waste. More commonly called garbage or trash, municipal waste consists of everyday items such as product packaging, grass clippings, bottles, food scraps, newspapers, furniture, clothing, appliances, paint and batteries.
Solid Waste Management - What Is Municipal Solid Waste?
A municipal solid waste is any discarded material that has been determined to not be a hazardous waste, or which is excluded or exempted under various sections of the Resource Conservation and Recovery Act (RCRA). For example, household and agricultural wastes are excluded, even if they otherwise might be considered hazardous. Other solid wastes that are excluded from the definition of hazardous waste include:
- Mining overburden
- Fossil fuel combustion waste
- Oil, gas, and geothermal wastes
- Trivalent chromium wastes
- Mining and mineral processing wastes
- Landfill leachate or gas condensate derived from certain listed wastes
- Cement kiln dust
- Arsenically treated wood
- Petroleum contaminated media and debris from underground storage tanks
- Injected groundwater
- Spent chloroflurocarbon refrigerants
- Used oil filters
- Used oil distillation bottoms
In addition, the term "solid," when used in relationship to "waste" has a specific definition. A "solid" waste includes any waste material that is physically a solid, a liquid or a confined gas.
Solid Waste Management - What Is A Discarded Material?
When dealing with things that are regulated, such as the disposal of waste, everything has a specific legal definition. This is true for waste, and terms such as "discarded material" have a legal definition. A discarded material is defined as:
- A material that has been abandoned by, or is being stored or treated in preparation for, being disposed of, burned or incinerated.
- Any recycled material, or materials that are being accumulated, stored, or treated before recycling. A material is considered to be a recycled material if it is:
- applied to or placed on the land in a manner that constitutes disposal.
- used to produce products, or mixed into products, that are applied to or placed on the land.
- used to produce a fuel, or is contained in a fuel that is burned for energy recovery.
- a reclaimed material. Reclaimed materials may include spent materials, sludges, by-products and scrap metals.
- Considered inherently waste-like. These are materials such as:
- dioxin bearing wastes
- some secondary materials fed to a halogen acid furnace
- A military munition identified as a solid waste.
The Solid Waste Management Hierarchy
The EPA has ranked waste management strategies in order of preference based on their impact on the environment. This ranking encourages practices that reduce the amount of waste going into landfills. These strategies include waste prevention, recycling, and composting. The solid waste management hierarchy is:
- source reduction (including reuse)
- recycling and composting
- energy recovery
- treatment and disposal
Solid Waste Management - Source Reduction and Reuse
Source reduction is also known as waste prevention. The objective is to eliminate or reduce waste at the source. Source reduction can be done in many ways. Common methods include:
- reusing or donating items - this eliminates the need to manufacture new items
- buying in bulk - reduces the amount of packaging that needs to be used
- reducing packaging - packing items using fewer materials reduces costs and waste
- redesigning products - designing products to produce less waste
Source reduction is also an important consideration in manufacturing. Using light-weight packaging, applying lean manufacturing techniques to reduce waste, and the reuse of materials are becoming more frequently used practices.
Source reduction can:
- Save natural resources
- Conserve energy
- Reduce pollution
- Reduce the toxicity of waste
- Save money
However, not all commonly accepted source reduction methods actually reduce waste. A study done at MIT in 2011 determined that remanufacturing, a commonly recommended method of source reduction, has either no benefit, or a negative benefit. The study is reported on in an article in MIT news, titled "When Is It Worth Remanufacturing." It states that:
"Out of 25 case studies on products in eight categories done by a team led by Professor of Mechanical Engineering Timothy Gutowski, there were just as many cases where remanufacturing actually cost more energy as cases where it saved energy. And for the majority of the items, the savings were negligible or the energy balance was too close to call."
Solid Waste Management - Recycling/Composting
Recycling is a series of activities that includes the collection of used, reused, or unused items that would otherwise be considered waste; sorting and processing the recyclable products into raw materials; and using the recycled raw materials to make new products. Recycling also can include composting of food scraps, yard trimmings, and other organic materials.
By eliminating the need to obtain new raw materials, recycling:
- reduces the emissions of some hazardous gases and water pollutants
- it saves energy
- provides valuable raw materials to industry
- conserves resources for future use
- reduces the need for new landfills and waste combustors
Solid Waste Management - Energy Recovery
Energy recovery from waste involves the conversion of non-recyclable waste materials into useable heat, electricity, or fuel through a variety of processes, including combustion, gasification, pyrolization, anaerobic digestion, and landfill gas recovery.
Waste to energy projects, using combustion and conventional steam turbines, became very popular in the 1980's and early 1990's. However, furnace corrosion and other problems have limited the use of combustion heat recovery technology to locations where landfill space is very limited and no other options are available. No new waste to energy facilities, using combustion, have been built since the mid-1990's.
Solid Waste Management - Landfills
Landfills are the most common form of waste disposal. They are an important component of an integrated solid waste management system. Even when waste is incinerated, although the volume of waste is reduced by about 90%, there is still waste that must go to a landfill.
Landfills that accept municipal solid waste are primarily regulated by state, tribal, and local governments. In addition, the EPA has established national standards that landfills must meet. As a result, today's landfills are designed to comply with stringent design, operation, and closure requirements.
Energy can be produced from a landfill. Methane gas, a by-product of decomposing waste, can be collected and used as fuel to generate electricity or heat. Landfill sites may also have other uses. For example, after a landfill is capped, the land may be used for recreation sites such as parks, golf courses, and ski slopes.
In some cases transfer stations are needed to efficiently transport waste to a landfill. Transfer stations are facilities where municipal solid waste is unloaded from local collection vehicles, briefly held and accumulated, and then loaded onto larger, long-distance transport vehicles for shipment to a landfills or other treatment or disposal facilities.