HPRC undertook this life cycle assessment (LCA) literature survey to provide the industry additional background on the environmental impacts of the various plastics disposal methods so they can make a more informed choice.
The familiar “3Rs” encourage us to reduce, reuse, and recycle, in that order of preference. An extension of this waste hierarchy concept, which is used in different versions to inform waste management policy worldwide, ranks recycling above energy recovery (waste-to-energy) or recovery of materials or fuels from waste and disposal to landfill as the least preferred option.
An LCA quantifies the environmental impacts of a product or service throughout its life cycle, from raw material extraction to end-of-life disposal. The life cycle inventory (LCI) phase of an LCA captures the resource inputs and the product, waste, or emission outputs for each process step in the life cycle. The Life Cycle Impact Assessment (LCIA) phase quantifies potential environmental impacts based on the LCI such as global warming potential.
HPRC conducted a literature search for waste management LCA studies and reviewed 17 out of about 50 studies identified.
Waste Disposal Methods
The EPA’s waste hierarchy defines the following waste management options, in order of preference:
Source Reduction & Reuse – for example reusing or donating, product re-design, or reducing packaging
Recycling/Composting – recycling of materials otherwise considered waste through collection, sorting, processing into new raw materials, and re-manufacturing into new products; or composting of organic waste e.g., food waste or yard trimmings
Energy Recovery – conversion of waste into heat, electricity or fuel (waste-to-energy) including combustion, gasification, pyrolization, anaerobic digestion, and landfill gas recovery 4. Treatment & Disposal – disposal landfills meeting stringent design, operation, and closure requirements; methane gas may be collected and used as fuel.
Given this complex landscape of waste management options, HPRC sought to understand how recycling fits into the larger context of waste management options and whether advancing recycling makes sense from an environmental perspective.
Mechanical Recycling Back to Polymer
Plastic waste may be recovered and mechanically processed for use in the manufacturing of plastic products. Single-polymer plastic streams are the most straightforward to recycle because recycling processes can be conducted without concern for immiscibility issues (where the polymers separate, similar to separation that occurs with mixtures of oil and water). The main challenges for mechanical recycling are heterogeneity and contamination. Separation, washing and preparation of [plastic solid waste] are all essential to produce high quality, clear, clean and homogenous end-products.
Feed Stock Recycling
Feedstock recycling is one of the newer methods to recycle plastics. Sometimes also referred to as chemical recycling, feedstock recycling can be defined as attempting to recover the basic raw materials (monomers) from the plastic. These raw materials can then be reused in various chemical and industrial processes.
Incineration with Energy Recovery
Waste incinerators are furnaces for burning waste and there are a number of types that are in current use around the world, ranging from primitive burn piles and barrels to highly sophisticated facilities that may involve fluidized beds and produce electricity. Incinerators with energy recovery systems generate steam that can be used either directly in municipal heating systems or to rotate turbines to generate electricity.
Landfills include any site where waste is dumped and confined over a relatively small area and compacted to reduce volume as much as possible. The wastes are then covered by soil in order to bury them.
Results and Conclusions for Healthcare
Overall, the Life Cycle Assessment studies reviewed concluded that mechanical recycling of waste plastics has a lower environmental impact than other disposal options, particularly due to the benefits of avoiding virgin plastic production.
The findings confirm the waste hierarchy guidance to pursue mechanical recycling as the most preferred waste management option after source reduction and reuse as a strategy for environmental protection and natural resource conservation. The demand for recycled resins, low plastic waste recycling rates, and ongoing technological advances suggest that there is potential for mechanical recycling to grow.