As human populations continue to grow and consume it is critical that waste management systems take into consideration the sustainably issues related to product design, manufacturing, and disposal.
Waste management systems should aim to achieve maximum practical benefits from products while generating the minimum amount of end waste. With this goal in mind, some waste reduction and management actions are considered more impactful than others.
One such example is illustrated by the figure below;
Another well known, albeit simpler, waste hierarchy, is the Three R’s:
- Reduce: prevent the generation of waste
- Reuse: seek alternative uses of waste
- Recycle: convert waste materials into new products
Popularized in the 1970’s, the Three R’s have been integral in communicating municipal recycling programs and reduction goals to the general public.
The Three R’s model has since been expanded to include additional actions with a focus on reducing the consumption of goods (and associated waste creation) at the consumer level.
Modern or sanitary landfills are areas used to dispose of waste which are isolated from the external environment both underground (with a liner) and above (with soil or another cover).
Landfill sites are separated from the environment to both minimize ground and surface water contamination as well as prevent mosquitoes and other disease carrying pests from breeding on site.
Canada is home to approximately 2400 active landfills, both public and private (Wilkins, 2017). When designing a new landfill, efforts are made to minimize negative effects on the environment with strict guidelines that must be followed in order comply with the Environmental Protection Act (Government of Ontario, 2012). These guidelines include:
- Site design report including a site-specific design and two generic design options.
- Implementation of a bufferarea, surface water and gas control, on site roads and structures and a final cover design.
- Site must include a liner and leachate collection system and a contingency plan for leachate control.
- Operation and monitoring facilities for groundwater and surface water.
- Site closure and post-closure care requirements; and final assurance requirements for private sector landfills.
Incineration is a method of waste management where organic materials in waste are combusted in a controlled environment. The products of this process are ash, fluegas, and heat.
The ash produced primarily consists of inorganic components found in the original material which are turned into particulatessuspended in flue gas.
The flue gas is usually cleaned of any gaseous contaminants, treated, and sent through emission tests before being released into the atmosphere (Tammemagi, 1999).
During incineration, minimum burning temperatures must be maintained to ensure that complete combustion occurs.
If these temperatures are not maintained, or if a limited amount of oxygen is available, incomplete combustion will occur instead (Waste Incineration and Public Health, 2000). Incinerators would then produce carbon monoxide in addition to the other undesirable by-products.
Incineration is a divisive topic in waste management. Under optimal conditions, there are several potential benefits to incineration. The key points are:
- It can reduce the volume of waste sent to landfills by an average of 90% (Tammemagi, 1999). This can extend the lifetime of existing landfills and remove the necessity to create new landfills, especially in densely populated areas.
- The hazardous wastes found in organics and pharmaceuticals are destroyed in the incinerator, reducing the number of contaminants that could otherwise leach into the ground if the waste was left in landfill.
- The heat generated by this process can be used as energy with less environmental impact than non-renewable energy sources such as oil and coal (see Section 3.5 for more information).
Despite these benefits, there are almost as many arguments against incineration including;
- The waste that goes into incinerators may include improperly sorted materials such as plastics and compostable organics that could have been recycled or composted (Conserve Energy Future, 2019).
- Incineration facilities are often expensive, which could divert funds away from recyclingprograms.
- This process requires a constant flow of combustible materials into the incinerator to maintain operational temperatures. While not immediately problematic, it does mean this system of waste disposal encourages a static rate of consumption.
- The airborne by-products of the combustion process can include particulate matter and toxic gases that contribute to acid rain and respiratory health issues. The residual solid waste requires special handling and must be disposed of in a landfill.
3. Selling Waste
Processing or storing waste locally can be a burden on the community and may be undesirable for social or economic purposes. Governments may choose to transport their waste to other cities, provinces, or countries for disposal or further processing.
This relieves the affect population of the responsibility of managing their own waste. While not uncommon, this practice can prove to be problematic, as waste is frequently transported to countries with lower environmental regulations to reduce costs. This can result in significant environmental contamination and negative impacts on local populations.
Waste diversion encompasses a range of strategies focused on reducing the amount of waste requiring disposal. Waste diversion has the obvious benefits of preserving landfill capacity and reducing the environmental footprint of creating, disposing and storing waste.
Diversion also helps avoid the costs and environmental degradation associated with the extraction and processing of virgin materials. To ensure the success of the various diversion strategies, it is imperative that both residential and commercial sectors participate in these programs.
Waste diversion is an increasingly important aspect of solid waste management, as the capacity of existing landfills is finite. A recent study conducted by the Ontario Waste Management Association found that landfill capacity in Ontario will be reached by 2032 if waste production rates remain the same (Jones, 2019).
Within Ontario there are both government and industry-based diversion programs.
Composting is a natural biological process that converts organic material into a stable humus-like product (Compost Council of Canada, 2010). During the composting process, microorganisms break down organic material into simpler, smaller units.
In addition to improving diversion rates, composting produces is a high-quality fertilizer which can be used locally in parks and green spaces or by residents.
As of 2007, there were an estimated 350 centralized composting facilities operating in Canada. These facilities processed the household organic and yard wastes generated by approximately 17 million Canadians (Van der Werf & Cant, 2007).
Composting facilities may employ one of many methods, but the three most common are the in-vessel method, the aerated static pile method, and the windrow method (Compost Council of Canada, 2010).
A variety of compost methods used in Canada are described below;
In-vessel Method: organic material breaks down inside of structures such as drums, silos, or batch containers. Covered or open channels may also be used. Material is aerated and mechanically turned and controlled. Compost must be cured after it is processed. This method can process large volumes of virtually any organic waste.
The capacity and space required is determined by the size of the vessel (EPA, 2016).
Aerated Static Pile Method:organic materials are formed into large piles which are aerated by drawing air into the pile or forcing air out. Organic material is not turned in this process. This method is appropriate for relatively homogenous organic waste including yard waste and household organics. It is not well suited to process animal by-products or grease (EPA, 2016).
Windrow Method:organic material is placed in elongated piles, called windrows, which are mechanically turned. This method is suitable for large volumes of organic waste but requires significant land. A diverse variety of organic wastes including yard wastes, grease, liquids, and animal by-products (i.e. fish or poultry wastes) can be composted using this method (EPA, 2016).
Composting is also a useful technique for managing agricultural waste like manure. When added to soil, composted animal waste can improve soil structure and increase the availability of macronutrient and micronutrients (Statistics Canada, 2004).
Solid manure should be composted in an aerobic treatment to kill pathogens and reduce volume and odours. Should this material be processed in an anaerobic environment, or an environment without oxygen, the manure will not decompose completely and will form compounds toxic to plants and low in available nutrients in addition to methane (Newport, 2006).
The final product of aerobic treatment of manure is a stable humus that is easy to handle and can be used as a fertilizer. Liquid or semi-solid manure can be treated either by separating water from manure solids through drying, or by storing manure in anaerobic digesters, converting organic matter into methane and carbon dioxide.
Other treatment methods include basic sewage procedures such as filtering liquid manure through constructed wetlands or artificial marshes where nutrients are naturally removed or captured by vegetation (Statistics Canada, 2004).
Recycling is the process by which previously used materials are converted from one form to another. How a material is recycled is greatly dependant on what that material is – paper, aluminum, and plastic are all treated differently.
Recycling reduces the demand for virgin materials, redirects from landfill or incineration, saves energy, and supports the green economy. Recycling is most prevalent in homes and schools. Within Canada, the recycling process can be broken down into seven major steps (RecycleBC, 2019):
- Recycling begins at the source; materials are collected on a set schedule or taken to local collection facilities.
- Materials are transported to a Material Recovery Facility (MRF pronounced “merf”).
- Once at the MRF materials are loaded onto a conveyor belt to begin the sorting process.
- Large non-recyclable items are removed manually. Other materials continue down the conveyer belt and are separated into specific categories using equipment such as rotating drum screens, magnetic separators, optical sorters, and air classifiers.
- Sorted materials are baled, loaded into trucks, and prepared for shipping or storage.
- Bales are shipped to material manufacturers to make new raw materials. Plastics are shredded and washed, paper is pulped and pressed, and metals are shredded, smelted, and rolled.
- Some materials are recycled back into their original products; others are made into new products and sold back to consumers.
There are two broad methods of recycling that an item can undergo – upcycling and downcycling.
Upcycling is used to describe when materials are reused without degrading their quality. Items produced from upcycling are of equal or greater value than the original material(s) used in the process. This conserves resources, prolongs the life of materials, and can make a product more attractive to consumers who have sustainability on their mind (Gumtree, n.d).
Conversely, downcycling is when materials are converted into something of lesser value. While some products can be repeatedly reproduced, some materials slowly break down with time as they go through the recycling process. Despite this, downcycling reduces the need to use raw materials for these lesser yet still valuable products. (Resource Center, n.d).
While there are many advantages to recycling, there are also barriers to implementation. Approximately 11% of plastic waste is recycled in Canada, which means that a large percentage of plastic waste ends up in landfills, incinerators, lakes, oceans, parks, and other natural ecosystems.
There is also a wide variety of plastics and only certain types may be recycled depending on the community. While recycling can play a bigger role in reducing the rate of pollution, the process has not been widely embraced in many communities and is still a small part of a long-term success plan (Conserve Energy Future, n.d).
The costs of collecting waste, transporting it to a handling facility, sorting it, cleaning it, repackaging it, and transporting it again is almost always more expensive then landfilling that same waste in a local facility.
6a) Recycling Paper
Paper comes in many forms, from printer paper to corrugated cardboard. A 2014 study shows that paper products make up approximately 26% of municipal solid waste (Giroux, 2014).
Paper recycling programs are widely established in urban areas and are usually operated and funded by some level of government.
As paper products are easily recyclable or compostable, some provinces such as Nova Scotia, PEI, and Quebec have banned their disposal into landfills (Langlois-Blouin, 2017).
The most important factor in paper recycling is the length and strength of the fibres in the paper materials that are to be recycled. The recycling process shortens the fibers, making the resulting paper weaker and less durable.
After being recycled 5-7 times, the fibres are typically too short to be recycled again. Instead, the material is turned into paper paste and used to create items such as newspapers or egg cartons (PPEC, n.d.). For more on how paper is recycled, see the Student Activity at the end of the section.
Most paper products are recyclable, but some communities are too far away from a recycling mill for recycling to be an economically viable solution.
In these communities (and in others, especially when the paper materials are soiled in some way), paper can be composted with other household organic waste as an alternative diversion method (Giroux, 2014). Paper can add a decent amount of carbon to composted materials, which can make for a more nutrient-rich compost (PPEC, n.d.).
6b) Recycling Plastics
Plastic is a malleable material that can consist of a wide range of synthetic or organic polymers. It makes up a highly visible portion of the waste stream mostly due to its versatility.
From lightweight bottles made from PET to flexible hoses made from PVC to food containers made of polystyrene, plastics can be used for just about anything.
As plastic is a very broad category of materials, recycling them is a complex issue with no single solution. For one, recyclable plastics may be contaminated with non-plastic materials or different types of plastic, which could compromise any new products made from those materials.
As such, recycled plastics tend to be used for less structurally demanding items than the original products (Rodriguez, 2019).
Every recycling program has specific rules about what plastics can and cannot be recycled (Rodriguez, 2019). Certain plastic materials are known to cause problems for Blue Box systems in Ontario.
Black plastic, plastic films, laminates, and polystyrene are all difficult or costly to recycle, and as such are not often acceptable items in blue boxes (Lindsay, 2019).
Plastic as a material is not biodegradable like paper, or inert like glass. It does break down, but only into smaller plastics.
There has been some research on bioplastics, or plastics made from more organic components, but they haven’t been successful on a large scale due to the production costs and problems with stability (Rodriguez, 2019).
6c) Recycling Aluminum
While a variety of metals are recyclable, the most commonly recycled metal in municipal Blue Box collections is aluminum.
Aluminum is used in a wide variety of products and is an endlessly recyclable material. Its basic properties are not altered with physical or mechanical processing, allowing it to be recycled repeatedly without any loss of quality.
Nearly 75% of all aluminum ever produced is still in circulation today (The Aluminum Association, 2011).
Recycled aluminum requires less energy than using new materials. To process, aluminum goods (cans, aluminum foil, baking trays, and so on) are cleaned, sorted, and pressed into bales of metal. These bales are shredded, allowing for the metal to be melted more evenly when it is fed into the furnace.
The resulting ingotsof aluminum are rolled into thin sheets that can then be used to make drink cans, foil, and other products that are near identical to the products that initially went in. This entire cycle can take place over the space of as little as six weeks (The Aluminum Association, 2011).
As there is no limit to how many times aluminum can be recycled, it is by far the most economically sustainable material to recycle (Jarvis and Robinson, 2019). Its high value can generate a considerable portion of the revenue to be found in recycling and subsidizes the recycling of lower-value materials, making municipal recycling programs possible (The Aluminum Association, 2011).
Not All Plastics Are Made Equal!
Plastics may be some of the most common materials we encounter in our day to day lives, but not all plastics are made equal. Different plastics are used in different ways depending on the properties of the materials.
To differentiate between types of plastic, check the bottom of the product! Plastic products are all stamped with a symbol that indicates what exactly hey are made of (American Chemistry Council, n.d.).
|PolyethyleneTerephthalate (PET,PETE,polyester)||An excellent barrier to oxygen, water, and carbon dioxide, this plastic is clear and tough. It is commonly used in water bottles and textiles. This is the most commonly used and recycled plastic.|
|High DensityPolyethylene(HDPE)||A relatively stiff material with resistance to most solvents. Milk jugs, laundry detergent containers, and shopping bags can all be made from HDPE. It is tougher than PET, and almost as common.|
|PolyvinylChlorate(PVC)||This plastic has high impact strength and is resistant to grease, oils, and chemicals. It is best known for its use in pipes, but it can also be used for medical tubing, wire jacketing, and window cleaner spray bottles.|
|Low DensityPolyethylene(LDPE)||This flexible and relatively transparent plastic can be used to make condiment bottles and toys, but is mostly used in plastic films. Shrink wrap, grocery bags, and the coating for paper coffee cups are made from LDPE.|
|Polypropylene(PP)||With a high melting point, this plastic can withstand high temperatures. It is great for holding hot liquids. Medicine bottles, takeout containers, and straws can all be made from LDPE.|
|Polystyrene (PS)||This plastic is incredibly versatile. In a rigid form, it can be used to make products like CD cases. Foamed, it is an excellent insulator with low thermal conductivity, lending itself to use as packaging for hot items with a short shelf life or as protective packaging (ie. packing peanuts).|
|Other||Use of this code means that some miscellaneous plastic has been used in the product. It can be a single uncommon plastic, or a mixture of different materials. These types of plastics are often not recyclable, as their contents are unknown.|
7. Recycling Glass
As one of the oldest synthetic materials, glass has played a role in human societies for thousands of years. Glass does not decompose, release GHGs on its own, nor does it leech harmful substances into its surrounding environment. It is a readily recyclable material that can be melted and reformed repeatedly with no loss to performance in a process that is less energetically demanding than outright creating new glass (Dyer, 2014).
While recycling glass is an efficient process, simply reusing glass bottles saves time and energy. Glass bottles can be used an average of fifteen times before being recycled into new glass bottles (Brewers Retail Inc, 2019).
Many recycling systems include container deposit schemes wherein a consumer pays a small deposit that is tied into the price of the item and is refunded that amount upon the return of the glass product (Dyer, 2014).
In Ontario, there is the Ontario Deposit Return Program (ODRP) run by the Beer Store. In 2018, 94% of all glass bottles sold by The Beer Store and LCBO (both reusable and not) were returned through this program, keeping glass out of landfills, and allowing municipal Blue Box programs to focus their efforts on other recyclable materials (Brewers Retail Inc, 2019).
Like paper, glass has been banned from certain landfills in places such as Vancouver and Nova Scotia (Giroux, 2014), and for good reason. Not only can glass be bulky and remain intact for an exceedingly long time in landfills, it is also not combustible and could detract from incineration processes by acting as a heat sink (Dyer, 2014).
8. Renewable Energy
Renewable energy is energy derived from natural processes that are replenished at a rate that is equal to or faster than the rate of which they are consumed (Natural Resources Canada , 2017). By this definition, utilizing the near constant stream of waste going into landfills, wastewater treatment plants, and elsewhere to generate energy is renewable.
There are many ways to process waste and transform it into energy, either directly or through a fuel of some kind. Municipal wastes are heterogeneous, containing materials that vary in size, shape, and composition.
Read Also : Characteristics of Hazardous Wastes
Direct combustion of these materials (otherwise known as incineration) is the simplest way to convert them to energy. It is the most accessible conversion method, as it can handle a wide variety of materials and is less sensitive to fluctuations in size, shape, and composition. (Helsen, 2010).
Incineration can utilize plastic waste, which cannot undergo many other transformations to energy (Lee et al, 2019).
Other conversion methods have more specific requirements for what types of materials they can process. To make these systems more efficient, waste needs to undergo pre- treatment that includes but is not limited to size reduction, sorting, drying, or even pelletizing materials.
This pre-treatment generally means that these methods to convert waste to fuel are done on a smaller scale than incineration, which in turn allows for more control over the temperature and pressure within the various reactors that may be used from that point onwards (Helsen, 2010).
Once materials have been suitably processed and sorted, they are converted into a fuel of some description. These fuels can be solid, liquid, or gaseous depending on the process used to create them (Helsen, 2010). Converting energy to fuel allows for the transportation and storage of energy in a manageable form that can be used by a broader audience.
One such example is biogas (methane), a product of anaerobic digestion. As mentioned in Section 2, the anaerobic digestion of organic material leads to the production of methane. However, methane produced in a controlled environment can be contained and used as a replacement for natural gas in providing heat and energy wherever it is required.
The by- products of combusting methane are carbon dioxide and water vapour, which is not only less harmful to the atmosphere than methane, but also generally less harmful than the by-products of combusting fossil fuels. (Lee et al, 2019).