Solid Waste & Recycling


Energy to Waste?

Over the past eighteen months readers of this magazine have been presented with a province by province review of Canadian beverage-container recovery programs. The recent understanding of provincial d...

Over the past eighteen months readers of this magazine have been presented with a province by province review of Canadian beverage-container recovery programs. The recent understanding of provincial deposit-return system characteristics and their financial costs support the often-asserted belief that such systems are the most cost effective approach to recover high percentages of beverage containers for reuse and recycling.

But certain industry stakeholders point out that these materials represent a small portion of the waste stream by weight. They dismiss the high rates of beverage-container recovery through these programs as unimportant (in terms of the total tonnage of waste in the waste stream). Accordingly, they characterize deposit-refund system costs as unnecessary.

From coast to coast, weight based measures are the metric of choice for assessing waste management environmental performance — “tonnes diverted equals environment protected,” so the inference goes. Simple and easy to understand, weight-based measures suit both public policy makers and the agenda of commercial interests. For example, in many jurisdictions (most notably Ontario) weight-based diversion has effectively deflected policy-makers’ attention away from lightweight, voluminous packaging materials (e.g., beverage containers) to weighty materials such as paper and organic wastes. Hence the often heard question, “Why all the talk about soft drink containers when they are only two per cent of the waste stream?”

Well, what of that two per cent?

The environmental merit of efforts to manage that two per cent of the waste stream can be measured (along with all other fractions of waste) in a different way. In our new approach we no longer look at weight diverted from landfill as a measure of system performance but rather place recovery priority on the most energy and emissions intensive materials in the waste stream. In other words, a tonne of waste is no longer simply a tonne of waste but also a function of the energy and emissions profile of the materials that make up its weight.

The data in the table on page 9 allows us to explore more fully the intensity of various materials relative to their composition of the waste stream by weight. The table identifies each component of the waste stream:

Column A: The number of U.S. short tons generated in the U.S. in 1997.

Column B: The percentage of the total waste stream for each material by weight.

Column C: “Divertibility” (i.e., material that is commercially recyclable and currently collected via recovery programs) as indicated by its percentage of the total amount of “divertible” waste.

Column D: The GHG emissions (in metric tonnes of carbon equivalent or MTCE) associated with replacing each ton of material if landfilled.

Column E: Each material’s percentage GHG contribution to replace a ton of landfilled waste.

Column F: Leading indicators (i.e., where we should direct our efforts).

While the data in the table are from the U.S., the percentage waste composition for each material and the per ton GHG emissions are wholly adequate for the purposes of understanding where Canadians should focus their waste diversion efforts.

So what does the table tell us?

From it we see that, given current diversion practices and waste stream composition, about 75 per cent of the waste stream is “divertible.” (Note that wood waste is largely banned from landfill and the other miscellaneous materials are not subject to diversion through municipal waste management programs.) If we only consider “divertible” materials and take the ratio of each material’s percentage GHG contribution (Column E) to its percentage of the “divertible” waste stream by weight (Column C), we create an indicator that tells us where to direct our efforts (Column F). The higher the ratio, the more avoided emissions associated with recovery of a given material from the waste stream.

Interestingly, the greatest ratio (2.4) is associated with the beverage container category. All containers (including both beverage and non-beverage containers) and paper follow with ratios of 1.7 and 1.2 respectively. Organic wastes come in a very distant fourth (ratio of 0.01).

Key indictors: aluminum and PET

These findings warrant some further discussion. As a category, beverage containers lead in “embodied emissions” primarily because of that stream’s aluminum content and to a lesser extent the presence of PET plastic. While aluminum cans (ratio 7.6) only comprise 1.4 per cent of the entire waste stream by weight (and 1.9 per cent of the divertible waste stream by weight) they contributes a whopping 14 per cent of the emissions embodied in a ton of divertible waste sent to landfill.

This means that those 2.13 billion cans embody the equilavent of 14.8 per cent of the Pickering plant’s total electricity output last year – a demand that would take the station 54 days of operation to fulfill.

Now let us consider energy — a widely accepted “indicator” of environmental intensity (e.g., GHG emissions used to produce and transport a product are largely a function of energy consumption in the form of fossil fuels). Specifically, let us consider the energy embodied in the aluminum can, of which 2.13 billion (or 36,156 tons) were used by the soft drink industry in Ontario in 1998.

The manufacture of the rolled-aluminum sheet (from virgin materials) that’s used to make these cans consumes the equivalent of about 1.94 TWh of energy (1.94 teraWatt-hours or 1.94 thousand billion Watt-hours) from the time raw materials are extracted through to final production. To put the energy embodied in these cans into perspective, consider that Ontario’s Pickering nuclear station generated about 13.1 TWh in 1999. This means that those 2.13 billion cans embody the equivalent of 14.8 per cent of the Pickering plant’s total electricity output last year — a demand that would take the station 54 days of operation to fulfill.

But not all of a typical can is made from virgin materials. Producing aluminum cans from recycled aluminum requires considerably less “embodied energy” (and generates fewer emissions) than using virgin materials. However, less than 50 per cent of the cans sold in Ontario are recovered and sent for recycling in the U.S. As a result, the scrap aluminum sent to places such as Oswego, N.Y., Greensboro, Ga., and Berea, Kt. makes less than two trips before being landfilled.

Whatever the flow of recycled and virgin aluminum in metals markets, the 20,000 to 25,000 tonnes of aluminum cans landfilled in Ontario each year represent an additional 20,000 to 25,000 tonnes of aluminum that has left the market which will eventually have to be produced from virgin materials. As such, this lost mass of aluminum represents an enormous amount of embodied energy and emissions (not to mention significant lost scrap revenues at $1,250 a tonne). That Ontario uses less than half of the aluminum in the waste stream to financially subsidize the collection of less energy and emissions intensive materials while the majority portion of the aluminum in the waste stream is landfilled is quite ironic.

PET plastic containers are also relatively emissions intensive (ratio 2.5 per cent emissions to per cent weight) largely as a result of the materials and process energy required to produce PET from crude oil. Like cans, these containers also have a recovery rate below 50 per cent.

Glass, paper and organics

Glass containers have an altogether different emissions profile in that their percentage weight in the waste stream exceeds their emissions contribution to a ton of waste. (See table.) In 1994, the study Energy Implications of Glass-Container Recycling was prepared by the Energy Systems Division of Argonne National Laboratories and the National Renewable Energy Laboratory (both of which are part of the U.S. Department of Energy laboratory system). The authors summarize their finding regarding glass recycling by stating that, “Recycling of glass containers sa

ves some energy but not a significant quantity compared to reuse.” They further qualify their observations by stating that, “Recycling saves the energy required for raw-material production and transportation, but it uses additional energy to process and transport the recovered materials. These two quantities of energy are approximately equal.” The authors conclude by saying that, “in order of greatest energy saved, the options for disposition of glass containers are reuse, recycling to the same product, recycling to a lower-value product, and landfill.”

Paper embodies a significant amount of emissions although these “emissions” are not really emissions at all — they represent the carbon that would have been sequestered in tree fibre had the trees not been cut down and pulped to produce paper. Thus for every ton of paper landfilled one can estimate the carbon equivalents generated by the extraction of wood required to replace it. Clearly, given that paper comprises almost 40 per cent of the waste stream by weight and 64 per cent of the “embodied emissions” in a ton of divertible waste, its recovery and recycling offers a significant opportunity to avoid GHG emissions (as well as conserve landfill space). Of note, office paper is the most emissions intensive (ratio 2.7), largely as a result of the additional chemical and mechanical processes required for its manufacture.

Because of their significant mass, much attention has been given to the diversion of yard trimmings and food wastes from the waste stream. However, from an avoided GHG perspective (and an embodied energy perspective) both waste materials are relatively benign (ratio .01). The primary expenditure of energy associated with these wastes is that required to haul them to compost sites. Of note, the negative GHG emissions associated with landfill of yard trimmings are the result of carbon storage that results from their failure to degrade fully in landfill.

From our findings it’s clear that provinces that have focused on deposit-return systems as a first step in broader provincial stewardship programs have received the greatest energy and emissions “bang for their buck.” In addition, while providing us with new insights into the merits of various waste management strategies, this energy and emissions approach also vindicates those people who have complained loud and long about that seemingly innocuous “two per cent” of the waste stream.

Usman Valiante is principal of General Science Works Inc., a corporate and public policy research consulting firm in Toronto, Canada.

Energy & Emissions Profiles of Municipal Solid Waste

U.S. short tons2 % of waste % of GHG MTCE/ % GHG Ratio
stream by “divertible” ton to replace contribution/ Column E
weight waste material ton to replace to
stream by landfilled1,3 material Column C
weight landfilled
Newspaper 13,490,000 6.22% 8.30% 0.25 5.27% 0.6
Office paper 7,040,000 3.24% 4.33% 1.06 11.67% 2.7
Corrugated cardboard 30,160,000 13.90% 18.55% 0.44 20.74% 1.1
Mixed paper 33,150,000 15.28% 20.39% 0.51 26.43% 1.3
Paper and paperboard 83,840,000 38.64% 51.56% 64.11% 1.2
Glass beverage bottles 6,788,000 3.13% 4.17% 0.15 1.59% 0.4
Other glass containers 5,222,000 2.41% 3.21% 0.15 1.22% 0.4
Steel beverage cans 3,100,000 1.43% 1.91% 0.85 4.12% 2.2
Other steel 9,230,000 4.25% 5.68% 0.85 12.26% 2.2
Aluminum cans 3,010,000 1.39% 1.85% 3.00 14.12% 7.6
Other non-ferrous 1,270,000 0.59%
Plastics 21,460,000 9.89%
Blow molded HDPE 966,409 0.60% 0.59% 0.62 0.94% 1.6
Blow molded LDPE 16,107 0.01% 0.01% 0.90 0.02% 2.3
Blow molded PET 805,341 0.50% 0.50% 0.99 1.25% 2.5
Other plastic 19,672,143 9.07%
All containers 29,137,857 13.43% 17.92% 30.18% 1.7
Beverage containers 14,685,857 6.77% 9.03% 22.03% 2.4
Rubber and Leather 6,590,000 3.04%
Textiles 8,240,000 3.80%
Wood 11,570,000 5.33% Banned from landfill
Other 3,760,000 1.73%
Food Wastes 21,910,000 10.10% 13.47% 0.15 5.14% 0.4
Yard trimmings 27,730,000 12.78% 17.05% -0.11 -4.77% -0.3
Miscellaneous organics 3,250,000 1.50%
Total “divertible” organic waste 49,640,000 22.88% 30.53% 0.37% 0.01
Other wastes 54,352,143 25.05%
Total waste 216,970,000 100.00%
Total “divertible” waste 162,617,857 74.95%
1) Greenhouse Gas Emissions From management of Selected Materials in Municipal Solid Waste US EPA 530-R-98-013 September 1998
2) Characterization Of Municipal Solid Waste In The United States: 1998 Update US EPA A530-; 3) MTCE – metric tonnes carbon equivalent

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