Solid Waste & Recycling


Life-Cycle Analysis Scenarios

Environment and Plastics Industry Council (EPIC), in collaboration with Corporations Supporting Recycling (CSR), has developed a model to help assess the environmental performance of various waste man...

Environment and Plastics Industry Council (EPIC), in collaboration with Corporations Supporting Recycling (CSR), has developed a model to help assess the environmental performance of various waste management practices and strategies. This integrated waste management (IWM) model baselines the current practices of a municipality and allows one to construct “what if” scenarios of possible changes to that municipality’s waste management system. The model — which employs life-cycle analysis methodology — is able to convert the outputs into terms that are understandable to the general public, such as emissions from a number of vehicles or electricity consumed by a given number of households in a year.

One area in which this tool could prove useful is in the evaluation of waste management practices with respect to greenhouse gas (GHG) emissions. GHG emissions have become a great concern since the Kyoto conference in 1997. According to the Kyoto Protocol, Canada has agreed to a 6 per cent reduction in 1990 emission levels by 2010. However, forecasters predict that Canada will increase emissions in 2010 by 19 per cent of 1990 values. This means that a total reduction of 25 per cent must be achieved to reach the goal by 2010.

The executive summary of a paper from the Federation of Canadian Municipalities on GHG emissions from solid waste management states, “Most important, waste contributes about one sixth of Canada’s greenhouse gas inventory,” which implies that the potential exists for substantial reductions from waste management practices.

Model mechanics

Several different types of emissions can be examined.

The IWM model, for example, begins with the preparation of a base case. All current practices are entered into a database that is then analyzed to produce an environmental inventory. This inventory shows the current resource consumption both in terms of tonnes and equivalent burdens. These equivalent burdens are calculated to present the results in a form that is easier to visualize; emissions of “X” number of cars or the electricity consumed by “X” number of homes.

In the example of Calgary, Alberta the base case was generated for 1998 using information gathered in a residential waste composition study conducted by CH2M Gore and Storrie Ltd. in 1999. This study showed that in 1998 Calgary disposed of 260,000 tonnes of residential waste with a recycle recovery rate of approximately 20 per cent. It costs Calgary approximately $85 per tonne to collect and dispose of residential waste and approximately $100 per tonne to collect recyclable material, although this number does not reflect revenue generated by the recycled material. In addition to recycling programs offered by the City of Calgary, Calgary does have private recycling companies and the Alberta Beverage Container Deposit System, which combined close to 45,000 tonnes of material in 1998. (For results of the study, see Chart 1.)

Various elements of the city’s waste management practices were changed to reflect the scenarios. (See Table 1.)

The “Waste Management Inventory” tracks the environmental impact of dealing with the waste material from the time it is removed from the home until it is converted into useful material or finally disposed (i.e., recycled to a useful form, considered inert landfill material, or is an air or water emission).

While the Waste Management Inventory operates according to a more local scale, the “Net Life Cycle Inventory” measures the effect of waste management changes on a more global scale. This inventory tracks environmental benefits of the waste management practice, e.g., recycling recovered material or energy displacement due to the production of virgin materials or energy. This type of inventory is further examined in this article.

Net life-cycle

In general, every change, no matter how small, has an effect on the GHG emission rates. All the improvements show a reduction in the emissions generated by landfill operations. Perhaps the most startling result is that due to a program of landfill gas and energy recovery, this program would have reduced emissions to the equivalent of 70,000 cars in one year. This improvement seems to have the greatest effect on emission levels and suggests the pursuit of landfill gas and energy recovery technology is worthwhile as a method of substantially reducing GHG emissions. (For a summary of results, see Chart 2.)

By examining environmental inventories, and specifically the tonnage of carbon dioxide equivalents emitted, the model indicates a 50 per cent reduction in the production of GHG gases. Combined with the effects of recycling and composting, gas recovery from landfills could be a way to meet Kyoto Protocols.

The drawback to landfill gas recovery is that the technology is fairly new and the process can be expensive to implement in new landfills or to retrofit capped landfill sites. Given that local governments operate most landfills, budget constraints are a major roadblock to these projects. One method to counteract this problem is the idea of trading GHG emission reduction credits. The general idea behind this concept is that companies that exceed their regulated emission reduction targets get a credit equal to the reduction they have achieved below regulated levels. These companies can then sell or trade the emissions to other industries that are not meeting their regulated emission reduction levels.

The International Council for Local Environmental Initiatives (ICLEI) has prepared an introductory primer to describe the concepts behind GHG emission reduction trading. It also describes two pilot projects in Canada that are currently underway to determine the effectiveness of this trading idea. The first project, initiated in 1996, is the Pilot Emission Reduction Trading (PERT). Initially this project traded in NOx and VOC emissions, but expanded in 1997 to include SO2, CO, and CO2 emissions. The Greenhouse Gas Emission Reduction Trading (GERT) trades solely GHG emission reductions. Both programs use registries to record pertinent information and the emissions traded.

Although emission-trading prices are not set, they do not have to be “sold” in the traditional sense. Partnerships between local governments and private industry could be made such that a private company with large GHG emission rates could provide governments with the means to implement a gas recovery program, and the ownership of the credits could be negotiated between the two.

An excellent example of this is the City of Edmonton and Transalta partnership, in which Transalta built and operates a state of the art composting facility and Edmonton pays a tipping fee to provide the garbage (see Composting Matters in the December/January 2001 edition). Through this partnership, Transalta gained both from the revenue and GHG emission credits. Edmonton was spared the cost of the facility and it gained a location to divert residential garbage, thus extending the life of the existing landfill.

While gas and energy recovery arguably leads to the largest reduction, the contributions of recycling and composting should not be ignored. Recycling displaces the production of virgin materials and the GHGs associated with their manufacture. Composting in turn converts organic material directly to CO2 while, if the organics were disposed to landfill, methane would be produced with a GHG potential 21 times that of CO2. In addition, recycling and composting reduce the amount of material sent to landfills, which is especially important for municipalities with limited space.

Chart 2 also indicates the penalty for areas with no waste diversion programs. For instance, the chart indicates that had Calgary landfilled all the waste generated in 1998 the emissions equivalent to 28,000 cars would have been released. This result is equally significant to the results for landfill gas and energy recovery. The model in the “zero diversion” scenario indicates that any sort of waste diversion plan would contribute to an overall reduction in global GHG emissions.

The model can

also provide an estimate of the environmental impact of current waste management strategies. Most municipalities are faced with budget restraints and this may be a tool that could indicate the biggest bang for the buck.

The model is not intended to be a stand-alone tool but to serve as a guide to supplement the tools and means currently available to community official. All waste management processes are not considered. For instance, the current version does not address anaerobic digestion (biogasification of waste). A module describing this option is under development. See for a link to more information and updates on model revisions.

Changes Made to Base Case for Each Scenario


50 per cent Increase in City Recycling

Increased amount of material recycled and adjusted other amounts accordingly

Increased mileage of recycling truck travel

Decreased mileage of garbage trucks travel

Changed recycle recovery rates to account for increases in recycling

Increased Composting

Increased amount of material composted and adjusted other amounts accordingly

Increased mileage of yard waste trucks

Landfill Gas and Energy Recovery

In the Landfill Screen set the Gas Recovery at 50 per cent efficiency and Energy Recovery at 18 per cent efficiency

Combination of Landfill Gas and Energy Recovery and Increased Composting

Entered changes for Increased Composting and Gas and Energy Recovery

Zero Diversion

Changed amount of material landfilled set all other amounts to zero

Increase mileage of garbage trucks and set other truck distances to zero

Kristina Gray, EIT, is a project manager with the City of Calgary Solid Waste Services, Alberta.

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