Greenhouse Gas Emissions

If all residential scrap metal were recycled,
how much greenhouse gas (GHG)
emission savings would be realized?

What are greenhouse gas emissions? The Intergovernmental Panel on Climate Change (IPCC) provides the following definition: "Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of infrared radiation emitted by the Earth's surface, the atmosphere and clouds. This property causes the greenhouse effect. Water vapour (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ozone (O3) are the primary greenhouse gases in the Earth's atmosphere."¹ The U.S. Environmental Protection Agency (EPA) defines emissions as "Releases of gases to the atmosphere (e.g., release of carbon dioxide during fuel combustion). Emissions can be either intended or unintended releases."

What is the connection between GHG emissions and recycling? In short, recycling eliminates the emissions associated with raw materials extraction and processing. The primary reason for this is that it requires less energy to recycle an end-of-life product into a new product than it does to make that item from raw inputs, such as ore or trees.

The relationship between waste management and GHG emissions has been examined by a number of agencies such as the U.S. EPA³ and the Canadian Plastics Industry Association. Natural Resources Canada (via Action Plan 2000 on Climate Change) and Environment Canada are working together to update and improve the Canadian numbers and this work will be finalized by September 2005.

Before GHG emission savings can be calculated for recycled scrap metal, it is necessary to estimate the amount of scrap metal that is ferrous and nonferrous.

First, it is very difficult to determine the average composition figure for scrap metal. There are just too many variables at play. But from recent waste characterization studies it is possible to develop some rough numbers that can be used to calculate GHG emissions. From various sources, therefore, it is assumed that 79% of residential metal scrap is ferrous and the remaining 21% is nonferrous.⁶

Based on the earlier assumption that Canadian households discard 116 000-232 000 tonnes of metal scrap per year, approximately 92 000-184 000 tonnes are ferrous and 24 000- 48 000 tonnes are nonferrous scrap. The primary components of nonferrous scrap are aluminum and copper, but further analysis is required to determine more realistic percentages. Although there is other metal present, it is assumed that 80% is aluminum and 20% is copper for the GHG projection provided below.

Second, the establishment of GHG emission factors for different "waste" materials is an evolving science. The following rounded GHG emission numbers are not finalized but are provided as interim values in order to develop order-of-magnitude projections. They will be updated (July 2005) as our collective understanding of the issue improves.

• For every tonne of ferrous metal recycled, the GHG emission reductions are 1 tonne of equivalent carbon dioxide (eCO2).⁷
• For every tonne of aluminum recycled, the GHG emission reductions are 6 tonnes of eCO2.⁸
• The GHG emission factor for copper has not yet been calculated in Canada; however, international data suggest that for every tonne of copper recycled, the GHG emission reductions are 4 tonnes of eCO2.⁹

If all the residential scrap metal currently discarded were to be recycled, then Canada would reduce its GHG emissions by 226 000-456 000 tonnes of eCO2 annually. So how can all of this incredibly valuable recyclable metal material be diverted from disposal?