Concept

The Merriam-Webster Dictionary defines footprint as:

1. an impression of the foot on a surface;
2. the area on a surface covered by something

Similarly, the ecological footprint (EF) represents the area of land on earth that provides for resources consumed and that assimilates the waste produced by a given entity or region. It is a composite index (see Module Sustainability Metrics and Rating Systems) that represents the amount of biologically productive land and water area required to support the demands of the population in that entity or region The EF is beneficial because it provides a single value (equal to land area required) that reflects resource use patterns (Costanza, 2000). The use of EF in combination with a social and economic impact assessment can provide a measure of sustainability’s triple bottom line (Dawe, et al., 2004). It can help find some of the “hidden” environmental costs of consumption that are not captured by techniques such as cost-benefit analysis and environmental impact (Venetoulis, 2001). Using the ecological footprint, an assessment can be made of from where the largest impact comes (Flint, 2001).

Next, we will discuss the how an EF is calculated.

Methodology

The ecological footprint methodology was developed by William Rees and Mathis Wackernagel (1996), and consists of two methodologies:

1. Compound calculation is typically used for calculations involving large regions and nations and is shown in Figure Compound Calculation Steps for Ecological Footprint Analysis. First, it involves a consumption analysis of over 60 biotic resources including meat, dairy produce, fruit, vegetables, pulses, grains, tobacco, coffee, and wood products. That consumption is then divided by biotic productivity (global average) for the type of land (arable, pasture, forest, or sea areas) and the result represents the area needed to sustain that activity. The second part of the calculation includes energy generated and energy embodied in traded goods. This is expressed in the area of forested land needed to sequester CO₂ emissions from both types of energy. Finally, equivalence factors are used to weight the six ecological categories based on their productivity (arable, pasture, forest, sea, energy, built-up land). The results are reported as global hectares (gha) where each unit is equal to one hectare of biologically productive land based on the world’s average productivity. We derive sub-national footprints based on apportioning the total national footprint between sub-national populations. The advantage of this method is that it captures many indirect of effects of consumption so the overall footprint is more accurate.
2. Component-based calculation resembles life-cycle analysis in that it examines individual products and services for their cradle-to-grave resource use and waste, and results in a factor for a certain unit or activity. The footprint is typically broken down into categories that include energy, transportation, water, materials and waste, built-up land, and food. This method is better for individuals or institutions since it accounts for specific consumption within that entity. However, it probably under-counts as not all activities and products could practically be measured or included. It also may double-count since there may be overlap between products and services.

Compound Calculation Steps for Ecological Footprint Analysis Figure shows the compound calculation steps for ecological footprint analysis. Source: C. Klein-Banai.

What the Results Show

When looking at the sub-national level, it is useful to be able to examine different activities that contribute to the footprint such as energy, transportation, water, waste, and food. In both types of calculations, there is a representation of the energy ecological footprint. We utilize conversion factors that account for direct land use for mining the energy source and the land required to sequester any carbon emitted during combustion, construction, or maintenance of the power source. It should be noted that no actual component-based calculations have been done for nuclear power. The practice has been to consider it the same as coal so as to account for it in some way. A discussion of the merits of this method can be found in Wackernagel et al. (2005).

Transportation is another activity that can be examined at the sub-national level. The transportation footprint maybe considered part of the energy footprint, or separately, but is basically based on the energy consumption for transportation. It may also include some portion of the built-up land.

The hydroprint, or water-based footprint, measures the amount of water consumed in comparison to the amount of water in the land catchment system for the geographical area being footprinted. It can represent whether the entity is withdrawing more or less water than is naturally supplied to the area from rainfall.

The wasteprint, or waste-based footprint, is calculated using commonly used component-based factors that have been calculated and compiled in a number of publications and books. Food production requires energy to grow, process and transport, as well as land for growing and grazing. The factors are derived using the compound calculation for a certain geographical area. See Case Study: Comparing Greenhouse Gas Emissions, Ecological Footprint and Sustainability Rating of a University for an example of this kind of ecological footprint analysis. This kind of analysis can show us how a nation, region, organization, or individual uses the planets resources to support its operation or life style, as well as what activities are the primary contributors to the footprint. In the next section, we will look at some national footprints.

Ecological Footprint Comparisons

Ecological Footprints of Select Nations Graph shows the ecological footprints of select nations. The bars show average EF in global hectares per person for each nation. Each color on the bar represents the different types of land. Source: © 2010 WWF (panda.org). Some rights reserved. Living Planet Report, 2010 , figure under CC BY-SA 3.0 License

The Living Planet Report prepared by the World Wildlife Fund, the Institute of Zoology in London, and Wackernagel’s Global Footprint Network reports on the footprints of various nations. Figure Ecological Footprints of Select Nations displays the footprint of several nations as shown in the report. The bars show average EF in global hectares per person for each nation. Each color on the bar represents the different types of land. Here we see that the United Arab Emirates has the largest footprint of 10.2 gha per person, with the majority of its footprint due to carbon (same as energy land described above). Whereas Latvia has the lowest footprint displayed at 6.0 gha per person, with the majority of its footprint due to forestland.

United States’ Ecological Footprint Figure shows the United States’ Ecological Footprint compared to the global average. Source: © 2010 WWF (panda.org). Some rights reserved. Living Planet Report, 2010, figure under CC BY-SA 3.0 License

Figure United States’ Ecological Footprint shows the national footprint in 2007 of the United States as 7.99 gha per person both with a bar display and with specific metrics on the right that show the exact footprint and the United States’ ranking among all nations in the report (e.g. carbon is 5.57 gha and ranks 3^rd largest overall). The bar to the left expresses the world average. The United States’ footprint of 7.99 gha stands in contrast to the earth’s global biocapacity of 1.8 gha per person. Globally, the total population’s footprint was 18 billion gha, or 2.7 gha per person. However, the earth’s biocapacity was only 11.9 billion gha, or 1.8 gha per person. This represents an ecological demand of 50 percent more than the earth can manage. In other words, it would take 1.5 years for the Earth to regenerate the renewable resources that people used in 2007 and absorb CO₂ waste. Thus, earth’s population used the equivalent of 1.5 planets in 2007 to support their lives.

Scoping the Inventory

The first step in measuring carbon footprints is conducting an inventory is to determine the scope of the inventory. The World Business Council for Sustainable Development (WBCSD) and the World Resource Institute (WRI) defined a set of accounting standards that form the Greenhouse Gas Protocol (GHG Protocol). This protocol is the most widely used international accounting tool to understand, quantify, and manage greenhouse gas emissions. Almost every GHG standard and program in the world uses this framework as well as hundreds of GHG inventories prepared by individual companies and institutions. In North America, the most widely used protocol was developed by The Climate Registry.

The GHG Protocol also offers developing countries an internationally accepted management tool to help their businesses to compete in the global marketplace and their governments to make informed decisions about climate change. In general, tools are either sector-specific (e.g. aluminum, cement, etc.) or cross-sector tools for application to many different sectors (e.g. stationary combustion or mobile combustion).

Scopes of a Greenhouse Gas Emissions Inventory Figure shows the three scopes of a greenhouse gas emissions inventory. Source: New Zealand Business Council for Sustainable Development, The challenges of greenhouse gas emissions: The “why” and “how” of accounting and reporting for GHG emissions (2002, August), figure 3, p. 10.

The WRI protocol addresses the scope by which reporting entities can set boundaries (see Figure Scopes of a Greenhouse Gas Emissions Inventory). These standards are based on the source of emissions in order to prevent counting emissions or credits twice. The three scopes are described below:

• Scope 1: Includes GHG emissions from direct sources owned or controlled by the institution – production of electricity, heat or steam, transportation or materials, products, waste, and fugitive emissions. Fugitive emissions are due to intentional or unintentional release of GHGs including leakage of refrigerants from air conditioning equipment and methane releases from farm animals.
• Scope 2: Includes GHG emissions from imports (purchases) of electricity, heat or steam – generally those associated with the generation that energy.
• Scope 3: Includes all other indirect sources of GHG emissions that may result from the activities of the institution but occur from sources owned or controlled by another company, such as business travel; outsourced activities and contracts; emissions from waste generated by the institution when the GHG emissions occur at a facility controlled by another company, e.g. methane emissions from landfilled waste; and the commuting habits of community members.

Depending on the purpose of the inventory the scope may vary. For instance, the EPA mandatory reporting requirements for large carbon dioxide sources require reporting of only Scope 1 emissions from stationary sources. However, many voluntary reporting systems require accounting for all three scopes, such as the ACUPCC reporting. Numerous calculator tools have been developed, some publicly available and some proprietary. For instance many universities use a tool called the Campus Carbon Calculator developed by Clean Air-Cool Planet, which is endorsed by the ACUPCC. Numerous northeastern universities collaborated to develop the Campus Carbon Calculator and the calculator has been used at more than 200 campuses in North America. It utilizes an electronic Microsoft Excel workbook that calculates estimated GHG emissions from the data collected.

Methodology

GHG emissions calculations are generally calculated for the time period of one year. Figure Steps for Preparing a GHG Emissions Report shows the steps for reporting GHG emissions. It is necessary to determine what the baseline year is for calculation. This is the year that is generally used to compare future increases or decreases in emissions, when setting a GHG reduction goal. The Kyoto Protocol proposes accounting for greenhouse gas emissions from a baseline year of 1990. Sometimes calculations may be made for the current year or back to the earliest year that data is available.

Steps for Preparing a GHG Emissions Report Figure shows the required steps to take when preparing a GHG emissions report. Source: C. Klein-Banai

Next, the institutional or geographic boundaries need to be defined. Also, the gases that are being reported should be defined. There are six greenhouse gases defined by the Kyoto Protocol. Some greenhouse gases, such as carbon dioxide, occur naturally and are emitted to the atmosphere through natural and anthropogenic processes. Other greenhouse gases (e.g. fluorinated gases) are created and emitted solely through human activities. The principal greenhouse gases that enter the atmosphere because of human activities are:

• Carbon Dioxide (CO2): Carbon dioxide is released to the atmosphere through the combustion of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of non-combustion reactions (e.g. manufacture of cement). Carbon dioxide is sequestered when plants absorb it as part of the biological carbon cycle.
• Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also come from farm animals and other agricultural practices and the degradation of organic waste in municipal solid waste landfills.
• Nitrous Oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, and combustion of fossil fuels and solid waste.
• Fluorinated Gases: Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (i.e. Chlorofluorocarbons (CFCs), hydrochlorofluorocarbon (HCFCs), and halons). CFCs and HCFCs are gases comprised of chloride, fluoride, hydrogen, and carbon. Halons are elemental gases that include chlorine, bromine, and fluorine. These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (“High GWP gases”).

Each gas, based on its atmospheric chemistry, captures different amounts of reflected heat thus contributing differently to the greenhouse effect, which is known as its global warming potential. Carbon dioxide, the least capture efficient of these gases, acts as the reference gas with a global warming potential of 1. Table Global Warming Potentials shows the global warming potential for the various GHGs.

GHG emissions cannot be easily measured since they come from both mobile and stationary sources. Therefore, emissions must be calculated. Emissions are usually calculated using the formula:

where A is the quantification of an activity in units that can be combined with emission factor of greenhouse gas g (Fg) to obtain the resulting emissions for that gas (Eg).

Examples of activity units include mmbtu (million British Thermal Units) of natural gas, gallons of heating oil, kilowatt hours of electricity, and miles traveled. Total GHG emissions can be expressed as the sum of the emissions for each gas multiplied by its global warming potential (GWP). GHG emissions are usually reported in metric tons of carbon dioxide equivalents (metric tons CO₂-e):

Eg is usually estimated from the quantity of fuel burned using national and regional average emissions factors, such as those provided by the US Department of Energy’s Energy Information Administration.

Emission factors can be based on government documents and software from the U.S. Department of Transportation, the U.S. Environmental Protection Agency (EPA), and the U.S. Department of Energy, or from specific characteristics of the fuel used – such as higher heating value and carbon content. Scope 3 emissions that are based on waste, materials, and commuting are more complex to calculate. Various calculators use different inputs to do this and the procedures are less standardized. See Case Study: Comparing Greenhouse Gas Emissions, Ecological Footprint and Sustainability Rating of a University for an example of these kinds of calculations.

Greenhouse gas emissions inventories are based on standardized practice and include the steps of scoping, calculating, and reporting. They are not based on actual measurements of emissions, rather on calculations based on consumption of greenhouse gas generating materials such as fossil fuels for provision of energy and transportation or emissions from waste disposal. They can be conducted for buildings, institutions, cities, regions, and nations.

Carbon Footprint Comparisons

Comparison of carbon footprints reveal interesting differences between countries, particularly when compared to their economic activity. The World Bank tracks data on countries and regions throughout the world as part of their mission to “fight poverty…and to help people help themselves and their environment” (World Bank, 2011). Table Gross Domestic Product (GDP) and Emissions for Select Regions, 2007 shows the results for GHG emissions and gross domestic product for various regions of the world. It is interesting to note that the United States’ emissions per capita (19.34 mt e-CO₂) are more than four times the world average. The United States’ economy makes up one fourth of the world GDP.