Two Feet – Two Approaches: A Component-based model of ecological footprinting

 

Craig Simmons

Kevin Lewis

© Best Foot Forward

 

 

 

 

When Best Foot Forward first embarked upon the EcoCal^TM project in early 1996, a household ecological footprint calculator developed for the UK environmental charity Going for Green, there was little guidance on how one might calculate the ecological footprint of items such as transport, primary energy use, waste, and so on, at a domestic level.

 

Working initially with CAG Consultants we slowly developed a set of algorithms for converting activity data into land area ‘footprint’ equivalents using information gleaned from a variety of official sources and academic works (Department of Trade and Industry 1997, C.A.G Consultants 1996, Department of the Environment 1996 and Whitelegg 1993 for example). This calculation method has now matured into what we have termed 'component-based' footprinting. This was developed contemporaneously with the 'compound' footprinting calculation method pioneered by Mathis Wackernagel (see Wackernagel et al.1997, 1999 for example).

 

This paper describes the component-based model, its advantages and disadvantages, and concludes by comparing the results of a footprint study of the island of Guernsey undertaken using both compound and component analyses.

 

The Component-based model

 

Our focus has always been on the use of ecological footprinting to measure the impact of different lifestyles, organisations,  sub-national regions, products and services rather than larger governmental units. Our model reflects this by adopting a ‘bottom-up’ analytical approach to the derivation of footprint values (Simmons & Chambers 1998).

 

In the component-based model the ecological footprint values for certain activities are pre-calculated using data appropriate to the region under consideration. For example, to calculate the impact of car travel data on fuel consumption, manufacturing and maintenance energy, land take and distance travelled is sourced for the Country in question – then an average ecological footprint estimate derived for a single passenger-km or other appropriate unit (see Table 1). This can then be used to calculate the impact of vehicle use at the individual, organisational or regional level as required. The land categories originally proposed by Wackernagel & Rees (1996) are essentially retained; energy land, built (or degraded) land, bioproductive land and sea and biodiversity land.

 

Table 1: An example analysis for the footprint of UK car travel per passenger-km.

COMPONENT	Inputs	CO2 Emissions	Built-Upon Land	FOOTPRINT
1Petrol	0.094 Litres/Km	0.22 CO2/Kg		0.000043i Ha/Car Km
2Maintenance &   Manufacture	0.0423 Litres/Km equivalent	0.10 CO2/Kg		0.000019ii Ha/Car Km
3Road Space a	2,581,747 Ha		2,581,747 Ha
4Car Road Share b	86%
5Car Kms c	362,400,000,000
6Car Occupancy d	1.6 persons
Calculation			(a*b)/c	(i+ii+iii)/d
FOOTPRINT			0.00000613iii Ha/Car Km	0.000043 Ha/passenger-km

¹ Department of the Environment, Transport and the Regions (DETR 1997)

² Wackernagel and Rees (1996) state this as 45% of the fuel energy

³ DETR (1997) report the length of road types and we have here assumed a conservative average road

  width of 7m.

⁴ DETR (1997)

⁵ British Road Federation (BRF 1998)

⁶ DETR (1999) personal communication with the National Travel Survey

 

The same process can be undertaken for other forms of travel as well as energy, waste, food and so on. When calculating the ecological footprint of an organisation or region we typically look at the 24 components set out in Table 2. Our aim is to capture the majority of anthropogenic impacts. According to the sensitivity required, components such as food might be sub-divided further or categories omitted when they are not applicable. To avoid double counting the energy used for the production and transportation of goods for example, the values for primary energy use and freight transport are adjusted based on assumptions about embodied energy. Similarly, adjustments are made for any double counting of built land.

 

Table 2: List of component impacts considered for sub-national regions

COMPONENT IMPACTS
Electricity (GWh) - domestic	Food (t)
Gas (GWh) - domestic	Wood Products (m3 WRME1)
Electricity - other (GWh)	Built Land (ha)
Gas - other (GWh)	Recycled waste(tonnes) - glass
Travel by car (Passenger 000's km/yr)	Recycled waste-paper and card (tonnes)
Travel by bus (Passenger 000's km/yr)	Recycled waste-metals  (tonnes)
Travel by train (Passenger 000's km/yr)	Recycled waste-compost (tonnes)
Travel by air (Passenger 000's km/yr)	Recycled-other domestic(tonnes)
Road haulage (000 tonne-kms/yr)	Waste - household (tonnes)
Rail freight (000 tonne-kms/yr)	Waste - commercial (paper, metal etc.) (tonnes)
Sea freight (000 tonne-kms/yr)	Waste - inert (brick, concrete etc.) (tonnes)
Air freight (000 tonne-kms/yr)	Water - household (m3)

 ¹WRME = Wood Raw Material Equivalents

 

Of course, data sources rarely agree. For example, the average amount of carbon dioxide produced by a tonne-km transported by air is variously given as 795 grammes (British Airways 1996), 1206 grammes (Whitelegg 1997) and 1642 grammes (derived from Whitelegg 1997 and IPCC 1996). Estimates are based on different assumptions, methodologies and samples. Part of our methodology therefore involves a sensitivity analysis using a range of data sources to determine the most representative footprint conversion factors. To give an example, Table 3 shows the variation in data sources for the embodied energy and built land associated with wind generated power. Table 4 shows a range of ecological footprint results possible depending on which combination of sources is used.

 

Table 3 Differing values for the embodied energy and built land associated with wind power.

Component	Data Embodied Energy (Mwh/GWh) Built-upon Land (m2/kWh)	Reference
Embodied Energy	142	Stelzer 19941
	44	Stelzer 19942
	36	Derived from American Wind Energy Association (1998)1
	27	Derived from American Wind Energy Association (1998)2
	11	Derived from American Wind Energy Association (1998)3
Built-upon Land	0.12	Derived from American Wind Energy Association (1998)4
	0.006	Derived from American Wind Energy Association (1998)5
	0.0029	Wackernagel & Rees (1996)
	0.0015	Stelzer 19943
	0.0011	Worldwatch Institute (1995)

 

 

Table 4: Ecological footprint results obtained from differing data sources.

Footprint (Ha/GWh)	Reference Data
1.81	American Wind Energy Association (1998)3 & Wackernagel & Rees (1996)
4.33	American Wind Energy Association (1998)2 & Derived from American Wind Energy Association (1998)5
15.73	American Wind Energy Association (1998)2 & Derived from American Wind Energy Association (1998)4
18.08	Stelzer 19942 & American Wind Energy Association (1998)4
20.24	Stelzer 19941 & American Wind Energy Association (1998)5

 

 

Advantages and Disadvantages

 

Our 'component-based' approach is not intended to be in any way a replacement for 'compound' footprinting. Each method has its benefits and uses - they are very much complimentary styles of analysis. They can be considered to be different kinds of ecological tape measures, both of which are trying to capture the same basic environmental impacts using the same evaluation unit. The analysis method  you choose depends on the accuracy you require and the features of the item being measured. This paper briefly considers two key aspects of the component-based model; accuracy and utility.

 

Accuracy

 

Compared to a compound approach, where material flows are measured primarily at a National level, component-based footprinting is more sensitive to underlying data variations.  If one has access to the data necessary to track material flows and energy usage then the more accurate result will be obtained by undertaking a compound analysis. 

 

However, our experience is that even in the UK, with a long history of data collection and analysis, the sort of information required for a complete compound analysis is rarely available at the sub-national level. A compound analysis relies heavily on trade data – details of primary imports, exports, and production – to permit the calculation of domestic consumption). Where there is no regulated trade between regions then the most accurate source of consumption and pollution data is usually that recorded by individual providers of goods and services. This is then aggregated to the required level. For example, the volume of waste produced at the level of UK regions is not determined by geographically disaggregating National material flow data but by aggregating local authority returns (Biffa 1997).

 

Within this context, one advantage of component-based footprinting becomes apparent. As can be seen from Table 2, the data demands of the component-based approach are more easily met by existing local sources (Regional Trends for the UK for example).

 

Compound footprinting has been used to calculate the footprint of a region by the application of proxy indicators to represent variations in some of the aspects of local consumption (see Wackernagel 1998). However, this is more restrictive than the component-based approach and the substitution of proxy measures results in higher levels of error thus offsetting one of the main benefits of the compound approach.

 

Nonetheless, a compound approach to the footprinting of a region does have the advantage of compatibility with the national picture that may, in certain circumstances, outweigh any other considerations.

 

Utility

 

One of the often quoted advantages of the ecological footprint concept is the way in which it resonates with the public at large. This is illustrated by the fact that despite its relatively recent formulation, footprinting is now in widespread use in education, public policy and awareness campaigns. (see People & Planet 1999, Simmons 1998, Levett 1998, Simmons and Chambers 1998, CoEd Communications 1997and Sustainable London Trust 1995. Online education resources that use footprinting include the Centre for a Sustainable Future <www.csf.concord.org/esf>, Best Foot Forward Ltd. <www.bestfootforward.com>, The University of Texas <http://www.esb.utexas.edu/drnrm/WhatIs/ecofootprint.htm> and WWF CANADA <http://www.wwfcanada.org/cgi-bin/database-cgi/ecofoot.pl>).

 

Component-based footprinting seeks to build on this strength with its pedagogical structure. Individuals, organisations and decision-makers are more easily able to explore the impact of their actions, and those of other economic players, by manipulating and evaluating the various components; something which is more difficult with a compound approach.

 

A simple example of the use of footprinting primarily as a communications and awareness raising tool can be found in the ‘Global Steps^TM’ game (Best Foot Forward 1999) – a set of 8 cards each representing a component.   Table 5 sets out the component descriptions and associated footprint values based on UK data. This has successfully been used in workshops with students, practitioners and policy-makers to explore personal environmental impacts (People and Planet 1999, Barrett 1999).

 

Table 5: Global Steps components and scores (in 100m² units)

Component	Description	High Score	Description	Low Score
Food	"You pay little attention to how far your food has been transported"	10	"You make a particular effort to buy mostly fresh and locally grown food"	5
Paper	"You regularly buy newspapers and books"	20	"You share newspapers and usually borrow books rather than buy them"	5
Electricity	"You use standard appliances, often left on standby, and have high bills"	40	"You use low energy appliances, always turn them off and have low bills"	15
Heating	"You keep your home warm, have poor insulation and high heating bills"	50	"You use your heating sparingly, have good insulation and low bills"	30
Waste	"You recycle little or none of your waste"	30	"You reduce waste where possible, and recycle most of the rest"	10
Holiday	"You usually take short flights (e.g. Europe) or overland trips"	10	"You take at least one long haul flight per year (e.g. to the USA or Asia)"	55
Transport	"You travel mostly by car"	80	"You travel mostly by public transport, cycling or walking"	20
Water	"You take lots of baths, have a dishwasher, hosepipe etc."	15	"You take mostly showers, and don't have a dishwasher or hosepipe"	5

 

Tools such as EcoCal^TM and EcoCal for Schools^TM (developed by BFF for Going for Green), developed for use by UK households and school pupils respectively, demonstrate a more sophisticated use of the component-based model to assist in the teaching of sustainable development principles.

 

Guernsey’s Big Feet

 

In order to validate the component-based approach, the authors collaborated with John Barrett, a doctoral student at the Liverpool John Moores University on his study of the Channel Island of Guernsey off the South Coast of England. There are compelling and practical reasons to study Guernsey. It has a per capita GNP greater than that of the United States., the economy is almost exclusively dependent on international finance, it is a self-governing island and it has signed no international environmental agreements. Furthermore, its isolation and small size means that data is more easily available to perform both compound and component-based analyses.

 

Tables 6 shows the summary component-based ecological footprint analysis of the island. The total and  per capita footprints have been adjusted to avoid double-counting of energy and built land. This  adjustment is small in the case of Guernsey which imports almost all of its goods and materials. The final adjusted per capita footprint is 8.51 hectares.

 

Table 7 shows a summary of the compound analysis. The per capita footprint derived by this method is 8.28 hectares per capita, slightly less than the component-based estimate.

 

Table 6: Summary of Guernsey component-based analysis; algorithms based on 1997-1999 data

 

Sources: Guernsey Electricity, Guernsey Gas Group, Economics and Statistics Review, Vehicle Registration and Licensing, Waste Assessment Strategy, Guernsey IDC (D Hackley), Guernsey Board of Admin,  Guernsey Water Board.

 

Table 7: Summary of Guernsey compound analysis; algorithms based on 1994 data (Barrett 1999)

 

ECOLOGICAL FOOTPRINT (per capita)
Category	total	equiv.	equivalent
		Factor	total
	[ha/cap]	[ - ]	[ha/cap]
fossil energy	4.87	1.14	5.55
arable land	0.35	2.82	0.99
pasture	1.09	0.54	0.59
thereof on arable land	?	2.82	-
forest	0.74	1.14	0.84
built-up area	0.00	2.82	0.00
sea	1.45	0.22	0.31