Calcul des facteurs d'intensité d'empreinte écologique pour le projet ADEME Délégation régionale Nord Pas de Calais

La présente section détaille le calcul du jeu de facteurs d'intensité d'empreinte écologique (Footprint Intensity - FI) qui a été utilisé dans les tableurs spécifiquement élaborés pour le projet ADEME. Les sources sont également précisées.

Ces facteurs représentent ici l'empreinte écologique totale requise pour fournir et régénérer une quantité donnée de ressource ou assimiler une quantité donnée de déchet. En effet, les comptes nationaux d'empreinte écologique (National Footprint Accounts - NFA) contiennent un tableau de facteurs d'intensité d'empreinte écologique (Footprint Intensity Table - FIT) exprimés en hectares globaux par unité de mesure de flux. Toutefois, ces facteurs ne sont calculés que pour les matières premières les plus courantes voire pour quelques matières secondaires. En outre, ces facteurs ne correspondent généralement qu'à une seule utilisation des surfaces, et donc qu'à une seule étape du cycle de vie de ces matières : la production par les écosystèmes d'où la dénomination d'empreinte écologique des matières brutes. Au contraire, une empreinte écologique totale se calcule pour une ressource (ou un déchet) sur l'ensemble des utilisations de surfaces (mutuellement exclusives) qu'elle nécessite tout au long de son cycle de vie. Par exemple, le facteur disponible dans ce tableau des NFA pour le cas du blé représente uniquement les hectares globaux de terres arables nécessaires pour produire une tonne de cette céréale sans prendre en compte d'éventuelles étapes ultérieures de transformation et de transport.

En revanche, un facteur est disponible pour chaque tonne de dioxyde de carbone absorbée par les forêts, ce qui autorise alors des calculs fondés sur le concept d'énergie grise pour passer de l'empreinte écologique des matières brutes à une empreinte écologique totale.

Facteurs d'intensité d'empreinte pour les énergies

L'empreinte écologique spécifiquement générée par la consommation d'énergie, également appelée empreinte énergétique (Carbon Footprint - CF), prend en compte la consommation des énergies fossile, hydraulique, grise et nucléaire. La production d’énergie n’est pas nécessairement liée à l’utilisation d’une superficie. Par conséquent, la méthode de l'empreinte écologique convertit la consommation de vecteurs énergétiques d'origines diverses en surfaces hypothétiques. Ainsi, l’empreinte énergétique ne représente pas la superficie de champs pétrolifères ou de mines de charbon mais la surface requise pour absorber le dioxyde de carbone (et les autres gaz à effet de serre selon les équivalences en vigueur) qui résulte de la combustion, et ceci de manière à ne pas augmenter la concentration de gaz à effet de serre dans l’atmosphère. Les calculs des facteurs d'intensité d'empreinte écologique pour les énergies se basent alors sur la capacité d’absorption du dioxyde de carbone par les forêts et les océans, selon les règles édictées par le Groupe d’experts Intergouvernemental sur l’Evolution du Climat (GIEC).

Facteur d'intensité d'empreinte pour l'énergie grise (énergie indirecte)

Une part importante de l'empreinte écologique de produits (biens ou services) correspond à l'énergie grise, c'est à dire la quantité d’énergie nécessaire pour produire, fabriquer, transporter et éliminer un produit. Les données nécessaires au calcul de cette énergie indirecte pour un produit sont généralement issues d'Analyses de Cycle de Vie (Life Cycle Analysis ou Life Cycle Assessment - LCA). En effet, cette méthodologie standardisée d'évaluation des impacts environnementaux nécessite de comptabiliser les matières et les énergies utilisées à chaque étape du cycle de vie d'un produit. L'inventaire du cycle de vie quantifie donc du "berceau à la tombe" les flux entrants et sortants associés au système étudié, directement ou indirectement. Les données peuvent également provenir d'Analyses de Flux de Matières et d'Energies (Material Flow Analysis - MFA). Cette autre méthodologie suit en effet le devenir des matières et des énergies au sein de l’anthroposphère (dans une activité économique, dans une filière industrielle, sur un territoire, etc.) selon la même perspective de bilan quantitatif sur le cycle de vie.

Une fois quantifiée, cette énergie grise contenue dans les produits est alors convertie en empreinte écologique correspondante (empreinte énergétique) selon 3 étapes de calcul :

Conversion des énergies en émissions de gaz à effet de serre

Conversion des émissions de gaz à effet de serre en surfaces énergétiques

Conversion des surfaces énergétiques en empreinte écologique

An important part of the footprint of final products or consumables is related to the indirect energy, i.e. the energy which is needed to produce this product. Data on indirect energy input (IEI) are calculated in so called Life Cycle Assessment analyses. In LCA, the energy input during the entire life cycle of a product is investigated. Data on indirect energy input are converted into footprint data in three steps :

Step 1: the IEI, typically expressed in MJ, is converted into CO2 emissions assuming that a “world average energy mix” was used in the production phase. This assumption is done because LCA data do not provide details on the specific energy sources used. One MJ of this “world average energy mix” represents 69,8 gram of CO2, i.e. a CO2 emission factor of 69,8 gCO2/MJ

2001 - basis

Energy intensity

Carbon intensity

World Energy Consumption

|||

Coal

44,76

0,025800

2243,10

|44,76|0,020000|3517,10

Natural gas

44,76

0,015300

2219,50

|44,76|0,020388|601,00

Hydro

44,76

584,70

| | |9165,40

World average carbon intensity

0,019031

Table 2 World energy consumption, energy intensity and carbon intensity taken from International Energy Agency and British Petroleum statistics (National Footprint Accounts 2002)

Step 2: the amount of CO2 emissions is then converted into energy land via the “sequestration factor”, which is the surface of energy land needed for the sequestration of one kg of CO2. From the International Panel on Climate Change, the world average terrestrial sequestration factor equals 1 ton of carbon per hectare of forest areas. Taking into account the percentage not absorbed by oceans (72,616%), the world average sequestration factor results in 1,377 tC/ha. Converting into CO2, it represents 5,049 tons of CO2 per hectare of energy land or 0,198 hectare of energy land per ton of CO2. This results in a “sequestration factor” of 1,98 m2/kgCO2, i.e. 0,5049 kgCO2/m2.

Step 3: the amount of energy land is then converted into global bioproductive land or energy footprint by applying the “equivalence factor” for energy land, i.e. multiplying by 1,38 m2gbpl/m2 (for these 2005 calculations although the 2006 equivalence factor is 1,34).

From using 69,8 gCO2/MJ together with 0,5049 kgCO2/m2 and 1,38 m2gbpl/m2, it can be calculated that 1 MJ of indirect energy input represents an ecological footprint of 0,19 m2gbpl, i.e. 0,19 m2gbpl/MJ.

Facteurs d'intensité d'empreinte pour les vecteurs énergétiques

Direct energy inputs, i.e. the use of heating fuel, are treated more straightforward. IPCC data sources report CO2 emission factors for all kinds of energy sources. From these CO2 emissions, the ecological footprint is easily calculated by applying step 2 and 3 from the calculation mentioned for indirect energy. It can e.g. be calculated that 1 kg of CO2 represents an ecological footprint of 2,73 m2gbpl, i.e. 2,73 m2gbpl/kgCO2.

Electricité

Fioul domestique

Gaz naturel

Facteurs d'intensité d'empreinte pour les sols mobilisés

The number of global hectares required to produce a given quantity of resource or absorb a given quantity of waste, usually expressed as global hectares per tonne. The National Footprint Accounts calculate a primary Footprint Intensity Table for each country, which includes the global hectares of primary land use type needed to produce or absorb a tonne of product (i.e., global hectares of cropland per tonne of wheat, global hectares of forest per tonne carbon dioxide).”

Footprint conversion factors
From consumption data to footprint data
Ecolife / Institut Angenius

General

The ecological footprint measures humanity’s demand on the biosphere in terms of the area of biologically productive land and sea required to provide the resources we use and to absorb our waste. The ecological footprint includes all the cropland, grazing land, forest and fishing grounds required to produce food, fibre and timber, to absorb the wastes emitted in generating energy and to provide space for infrastructure.

The ecological footprint methodology adopts the following categories of bioproductive land :
cropland : land exploited for crop breeding
grazing land (pasture) : land exploited for breeding cattle
fishing land (marine or inland water) : sea exploited for fishing
woodland (forest) : land exploited for wood
built-up land : land exploited for infrastructure (buildings, roads,…)
energy land : the area of forest needed for the sequestration of CO2 emitted in the combustion of fossil fuels

In calculating ecological footprint values from consumption data, every ‘consumption flux’ is analysed in terms of its demand on any of these categories of bio-productive land. E.g. a flux meat will be ‘converted’ into certain amounts of grazing land (for grazing animals), cropland (crop-based fodder) and energy land (for the energy needed in the farming infrastructure and in the production of ‘consumption-ready’ meat). To be completely correct, also a small amount of built-up land (or cropland; see above) should be taken into account for the surface occupied by the cattle farm. Similarly, 1 km of car-transport is disentangled into energy land, both for the fuel consumption as well as the production and maintenance of the car and road-infrastructure, and in built-up land (or cropland; see above) for the surface occupied by roads, parking lots, etc. Most of these factors can be adopted from the Global Footprint Network accounts (e.g. agricultural production yields taken from Food and Agricultural Organization statistics). Energy use, and especially indirect energy use is more complicated (see below).

Each of the footprint categories has a specific bioproductivity: the average amount of biomass that can be produced or absorbed per year. This specific bioproductivity is calculated based on world averages from FAO. The ratio between specific (e.g. cropland or woodland) productivity and ‘average’ bioproductive (global bioproductive land; gbpl) land is expressed in the “equivalence factors” below.

Cropland

Grazing land (pasture)

Fishing land

Woodland (forest)

Built-up land

Energy land

|||||||

Table 1 Equivalence factors in gha/ha (Living Planet Report 2006)

From this table can e.g. be deducted that a world average m2 of cropland is 2,21 times more bioproductive than one m2 gbpl or global bioproductive land. This equivalence factor enables us to add up the different demands on different sorts of bioproductive area to one number: the ecological footprint. In this way, it is possible to compare e.g. fresh milk (which has mainly a grazeland footprint) with a wardrobe (which has mainly a woodland footprint) in terms of impact on the bioproductive capacity.

In order to compare biocapacities between countries and region, another correction factor is introduced : “yield factors”. Belgian cropland e.g. is 2,44 times more bioproductive than world average cropland. One hectare of cropland used in Belgium (for e.g. the building of a sports facility) represents 2,44 hectares of world average cropland (yield factor) and thus 5,4 global hectares in 2006 (= 2,44 ha * 2,21 gha/ha as equivalence factor).

In conclusion :
In a first step, every basic unit of a flux (e.g. 1 km, 1 kg,…) will be converted into surfaces of average bioproductive cropland, woodland,… and amounts of both direct and indirect energy. The latter are converted into energy land via the amount of CO2 emitted.
In a second step, by applying the respective equivalence factors, all categories of bioproductive land (cropland, …) are converted into one number : the total surface of global bioproductive land, i.e. the ecological footprint.

Energy

An important part of the footprint of final products or consumables is related to the indirect energy, i.e. the energy which is needed to produce this product. Data on indirect energy input (IEI) are calculated in so called Life Cycle Assessment analyses. In LCA, the energy input during the entire life cycle of a product is investigated. Data on indirect energy input are converted into footprint data in three steps :

Step 1: the IEI, typically expressed in MJ, is converted into CO2 emissions assuming that a “world average energy mix” was used in the production phase. This assumption is done because LCA data do not provide details on the specific energy sources used. One MJ of this “world average energy mix” represents 69,8 gram of CO2, i.e. a CO2 emission factor of 69,8 gCO2/MJ

2001 - basis

Energy intensity

Carbon intensity

World Energy Consumption

|||

Coal

44,76

0,025800

2243,10

|44,76|0,020000|3517,10

Natural gas

44,76

0,015300

2219,50

|44,76|0,020388|601,00

Hydro

44,76

584,70

| | |9165,40

World average carbon intensity

0,019031

Table 2 World energy consumption, energy intensity and carbon intensity taken from International Energy Agency and British Petroleum statistics (National Footprint Accounts 2002)

Step 2: the amount of CO2 emissions is then converted into energy land via the “sequestration factor”, which is the surface of energy land needed for the sequestration of one kg of CO2. From the International Panel on Climate Change, the world average terrestrial sequestration factor equals 1 ton of carbon per hectare of forest areas. Taking into account the percentage not absorbed by oceans (72,616%), the world average sequestration factor results in 1,377 tC/ha. Converting into CO2, it represents 5,049 tons of CO2 per hectare of energy land or 0,198 hectare of energy land per ton of CO2. This results in a “sequestration factor” of 1,98 m2/kgCO2, i.e. 0,5049 kgCO2/m2.

Step 3: the amount of energy land is then converted into global bioproductive land or energy footprint by applying the “equivalence factor” for energy land, i.e. multiplying by 1,38 m2gbpl/m2 (for these 2005 calculations although the 2006 equivalence factor is 1,34).

From using 69,8 gCO2/MJ together with 0,5049 kgCO2/m2 and 1,38 m2gbpl/m2, it can be calculated that 1 MJ of indirect energy input represents an ecological footprint of 0,19 m2gbpl, i.e. 0,19 m2gbpl/MJ.

Direct energy inputs, i.e. the use of heating fuel, are treated more straightforward. IPCC data sources report CO2 emission factors for all kinds of energy sources. From these CO2 emissions, the ecological footprint is easily calculated by applying step 2 and 3 from the calculation mentioned for indirect energy. It can e.g. be calculated that 1 kg of CO2 represents an ecological footprint of 2,73 m2gbpl, i.e. 2,73 m2gbpl/kgCO2.

Specific footprint factors
In the following section, footprint factors used in Milieubarometer for some selected consumption fluxes are explained in more detail. For these specific factors, only the categories of cropland (used as building surface), woodland and energy land will be relevant.

Built-up area (sol mobilisé)

|| ||||

1 m2 built-up area

5,32

5,32

1 m2 of cropland used for building in Belgium represents 2,44 m2 of world average cropland (yield factor) and thus 5,32 m2gbpl (2,18 m2gbpl/m2 as 2005 equivalence factor for cropland although the 2006 equivalence factor is 2,21).

Soil surface (surface construite)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 m2 soil surface


16,72
16,72

Via the soil surface an estimate is made of the amount of indirect energy that is needed to build, maintain and repair the building. This number is then divided over an estimated lifetime of 65 years. The Dutch IVEM study (Kok, R., R.M.J. Benders, H.C. Moll. 2001 Energie intensiteiten van Nederlandse consumptieve bestedingen anno 1996. IVEM onderzoeksrapport nr. 105, Groningen) quotes the following numbers :

88 MJ/m2/year for apartments
94 MJ/m2/year for a house-in-a-row
121 MJ/m2/year for a stand-alone house

As there are no data for office-buildings, 88 MJ/m2/year is adopted as a lower limit estimate for the indirect energy ‘contained’ in buildings. As explained above for indirect energy, this 88 MJ of indirect energy represents 16,72 m2gbpl.

Electricity (électricité)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 kWh end-use electricity


1,91
1,91

The footprint for electricity is directly calculated from the reported CO2 emissions from the electricity sector in Belgium (Beroepsfederatie van de Producenten en Verdelers van Elektriciteit in België BFE - Statistical Yearbooks of the Federation of Producers and Distributors of Electricity in Belgium). From these electricity production data, a number of 0,70 kg CO2 per kWh end-use is derived2. Combined with the CO2 sequestration factor and the equivalence factor, this gives 1,39 m2 of energy land equivalent with an ecological footprint of 1,91 m2gbpl.

Heating fuel (fioul ou mazout)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 L heating fuel


9,07
9,07

In the calculation of the footprint for heating fuel an estimate is made of the fuel lost and used in the process of exploitation, transport and refinery stage via the ‘processing factor’. Based on data from VITO - Flemish Institute for Technological Research, a ‘processing factor’ of 123,6 % is adopted for heating fuel, i.e. the input of 1,236 liter of fuel is needed to produce 1 liter of ready-to-use fuel.
Burning 1 litre of fuel results in the emission of 2,688 kg CO2 (IPCC emission data). Combined with the CO2 sequestration factor, this results in 6,58 m2 of energy land per liter of heating fuel which is equivalent with an ecological footprint of 9,07 m2gbpl.

Natural gas (gaz naturel)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 kWh natural gas


0,64
0,64

This calculation is equivalent to that for heating fuel (see above). For natural gas, a processing factor of 115,2% (VITO) and a CO2 emission factor of 0,202 kgCO2/kWh (IPCC emission data) are adopted. This results in an ecological footprint of 0,64 m2gbpl per kWh of natural gas.

Tap water (eau de ville)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 m3 tap water


1,01
1,01

For water, only the energy used in the exploitation, treatment, purification and transport is taken into account. The study Sharing Nature’s Interest (Sharing Nature's Interest: Ecological Footprints as an Indicator for Sustainability, Nicky Chambers, Craig Simmons and Mathis Wackernagel, 2000. Earthscan, London) mentions a number of 370 kg of CO2 that is emitted for the ‘production process’ of 1000 m3 of clean tap water. This results in an ecological footprint of 1,01 m2gbpl for 1 m3 of tap water.

Sea water (eau de mer)

As only the energy used in the exploitation, treatment, purification and transport of water is taken into account, the ecological footprint for sea water is equal to zero.

Transport

Two footprint categories are taken into account for transport :
a cropland footprint part resulting from the surface occupied by the specific transport infrastructure, i.e. road network for transport by car; railway network for transport by train, etc.
an energy footprint part from the transport fuel used as well as from the indirect energy used in the construction and maintenance of both the transport means (i.e. car, train, bus, etc.) and the infrastructure (roads, railways, etc.).

Individual car travelling (voiture individuelle)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 car-km
(diesel)

0,0835
0,996
1,08
1 car-km
(benzine)

0,0835
1,053
1,14
1 car-km
(LPG)

0,0835
0,783
0,87

The cropland footprint for road-travel in Belgium is calculated as follows. Taken from the Belgian National Institute for Statistics (1999), the total surface of the Belgian road infrastructure is divided by the total amount of ‘item-transport-km’, i.e passenger-km (travelling) and ton-km (freight). This results in an average amount of 0,01 m2 of Belgian cropland per ‘item-transport-km’. Combined with a Belgian average car occupance of 1,4 persons per car, a yield factor of 2,44 for Belgian cropland and an equivalence factor of 2,18 for world average cropland, this results in a cropland footprint of 0,0835 m2gbpl per car-km.

The energy footprint for car-travel is calculated in two steps and is here illustrated in the cases of diesel, benzine and liquified petroleum gas cars.

In a first step, the energy footprint resulting from the fuel used is calculated. This is done similar to the heating fuel case (see above) and based on data from VITO and IPCC.

Diesel :
- Average fuel consumption car : 0,073 L/km
- Processing factor : 123,6%
- CO2 emission factor : 2,69 kgCO2/L
Benzine :
- Average fuel consumption car : 0,086 L/km
- Processing factor : 129,8%
- CO2 emission factor : 2,30 kgCO2/L
LPG :
- Average consumption : 0,101 L/km
- Processing factor : 119,1%
- CO2 emission factor : 1,59 kgCO2/L

Based on these data a total CO2 emission per car-km is calculated. Combined with the CO2 sequestration factor and the energy land equivalence factor, an energy footprint is calculated.

Diesel : 0,664 m2gbpl/car-km
Benzine : 0,702 m2gbpl/car-km
LPG : 0,522 m2gbpl/car-km

In a second step, an ‘uplift’ factor of 50% (Redefining Progress - Household Evaluation Spreadsheet) is applied to the energy footprint to account for :
- Production and maintenance of the car
- Construction and maintenance of road infrastructure

This results in a final energy footprint per car-km.

Diesel : 0,996 m2gbpl/car-km
Benzine : 1,053 m2gbpl/car-km
LPG : 0,783 m2gbpl/car-km

Taken together with the cropland footprint part, this results in a total ecological footprint per car-km.

Diesel : 1,08 m2gbpl/car-km
Benzine : 1,14 m2gbpl/car-km
LPG : 0,87 m2gbpl/car-km

For Milieubarometer, a global average number of 1,10 m2 per car-km was adopted, based on these numbers and the composition of the Belgian car-park.

Diesel : 54,8%
Benzine : 44,4%
LPG : 0,7%

Shared car travelling (voiture partagée)

See the calculation for individual car travelling above. The footprint result obtained for individual car travelling is divided by three and thus results in 0,37 m2gbpl per km travelled by ‘shared car’. It is supposed that people who are ‘car-pooling’ are on average with three in one car.

Fuel consumption (diesel, essence et GPL)

From an average fuel consumption for a car and a total ecological footprint per car-km, a total ecological footprint of fuel consumption is deducted.

Diesel : 14,79 m2gbpl/L
Benzine : 13,25 m2gbpl/L
LPG : 8,61 m2gbpl/L

Train travelling (train)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 passenger-train-km

0,0207
0,2033
0,22

Similar to road-transport, the cropland footprint for train-travel in Belgium is calculated as follows : the total surface of the Belgian railway infrastructure is divided by the total amount of ‘item-transport-km’, i.e passenger-km and ton-km (freight). This results in an average amount of 0,004 m2 of Belgian cropland per ‘item-transport-km’. Combined with the yield factor for Belgian cropland and the equivalence factor for world average cropland, this results in a cropland footprint of 0,0207 m2gbpl per passenger-train-km.

For the energy footprint for train-travel, the calculation relies on data from the Dutch IVEM study which reports both direct and indirect energy consumption for public transport per passenger-km. For train-transport, 0,87 MJ of direct and 0,20 MJ of indirect (construction and maintenance of railway infrastructure including trains) energy per person-km are reported. Both direct and indirect energy are accounted as ‘world-average energy mix’ because we assume that the direct energy data are concerned with primary energy, not with secondary energy such as electricity used for train transport. This means that the methodology for indirect energy is applied (see above) resulting in an energy footprint of 0,20 m2gbpl per passenger-train-km.

Taken together with the cropland footprint part, this results in a total ecological footprint of 0,22 m2gbpl per passenger-train-km.

Airplane travelling (avion)


Forest land (m2 gbpl)
Cropland (m2 gbpl)
Energy land (m2 gbpl)
Total Ecological Footprint (m2 gbpl)
1 passenger-aircraft-km


0,73
0,73

The cropland footprint for air-travel cannot be calculated because of its international character, i.e. all surfaces of all airports and landing strips should be known together with the item-transport-km worldwide. This aspect would be negligible anyway.

For the energy footprint for air-travel, the calculation relies on data from Choose Climate3 which reports both direct and indirect energy consumption for air transport. Concerning direct energy (i.e. kerosene) consumption, the following data are used for a typical aircraft such as a Boeing 747 with 370 seats and 80% of occupation :
- Consumption of 7840 kg of kerosene for 250 km take-off and landing.
- Consumption of 10,1 kg of kerosene per kilometer at cruising speed.

An energy footprint of 12,76 m2gbpl per kg kerosene is calculated from the following data regarding kerosene (VITO and IPCC) :

Kerosene :
- Processing factor : 129,8%
- CO2 emission factor : 3,597 kgCO2/kg (nearby 2,5 kgCO2/L)

For a 1000 km flight this results in 0,664 m2gbpl per passenger-aircraft-km, i.e.:

- for take-off and landing : 337,97 m2gbpl per passenger- aircraft
- for every km at cruising speed : 0,435 m2gbpl per passenger-aircraft

Finally, a 10% uplift factor, similar to the train case, is applied in order to account for construction and maintenance of air-traffic infrastructure including airplanes. This results in a total ecological footprint of 0,73 m2gbpl per passenger-aircraft-km.

It may be clear that this calculation is subject to a lot of uncertainties (i.e. aircraft type, occupation, fuel consumption,…) and this result has to be regarded as a first estimate.

Freight by water and by road (fret maritime, fret routier)

Milieubarometer does not contain footprint factors for freight.
Besides the numbers used in the ADEME report, an estimation could be done based on the Dutch RIVM study4 (Energiegebruik en emissies per vervoerwijze - Energy consumption and emissions per transport mode ; RIVM-report nr. 773002 007). In this study the following CO2 emission factors are given for different transport modes. These data include the indirect energy from the ‘processing factor’ (see ‘heating fuel’).

Delivery van : 786 gCO2/ton-km
Truck : 123 gCO2/ton-km
Train : 44 gCO2/ton-km
Inland boat / craft : 44 gCO2/ton-km

Combined with the CO2 sequestration factor and the equivalence factor for energy land, this results in the following total ecological footprint :

Delivery van : 2,15 m2gbpl/tonkm
Truck : 0,34 m2gbpl/tonkm
Train : 0,12 m2gbpl/tonkm
Inland boat / craft : 0,120 m2gbpl/tonkm

Waste

In Belgian waste statistics, only four fractions are documented : paper, metal, glass and plastics. For each of these fractions, the indirect energy input for the basic material is taken into account (datas from Redefining Progress - Household Spreadsheet). For paper, also wood consumption is taken into account. In Milieubarometer, the collected data concern the amounts of each fraction which are separately collected and thus are supposed to be 100% recycled. For plastics which are not recycled, an extra energy footprint factor is taken into account resulting from the CO2 emissions from combustion. These assumptions are “conservative estimates” because in the case that exact numbers are not available, footprint values are rather underestimate than overestimate.

Paper :

For non-recycled printed paper, following data are available :
- Indirect energy input : 100 MJ/kg
- Forest land needed to produce the pulp needed for paper : 7,01 m2/kg

This results in an ecological footprint of 28,67 m2gbpl per kg of printed paper.

For recycled printed paper, following data are available :
- Indirect energy input : 84,25 MJ/kg
- Forest land needed to produce the pulp needed for recycled paper : 1,42 m2/kg

This results in an ecological footprint of 17,97 m2gbpl per kg of recycled printed paper.

Glass :

For non-recycled glass, following data is available :
- Indirect energy input : 100 MJ/kg

This results in an ecological footprint of 19 m2gbpl per kg of non-recycled glass.

For recycled glass, following data are available :
- Indirect energy input : 84,25 MJ/kg

This results in an ecological footprint factor of 16,01 m2gbpl per kg of recycled glass.

Aluminium :

For non-recycled aluminium, following data is available :
- Indirect energy input: 250 MJ/kg

This results in an ecological footprint of 47,5 m2gbpl per kg of non-recycled aluminium.

For recycled aluminium, following data is available :
- Indirect energy input : 12,5 MJ/kg

This results in an ecological footprint of 2,4 m2gbpl per kg of recycled aluminium.

Other metals :

For non-recycled metals, following data is available :
- Indirect energy input : 60 MJ/kg

This results in an ecological footprint of 47,5 m2gbpl per kg of non-recycled metals.

For recycled metals, following data is available :
- Indirect energy input : 51 MJ/kg

This results in an ecological footprint of 47,5 m2gbpl per kg of non-recycled metals.

Plastics :

For non-recycled plastics, following data are available :
- Indirect energy input : 50 MJ/kg
- Extra CO2 emission from combustion: 3,95 kgCO2/kg

This results in an ecological footprint of 20,29 m2gbpl per kg of non-recycled plastics.

For recycled plastics, following data is available :
- Indirect energy input : 15 MJ/kg

This results in an ecological footprint of 2,85 m2gbpl per kg of non-recycled plastics.

The footprint factors used in Milieubarometer for Mixed waste (déchets en mélange) and PMD (i.e. 41,9% of Plastic bottles and flasks, 32,8% of Metal packing-material and 12,6% of Drink cartons separately collected for recycling ; Plastic - métaux) are based on statistics about the average composition of collected waste in Belgium.

Detailed calculation for CO2 emission factor :
0,019 tC/GJ * 44/12 tCO2/tC * 1000000 g/t / 1000 MJ/GJ = 69,8 gCO2/MJ

Detailed calculation for sequestration factors :
1 tC/ha / 0,72616 * 44/12 tCO2/tC = 5,049 tCO2/ha
1 / 5,049 tCO2/ha = 0,198 ha/tCO2
0,198 ha/tCO2 * 1,38 gha/ha = 0,273 gha/tC02
0,198 ha/tCO2 * 10000 m2/ha / 1000 kg/t = 1,98 m2/kgCO2

1 tC/ha / 0,72616 / 1,38 gha/ha = 0,998 tC/gha
0,998 tC/gha * 44/12 tCO2/tC = 3,66 tCO2/gha

Detailed calculation for indirect energy factor :
1 tC/ha / 0,72616 * 44/12 tCO2/tC = 5,049 tCO2/ha
5,049 tCO2/ha / 10000 m2/ha * 1000 kg/t = 0,5049 kgCO2/m2
0,5049 kgCO2/m2 / 1,38 m2gbpl/m2 = 0,3658 kgCO2/m2gbpl
0,0698 kgCO2/MJ / 0,3658 kgCO2/m2gbpl = 0,19 m2gbpl/MJ

Detailed calculation for direct energy factor :
1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 2,73 m2gbpl/kgC02
1 / 0,3658 kgCO2/m2gbpl = 2,73 m2gbpl/kgCO2

Detailed calculation for built-up area factor :
1 m2 * 2,44 * 2,18 m2gbppl/m2 = 5,32 m2gbpl/m2

Detailed calculation for soil surface factor :
88 MJ/m2 * 0,19 m2gbpl/MJ = 16,72 m2gbpl/m2

Detailed calculation for electricity factor :
0,70 kgCO2 * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 1,91 m2gbpl/kWh
0,70 kgCO2 / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 1,91 m2gbpl/kWh
0,70 kgCO2 / 0,3658 kgCO2/m2gbpl = 1,91 m2gbpl/kWh

Detailed calculation for heating fuel factor :
1,236 L * 2,688 kgCO2/L * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 9,07 m2gbpl/L
1,236 L * 2,688 kgCO2/L / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 9,07 m2gbpl/L
1,236 L * 2,688 kgCO2/L / 0,3658 kgCO2/m2gbpl = 9,07 m2gbpl/L

Detailed calculation for natural gas factor :
1,152 * 0,202 kgCO2/kWh * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 0,64 m2gbpl/kWh
1,152 * 0,202 kgCO2/kWh / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 0,64 m2gbpl/kWh
1,152 * 0,202 kgCO2/kWh / 0,3658 kgCO2/m2gbpl = 0,64 m2gbpl/kWh

Detailed calculation for tap water factor :
0,370 kgCO2/m3 * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 1,01 m2gbpl/m3
0,370 kgCO2/m3 / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 1,01 m2gbpl/m3
0,370 kgCO2/m3 / 0,3658 kgCO2/m2gbpl = 1,01 m2gbpl/m3

Detailed calculation for individual car travelling factors :
1 760 820 000 m2 / 157 705 000 000 item-transport-km = 0,0112 m2/item-transport-km
0,0112 m2/item-transport-km * 1,4 item-transport/car= 0,0157 m2/car-km
0,0157 m2/car-km * 2,44 m2/m2 * 2,18 m2gbpl/m2 = 0,0835 m2gbpl/car-km

1,236 * 0,073 L/car-km * 2,69 kgCO2/L = 0,243 kgCO2/car-km (diesel)
0,243 kgCO2/car-km * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 0,664 m2gbpl/car-km (diesel)
0,243 kgCO2/car-km / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 0,664 m2gbpl/car-km (diesel)
0,243 kgCO2/car-km / 0,3658 kgCO2/m2gbpl = 0,664 m2gbpl/car-km (diesel)

1,298 * 0,086 L/car-km * 2,30 kgCO2/L = 0,257 kgCO2/car-km (benzine)
0,257 kgCO2/car-km * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 0,702 m2gbpl/car-km (benzine)
0,257 kgCO2/car-km / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 0,702m2gbpl/car-km (benzine)
0,257 kgCO2/car-km / 0,3658 kgCO2/m2gbpl = 0,702 m2gbpl/car-km (benzine)

1,191 * 0,101 L/car-km * 1,59 kgCO2/L = 0,191 kgCO2/car-km (LPG)
0,191 kgCO2/car-km * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 0,522 m2gbpl/car-km (LPG)
0,191 kgCO2/car-km / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 0,522 m2gbpl/car-km (LPG)
0,191 kgCO2/car-km / 0,3658 kgCO2/m2gbpl = 0,522 m2gbpl/car-km (LPG)

1,5 * 0,664 m2gbpl/car-km = 0,996 m2gbpl/car-km (diesel)
1,5 * 0,702 m2gbpl/car-km = 1,053 m2gbpl/car-km (benzine)
1,5 * 0,522 m2gbpl/car-km = 0,783 m2gbpl/car-km (LPG)

0,0835 m2gbpl/car-km + 0,996 m2gbpl/car-km = 1,08 m2gbpl/car-km (diesel)
0,0835 m2gbpl/car-km + 1,053 m2gbpl/car-km = 1,14 m2gbpl/car-km (benzine)
0,0835 m2gbpl/car-km + 0,783 m2gbpl/car-km = 0,87 m2gbpl/car-km (LPG)

(1,08 m2gbpl/car-km * 0,548 + 1,14 m2gbpl/car-km * 0,444 + 0,87 m2gbpl/car-km * 0,007) = 1,10 m2gbpl/car-km

Detailed calculation for fuel consumption factors :
1,08 m2gbpl/car-km / 0,073 L/car-km = 14,79 m2gbpl/L (diesel)
1,14 m2gbpl/car-km / 0,086 L/car-km = 13,25 m2gbpl/L (benzine)
0,87 m2gbpl/car-km / 0,101 L/car-km = 8,61 m2gbpl/L (LPG)

Detailed calculation for train travelling factor :
57 420 000 m2 / 14 774 110 000 item-transport-km = 0,004 m2/item-transport-km
0,004 m2/passenger-train-km * 2,44 m2/m2 * 2,18 m2gbpl/m2 = 0,0207 m2gbpl/passenger-train-km

(0,87 MJ/passenger-train-km + 0,20 MJ/passenger-train-km) * 0,19 m2gbpl/MJ = 0,2033 m2gbpl/passenger-train-km

0,0207 m2gbpl/car-km + 0,2033 m2gbpl/car-km = 0,22 m2gbpl/passenger-train-km

Detailed calculation for airplane travelling factor :
1,298 * 3,597 kgCO2/kg = 4,67 kgCO2/kg (kerosene)
4,67 kgCO2/kg * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 12,76 m2gbpl/kg (kerosene)
4,67 kgCO2/kg / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 12,76 m2gbpl/kg (kerosene)
4,67 kgCO2/kg / 0,3658 kgCO2/m2gbpl = 12,76 m2gbpl/kg (kerosene)

(7840 kg/flight * 12,76 m2gbpl/kg) / (0,8 * 370 passenger-aircraft) = 337,97 m2gbpl/passenger-aircraft-flight
(10,1 kg/km * 12,76 m2gbpl/kg)/ (0,8 * 370 passenger-aircraft) = 0,435 m2gbpl/passenger-aircraft-km
(337,97 m2gbpl/passenger-aircraft-flight + 0,435 m2gbpl/passenger-aircraft-km * 750 km/flight) / 1000 km/flight = 0,664 m2gbpl/passenger-aircraft-km

1,10 * 0,664 m2gbpl/passenger-aircraft-km = 0,73 m2gbpl/passenger-aircraft-km

Detailed calculation for freight factors :
0,786 kgCO2/ton-km * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 2,15 m2gbpl/ton-km (van)
0,786 kgCO2/ton-km / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 2,15 m2gbpl/ton-km (van)
0,786 kgCO2/ton-km / 0,3658 kgCO2/m2gbpl = 2,15 m2gbpl/ton-km (van)

0,123 kgCO2/ton-km * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 0,34 m2gbpl/ton-km (truck)
0,123 kgCO2/ton-km / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 0,34 m2gbpl/ton-km (truck)
0,123 kgCO2/ton-km / 0,3658 kgCO2/m2gbpl = 0,34 m2gbpl/ton-km (truck)

0,044 kgCO2/ton-km * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 0,12 m2gbpl/ton-km (train / boat / craft)
0,044 kgCO2/ton-km / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 0,12 m2gbpl/ton-km (train / boat / craft)
0,044 kgCO2/ton-km / 0,3658 kgCO2/m2gbpl = 0,12 m2gbpl/ton-km (train / boat / craft)

Detailed calculation for paper factors :
100 MJ/kg * 0,19 m2gbpl/MJ = 19 m2gbpl/kg
7,01 m2/kg * 1,38 m2gbpl/m2 = 9,67 m2gbpl/kg
19 m2gbpl/kg + 9,67 m2gbpl/kg = 28,67 m2gbpl/kg

84,25 MJ/kg * 0,19 m2gbpl/MJ = 16,01 m2gbpl/kg
1,42 m2/kg * 1,38 m2gbpl/m2 = 1,96 m2gbpl/kg
16,01 m2gbpl/kg + 1,96 m2gbpl/kg = 17,97 m2gbpl/kg

Detailed calculation for glass factors :
100 MJ/kg * 0,19 m2gbpl/MJ = 19 m2gbpl/kg

84,25 MJ/kg * 0,19 m2gbpl/MJ = 16,01 m2gbpl/kg

Detailed calculation for aluminium factors :
250 MJ/kg * 0,19 m2gbpl/MJ = 47,5 m2gbpl/kg

12,5 MJ/kg * 0,19 m2gbpl/MJ = 2,4 m2gbpl/kg

Detailed calculation for metals factors :
60 MJ/kg * 0,19 m2gbpl/MJ = 11,4 m2gbpl/kg

51 MJ/kg * 0,19 m2gbpl/MJ = 9,69 m2gbpl/kg

Detailed calculation for glass factors :
50 MJ/kg * 0,19 m2gbpl/MJ = 9,5 m2gbpl/kg
3,95 kgCO2/kg * 1,98 m2/kgCO2 * 1,38 m2gbpl/m2 = 10,79 m2gbpl/kg
3,95 kgCO2/kg / 0,5049kgCO2/m2 * 1,38m2gbpl/m2 = 10,79 m2gbpl/kg
3,95 kgCO2/kg / 0,3658 kgCO2/m2gbpl = 10,79 m2gbpl/kg
9,5 m2gbpl/kg + 10,79 m2gbpl/kg = 20,29 m2gbpl/kg

15 MJ/kg * 0,19 m2gbpl/MJ = 2,85 m2gbpl/kg