The ImPACT equation

The ImPACT equation gives a simple mathematical expression of the different factors that contribute to environmental impact, and the actions that people can take to reduce the impact. The equation reads:

Im = P x A x C x T,

with

Im = the environmental Impact of the consumption activity of a population

P = the Population size: the number of People performing the activity

A = the Activity factor: the Amount of useful consumption units consumed per person. Useful consumption refers to the consumption of something useful: distance travelled, heat, light, print jobs, food…

C = the Coefficient of environmental impact: the average impact per unit of primary Consumption. Primary consumption refers to the consumption of something basic: energy, water, paper, crops…

T = the Transfer efficiency or Technology efficiency factor: the average amount of primary consumption units per useful consumption unit. A primary consumption quantity is transferred into a useful consumption quantity, and this factor measures the efficiency of this transformation process.

These four factors indicate four different strategies to lower the environmental impact of a group of people. The ImPACT equation says that People can ACT, where ACT refers to three different kinds of actions that individuals can take (reducing the three factors A, C and T). The fourth possible strategy is the reduction of the population size P: stopping overpopulation by e.g. investing in fair conditions for voluntary pregnancy limitation (education, access to means of family planning, women rights,…).

Some examples will clarify the ImPACT expression.

Travelling (energy consumption)

CO2-emission = number of persons x kilometer travelled per person x CO2-emission per energy consumed x energy consumed/km

To reduce these CO2-emissions, there are four strategies.

1) reduce population size

2) reduce the number of kilometers travelled per person, by avoiding unnecessary travel, planning and combining movements, increasing the number of people in vehicle (carpooling and use of public transport),…

3) reduce CO2-emissions (from the burning of fossil fuels), by taking bike or sailboat (instead of internal combustion engine vehicles), driving electric cars using renewable energy,…

4) reduce energy consumed per kilometer travelled, by increasing the (engine, aerodynamic,…) efficiency of cars,…

Lighting (energy consumption)

            CO2-emission = number of persons x light hours per person x CO2-emission per energy consumed x energy consumed per light hours

The four strategies for impact reduction are

1) reduce population size

2) reduce light hours per person, by reducing the amount of light (turning off some light bulbs), reducing the amount of hours (switching off unnecessary lights), sharing lightened rooms with other people

3) reduce CO2-emissions per energy consumed, by using green electricity

4) reduce energy consumed per light hours, by using eco-efficient light bulbs,…

Heating (energy consumption)

            CO2-emissions  = number of persons x degree hours per person x CO2-emissions per energy consumed x energy consumed per degree days

The four strategies for impact reduction are

1) reduce population size

2) reduce degree hours per person, by reducing the temperature (lowering the thermostat), reducing the number of hours (turning off heating when leaving room), sharing heated rooms with other people

3) reduce CO2-emissions per energy consumed, by using soar heating, natural gas instead of coal,…

4) reduce energy consumed per degree hours, by insulating houses, using efficient heating installation…

Washing (water consumption)

            Drinking water consumption = number of persons x number of washes per person x                         amount of drinking water per water used x water used per wash

The four strategies for impact reduction are

1) reduce population size

2) reduce washes per person, by avoiding unnecessary washes, sharing washes with other people,..

3) reduce drinking water per water consumed, by using rainwater

4) reduce water used per wash by using water efficient machines, hand wash, avoid unnecessary rinsing,…

Printing (paper consumption)

            Deforestation = number of persons x number of print jobs per person x                         deforestation per kg paper used x kg paper used per print job

The four strategies for impact reduction are

1) reduce population size

2) reduce number of print jobs, by avoiding unnecessary printing

3) reduce deforestation per kg paper used, by using recycled paper

4) reduce amount of paper used per print job, by printing double sided, using smaller font size, rescale format, re-use paper…

Eating (food consumption)

Land occupation = number of persons x amount of food eaten per person x land use per kg food produced x kg food produced per kg food eaten

The four strategies for impact reduction are

1) reduce population size

2) reduce amount of food eaten, by avoiding sweets, oversized portions,…

3) reduce land use per kg food produced, by avoiding animal products, refined products (sugar, refined grains,…), oils and fats, low yield crops,…

4) reduce food produced per kg food eaten, by avoiding food waste

The three ACT strategies refer to the three E’s and three R’s of energy and resource use.

Energy use and emissions (of CO2,…)

A = Reduce energy consumption – Energy sufficiency

C = Renewable energy – Energy change

T = Refine energy consumption – Energy efficiency

This is the ‘trias energetica’

Resource use (or water use)

A = Reduce

C = Recycle (or Rainwater use)

T = Re-use

These are the 3 R’s of the waste hierarchy.

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