Technology, environment and society
If the population grows 0.8% per year and output per person 2%, halving emissions in 25 years requires energy and carbon per unit of output to fall by more than 5% per year.
01A two-way relationship
Technology is not neutral with respect to the environment: every technique changes which resources are extracted, what energy is used and what waste is generated. But it does not determine it alone either: the impact depends on how many people use it, how much they consume and what decisions societies make about it. The steam engine, electrification, the automobile and the mobile phone changed production, cities and the relationship with the environment all at once. The ethical and social framework of the profession was covered in sustainable development and in social impact, in Engineering and Society.
02The IPAT identity
Paul Ehrlich and John Holdren proposed in 1971 to break environmental impact down into three factors:
Applied to carbon dioxide emissions, the decomposition is known as the Kaya identity:
03Efficiency, rebound and decoupling
Improving efficiency does not guarantee consuming less. William Stanley Jevons observed in 1865 that more efficient steam engines increased coal consumption in England, because they made new uses profitable: this is the Jevons paradox. In a milder form, the rebound effect says that part of the savings from an efficiency improvement is lost because the service becomes cheaper and is used more. LED lighting consumes far less per lumen, and more spaces are lit for longer.
We speak of decoupling when output grows and impact does not follow. It is relative if the impact grows more slowly than output, and absolute if it falls while output grows. Only absolute decoupling reduces the harm.
The emissions of a country in an index that equals 100 in 2025, projected to 2050 with constant annual rates for each factor. The dotted line is a target of halving emissions.
04Assessing technologies
Faced with a new technology there are questions that engineering can answer with data: how much energy and materials it consumes over its whole life cycle, what waste it leaves, who benefits and who is harmed, what happens if it spreads widely. Technology assessment and the precautionary principle, which asks that protective measures not be postponed for lack of scientific certainty when there is a risk of serious harm, are the institutional tools for doing so before the effects become irreversible. The precautionary principle appears in the 1992 Rio Declaration and in Argentina’s General Environmental Law, which is covered in the unit on the environmental legal framework.
05In the laboratory
Look up in public energy and emissions databases the four Kaya factors for Argentina for two years a decade apart and calculate the contribution of each one to the change in emissions.
Estimate the energy that the lighting of a house used with incandescent lamps and the energy it uses today with LEDs, counting the number of light points and the hours of use.
Discuss in a group a recent electronic technology using the three IPAT factors: who uses it, how much they use it and how much impact each use has.
06Common mistakes
- Believing that efficiency alone reduces impact. The rebound can offset it.
- Confusing relative with absolute decoupling. Emissions growing less than GDP does not mean they fall.
- Reading IPAT as a causal model. It is an identity: the factors influence each other.
- Attributing the whole problem to a single factor. Population, consumption and technology act together.
07Self-assessment
Which two factors of the Kaya identity depend on technology?
The energy intensity of output and the carbon intensity of energy.
At what annual rate must emissions fall to be halved in 25 years?
\( 0.5^{1/25} - 1 \approx -2.7 \) % per year.
What is the Jevons paradox?
That an efficiency improvement can increase the total consumption of the resource, because it makes its use cheaper.
What is the difference between relative and absolute decoupling?
In relative decoupling the impact grows more slowly than output; in absolute decoupling it falls while output grows.
08Further reading
- Vaclav Smil. Energy and Civilization: A History. MIT Press, 2017. The history of humanity told through energy sources and their consequences.
- Tim Jackson. Prosperity without Growth: Economics for a Finite Planet. Earthscan, 2009. Spanish edition: “Prosperidad sin crecimiento”, Icaria, 2011. Decoupling analyzed with the IPAT identity, and its limits.
- Langdon Winner. The Whale and the Reactor: A Search for Limits in an Age of High Technology. University of Chicago Press, 1986. Spanish edition: “La ballena y el reactor”, Gedisa, 1987. A classic on the political dimension of technological decisions.