Fossiilisisuus

Fossiilisisuus is a concept used to describe the degree to which a system—such as an economy, a sector, or a technology—depends on fossil fuels or fossil-based processes. It encompasses both the energy mix and the broader industrial structure that relies on carbon-intensive inputs and emissions. A high fossiilisisuus indicates substantial use of coal, oil, or natural gas and often greater exposure to fossil fuel price volatility and supply disruptions. A low fossiilisisuus suggests a transition toward low-carbon energy sources and decarbonized technologies.

The term is derived from the Finnish words fossiili "fossil" and -isuus indicating a state or quality, with the infix -sis- forming the compound noun. In practice, the term is often used alongside related concept fossil dependence or fossil reliance.

Measurement and analysis typically focus on the share of final energy consumption derived from fossil fuels, the carbon intensity of the energy supply, and the dependence on imported fossil fuels. Data come from energy balances, environmental accounts, and policy assessments. The concept is used in energy policy, climate planning, and corporate sustainability to identify transition needs and risks.

Policy implications include reducing fossiilisisuus through electrification, energy efficiency, diversification of energy sources, and the deployment of renewable energy and low-carbon technologies. Decarbonization strategies aim to lower the fossilisisuus of transport, heating, and industry while maintaining energy security.

See also: fossil fuels, energy transition, decarbonization, energy mix, carbon intensity.