Environmental issues

This session introduces the main impacts of energy on the environment.

As this course does not aim to deal with all environmental issues, we only briefly analyze here those issues that could have very long consequences.

Course reference:

• Chapter 8

To follow the presentation, go to the next step

Three types of pollution

• soil pollution
• water pollution
• physicochemical origin
• nuclear origin
• air pollution
• acidification
• climate change
• radioactivity

Pollution reduction

• accidental pollution
• increase the systems’ security
• develop depollution means
• systematic pollution
• adoption of cleaner technologies
• addition of decontamination processes

Greenhouse effect

• absorption by CO₂
• λ₁ = 4.5 μm
• λ₂ = 14.5 μm
• solar radiation
• visible 0.4 – 0.8 μm

Main absorbing gases

• water vapor H₂O
• carbon dioxide CO₂
• methane CH₄
• nitrous oxide N₂O
• chlorofluorocarbons (CFC R11 and R12)
• some noble gases

Contributions to the increase of the greenhouse effect

• carbon dioxide CO₂: 77 %
• methane CH₄: 14 %
• nitrous oxide N₂O: 8 %
• chlorofluorocarbons: 1 %

Energy-related activities share

• CO₂
• combustion of fossil fuels: 74 %
• deforestation
• N₂O
• combustion of fossil fuels and biomass: 70 %
• CH₄
• fermentation of organic matter
• distribution and use of fuels: 10-30%

Distribution of greenhouse gas emissions

Mechanisms of the greenhouse effect

• many uncertainties
• interactions between clouds, oceans, and polar ice caps
• size and nature of CO₂ sources and sinks
• radiative forcing
• global warming potential (GWP)
• relative ability of a gas to participate in radiative forcing, (set at 1 for CO₂)

Global warming potential GWP

• factors taken into account for a gas
• amount of emissions
• absorption properties in the infrared
• residence time in the atmosphere (ITH)
• for complex technologies
• indirect effect corresponding to the energy consumed by the plant during its lifetime
• total equivalent warming impact (TEWI)

Evolution of greenhouse gas concentrations

Global emissions

• USA, Russia and China, are responsible for more than half the amount of CO₂ emitted worldwide
• national and international policy negotiations
• Intergovernmental Panel on Climate Change (IPCC)

Global challenge of unprecedented scale

• prospects
• steady economic growth
• 85% of energy needs are provided by fossil fuels
• → doubling of current CO₂ emissions by 2050
• major difficulty
• the strong link between CO₂ emissions and economic growth

Depletion of the ozone layer

• mechanism:
• Cl + O₃ → Cl O + O₂
• Cl O + O₃ → Cl + 2 O₂
• due to many gases, particularly CFCs
• 60% directly related to energy applications
• ozone depletion potential (ODP) = 1 for R11 (CFC)

International negotiations

• Montreal Protocol
• technological race between manufacturers
• battle between a few large industrial companies

CFC replacement fluids

• hydrochlorofluorocarbons (HCFC)
• close on the chemical level
• non-zero ODP
• hydrofluorocarbons (HFC)
• zero ODP
• main drawback: very high GWP
• non-halogenated fluids
• blends

Acid rain

• emissions of sulfur and nitrogen oxides
• energy uses responsible:
• electricity generation
• transport
• heating of facilities
• measures:
• catalytic converters for automobiles
• prior desulphurization for thermal power
• new combustion techniques

Decrease of SO₂ and NOx emissions

SO₂: dotted curve

NOx: solid curve

Environmental issues

This session provided an overview of the main impacts of energy on the environment.

Many sources of information allow you to work your way through what has been presented here.