Non-renewable energy sources are finite and cannot be replenished on human timescales. VCE Environmental Science requires understanding of five key non-renewable sources: oil, coal, natural gas, coal seam gas and nuclear.
Formation: Ancient plant material compressed over millions of years into carbon-rich rock.
Types: Lignite (lowest grade) → sub-bituminous → bituminous → anthracite (highest grade, most energy dense)
How it generates electricity:
1. Coal is pulverised and combusted in a boiler
2. Heat converts water to steam
3. Steam drives turbines connected to generators
Environmental impacts:
- Highest CO$_2$ emissions per kWh of any fossil fuel (~820 g CO$_2$e/kWh)
- Emits SO$_2$ (acid rain), NO$_x$, particulates (air quality and health impacts)
- Coal ash contains heavy metals and can leach into groundwater
- Open-cut mining significantly disturbs land and waterways
- Thermal pollution from cooling water discharge
Australia: Major coal exporters; coal still generates a large proportion of electricity in eastern Australia; declining as renewables expand.
Formation: Ancient marine organisms buried and transformed into hydrocarbons over millions of years.
Primary uses: Transport fuels (petrol, diesel, jet fuel), lubricants, petrochemical feedstocks — less important for electricity generation.
Environmental impacts:
- Oil spills: catastrophic marine and coastal ecosystem damage
- Combustion emits CO$_2$, NO$_x$, particulates
- Refining produces hazardous waste streams
- Drilling operations disturb sensitive ecosystems
Formation: Associated with oil deposits; primarily methane (CH$_4$) with smaller amounts of ethane, propane, butane.
How it generates electricity:
- Combined cycle gas turbine (CCGT): Gas turbine generates electricity; waste heat produces steam for a second turbine — ~55–60% efficiency (higher than coal at ~35–45%)
Environmental impacts:
- Lowest CO$_2$ emissions of fossil fuels (~490 g CO$_2$e/kWh for CCGT)
- However: fugitive methane emissions from extraction and distribution significantly increase lifecycle emissions
- CH$_4$ is ~28–36× more potent than CO$_2$ as a GHG over 100 years
What it is: Methane (CH$_4$) trapped in coal seams at depth. Extracted by drilling wells and pumping out groundwater to reduce pressure, releasing the gas.
Environmental concerns unique to CSG:
- Groundwater impacts: Dewatering coal seams can deplete or contaminate aquifers that communities rely on
- Fugitive emissions: Well leakage and equipment failure can release methane
- Land access conflicts: Wells require access across agricultural land
- Chemical use: Some operations use hydraulic fracturing (fracking) — chemical-laden water injected at high pressure to fracture rock and release gas; risk of contaminating groundwater
Australian context: Major operations in Queensland (Surat and Bowen Basins) and proposed developments in NSW — highly contested due to water security concerns.
Mechanism: Nuclear fission — uranium-235 or plutonium-239 atoms split, releasing enormous heat → steam → turbine → generator.
Environmental impacts:
- Low operational GHG emissions (~12 g CO$_2$e/kWh lifecycle — comparable to wind and solar)
- Radioactive waste: Spent fuel remains highly radioactive for thousands of years; long-term storage remains a global challenge
- Uranium mining: Environmental disruption; radioactive tailings
- Cooling water: Large volumes of water required (thermal pollution)
- Accident risk: While rare, accidents can be catastrophic (Chernobyl 1986, Fukushima 2011)
Australia: Large uranium reserves but no nuclear power plants; political and regulatory barriers; Nuclear Non-Proliferation Treaty obligations.
| Source | GHG (g CO$_2$e/kWh) | Key Advantage | Key Disadvantage |
|---|---|---|---|
| Coal | ~820 | High energy density; reliable | Highest emissions; air pollution |
| Oil | ~650 | Energy dense; versatile | Spill risk; transport sector |
| Natural gas | ~490 | Lower emissions than coal; flexible | Fugitive methane; still fossil fuel |
| Coal seam gas | ~490+ | Uses existing gas infrastructure | Groundwater risk; fugitive emissions |
| Nuclear | ~12 | Low-emission base load | Radioactive waste; high capital cost |
COMMON MISTAKE: Students often claim nuclear produces ‘no emissions’. Nuclear has very low lifecycle emissions but is not zero — uranium mining, construction and decommissioning all involve emissions. Always specify ‘low lifecycle GHG emissions’.
