Emissions from electricity production are the single biggest source of manmade greenhouse gas emissions that are accelerating climate change. Around two thirds of all our emissions come from energy production, and roughly a third of those are from electricity production.

The world is electrifying. Electricity can increase productivity in the developing world, and on the other hand, electricity can replace the direct burning of fuels for example in heating, transportation and industrial processes.

It makes a huge difference how this electricity is produced, and what are its lifecycle emissions.

The picture above presents the median emission values of various electricity production methods according to Intergovernmental Panel on Climate Change (IPCC 2014[i]). The values are median, so there can be great variability on individual cases, but these values can be used as a rule of thumb to when comparing electricity sources. It is obvious that methods based on burning fuels have the highest emissions.

When hydrocarbons, meaning coal, lignite, oil, peat, natural gas or even firewood are burned, the carbon in them is combined with oxygen. The result is heat and carbon dioxide, which is a greenhouse gas. Over 85 percent of our primary energy is produced by burning. Coal is the dirtiest, with median value of 820 grams of carbon dioxide per kilowatt hour of electricity produced (gCO2/kWh). One kWh or electricity is enough to heat the sauna for less than 10 minutes, or cook perhaps half an hour with an electric stove[ii]. With natural gas, the emissions are roughly half of what coal has, at 490 gCO2/kWh.

Over 85 percent of our primary energy is produced by burning

When biomass is burned, even more carbon is often released than from coal. The somewhat of a relief from climates point of view is that the carbon will be sequestered back if and when the plants regrow. The carbon released from biomass gets recycled relatively fast in the atmosphere, while the burning of fossil fuels adds new carbon to the system, carbon that was in a long term storage as fossil fuels deep underground. So while biomass is not low-carbon when burned, we have agreed that, depending on what kind of biomass is in question, it is more or less carbon neutral[iii].

As the image shows, even those sources not based on burning have some emissions, often a few percent compared with burning. These emissions come from the whole life-cycle of the power plant, and are due to the fact that they are built and maintained in a world that runs largely on fossil fuels. Materials are mined and transported with machines and vehicles that run on oil, and steel and cement manufacturing releases non-energy related emissions with current technologies that are used to produce them. The nuclear value also includes uranium mining, enrichment and fuel fabrication, transportation, decommissioning the plants, storing nuclear waste and so forth.

For practical purposes, one can assume that all the energy sources that are not based on burning are low carbon. Nuclear, hydro and wind are the lowest, as they have smallest shares of materials and other energy expenditures associated with them.

One thing that is missing from the values is the infrastructure that is needed to produce reliable energy services our society is dependent on. If that is also considered, the values for intermittently producing energy sources such as wind and solar tends to rise. They require much more additional infrastructure and facilities to ensure that the electrical grid stays stable and the lights of society stay on.

The electric grid is somewhat of a unique energy system, as it requires that production and demand stay balanced at all time. If the gap between them grows too large, appliances are at risk of breaking up and the grid could have brownouts or rolling blackouts. There are numerous mechanisms in the grid that help keep the voltage stable and within set limits in cases of fluctuations of demand or even when a power plant unexpectedly drops out for some reason. But it is also an inevitability that when the amount of variable production increases in the grid, it will become ever more challenging to follow the fluctuations of demand, sudden surprises such as power plant or connection failures and the variability or intermittent production.

Regrettably, this load-following is often done with burning natural gas or coal, as most areas do not have enough hydro power available. The problems with intermittent production start usually to manifest themselves when their combined share rises to perhaps twenty or more percent of the annual electricity production. 

Here are the rough average emissions for few countries, along with the main sources of electricity (in order of importance).

COUNTRY Emissions per kWh Main electricity sources
Norway under 50 gCO2/kWh Hydro
Sweden under 50 gCO2/kWh Hydro, nuclear, wind
Switzerland under 50 gCO2/kWh Hydro, nuclear
France around 50 gCO2/kWh Nuclear, hydro
Finland around 100 gCO2/kWh Nuclear, hydro, biomass, coal+nat.gas (mostly combined heat&power)
Denmark around 350 gCO2/kWh Wind, coal
UK around 450 gCO2/kWh Nat.gas, coal, nuclear, wind
Germany around 500 gCO2/kWh Coal, Lignite, nuclear, wind

 

References

[i] IPCC AR5 WG3 Annex III, Technology-specific cost and performance parameters, https://www.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_annex-iii.pdf. Table A.III.2, page 1335.

[ii] If the electric stove has maximum power of 2 KW per cooking plate, and it stays on maximum power all the time, it will use one kWh of electricity in 30 minutes.

[iii] This assumed carbon neutrality has been hotly debated at length on the EU level for example.