CO2 balance of large-scale electricity production: nuclear good, biogas best

A new life-cycle study prepared by Germany's Öko-Institut (Institute for Applied Ecology) looks at 16 different power systems and the greenhouse gas emissions balance as well as the cost of offsetting the CO2 emissions of the electricity generated from these systems.

The research [*German] was prepared as a working paper to guide discussions about the future of nuclear power in Europe. In many EU-member states, the issue is extremely controversial, as several governments have decided to phase out this energy source. But the twin-problems of climate change and energy security have re-opened the debate, with advocates saying nuclear power is very clean and that the benefits of the technology far outweigh the risks associated with it. The report on mitigating global warming, published recently by the Intergovernmental Panel on Climate Change, has included nuclear power as a technology that may contribute positively to strategies aimed at reducing climate-destructive emissions (earlier post). However, not withstanding the good CO2 balance of electricity from nuclear, the Öko-Institut advises against the technology for a series of reasons (see below).

Nuclear good, biogas best
The study by the Öko-Institut contains a comparison of the amount of greenhouse gases released over the entire life-cycle of 16 different power systems - wind, solar, biogas, hydropower, nuclear, natural gas and coal, in different configurations - per unit of electricity produced (see table1). Of course, renewables score very well, but nuclear does so too, emitting 6 times less CO2 than common power plants using brown coal (lignite). Most importantly, biogas used in a combined heat-and-power plant with district heating has the best balance by far and actually results in a negative emissions system. This is so when the feedstock for biogas is derived from biomass waste-streams:
bioenergy :: biofuels :: sustainability :: coal :: natural gas :: nuclear :: renewables :: wind :: solar :: biogas :: climate change :: greenhouse gas balance ::

The study did not look at 'Bio-energy with Carbon Storage' (BECS) systems, which would score even better. It does include a rather detailed calculus of the net and gross GHG balance of the different technologies, as well as a separate balance for the heat and the power part of the system (in as far as it concerns CHP and cogeneration plants).

Importantly, the study has not taken into account the greenhouse gases released during the mining, transformation and transport of the fuels and materials used in the power system (e.g. the GHG's released during the production of the materials used for the construction of wind turbines have not been taken into account, neither the emissions that enter the atmosphere when fuel is transported to power plants, etc...). But in any case, the comparison offers a basic overview of which technologies will offer the best opportunity to fight climate change.

Note that for all systems that actually 'burn' a fuel (coal, brown coal, biogas, natural gas, nuclear), combined heat and power/cogeneration systems naturally offer considerable advantages over ordinary power plants; their higher costs are largely negated by the large amount of carbon dioxide emissions they save.

Costs of offsetting carbon emissions
The report also looks at how much it would cost to offset the emissions of a particular power system. Here again, biogas scores best (apart from efficiency increases, which score even better). As table 2 (click to enlarge) indicates, brown coal, imported coal and natural gas in cogeneration plants shows a negative offsetting cost, but this is so because the baseline is coal in ordinary plants. This simply means switching to cogeneration plants is a highly cost-effective option.

The costs associated with offsetting the CO2 generated by offshore wind and nuclear power (with a balanced mix of uranium supplies), are relatively low, but for onshore wind and imported solar electricity, costs are more than three and four times as high as those for biogas.

To know the carbon offsetting costs of different technologies allows decision makers to assess whether it is worth investing in a particular power system, depending on the value of carbon (as it is set on markets like the European Emissions Trading Scheme - ETS). The other major and most obvious factor determining these decisions is simply the cost of generating electricity. Renewables have a clear disadvantage over fossil fuels and nuclear here, but the gap is closing (table 3, click to enlarge). These numbers are largely consistent with those of other studies (but note that the Öko-Institut did not take into account solid biomass, which has become quite competitive with fossil fuels - earlier post).

Depending on the evolution of carbon prices, fossil fuel prices and government incentives, we will see a smaller or larger number of large-scale renewable energy systems appear in the future.

Nuclear should be phased out
The Öko-Institut stresses that, despite the interesting CO2-balance of electricity generated from nuclear power, the technology must be phased out for a set of different reasons: (1) the risks associated with nuclear remain high, and the waste problem has not been solved, (2) uranium supplies are finite and may peak relatively soon, certainly given the fact that rapidly developing countries are investing heavily in the technology, which drives up prices and depletes uranium resources, (3) fourth generation nuclear power plants (which recycle spent fuel) are experimental and there is no clear evidence for the viability of these reactors, neither a clear assessment of their costs or a time-frame indicating when they could be realistically built, (4) finally, the potential for renewables is large enough to make the transition to a post-nuclear future.

When it comes to this potential, we only need to refer to recent studies on biogas in Europe, which estimate that the Union can produce some 500 billion cubic metres of the natural gas equivalent renewable, clean and low-carbon biomethane by 2020-30 (earlier post). This means the continent can replace all imports from Russia, or supply the energy needed to decommission a substantial number of Europe's 173 nuclear plants. Adding other (more costly) renewables like wind, solar and hydro gives us a strong enough portfolio of alternative energy sources with which to enter the post-nuclear future.

This kind of studies is important for decision makers in the Global South, who are not burdened yet by old technologies and the political lobbies that have been created around them. By making smart decisions based on historic and current data from highly industrialised nations they can 'leapfrog' straight into a cleaner, more sustainable and greener future.

More information:
Öko-Institut, Uwe R. Fritsche: Treibhausgasemissionen und Vermeidungskosten der nuk-learen, fossilen und erneuer-baren Strombereitstellung [*.pdf] - March 2007.

Öko-Institut: Studie des Öko-Instituts zeigt CO2-Bilanz von Strom auf - March 14, 2007.