Studies can prove whatever you want them to

Even that a cogeneration unit on natural gas can compete with nuclear energy in terms of CO₂ emissions

It is often difficult to see the wood for the trees on the present day energy landscape. There are probably as many contradictory studies being carried out on how to reduce greenhouse gas (GHG) emissions as there are on how to lose weight. If a study is published today 'proving' that a diet without potatoes is the most effective, you can be sure that tomorrow someone will launch the Potato Diet, 'losing weight by eating as many potatoes as you want!'

How green is biomass? How green are photovoltaic cells? What amount of CO₂ emissions is attributable to nuclear energy? What is the cost of nuclear energy? Is carbon capture and storage a sustainable technology? Is cogeneration green? How big are the earth’s oil reserves? You can find studies that prove any position you want take on those subjects.

Sometimes you need to read further down the text

Recently, the German Federal Department for Environment, Protection of Nature and Nuclear Reactor Safety (Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit) put out a press release in which they claimed that 'a cogeneration unit on natural gas can compete with nuclear energy in terms of CO₂ emissions'. Much further down the text, they clarify this statement. If a building or industrial installation requires 2 kWh of heat and 1 kWh of electricity, a cogeneration unit on natural gas will produce less GHG emissions than the combination of electricity from nuclear energy and heat from fuel oil. Well yes, of course.

The problem is not necessarily in the studies

This press release reveals the origin of many contradictory results. In most cases, the problem is not the credibility of the studies themselves. The differences originate from the points of departure (what exactly are you comparing?), the interpretation of the results (what do the figures actually mean?), and the way the results are communicated (what will you tell the reader and what do you withhold or downplay?).

Whether it is 'economically sound to continue with nuclear energy', for instance, depends primarily on your starting point. Do you mean to continue with existing nuclear power plants, do you want to continue building new reactors on existing nuclear sites, or do you intend to create brand new nuclear sites? Are you taking the cost of nuclear waste into account? What about the risk of a nuclear accident? The same sort of situation arises when you address the question of whether 'cogeneration is green or not'. Will all the heat from the unit be consumed? And if yes, will it be consumed locally, or will it require heat transport?

Some general principles remain

It is usually dangerous to make generalisations about specific situations. The balance can often go in one direction or another, depending on case-specific conditions.

Does this mean that there are no general statements to make at all on energy and climate change mitigation? I do not think so. The following general principles remain firm:

• By eating less you will lose weight: reducing energy consumption will reduce GHG emissions
• A varied diet is good for your health: the optimal energy solution is a mix of various technologies

And, if you dare to cast doubt on those principles, I will provide you with a dozen credible studies that prove them correct.