Donnerstag, 11. Oktober 2012

Is Japan's nuclear-free pathway an environmentally friendly choice?

  By Sanghyun Hong / Prof. Barry W. Brook, Univ. of Adelaide   

On 14 September 2012, the Japanese Government considered a new policy that excited many self-proclaimed environmentalists and anti-nuclear power protestors. Following intense political wrangling, they proposed phasing out the use of nuclear power in Japan by 2040, replacing it with renewable energy (and fossil fuels). This decision, if carried through, has important environmental and financial implications that may come as a surprise to many.

The Fukushima Daiichi nuclear accident on 11 Mar 2011, caused by an earthquake-triggered tsunami, consigned the established Japanese electricity-generation plan to the dustbin. Along with it went Japan’s Kyoto-protocol commitments for greenhouse-gas mitigation.

Originally, the Japanese government had planned to increase nuclear power to 45% and renewables (including hydro) to 20% by the year 2030, up from 26% and 10% respectively in 2010. After the accident, the National Policy Unit in Japan hinted that the original plan was likely to be scrapped in favour of a new scenario, whereby the nuclear target was to be reduced to somewhere between 0–35% and the renewables target increased to 20–30%. Even with an increased share of renewables, the shift away from nuclear under any of the proposed scenarios will lead to greater use of fossil fuels.

To compare the proposed options fairly, we argue that it makes sense take a holistic view of their relative sustainability. To do this, we need to account for a range of environmental and socio-economic factors, including greenhouse-gas emissions, water consumption, land transformation, health and safety issues, and cost of electricity. One should use an evidence-based auditing method like multi-criteria decision-making analysis (MCDMA), which is transparent and relatively objective.

Our recent research (currently submitted to the journal Energy) uses MCDMA to show that even when the negative consequences of using nuclear power are properly factored in (and costs assigned to waste management, accident consequences, and so on), those scenarios with reduced nuclear power result in a less sustainable future in Japan.

In particular, the greenhouse-gas emissions of the nuclear-free scenario can reach up to about 430kg per megawatt hour. By comparison, in the 35% nuclear-power scenario, it is only 267kg per megawatt hour, in spite of the higher renewable energy share of the former. Except for the differing nuclear capacity, in all scenarios the ratio of coal to gas power had the largest influence on greenhouse-gas emissions.

Unfortunately, a high dependency on renewables without ongoing support for nuclear in Japan cannot cut the electricity generation sector’s greenhouse gas emissions unless some currently undeveloped alternative forms of cheap, large-scale energy storage are deployed in the future.

Efforts to increase the penetration of renewable energy in Japan are obviously a better pathway than a fossil-fuel-only future. However, Japan must face a number of realities.

It is not possible to supply 100% of Japan’s current electricity consumption using renewable energy, due to physical limits of generation on the densely populated island nation. As such, the nuclear-free scenario aims to replace a massive “greenhouse-gas free” energy source (nuclear), with other forms of zero-carbon energy sources (renewables). It does not seek to mitigate or displace dependence on coal, natural gas and oil.

The consequences of this choice are, obviously, losing the battle against global climate change. This is more serious than any known nuclear-power-related issues, such as waste management or accidental releases of radioactive material.

We all must understand that there is no “silver bullet” energy source which can solve all problems perfectly without any negative impacts to society and the environment. Trade-offs are, like death and taxes, inevitable.

Some examples: 
  • The life-cycle greenhouse-gas emissions of photovoltaic power are higher than nuclear power. 
  • According to RenewableUK, in United Kingdom, there had been about 1,500 wind-power-related accidents and four fatalities during 2007–2011. 
  • Manufacture of photovoltaic cells uses a mix of toxic chemicals. 
  • Wind turbines and solar thermal plants use relatively large amounts of concrete and steel per unit of electricity
  • Hydro requires massive land transformation. 
  • Intermittent renewable energy sources typically rely on natural-gas backup. 
Moreover, most countries are not able to supply 100% of their own electricity consumption from renewables due to physical limits (such as usable land that is not already dedicated to human use or for nature reserves). For instance, our Energy paper shows that Japan can theoretically meet 20–30% of their electricity consumption using non-hydro renewables. Although some countries are able to achieve a 100% renewable-powered electricity network (for example, Norway or Iceland; they both have plentiful hydro and/or near-surface geothermal resources), other forms of energy must be supplied, for heating, domestic-vehicle fuels, shipping and aviation, and industrial processes.

Even with major improvements in energy efficiency, we will need much more future electricity to manufacture synthetic fuels to replace the currently dominant role of mined liquid and gaseous hydrocarbons.

These comparisons do not mean that renewable energy is worthless, or that nuclear power is the only option. But they do illustrate the risks posed by arbitrarily closing off technology options.

To achieve a sustainable electricity network, the inherent trade-offs and workability of the whole system – now and into the future – need to be carefully balanced. Choosing one or two renewables might be helpful to reduce greenhouse gas emissions somewhat. But substituting renewables for existing and proposed nuclear, while also allowing dependence on fossil fuels to increase rather than diminish, as Japan now proposes, is irresponsible from an environmental and energy-security perspective.

Recognising this reality, talk is already emerging that the zero-nuclear policy may be shelved.

Climate change and its many consequences are arguably the greatest environmental threat facing humanity this century. Fossil-fuel combustion for electricity production is a major cause of the buildup of greenhouse gases, and its use must be mitigated heavily and eventually eliminated.

Nuclear fission, an abundant and zero-carbon energy technology, has an enormous potential to supply reliable baseload electricity and displace coal and gas power plants directly. Energy plans that expand the role of both nuclear and renewables make sense.

Policies that result in a swap of nuclear for coal and gas, and so increase emissions intensity, put us on the road to disaster.


LEXEGESE Editor's Note: The authors do not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article. They also have no relevant affiliations. This article was originally published at The Conversation. Read the original article.

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