Mon, Mar 10, 2014 - Page 9 News List

Capture and storage of carbon better than efficient use of energy

By David Hone  /  THE HAGUE, The Netherlands

Whether at UN climate-change summits or one of the many “green growth” forums, sources of renewable energy and energy efficiency are consistently regarded as the solution to global warming.

Even the coal industry adopted the efficiency line in its Warsaw Communique, released ahead of the UN’s COP19 summit in November last year.

However, a closer look at the global energy system, together with a more refined understanding of the emissions challenge, reveals that fossil fuels are likely to remain dominant throughout this century — meaning that carbon capture and storage (CCS) may well be the critical technology for mitigating climate change.

The widespread focus on efficiency and renewable energy sources stems from the dissemination of the Kaya Identity, which the Japanese economist Yoichi Kaya developed in 1993.

Kaya calculated carbon dioxide emissions by multiplying total population by per capita GDP, energy efficiency (energy use per unit of GDP) and carbon intensity (carbon dioxide per unit of energy).

Given the impracticality of winning support for proposals based on population management or limits on individual wealth, analyses using the Kaya Identity tend to bypass the first two terms, leaving energy efficiency and carbon intensity as the most important determinants of total emissions.

However, this convenient interpretation does not correspond to reality.

The rate at which carbon dioxide is being released into the ocean and atmosphere is several orders of magnitude greater than the rate at which it is returning to geological storage through processes like weathering and ocean sedimentation.

In this context, what really matters is the cumulative amount of carbon dioxide being released over time — a fact that the Intergovernmental Panel on Climate Change recognized in its recently released Fifth Assessment Report.

Since the industrial age began about 250 years ago, about 575 billion tonnes of fossil-fuel and land-fixed carbon — more than 2 trillion tonnes of carbon dioxide — have been released into the atmosphere, leading to a shift in the global heat balance and a likely 1oC increase in surface temperature (the median of a distribution of outcomes). At the current rate, a trillion tonnes of carbon, or about 2oC of warming, could be reached as early as 2040.

This view does not align with the prevailing mechanisms for measuring progress on emissions reduction, which target specific annual outcomes. While reducing the annual flow of emissions by, say, 2050 would be a positive step, it does not necessarily guarantee success in limiting the eventual rise in global temperature.

From a climate perspective, the temperature rise over time is arguably more a function of the size of the fossil-fuel resource base and the efficiency of extraction at a given energy price.

As supply-chain efficiency increases, so does the eventual extraction and use of resources and, ultimately, the accumulation of carbon dioxide in the atmosphere. This means that efficiency may drive, not limit, the increase in emissions.

Since the Industrial Revolution, efficiency through innovation has revolutionized just a handful of core energy-conversion inventions: the internal combustion engine, the electric motor, the light bulb, the gas turbine, the steam engine and, more recently, the electronic circuit.

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