The Recession may be Good for the Planet

The Recession May be Good for the Planet First published in my ‘Topical Science’ column in ‘The Westmeath Independent’ in 2012.

The month just ending may be the coldest December we have had in Ireland in living memory; nevertheless, on a global scale, 2011 is one of the three hottest years since records began. While northern Europe has had an unusually cold spell in the past month, the summer months saw an unprecedented heat wave. Remember those wild fires in Russia? When we have exceptionally cold weather, we tend to forget it is only a temporary blip in the overall upward trend of global warming, so we still need to watch our carbon footprint and try to reduce greenhouse gas emissions. As it happens, the recession is doing just that!

In October, the Environmental Protection Agency published provisional figures for greenhouse gas emissions in Ireland during the year 2009, which are estimated to come to a total of 63.32 million tonnes of carbon dioxide equivalent.

(Mt CO2 eq.) This figure is 7.9% lower than the 2008 emissions and the EPA attributes the reduction to the downturn in the economy. The biggest decrease was in the industrial & commercial sector, whose emissions are down by 20%.

Not surprisingly, within this sector, the cement industry showed the most dramatic decrease. Reports, which have been published annually by the EPA since 2005, show that CO2 emissions from the cement sector peaked in 2007, decreased by 11% between 2007 & 2008 and showed a huge drop of 38% or 1.3 Mt CO2 eq., between 2008 and 2009. Other sectors (energy, transport, residential, waste and agriculture) all showed some reductions, though less dramatic, in their CO2 emissions. Agriculture is still Ireland’s biggest contributor to greenhouse gases, but it showed only a slight reduction of 1.5% on the previous year. Agriculture contributed a whopping 29.1% of the total emissions in 2009, while Transport and energy shared second place at 21.1% each. The emissions from agriculture are mainly methane and nitrous oxide, but these are converted to CO2 equivalents for reporting purposes.

As far as reducing our contribution to global warming and meeting our commitments under the Kyoto Protocol are concerned, the reduction in greenhouse gas emissions is good news. Under the protocol, Ireland’s total greenhouse gas emissions for the five­year period from the start of 2008 to the end of 2012 must be below 314.18 Mt CO2 eq. This gives us an average limit of 62.84 million tonnes of carbon dioxide equivalents per year. This limit was actually exceeded in 2008, when the total emissions came to 67.68 Mt CO2 eq., but the total for 2009, at 62.32 million tonnes, is just under the limit. So if the

present trend continues, we are on track to stay within the limit. However, we should not rely on the economic downturn to ensure compliance with Kyoto and after all, we do hope that our economy will improve over the next few years! So steps need to be taken to ensure more efficient energy usage, a switch to renewable sources of energy where possible and different farming practices.

It should be pointed out that carbon dioxide is a natural component of our atmosphere and a vital necessity of life. Without it, our planet would be too cold to support life as we know it and there would be no photosynthesis by green plants and therefore no food supply. But the rising levels of atmospheric CO2, which have been observed in recent decades, are a cause for concern. Even though this gas accounts for only about one­third of one percent, by volume, of dry air, it warms our atmosphere because of the way in which it interacts with infrared radiation.

Carbon dioxide, methane, nitrous oxide and other ‘greenhouse gases’ are so­ called by analogy with the mechanism which operates in a greenhouse. To understand how this works, an elementary knowledge of ‘black body radiation’ (a concept encountered by students of physics) may help. A Black Body is a perfect absorber, because it absorbs radiation at all wavelengths of the electromagnetic spectrum. It looks black to our eyes, because all the colours of the visible spectrum are absorbed. But this spectrum also covers a huge range of frequencies which our eyes cannot detect, from the low energy, long wave radio waves, through microwaves, Infrared and visible radiation and on to ultraviolet, X­ray, and gamma­ray wavelengths. A black body emits energy at all wavelengths of the spectrum. But the intensity of the emission is not the same at all wavelengths and the pattern of emission depends on the temperature. Very hot bodies, such as the stars and our sun, have their maximum emission intensity in the ultraviolet and visible regions of the spectrum. To take an example of an object at a somewhat lower temperature, consider a poker, left in the fire. After a while it will glow red­hot, but not white­hot, showing that it is not radiating the higher­energy light waves, but only the longer wavelength, less energetic, red light. If a red hot poker is taken out of the fire and allowed to cool for a few minutes, it will cease glowing, as it is no longer emitting in the visible region of the spectrum, due to the lower temperature. However, if you bring your hand near it, you will feel the heat, showing that it is still radiating infrared (IR) energy which is invisible to our eyes, though we can sense it as heat. The earth itself, at a still lower temperature than the red­hot poker, behaves as a black body, with the maximum of its emission also occurring as IR radiation, though at longer wavelengths than the hot poker.

The glass of a greenhouse is transparent to visible light and so the sun’s energy in the visible part of the spectrum can pass right through the glass to be

absorbed by plants and the soil in the greenhouse. When they, in turn radiate energy, the maximum emission intensity will be in the infrared (IR). This energy becomes trapped in the greenhouse, as the glass does not transmit IR rays. If a car is parked in bright sunlight for a few hours, it traps heat in a similar way.

Carbon dioxide and other greenhouse gases in the atmosphere, such as methane (CH4) and nitrous oxide (N2O) produce a similar effect to that of glass.

Most of the sun’s harmful ultraviolet (UV) rays are filtered out by the ozone layer in the upper atmosphere, but the visible light rays penetrate through the atmosphere to reach ground level, where they warm the earth. This is possible because all of the naturally occurring atmospheric gases are transparent to visible light. The two major components of the atmosphere, oxygen and nitrogen, are transparent to Infrared radiation as well. This is because oxygen and nitrogen are elements with a very simple molecular structure. Their molecules contain two identical atoms; the molecular formula of nitrogen is N2 and that of oxygen is O2. The electron density is distributed in a symmetrical fashion in the molecules and so their vibrations do not interact with electromagnetic radiation at IR frequencies. If oxygen and nitrogen were the only gases present in our atmosphere, the IR radiation emitted by the earth would escape into space and the earth would be much colder than it is. However, the so­called ‘greenhouse’ gases are compounds rather than elements and are capable of absorbing infrared radiation because of the particular way in which their molecules vibrate, thus trapping the energy and warming the atmosphere in the process. As mentioned already, this has beneficial effects for life on earth, but too much warming could cause major climate change, melting of polar ice caps, rising sea levels and extensive flooding. So it is sensible to limit the emission of excessive amounts of greenhouse gases and this is what the Kyoto Protocol seeks to achieve.

It can be done; for example, Lagan Cement, based near Kinnegad, received an environmental excellence award earlier this year for significantly reducing their carbon footprint by substituting a portion of its non­renewable fossil fuel with green energy derived from solid recovered fuel.

Let us all try to use energy more efficiently, so that even when the economy begins to recover, as we hope it will, our greenhouse gas emissions stay within the Kyoto limits.