Architects memo no. 119: May 2015
carbon footprints - do they come in half sizes?

Carbon was one of the many materials formed after the ‘Big Bang’ and our planet got its allotted share when it aggregated and cooled into this rocky mass and, give or take a few possible gains due to meteor strikes, our allotment remains the same.

Because of the nature of the carbon atom, it became the principal building unit of life and, since the great ‘Oxygen Disaster’ of the Archean age, carbon dioxide (CO2) has been its vector. The great driving reaction of photosynthesis combines water and CO2 from the atmosphere to form complex carbohydrates, which is the basis of plant life and, of course, the complex food chain that eventually relies on plants for their survival.

At the death of the organism, putrefaction leads to its breakdown; returning it to its most basic molecular structure and releasing CO2 back into the atmosphere, where it once more becomes available for photosynthesis. This is the renowned ‘Carbon Cycle’, which school children are always taught in science class.

CO2 does not only take part in the photosynthesis; its mildly acidic nature leads it to react with alkali metals to form carbonates and bicarbonates. Soluble salts such as sodium bicarbonate readily re-releases the CO2 but metals, such as calcium and magnesium, sequester CO2 for very long terms.

Dig out a chunk of the Takaka hills and the almost pure calcium carbonate that comprises the marble spall contains 44% CO2 by weight. Likewise the chalk in the white cliffs of Dover and all of the limestone, dolomite and calcite deposits around the world.

This process of sequestering CO2 into the (relatively) insoluble rock continues with crustacean life; coral reef growth and the hydrolysis of ‘new’ calcium and magnesium containing rocks spewed up from the magma, such as has recently occurred in the formation of new islands off the coast of Tonga.

Another quirk of nature has seen vast quantities of carbon buried under the earth by natural events. Buried trees and other vegetation have formed coal, lignite and peat deposits while other smaller species, often marine, formed oil and gas. All of these ‘fossil fuels’ were once on the surface of the earth, enriching the biosphere and participating in photosynthesis and the carbon cycle.

Continued loss of carbon in this manner would obviously lead to loss of life as we know it. It has been suggested that CO2 levels of 180ppm (as has occurred during ice ages) compromise photosynthesis, which may lose complete viability at levels of 150ppm. The pre-industrial age levels of 300ppm were looking decidedly low.

Fortuitously, the bi-pedal infestation of earth known as man, quite selfishly and unknowingly, started the process of returning all of this precious, lost, carbon back into the biosphere. The ‘little ice age’ has been put firmly behind us as has the feared ‘mini’ ice age of the 60s and 70s. Warmth, unlike cold, has always been associated with burgeoning life.

The recent publication of the results of a 10 year survey of satellite data, co-led by Professor Albert van Dijk of the Australian National University, indicates surging plant growth – growth, he says, which more than compensated for the de-forestation taking place around the world in what he delightfully says “reflects a virtuous cycle in the warming climate.”

Climate has always changed for reasons not always known to us – the Antarctic was once tropical and the Sahara Desert shows glaciation marks. Smart as we are, it is probably a little too early in the piece for mankind to be considering bending the climate to its will!

Of course, it behoves us all not to be profligate with our resources but to husband them wisely. In Resene’s case, that continues to be to make paints and coatings in an ever smarter manner; increasing performance while reducing our impact on non-renewable raw materials, smarter use of energy in manufacture and distribution and the minimisation of waste.

But still we want to eat strawberries in August!

by Colin Gooch, Resene Technical Director

Download as a pdf. (You will need Acrobat Reader).

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