On storing Carbon in Soil

There’s a fair bit of talk going on right now around the issue of so-called ‘Carbon Sequestration’ in Soil, and most of it is avoiding the key issue. This of course is that there is only one good long term storage method for Carbon in the ground, invented by mother nature some 250 million years ago when there was an awful lot of the stuff sloshing around in those swampy humid Carboniferous forests: it’s called ‘fossil fuel’.  Although this stuff is all ‘Carbon’, it’s not all the same; Coal is pure Carbon alone, whereas Natural Gas is Carbon with Hydrogen – Methane, and Oil is Carbon with Hydrogen in chains – Hydrocarbons.  Also stored by mother nature is an interloper, Carbon Dioxide, and its relative Carbon Monoxide, in varying amounts mixed with natural gas.

 One needs to know this most basic science to understand the ‘Carbon Cycle’, where Carbon is used as a means to convert energy from the sun into plant and animal bodies.  Carbon exists in the atmosphere as Carbon Dioxide, which is a stable gas and a useless one; it is the final waste product of all living processes, following its ‘combustion’ in their metabolism, or its combustion by fire. In living plants and animals, compounds containing Carbon and Hydrogen – Carbohydrates and Hydrocarbons – are the energy source necessary for life. To extract their energy they are ‘burnt’ in the body by combining them with Oxygen, so the Carbon becomes Carbon Dioxide, and the Hydrogen becomes water – Hydrogen Dioxide.

 The other side of this cycle is performed only by plants, which use ‘photosynthesis’ – solar energy – to separate the Oxygen from the Carbon Dioxide and synthesise compounds such as fats and starches….

 Why this matters  is that there is currently far too  much oxidised Carbon in the atmosphere from which all the energy has been removed, and not enough energy and space for plants to remove it to restore the balance. We desperately need to restore this balance before the increasing CO2 overheats our home, and so look for ways to ‘sequester Carbon’ in the soil and take it out of circulation. This means it must be in a form that cannot be broken down by microorganisms, or eaten by animals or termites.  While some forms of ‘organic matter’ in the soil are very slow to decompose, ecosystems require that they eventually do; the only consequence otherwise is an accumulation of carbon such as happened in the Carboniferous era, or as happens in Peat bogs, where carbon compounds are prevented from breaking down because of lack of oxygen in waterlogged ground.  There is however one exception to this – Charcoal.

While various bodies, both governments, research stations, and private businesses, all try to promote the idea of ‘Carbon Farming, or sequestration, as an opportunity and a necessity, all such schemes fall down at the first two gates.  The first of these is that all  carbon that goes into the soil through natural processes will finally come out again, with no net gain. ( unless it is charcoal as the result of fire that gets buried)

 The second gate is that Charcoal is chemically much the same as Coal. So we may go to extraordinary lengths to safely  bury Carbon as Charcoal, for instance by growing tree crops, burning them for fuel in limited oxygen, and burying the Charcoal – while in the next paddock some bloke is digging up COAL. And until we stop mining and burning coal, and mining and exporting coal to be burnt ( what else?) we are simply kidding ourselves that our efforts have the slightest effect.

Some recent reports about the subject:

Background briefing on Carbon Farming:
The World Today on the Australian Terrestrial Carbon Budget:
Abstract of Aus terrestrial carbon budget:
Abstract. This paper reports a study of the full carbon (C-CO2) budget of the Australian continent, focussing on 1990–2011 in the context of estimates over two centuries. The work is a contribution to the RECCAP (REgional Carbon Cycle Assessment and Processes) project, as one of numerous regional studies. In constructing the budget, we estimate the following component carbon fluxes: net primary production (NPP); net ecosystem production (NEP); fire; land use change (LUC); riverine export; dust export; harvest (wood, crop and livestock) and fossil fuel emissions (both territorial and non-territorial). Major biospheric fluxes were derived using BIOS2 (Haverd et al., 2012), a fine-spatial-resolution (0.05°) offline modelling environment in which predictions of CABLE (Wang et al., 2011), a sophisticated land surface model with carbon cycle, are constrained by multiple observation types.
(If this seems incomprehensible, the key to its essence is in the ‘Net ecosystem production’ – a quantity based on various models which the report explains can vary so much as to be more than Australia’s total annual emissions, depending on whether it’s wet or dry for instance. The idea contained in the WT report, that soil is currently sequestering one third of Australia’s fossil fuel emissions, is to my mind a complete fabrication, and little more than wishful thinking. In any case, as related early in Background briefing’s report, since settlement Australia has lost 70% of the carbon in it soils. SO we need to replace ALL that before we’re even back to square one!)
But that’s just my view—  David Macilwain.

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