Addressing the carbon legacy

All around us the regulatory, investment and commercial impetus at last appears to represent a tsunami of change or 'tipping point' soon to deliver us into a low emissions, renewable energy-led future. Brilliant! While this is a critically important development and one that many passionate advocates have waited long to see (myself included), somewhere in the investment stampede the issue of 'legacy carbon' is largely being overlooked.

The issue of anthropogenic climate change in the modern area is essentially a colossal mass balance problem that has shifted carbon locked out of the biosphere for millennia in the form of fossil fuels, into the living system, at a pace that far outweighs the natural exchange of such material with the earth's crust. While solar panels, wind turbines, electric vehicles, energy efficiency or even green hydrogen avoid throwing too much fuel on the fire, so to speak, and bring us closer to a 'net zero' footprint at hopefully some point in the not too distant future, there is a whole truckload of additional material already circulating in the biosphere that by definition will continue to trap additional heat in the atmosphere until something is done to actively reduce it.

For all of the vitriolic debate, misinformation and conjecture about climate change over the last decade or so, I've never yet found someone who actually denies the existence of the greenhouse effect (though I'd not be surprised that they exist!). Remember that? It's the happy blanket of greenhouse gases in the atmosphere that over millennia has largely stabilised global mean temperature within a range that has enabled life as we know it to flourish. Without it, the average mean temperature on earth would be substantially colder at around -18C, or thereabouts, so it's somewhat difficult to argue that this is really quite an important part of our planet's regulatory system and central to human civilisation. It's a phenomenon that is quite easy to demonstrate scientifically and even a child can grasp the basic concept that if you add more blankets, then you simply trap more heat under the covers. Hence, to deny global warming as the outcome of our mass balance carbon problem, with climate change the inevitable result, is to deny the 1st Law of Thermodynamics itself.

What happens when a complex non-linear system such as the global weather system is pushed out of its comfortable range is not for me to speculate on, but there are many clever people who have built models to predict where things are headed and change is already occurring and is increasingly writ large - and the news is not good. So, with this in mind let's acknowledge that despite our best efforts and continuing innovation in clean energy and sustainability more generally, the fossil carbon genie is already out of the bottle and we'd better find a way to stuff some or all of it back in over the coming decades, or else all this innovation and momentum may be for nought.

While we arguably 'need' geological carbon capture and storage (or rather, we need the outcome, that is, reducing carbon in the biosphere), the technology, governance, development cost, engineering, CAPEX, OPEX and risk associated with delivering the abatement required on a planetary scale is difficult to comprehend. Well may it succeed in due course and I grudgingly have to admit that we probably need all options on the table right now, but it is a long way off delivering on its promise, if indeed it ever will.

Enter photosynthesis. In a sense, we don't need to invent machines to capture carbon because billions of years of evolution have already done this for us. It happens every day, predominantly in the world's oceans (as a function of sheer weight of biomass), albeit its effect is concentrated and most obvious in a range of terrestrial ecosystems, notably equatorial rainforests but also the vast forests of Canada, Scandinavia and the Russian steppes. Given that the overwhelming majority of land above water today is located in the northern hemisphere, and temperature plays a major role in the metabolic rate and activity of many organisms, we can actually see the lungs of the earth 'breathing out' in the winter (when photosynthetic activity overall is lower, leading to net greenhouse gas increase), and 'inhaling' in the warmer months (as terrestrial biomass gets active again, reducing the global concentration of CO2 in particular) - it's like looking at a global, self-regulating ECG readout on a seasonal basis.

Fast forward to the anthropocene and if there is one clear marker of the ability of the human species to impact and reshape the earth, it is has also been our ability to clear land and directly impact on this naturally occurring carbon fixation apparatus. Fortunately, the flip side of this has been the development of methods of plant husbandry, for both terrestrial and aquatic species, that have established sophisticated methods of 'industrial' photosynthesis (i.e. farming and forestry) that deliver biomass for a range of purposes, largely for food or fibre production. In addition to the still considerable remaining natural ecosystems that continuously shift carbon around the biosphere through an eternal cycle of birth, decay and rebirth, for all our faults we now possess the ability, knowledge and the systems already in place to actively manage this process ourselves.

Clearly, I am simplifying and there are of course many challenges associated with modern agriculture that are destructive and disingenuous from a climate mitigation perspective also. However, the good news is that this does not require a technical solution to be developed to achieve the primary goal of carbon fixation. Recent evolved thinking from the IEA and others is based on the same paradigm of geo-CCS albeit relates to the much-vaunted 'BECCS' (bioenergy with carbon capture and storage). This process attempts to accelerate our 'mass balance' redress by both displacing fossil fuel with bioenergy and burying the carbon emissions in geological reservoirs - conceptually sound and a step in the right direction, but practically and commercially challenging.

What is required to enable a carbon revolution and where an obvious opportunity exists, is in relation to a large-scale, distributed pyrolysis processing regime that takes managed biomass wastes that are converted to biochar, in addition to recovering energy along the way. In this way, some of the captured carbon can be 'locked' in the form of biochar, rather than being released to atmosphere through combustion or decay, and returned to the soil along with the trace elements and nutrients with it. Most importantly, beyond the host of benefits that this technique can offer to soil structure, microbial health, moisture retention, fertiliser offset, reduced NOx emissions and enhanced plant growth and productivity, there will be a proportion of this carbon that is 'non-labile' and that will stay fixed in the soil. This is in a practical sense a permanent fix that requires no technical breakthroughs and that will slowly fossilise this carbon over the coming millennia, once again returning it to the lithosphere. This is done without the risks, cost burden of ongoing management and the considerable inherent parasitic energy required to drive a geo-CCS process (regardless of the source of the carbon being sunk).

The solution for dealing with legacy carbon in our living system does exist and must be reprioritised and brought back into the dialogue - the biochar/soil carbon solution is and must be a part of the climate change solution, as it is the ONLY means we currently have at our disposal to safely 'put a cork in it'. It is scalable, low risk, achievable and affordable - in fact, it is truly 'value-adding' in all senses of the phrase and will help to reverse several hundred years of soil depletion to boot. The emergence of priority methods under the Emissions Reductions Fund in Australia relating to soil carbon are all important, and we now need to support the emergence of scalable pyrolysis technology to provide the primary conversion to biochar and to also stimulate 'formal' markets and demand for the product. Producing biochar doesn't have to be super-expensive or technically complex - it can be, by definition, quite 'agricultural'. Nevertheless, dealing with legacy carbon is fundamental to addressing what appears to be the 'baked in' impacts of climate change and can no longer be ignored.