In my original analysis of the new government’s Direct Action Plan (DAP), I relied upon tree sequestration for two reasons; firstly, it’s easier to visualise than soil sequestration and secondly, because the science is fairly uncertain with soil sequestration, there is a reasonable chance that trees will be employed to make up the numbers.
Yet, this remains the only real rebuttal I’ve faced with this analysis; DAP isn’t relying on wood harvest.
I’ve mused over this problem since and finally, I’ve come up with a reasonable solution; I’ll represent carbon simply as carbon.
The Graphite Tower
Graphite is probably the closest relevant form of carbon, at around 2.16 grams per cubic cm (range between 2.09g and 2.23g per cm3, which is equivalent to 2.16 tonnes per cubic metre.
Page 16 of DAP states that the plan aims to sequester 85 million tonnes of carbon annually by 2020. Dividing this number by the weight of a cubic metre of graphite, we are left with an annual target of carbon that amounts to 39.4 million cubic metres of graphite.
As one solid cube, the sides of this carbon block would be about 340m long.
If represented as a tower with a large, yet reasonable footprint of 70m by 80m, this tower would need to more than 6.6km high of solid graphite to represent the annual target set within DAP.
This is still a little abstract. We are unlikely to ever see a block or a tower so large.
Let’s think about it as graphite cubes the same size as sugar cubes.
Do you take one or two…?
A sugar cube is roughly 1.7cm on any side, with a volume of 4.9cm3. A graphite cube of this size would weigh 10.61grams.
To meet the annual soil sequestration target of 85 million tonnes of carbon as set out by DAP, we would need to bury more than 8,000 billion sugar cube sized blocks of graphite.
The Australian Bureau of Statistics projects an Australian population of around 28 million by 2020 (ABS 3222.0). If each man, woman and child did their equal bit to meet this annual target, they would individually bury over 750 sugar cube sized graphite blocks, at a weight of just over 8kg each and every day. For their efforts, DAP would reward them with about 8 cents each day for the 8kg of carbon they buried (meaning that it would take close to 2 months to save enough for a coffee).
Of course, this will not come down to each person, but rather farmers that can meet this challenge.
Assuming we had a million carbon farmers by 2020, each one would need to bury over 21 thousand sugar cube sized graphite blocks each and every day, roughly 232.7kg, and make $2.33 per day for their efforts.
Please hear me out…
This and my previous analysis of DAP are not designed to attack the merit of DAP at all. The targets are reasonable and it is good news to see the Coalition looking into environmental conservation early into their term in power.
My efforts are designed to point out that such targets inherently demand a huge and ongoing effort by stakeholders.
What is lacking from the conversation are the mechanisms and methodologies that the government plan to use to reach soil sequestration targets akin to every Aussie manually burying more than 8kg of carbon each and every day.
It also highlights another concern; holding capacity. Will the given sequestration method ensure ongoing storage of the carbon or will it eventually degrade and be returned to the atmosphere? If so, how long before it does and will we really be better off in the long run?
Relying upon environments is troublesome as well. For one thing, as noted in my initial analysis of DAP, environments are likely to change in their monthly sequestration amounts and if they are mature, the amount of carbon is likely to remain more or less stable, meaning less and less to the sequestration project.
Taking my own experience with an arid site which is in the state of recovery and assuming the average daily sequestration value is 1.5grams per m2, to meet even the per person target of 8kg per day, you would need an area of 5541m2, around half a hectare of mallee woodland. This is of course, only 1/28 millionth of the annual requirement (admitting that other environments would provide higher annual yield).
And what happens if we have a large bush fire or the area “matures”?
How will this government climb the 6.6km tower each and every year? That is the question I cannot answer and have yet to find answered in DAP or elsewhere.