The Fate of All Carbon

Guest post by David Archibald

The fate of all carbon is Davy Jones’ locker. Following the post on the imminent decline in world oil production and the effect that would have on agricultural operating costs at http://wattsupwiththat.com/2011/10/27/peak-oil-now-for-the-downslope/,

let’s have a look at what total peak fossil fuel production looks like and the effect that will have on climate. It will look something like this:

Figure 1: World Fossil Fuel Production 1800 – 2300

The figure is in millions of barrels of oil and its equivalent in energy content per annum. Peak production is in 2025. Coal production keeps rising until about 2050 but that is more than offset by the declines in oil and natural gas. China has the largest coal reserves on the planet of about one trillion tonnes. The United States is next with about 250 billion tonnes.

Figure 2: Fossil Fuel Production scaled against rate of increase of atmospheric carbon dioxide

There is high quality data on atmospheric carbon dioxide from 1959 from the Mauna Loa observatory. Plotted against the historic fossil fuel production profile, there is a good match fuel burned and what remained in the atmosphere. Carbon dioxide has a half life in the atmosphere of about five years. It is very rapidly exchanged with the biosphere and the top 100 metres of the ocean. There is almost no exchange between the atmosphere and the ocean below 100 metres. The oceans have fifty times as much carbon dioxide as the atmosphere and eventually the atmosphere will be in equilibrium with the whole ocean column instead of the top 100 metres. Note the dip in the rate of increase in 1992 associated with the cooling caused by Mt Pinatubo. Similarly, the current solar-driven cooling will be associated with a flatlining of the atmospheric carbon dioxide level as the cooling oceans will absorb more carbon dioxide.

Figure 3: Projected atmospheric carbon dioxide level 1800 – 3300

The oceans turn over every eight hundred years. So at one end of the oceanic conveyor, water in equilibrium with the current atmospheric carbon dioxide level is sinking towards Antarctica and at the other end, water in equilibrium with the pre-industrial level of carbon dioxide of about 300 ppm is coming to the surface and immediately taking carbon dioxide from the atmosphere to become in equilibrium with the current carbon dioxide level. The sum of these two effects is to take 0.25% of the carbon dioxide in the atmosphere and dissolve it in the oceans. If it weren’t for this effect, burning all the rocks we could economically burn would take the atmospheric carbon dioxide level to about 600 ppm. With it, the peak is going to be about 522 ppm in 2130.

From the current level of 390 ppm and with the heating effect of carbon dioxide being 0.1°C per 100 ppm, the consequential increase in atmospheric temperature will can look forward to may be another 0.15°C. This will simply be lost in the noise of the climate system. There is a far greater benefit. The extra 130 ppm-odd from the current level will increase agricultural productivity by 23%. So instead of the world producing 2.2 billion tonnes of grain, the same land area and water will be able to produce a further 500 million tonnes of grain. That increase would be able to sustain about 1,200 million people. Perhaps that is not a sustainable thing because the oceanic turnover will subsequently bury that aerial fertiliser in the deep oceans.

This figure also shows why higher atmospheric carbon dioxide levels have such a dramatic effect on plant growth. Plants can’t operate against the partial pressure differential between their cells and the atmosphere when the atmospheric content is below 150 ppm of carbon dioxide. During the depths of the glacials during the current ice age, which is three million years long so far, the atmospheric carbon dioxide level got as low at 172 ppm. Life above sea level came within a hair’s breadth of extinction due to lack of carbon dioxide. At the pre-industrial level of about 300 ppm, only 150 ppm was available to plants. At the expected atmospheric concentration of 522 ppm in 2130, that will be a 150% increase in useable carbon dioxide.

Figure 4: Energy Density per Litre

The next question is,”When carbon becomes rare and expensive, what will we be driving?” The future doesn’t look too bleak in that regard. As a fuel, ammonia has about half the energy density of LPG and handles like LPG in terms of the pressures and temperatures of storage. Ammonia is better than having no liquid fuel at all and can be made from nitrogen and hydrogen produced by electrolysis. The cost of electric power determines the production cost. There are credible attempts being made to produce ammonia from wind power. Electrolysis could handle the swings in power output from wind which electric grids are ill-suited to.

Figure 5: Competitive Price Ranges of Nitrogenous Fertiliser Feedstocks

It is said that half the World’s protein consumption comes from synthetically produced ammonia. Until recently, the most competitive feedstock has been natural gas. But with the natural gas price internationally linked to the oil price through the LNG market, it is being displaced by coal as the preferred feedstock. Coal-based urea plants have twice the capex of natural gas-based ones. The oil price that triggers a switch to coal is about $50 per barrel in energy equivalent terms. Above that level, coal is the preferred feedstock up to about $200 per barrel at which point wind energy may be viable and the coal has a high value use as feedstock for liquid fuels.

In the longer term, the cost of nuclear power will be the main determinant of transport and agricultural operating costs.