I wish GADS would have stuck with his hesitation, without displaying his ignorance of basic chemistry and the global gas cycles in defence of his precious fossil fuels. Let me elucidate:
Carbon (C), the fourth most abundant element in the Universe, after hydrogen (H), helium (He), and oxygen (O), is the building block of life. It’s the basic element that anchors all organic substances, from fossil fuels to DNA. On Earth, carbon cycles through the land, ocean, atmosphere, and the Earth’s interior in a major biogeochemical cycle (the circulation of chemical components through the biosphere from or to the lithosphere, atmosphere, and hydrosphere).
The global carbon cycle can be divided into two categories: the geological/ancient, which operates over large time scales (millions of years), and the biological/modern, which operates at shorter time scales (days to thousands of years).
The Global Carbon Stock
The Global Carbon Stock began billions of years ago, as planetesimals (small bodies that formed from the solar nebula) and carbon-containing meteorites bombarded our planet’s surface, steadily increasing the planet’s Carbon content. Today such increments to the planet’s Carbon stock have ceased, but the stock has become more compartmentalised.
Since those times, carbonic acid (a weak acid derived from the reaction between atmospheric carbon dioxide [CO2] and water) has slowly but continuously combined with calcium and magnesium in the Earth’s crust, to form insoluble carbonates (carbon-containing chemical compounds) through a process called weathering. Then, through the process of erosion, the carbonates are washed into the ocean and eventually settle to the bottom. The cycle continues as these materials are drawn into Earth’s mantle by subduction (a process in which one lithospheric plate descends beneath another, often as a result of folding or faulting of the mantle) at the edges of continental plates. The carbon is then returned to the atmosphere as carbon dioxide during volcanic eruptions.
The balance between weathering, subduction, and volcanism controls atmospheric carbon dioxide concentrations over time periods of hundreds of millions of years. The oldest geologic sediments suggest that, before life evolved, the concentration of atmospheric carbon dioxide may have been one-hundred times that of the present, providing a very different atmosphere and substantial greenhouse effect.
Fossil Carbon
The operation of life has been clearly demonstrated to change the chemistry of that atmosphere to what it is today. One of the most active agents of this change were oceanic plankton, photosynthetic microscopic phytoplankton that produce prodigious quantities of oxygen and biomass over time. Oxygen is released to the atmosphere and the biomass is consumed by respiring zooplankton (microscopic marine animals) within a matter of days or weeks. Only small amounts of residual carbon from these plankton settle out to the ocean bottom at any given time, but over long periods of time this process represents a significant removal of Carbon from the atmosphere. This slow removal of Carbon from the primary atmosphere into the fossil reservoir, while at the same time creating an atmospheric reservoir of oxygen, had a major effect on the maintenance of biotic homeostasis.
A similar process was repeated on the land, especially at Devonian times with the huge vegetation mass that covered the earth absorbing Carbon Dioxide, and then being mineralised in the lithosphere into coal, effectively removing that volume of carbon from earth’s atmosphere. The Oxygen released by these early prodigious forests contributed greatly to the current chemistry of the atmosphere.
Through this process, still active today, Carbon that enters the Lithosphere is removed completely from the biological cycle and becomes mineralised into cycles with ages of 100’s of millions of years.
The modern carbon cycle
On land, the major exchange of carbon with the atmosphere results from photosynthesis and respiration. During the daytime in the growing season, leaves absorb sunlight and take up carbon dioxide from the atmosphere. In the oceans, the planktonic cycle operates a similar photosynthetic cycle. Both create biomass. In parallel, plants, animals and substrate microbes consume this carbon as organic matter and return carbon dioxide to the atmosphere. When conditions are too cold or too dry, photosynthesis and respiration cease along with the movement of carbon between the atmosphere and the land surface. The amounts of carbon that move from the atmosphere through photosynthesis, respiration, and back to the atmosphere are large, and produce oscillations in atmospheric carbon dioxide concentrations. Over the course of a year, these biological fluxes of carbon are over ten times greater than the amount of carbon introduced to the atmosphere by fossil fuel burning. However, the fluxing carbon was a part of the biosphere and the Carbon that flowed in the biosphere had a very significant chemical signature of carbon isotopes, the ratio of 13C to 12C. This fluxing of biotic carbon happens in cycles of a few days to thousands of years, but maintains the same isotope ratio. It also maintains a quantity of the rare unstable isotope 14C. All carbon that lacks 14C or has a lower 13C/12C ratio does not belong in the modern or biotic cycle.
Today, sequestration seems to have taken the meaning of the ‘act of sequestration’ more than the ‘product of sequestration’. Most models on carbon sequestration examine growing plantations as opposed to maintaining established forest stocks. The equation is simple and straightforward; the carbon that is tied up in the biological cycles of the planet has value as sequestered carbon. The time horizon that the carbon can be sequestered for, contributes to the value of this stock. So that while the carbon fixed by a Wheatfield has a value because it sequesters carbon, this value is low because it can only sequester it for a time horizon under one year. By contrast a forest or peat bog represents a carbon stock that has time horizons of hundreds or thousands of years and has much higher sequestering values. However, there is no biological process that can sequester carbon for periods exceeding 100 million years, except through fossilisation.
So. the bottom line is this: “Whatever is said, there is no scientifically valid technology by which fossil carbon can be locked up for millions of years using biological processes. The use of carbon dioxide in photosynthesis to justify burning coal is a cheat, as pointed out above.
Please stop defending fossil fuels,they are biospheric toxins and will poison the planet ruin our children’s future!
RANIL SENANAYAKE
