Posts Tagged ‘Carbon’

There’s carbon and there is organic

August 19, 2020

Organic chemistry is the study of the structure, properties, composition, reactions, and preparation of compounds containing carbon.

Carbon, at 4,600 ppm (by mass) is the 4th most abundant element in the Milky Way galaxy after Hydrogen, Helium and Oxygen.

The abundance of the element Carbon on Earth is not accurately known and estimates vary from 300 ppm to 1,800 ppm (by mass). 

For historical, but no good logical, reasons, some carbon-containing compounds (e.g., carbonate anion salts carbon dioxide and cyanide salts), are not classified as organic compounds.

The most abundant organic compounds on Earth are the carbohydrates, and Cellulose is the most plentiful of the carbohydrates.

Carbon is the primary component of all known life on Earth, representing approximately 45–50% of all dry biomass. 

Carbon chauvinism is the assumption that if life exists elsewhere in the Universe, it will also be carbon-based.

All fossil fuels are organic compounds containing carbon.

And then there is organic farming.

 


 

Biofuels produce twice as much carbon dioxide per kWh as natural gas

October 31, 2013

Of course, carbon dioxide is proving to be of much less importance to global warming than the alarmists would have us believe. Sharply increasing carbon dioxide concentrations have had no impact on global temperatures for the last 17 – 18 years and the supposed link between man-made carbon dioxide emissions and global temperatures is looking very shaky.

It has been another “feel-good” assumption that burning wood, peat, bioethanol and biofuels in general are “carbon neutral”. But that is just wishful thinking. “… only about half as much CO2 per kWh is released when using natural gas rather than wood”.

“Both this and the original method used models of the forest. Models are by definition simplifications. The simplifications a researcher makes will vary according to the issues at hand, the questions being asked. You realise how much earlier analyses have oversimplified things when more refined models yield completely different answers.” 

ScienceNordic reports that scientists from the Cicero Centre for Climate Research and the Norwegian University of Science and Technology used a new method for quantifying the contributions of bioenergy to global warming as compared to fossil energy such as oil and gas.

But further research now indicates that the real climate effect of wood burning is less advantageous.

“By refining their method I determined that the emission of one kg of CO2 from biomass is the equivalent of about 1.25 to 1.5 kg fossil CO2.  So it’s much higher and less climate friendly,” says Bjart Holtsmark, a researcher at Statistics Norway.

In other words, if Holtsmark’s calculations are correct, the climate impact of using slow-growing forest wood for fuel is greater than the burning of fossil fuel, given a 100-year time frame.

Holtsmark says that the original method failed to account for how logging leaves behind dead tree parts. When trees are cut, a considerable amount of tree “waste” remains in the forest to rot and oxidise – and emit CO2.

“This aspect of the carbon balance sheet for bioenergy needs to be included,” he says. “The usual practice in forestry is to take out the trunks, while leaving the branches, treetops, stumps and roots. But the trunk only comprises half the tree’s living biomass.”

He explains that even if the branches and tops are taken out with the trunks, the stumps and roots will be left behind to oxidise into CO2. …… 

…. Holtsmark also asserts that the combustion of timber releases more carbon dioxide per kWh of heat energy than oil and gas.

“For example, only about half as much CO2 per kWh is released when using natural gas rather than wood. When this is taken into account, the picture for bioenergy from slow growing forests becomes even less advantageous.”

Further uncertainties in the Carbon cycle

July 4, 2013

The Carbon cycle is far from being fully understood or quantified. The absorption and release of carbon dioxide by the oceans and from biological plants and fungii – both on land and in the ocean – are a long way from being established. The amount of Carbon locked up in the earths crust is equally subject to great uncertainty.

A new paper shows that deep soils hold much higher levels of carbon than is usually assumed.

R. J. Harper, M. Tibbett, The hidden organic carbon in deep mineral soilsPlant and Soil, July 2013, Volume 368, Issue 1-2, pp 641-648

Abstract: Current estimates of soil organic carbon (SOC) are based largely on surficial measurements to depths of 0.3 to 1 m. Many of the world’s soils greatly exceed 1 m depth and there are numerous reports of biological activity to depths of many metres. Although SOC storage to depths of up to 8 m has been previously reported, the extent to which SOC is stored at deeper depths in soil profiles is currently unknown. This paper aims to provide the first detailed analysis of these previously unreported stores of SOC. ….. Mean SOC mass densities for each of the five locations varied from 21.8–37.5 kg C m−2, and were in toto two to five times greater than would be reported with sampling to a depth of 0.5 m.

PhysOrg reportsCurrent estimates of soil organic carbon are based largely on measurements to depths of 30 cm. This approach has evolved in North America and Europe, where soil is generally more shallow. 

However, many plant species have roots extending many metres deep, suggesting there is also carbon stored at such depth and inspiring researchers to explore the storage potential of deeper soils in older landscapes such as the Amazon or Australia. Researchers in the Amazon had previously sampled soils to 8 m. 

The researchers took soil measurements from samples taken to almost 40 metres deep at a range of sites in south-western Australia. They found that small amounts of carbon were present throughout the soils all the way to the bedrock, and that deep soils store up to five times more carbon than is normally reported.

Lead researcher Professor Richard Harper, an expert in water management and sustainability at Murdoch University said the findings extend our concept of the amounts and potential of carbon stored in soils.

“This carbon has been previously overlooked, and this opens up several lines of inquiry – for example, what happens to this carbon with land use change such as deforestation and reforestation?” Professor Harper said.

“There is likely more carbon stored in the world’s soils than previously considered. What will happen to this carbon – that is, will it be released as a result of either land-use change or climate change – is unknown. This is what we are working on now,” he said.

 

The never ending wonders of Carbon

January 27, 2011

Not just all life as we know it and coal and diamonds and graphite and carbon nanotubes and now the new wonder-world of  graphene.

Carbon also has the highest melting and sublimation point of all elements. At atmospheric pressure it has no melting point as its triple point is at 10.8 ± 0.2 MPa and 4600 ± 300 K, so it sublimates at about 3900 K.

File:Carbon basic phase diagram.png

Theoretical phase diagram of carbon: Wikipedia

Evidence is mounting that a new crystal form of carbon – body-centered tetragonal (bct) – something between diamond and graphene must exist. Simulations show that it must. It is now up to experimentalists to prove it.

Image: From "Ab Initio study of the formation of transparent carbon under pressure," by Xiang-Feng Zhou et al., in Physical Review B, Vol. 82, No. 13; October 29, 2010

From Scientific American:

Now evidence is mounting that there is yet another crystal structure to add to carbon’s catalogue of wonders: a material that could find applications in mechanical components whose hardness varies depending on the pressure to which they are exposed.

This new type of carbon was first observed in 2003, when researchers placed graphite, a stacking of chicken-wire-shaped networks of carbon atoms, under high pressure at room temperature. Under this “cold” compression, the graphite began to assume a hybrid form, between that of graphene and of diamond, but its exact nature was unknown.

Two computer simulation studies now suggest that cold-compressed graphite contains crystals of a structure called body-centered tetragonal, or bct, in addition to another type called M carbon. In bct, groups of four atoms are arranged in a square. The squares are stacked in an offset manner, and each square forms chemical bonds with four squares in the layers above and four below. A team led by Hui-Tian Wang of Nankai University in Tianjin, China, showed that during cold compression the transition to bct carbon results in a release of energy, which means it is likely to happen in the real world.

A Japanese and American team also conducted a simulation in which bct carbon produced x-ray patterns similar to those seen in the 2003 study. …. Whether bct carbon exists or can be synthesized in its pure form “is still a task for experimentalists to test.” 


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