BY DR. JOSE PALU-AY DACUDAO
AN ADDITIONAL point: Charcoal production through charring is one of the most massive activity by humans in tropical countries. Most of the charcoal is used in cooking as described in the following formula.
6 C + 6 O2 (free molecular oxygen in the atmosphere) → 6 CO2 (carbon dioxide emitted into the atmosphere)
Strictly speaking then, charcoal production for cooking is carbon neutral and is not a carbon sink.
However, massive amounts of char (rich in elemental carbon) are wasted in the process, from leftovers in the place where charring occurs to the place where cooking takes place. Thus, charcoal production worldwide is a carbon sink, as seen in the processes below.
Photosynthesis:
6 CO2 (carbon dioxide) + 6 H2O (water) → C6H12O6 (organic substance) + 6 O2 (oxygen)
Charring:
C6H12O6 (organic substance) → 6 C (elemental carbon) + 6 H2O (water)
Overall summary of the two above processes:
6 CO2 → 6 C (elemental carbon) + 6 O2 (oxygen)
In brief, in charcoal production or charring, atmospheric carbon dioxide is converted into elemental carbon and molecular oxygen. The elemental carbon is sequestered for a long time or permanently in the soil and oxygen just goes back into the air.
How about plastics? Plastics are carbon-rich compounds made mostly of hydrogen and carbon. Like lignin, they do not decompose easily.
The answer would be yes, if they are made from recently harvested organic matter. That organic material would have taken carbon dioxide away from the air in a recent geological instant. If transformed into plastic, then it would act as a carbon sink.
However, most plastic is made from petroleum. Thus no carbon dioxide was taken from the air in a recent geological instant. So plastic production is not a carbon sink.
As a side note, there have been alarming predictions of a plastic catastrophe. Plastics would inundate the continents and seas. It has not happened.
Most waste plastics tend to end up in the sea.
On shorelines and seas, they quickly get broken down by sand and wave action, and through the passage inside the intestinal tracts of various animals (such as krill), into microplastics. There is no study that definitively shows what eventually happens to these microplastics, but I strongly suspect they get physically broken down into progressively smaller molecules and that the smallest of these are simple hydrocarbons that are biodegradable. If they happen to have chlorine atoms attached, these compounds will be harder to biodegrade, by there are microbes capable of dehalogenation that can do it. (To be continued)/PN
