BY DR. JOSE PALU-AY DACUDAO
IN THE local setting, the traditional practice of charring plant remains in sugar cane fields after harvest amounts to the same thing. Ever wondered why the same soils in Negros have supported the growth of sugar cane for more than a hundred years without substantially deteriorating? It’s most probably due to traditional charring.
I’ve always wondered why agricultural techniques of other commercial crops (aside from sugar cane) do not plow in charred organic matter into the soil. Perhaps, we should experiment on doing this.
In the smelting of metal oxides, the same principle above can be applied. Elemental iron is by far the most commonly produced elemental metal. Note below what happens if charcoal is used to smelt iron oxides in order to produce elemental iron.
Equation for photosynthesis:
6 CO2 (taken from the atmosphere) + 6 H2O → C6H12O6 (organic substance) + 6 O2
Equation for charring/ carbonization (charcoal production):
C6H12O6 (organic substance) → 6 H2O (water) + 6 C (charcoal carbon)
Equation for the reduction of iron oxides in smelters:
FeO2 (iron oxide) + C (charcoal carbon) → Fe (elemental iron) + CO2
If we are actually strict about it, the final result is elemental iron and a net emission of oxygen into the atmosphere. The oxygen comes from the iron oxide. Elemental carbon in effect steals the iron oxide’s oxygen to form CO2. However, in the previous photosynthetic and charring process, atmospheric CO2 was reduced to the above elemental carbon with the net emission of O2. The final summary of the reducing process would be:
Iron oxide (FeO2 or Fe2O3 or Fe3O4) → elemental iron Fe + O2
The same is true for the smelting of aluminum oxides magnesium oxides and other metal oxides. If we use charcoal, there is no net emission of CO2 into the atmosphere.
(Note: Brazil has no significant coal deposits. Thus, it uses charcoal from commercially grown eucalyptus trees as the reducing agent in order to smelt iron oxides. Before the 19th century, much of the world actually used charcoal as the main reducing agent in order to produce elemental iron. China, India, EU nations, USA, Australia and so on at present just use coal because they have abundant sources of it, and thus it is cheaper the making charcoal.)
In summary, the carbon in charcoal is taken from the atmosphere, and so burning it or using it as a reducing agent in smelters just returns the CO2 that plants fixed in photosynthesis back into the atmosphere. Other words, charcoal usage is carbon-neural, meaning it does not result in a net CO2 emission into the atmosphere. (For comments and suggestions please email to mabuhibisaya2017@gmail.com)/PN
