Green pig iron is the name frequently used to distinguish and identify the pig iron produced with charcoal from renewable forest plantations, in comparison to that produced with coke from coal.
This is a very fair deference because it is a sustainable production that meets the requirements of environmental agencies.
Green pig iron requires the establishment of large areas of fast-growing forests. At each rotation age, usually 7 years, this wood is used to produce charcoal.
As it is widely known, all the plant organisms grow up through the photosynthesis, a biochemical reaction in which water and carbon dioxide are changed into carbohydrates under the sunlight energy. It is a natural process in which carbon sequestration and oxygen release promote a significant reduction in the impacts of greenhouse gases.
All the plants perform photosynthesis, however, because of their large leaf surface and their long cycle, trees are particularly efficient on this process. The physiology in living beings is always more intense in young organisms. A tree harvested at 7 years spent all its life capturing carbon dioxide from the atmosphere and releasing oxygen. Leaves and branches that fall on the ground become a mulch, which, over time will be incorporated to the soil where it remains indefinitely. Forest plantations constitute therefore a permanent sinker of carbon.
This balance can be summarized on the table below:
BALANCE OF CO2 IN THE PRODUCTION OF ONE TON OF PIG IRON
Source: Prof. Dr. Ronaldo S. Sampaio
| Production of pig iron – 1 t | Absorbs | Releases |
|---|---|---|
| Via Biomass | 890 kg of CO2 | 203 kg of O2 |
| Via Coke | 990 kg of O2 | 1.750 kg of CO2 |
In a sustainable production system, for each hectare being harvested there are other six in growth phase, capturing CO2 and releasing O2 in the atmosphere. It is appropriate to remember that a rotation age of 7 years means that the tree lived all its life in intense physiologic activity.
The amount of CO2 captured by the forest in growth more than compensate the amount of CO2 emitted by the mill. Of course, in such comparison one must consider the volume of wood that is needed to produce a certain amount of pig iron.
A recent research work carried out by CIT SENAI (CIT – Center for Innovation and Technology) has confirmed that in the whole process, i. e. since the forest planting until the final production and storage of pig iron, including accessory services, moving of vehicles and machines, transportation of raw materials and workers, the balance is positive. The following results were observed:
Emissions: 2,049 kgCO2e/t (kilograms of equivalent carbon dioxide per ton) of pig iron; absorption: 3,897 kgCO2e/t of pig iron; Balance: 1,848 kgCO2e/t of pig iron.
In Minas Gerais and in Brazil, the pig iron industry uses charcoal in practically 100% of the plants.
Photosynthesis is the largest chemical industry on Earth.