school energy&environment

Carbon sequestration

Forests help to remove carbon dioxide from the atmosphere and transform it, through photosynthesis, into carbon, which  the forests then “saved” in  the form of wood and vegetation. This process is called “carbon sequestration ”. Generally,  approximately 20% of the weight of trees consists of carbon, and the entire biomass of the forest acts as a “carbon absorption tank” . Also the organic material in the ground in the  forests, as for example  humus that derives from  the decomposition of dead plant material, acts as a carbon tank . In this way the forests can capture and store enormous amounts of carbon. In fact,  according to FAO, the forests of the planet and their undergrowth absorb a total of over a trillion tons of carbon, twice as much as the amount found in the atmosphere. In the balance between emissions and absorption of carbon dioxide, an ecosystem is considered a carbon sink  when it absorbs more carbon dioxide than the amount it emits. Instead, an ecosystem is known as a carbon source when it emits more CO₂ than what it absorbs. Carbon sequestered from the biomass is known as carbon stock.
In a forest, carbon is stocked in compartments :

• epigean biomass,  i.e. the live organic substance above ground;
• hypogean biomass, i.e. live organic substance underground;
• necromass, i.e.  dead organic substance in wood;
• litter, i.e. the dead organic substances on the  surface of the ground, such as  branches, leaves and animals;
• organic substance in the ground.