We often hear about biomass, a so-called energy that is cleaner than fossil fuel? But where does biomass originate and how can we use it to create a source of energy? And especially why do we say that biomass is “zero-carbon”?
What is its real impact on our environment in terms of greenhouse gas emissions?
The composition of biomass!
Biomasse constitutes the entirety of organic matter of vegetable and animal origin. Forests, marine and aquatic environments, parks and gardens, animal excrement, residue from timber for construction, industries generating byproducts, organic detritus, sewage… are all examples of biomass and are also a source of energy.
The process of transforming biomass into a source of energy
Biomass used mainly to create energy comes from wood, in various forms, such as logs, recovered wood, bark, wood chips …and residue such as detritus from paper mills, some building debris, household garbage, harvest residue…
The composition, as well as the residue of this matter, is still made up of carbon. That is why the combustion this matter creates is used to produce energy: namely, heat and electricity.
Cogeneration allows us to produce both heat and electricity from the same matter. Heat is recovered through combustion of biomass, then another part of that heat is used to produce electricity (a process that consists of using heat to warm up a water circuit, then its vapour is used to turn a turbine).
There are three forms of combustibles:
| Solid: | hardwood, wood shavings, granules… |
| Liquid: | The essence of wood, bioethanol… |
| Gaz : | Biomethane |
Therefore, the gas can also be used to create energy: which is why we speak of biogas combustion. Biogas comes from methanization, a process that consists of allowing organic matter, generally detritus, to ferment, in an oxygen-starved environment.
Biomass is “zero-carbon”!
The main advantage of this energy source is that it is neutral in carbon emissions. Scientists tell us that biomass is “zero-carbon” or even “carbon-neutral”.
Theoretically, when a source known as “zero-carbon” is consumed as an energy source, it is not supposed to create carbon dioxide (CO2) and it rejects only the exact quantity that it absorbed.
Biomass converted into energy emits very little greenhouse gas, compared to fossil sources. Why? Because biomass does not only emit CO2, it also absorbs it. Let us not forget that trees and plants absorb CO2 when they grow. Thanks to photosynthesis, they are able to transform carbon dioxide from the air, water and sunlight into energy and oxygen. This mechanism allows them to combat global warming. Thus every ton of wood grown is equivalent to 0.5 tonnes of fixed CO2.
Thanks to trees, the carbon cycle allows for a balanced report and an almost imperceptible impact on the environment.
However, in order to use the biomass, we must however expend quantities of energy originating mainly in fossil sources.
Prejudice: “Deforestation increases greenhouse gas emissions”
It is often said that deforestation increases greenhouse gas emissions, yet that is false! Deforestation does not emit any greenhouse gas concretely. However, it is true that deforestation contributes to an increase in greenhouse gas. If forests are less dense and fewer in number, they will contribute less and less to climate regulation through less absorption of CO2.
According to the FAO (the UN Food and Agriculture Organisation), the forest area of the planet has decreased by 5.2 million hectares every year from 2000 to 2010.
Nevertheless, not all countries are affected by deforestation, in particular Canada. In fact, North America as well as Europe, continue to see an increase in their forest area. Forest area is decreasing essentially in tropical regions, such as Latin America and Africa.
Wooded countries are far from being threatened by deforestation, Canada can therefore use its biomass to create energy.
Sources : ecohabitation et mtaterre.
Photos : YAB
