Direct vs. Indirect emissions
It appears that there’s a distinction between direct and indirect emissions from bioethanol.
The direct emissions are the emissions from the use of bioethanol when being burned in a car. More precisely it is the release of green house gases (GHG) in the atmosphere. Bioethanol is considered as less polluting than fossil fuels and, consequently, biofuels have also been named green fuels. How can it be less polluting? First of all, as we mentioned before, biofuels release less GHG in the atmosphere when being burned. Then, there is a sequestration of carbon through the growth of the feedstock (plants farmed to produce biofuels such as sugarcane). This carbon sequestration is also called “carbon uptake” credit. In this sense, theoretically, biofuels can reduce the emissions of GHG in the atmosphere, relative to fossil fuels.
However, biofuels started to be put into questions when considering the indirect emissions emitted when biofuels are being produced…
The indirect emissions refer to the emission of green house gases when the bioethanol is being produced. Indeed, bioethanol can be seen as a clean fuel since it doesn’t contaminate much when being burned in a car (direct emissions). However, when being produced, biofuel generates many indirect effects among which indirect emissions, especially when being farmed massively, like sugarcane in Brazil.
As an example: when farming bioethanol, farmers burn the sugarcane’s biomass or residues to make the manual harvesting easier. However, when being burned, the residues release carbon in the atmosphere, which is a really strong green house gas. This is what we call an indirect emission from the production of bioethanol. There are others indirect emissions like the use of fertilizers, contaminating the soils, but also the atmosphere since it releases nitrates. Another example would be the release of emissions due to the conversion of forests (or grasslands) into fields. Indeed, the trees sequestrate the atmosphere’s carbon. When being cut down, the process is reverted and the trees release the carbon they used to sequestrate.
All those effects produce emissions of green house gases in the atmosphere. In this sense, if biofuels first appear as green fuels and poor polluters, when regarding the indirect emissions they release, we can then put into questions their “green” characteristics…