The percentage of renewable sources in Brazil’s energy matrix is one of the topics presented in international forums to defend the country’s support for sustainable development and the fight against the climate emergency. An example of this is that, at the United Nations General Assembly, he is the president Luiz Inácio Lula da Silva (PT) as the former president Jair Bolsonaro (PL) said that most of Brazil’s electricity will be generated from clean, renewable sources.
According to the BEN (National Energy Balance) this yearprepared by the state body EPE (Energy Research Company), 87.9% of the Brazilian electricity matrix comes from renewable resources — biomass, hydraulic, wind and solar. Among these, water represents the largest share in electricity production: 61.9% of all renewable electricity in Brazil comes from this source.
However, even if the energy generated by hydroelectric plants is renewable, there is debate as to whether it is correct to classify it as a clean, i.e. non-polluting, source:
- Critics argue that the plants emit methane – one of the gases that causes the greenhouse effect – and that their construction generates various impacts on ecosystems, such as the alteration of animal habitats and the change in the characteristics of rivers;
- Defenders of the model, however, say that polluting emissions are significantly lower than those released by other energy sources and that the plants generate positive impacts on local economies, such as water supply and drought management.
OR To the facts they interviewed experts and consulted documents and studies to explain the discussion.
Not always. Depending on the model, the size of the structure and the location of installation, these structures can pollute as much or even more fossil energy sources — generated by the combustion of resources such as coal and oil e high gas emissions causes of the greenhouse effect.
Second list the IPCC (Intergovernmental Panel on Climate Change), hydroelectric plants can pose serious environmental problems and social impacts:
- Dams can alter ecological habitats, causing animal migration and causing changes in the characteristics and flow of rivers;
- The felling of local vegetation to build artificial reservoirs also causes the deforestation of plants;
- Current changes can also generate health problems by creating breeding grounds for mosquitoes that cause diseases such as malaria;
- Flooding of large areas causes inundated organic matter to generate methane, a gas that contributes most to climate change compared to carbon dioxide itself;
- Ultimately, the construction of the plants ends up forcing the region’s population to move.
Registration. Work at the Belo Monte plant has cleared a large area of forest to accommodate a reservoir (Tiago Costa/Ibama)
One UFJF study (Federal University of Juiz de Fora) published in 2016 analyzed 18 Brazilian power plants in the Amazon and found that six of them had greenhouse gas emissions comparable to those of thermoelectric power plants.
This happens because the abundance of vegetation and other living organisms makes the Amazon a region rich in organic matter. Therefore, when areas of the biome are flooded for the construction of hydroelectric plants, the biomass of the felled vegetation and the organic substance present in the soil decompose and generate carbon dioxide (CO₂) and methane. Emissions can be even greater if the area to be flooded is not cleaned properly during the construction process.
In an interview with To the facts, professor at the USP Geosciences Institute Dailson Bertassoli Júnior confirmed that emissions per inundated area tend to be higher in hydroelectric plants built in the Amazon region than in reservoirs outside of warmer areas. The problem, according to him, is that the hydroelectric potential near consumption centers is already well explored “and the new frontier is precisely the Amazon”.
Balbina. Created in 1987, the plant has flooded an area of 2,360 square kilometers and has an estimated emission of 7,000 tons of carbon per day (Prefeitura de Presidente Figueiredo)
Polluting hydroelectric plants. Considered a bad example in clean energy generation, the Balbina hydroelectric power plant, located on the Uatumã River, in the Amazon, has been identified by researchers as responsible for the release ten times more greenhouse gases compared to a coal-fired thermoelectric power plant.
The Belo Monte plant, located on the Xingu River, in Pará, has also been identified as responsible for increasing greenhouse gas emissions in the region, also operating at thread of water. This option is considered more environmentally friendly, as it generates energy solely from the force of the current, without the need to store large volumes of water.
One study conducted by the Institute of Geosciences estimated that, in addition to the decomposition of flooded organic matter, the slowing of the river flow caused by Belo Monte also increased the amount of sediment in the water. When they decompose, these sediments also generate methane.
Another facility identified as polluting is the Tucuruí power plant, located on the Tocantins River, in Pará. In a survey published by Inpa (National Institute for Amazon Research), biologist Philip Fearnside points out that, if all emissions are taken into account – starting from the construction of the dam, for example – “the impacts of Tucuruí’s global warming could even exceed those of the generation of fossil fuels”.
Counterpoints. In technical note regarding “greenhouse gas emissions in hydropower basins”, the EPE emphasizes that all forms of energy production have “some level of associated emissions”. The company maintains, however, that the maximum rate of emissions from hydroelectric plants is still significantly lower than the minimum rate of emissions from fossil fuels and that plants like Balbina are an exception.
Carlo Lenzi, executive president of Abragel (Brazilian Association of Clean Energy Generation, made up of companies in the hydroelectric sector), he claims Likewise: “All sources, even renewable ones, produce greenhouse gas emissions during their useful life due to emissions caused by the production, construction and operation of equipment.”
While highlighting the environmental impacts of this form of power generation, the IPCC also believes that the source “provides flexible and competitive electricity with low emissions, brings local economic benefits and promotes ancillary services such as municipal water supply, irrigation and drought management, navigation and recreation and flood control”.
Bertassoli Júnior points out that hydroelectric plants are not as much responsible for climate change as thermoelectric plants and argues that investments should be made in less polluting structures. “What the science shows is that there are poorly constructed reservoirs and that we need to take that into account when we build hydropower plants.”
Indeed, studies indicate that the level of emissions is related to the type of dam and may be proportional to the size of the facilities: after all, the larger the project, the greater the area deforested and flooded tends to be. According to the most recent data from Aneel (National Electric Energy Agency), there are 1,351 hydroelectric plants active in the country, which can be divided into three categories:
- 709 CGH (Hydroelectric Power Plants), with a delivered power of 875 thousand kW;
- 427 PCH (Small Hydroelectric Power Plants), which overall have a delivered power of 5.7 million KW;
- And 215 UHE (Hydroelectric Power Plants), for a total of 103 million KW of power granted.
Lenzi points out that the PCH and CGH reservoirs have flooded areas smaller than 15 km², making their reservoirs small compared to those of the HPPs. “Also we must consider that the vast majority of PCH and CGH are run-of-river plants, that is, they generate energy from the water that arrives in the basin and passes through the turbines, without reserving or accumulating water”, he says.
Lack of data. The lack of detailed investigations and reports from energy companies on the levels of polluting gas emissions prevents us from estimating how much hydroelectric energy produced in Brazil is actually clean, points out Bertassoli Júnior.
One of the major investigations carried out by government agencies, the Balcar project (Carbon Balance in Reservoirs), conducted by the Eletrobras Electrical Energy Research Center, for example, monitored only 11 deposits at Brazilian plants between 2011 and 2013. Of these, eight were operational.
OR own studio It is even underlined that the lack of field monitoring data before filling the tanks makes it difficult to estimate emissions, which were based on hypotheses and calculation models.
“It is a very controversial discussion, because there is no single methodology. Depending on the study, there will be a greater or lesser factor, and this emission is not accounted for at an international level”, explains Ricardo Baitelo, project manager of the Iema (Institute for Energy) and Environment).
Gisele Lobato collaborated.
References:
5. IPCC
6. WRI Brazil
7. UJFJ
8. EBC
10. USP Journal
11. Inpa
12. Abragel
13. Aneel
14. Cepel
Source: Terra
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