In a study published in Nature Climate Change, scientists show that the carbon dioxide emissions from Brazil’s steel production doubled in the 2000-2007 period, despite a decrease in the use of coal.
According to the researchers, Brazil used native charcoal, i.e. charcoal produced from native forests, to fuel the steel-production industry… which led to deforestation and, consequently, to higher carbon dioxide emissions.
Steel is one of the most-produced materials, with applications in many different fields, including construction and aerospace.
Steels are alloys of iron and carbon; depending on the applications, however, carbon content can vary and additional elements can be present in the alloy.
Manufacturers generally produce steel from iron ores, such as iron oxides (i.e. Fe2O3). To convert the oxide into metal, they must employ a reducing agent in the process. This is normally carbon (C) in the form of coal.
Carbon Dioxide Emissions
Due to the use of carbon, steel production results in the emission of a remarkable quantity of carbon dioxide (CO2). Literature data report that about 7% of the world anthropogenic (man-made) CO2 emissions are linked to steel manufacture.
These data cause concern, as CO2 is a greenhouse gas; according to some people, the increased CO2 atmospheric concentration is a cause of global warming. Moreover, the higher CO2 level is causing an increase in the acidity of the oceans.
Because of this, alternative strategies have been tested and implemented, to try to reduce the CO2 emissions associated with steel production.
One solution is to replace coal of fossil origin with coal of biomass origin, i.e. obtained from the wood of trees grown on non-forest land (plantation charcoal).
In principle, the use of plantation charcoal leads to a carbon neutral process, since the CO2 generated in the steel production can be offset by the plantation and the growth of the trees. This kind of process is recognized as a Clean Development Mechanism (CDM), according to the Kyoto Protocol agreement.
The Case of Brazil
These CDMs were used in steel manufacture in Brazil from the year 2000 onwards.
Now, some years later, a team of researchers looked in detail at the effects that CDMs had on CO2 emissions. They considered the period between the years 2000 and 2007.
The University of Queensland, CSIRO (Australia), and the Federal University of Minas Gerais (Brazil) published their results in Nature Climate Change on the 9th of February 2015.
Decoded Science spoke to Dr. Laura Sonter, leading scientist in this research; she explained the key points of this study.
“We found that carbon dioxide emissions from steel production in Brazil doubled between the years 2000 and 2007, despite a decline in the industry’s use of coal. We were surprised by these results and wanted to understand how this occurred.
Our data showed that the majority of biomass charcoal used for steel production was not sourced from plantation forests, but instead from native forests (native charcoal). This form of charcoal is not carbon neutral – it causes significant carbon dioxide emissions from deforestation.”
High CO2 Emissions
The results by Dr. Sonter and her colleagues show that steel manufactured using native charcoal can generate up to 9 times more CO2 emissions per tonne of steel produced than coal.
In 2000, only 11% of steel was produced using charcoal sourced from native forests; in 2007, however, this proportion increased to 25 %. Overall, this caused an increase in the total CO2 emitted, which raised from 91 to 182 M tonne, hence doubling. Moreover, the specific emissions increased from 3.3 to 5.2 M tons of CO2 per tonne of steel produced.
What Went Wrong?
According to Dr. Sonter:
“In Brazil a series of circumstances increased CO2 emissions from steel production. Demand for steel production increased, as did the industry’s reliance on charcoal, during a time when plantation forests were unable to supply increasing demands.
Our study shows that increasing plantation charcoal supply could have cut CO2 emissions by 79 %; however, broad scale expansion of plantation forests is limited by socio-economic costs and other potential indirect impacts on native forests.”
A Lesson to Be Learnt
The results of this study show that, to be effective, climate mitigation strategies must consider all sources of carbon emissions in any industrial process; just focusing on one aspect, in this case the minimization of coal use, proved not to be useful but, on the contrary, to have a negative effect. Dr. Sonter and her colleagues studied the case of Brazil, but there are other countries (i.e. China) which are implementing the same strategies. Therefore, it’s time to consider a serious revision of the carbon mitigation policies.
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