Cerri, Carlos., Bernoux, Martial., Maia, Stoecio., Cerri, Carlos., 2010. Greenhouse Gas Mitigation Options in Brazil for Land-use Change, Livestock and Agriculture. Scientia Agricola 67.
Cerri et al. addressed the GHG emissions of Brazil by focusing on the mitigation potential in each of the most emitting sectors to either sink more carbon or emit less. Business as usual scenarios were projected and mitigation strategies were extrapolated to measure the potential savings of various mitigation strategies by 2020. Their accounting strategy used two formulas to measure mitigation options. The first followed the 1996 Guidelines for National Greenhouse Gas Inventories given by the International Panel on Climate Change. The second was a tool to evaluate carbon balance impacts of forestry and agriculture management on GHG emissions developed by the Food and Agriculture Organization of the United Nations. Both metrics were used to evaluate the GHG implications of the changing dynamics of forestry, agriculture and energy in Brazil.
The most significant contributer to climate change in Brazil is deforestation. The Amazon rainforest is a vast natural carbon sink. Rainforest ecosystems sequester more carbon naturally than almost any other kind. In calculating Brazil’s contribution to climate change the preservation of this forest represents the largest mitigation potential. In 2007 the Brazilian government adopted a policy which sets the goal of decreasing the rate of deforestation by 30% every set of three years. The current rate is 12,185 square kilometers per year and but considering this government goal the rate by 2020 could be less than half of the current pace. From a GHG management perspective the forests are a crucial carbon sequestration oppurtunity. Although many Brazilian forests are under heavy threat the replanting of forests is also a consideration for GHG management.
In Brazil the enteric fermentation from cattle is the third largest contributor to carbon dioxide emissions and the largest to methane gas emmissions. Brazil accounts for a quarter of the developing world’s milk production and one fifth of it’s meat production so mitigation of cattle based emissions will have relatively large impacts. There are a variety of means to reduce this source of GHG: breeding to select for breeds which emit less methane, improving productivity of meat and milk productivity so less cattle are required for the same amount of product, manure management which focuses on correctly using waste as an organic fertilizer so as to sink carbon back into the soil rather than have it be released gaseously, and the use of digestors which capture the methane from cattle and convert it into a usable fuel.
Tillage of Brazilian fields releases significant GHG. Rather than remain in the soil, carbon is released when the topsoil is turned over yearly to add fertilizer, shape beds and remove weeds. The alternative to this practice is to convert land into a no till system which allows the soil to hold more water and increase it’s stability against erosion. Tilling integrates air into deeper layers of soil stimulating microbial activity, this results in the increases decomposition of organic material which releases greater amounts of carbon from the soil. In this way previously tilled fields which have been depleted of carbon over years represent a vast potential carbon sink. There are currently 28 HA of no till land in production in Brazil and the government climate mitigation efforts aim for 40 HA of no till land by 2020.
In addition to these main sources of agricultural and forestry GHG mitigation, the paper also covered several other methods which, while not as significant individually, could also add up to large GHG reduction if all enacted effectively. These include reducing methane released from decomposing matter in flooded rice fields through better water management and increasing the sustainable production and use of bio-ethanol and biodiesel.
The authors estimated that increasing carbon sinks represent 19-39% of mitigation potential and reducing emissions represents 61-81%. Since the authors accounted for the increased use of bio fuel crops as a GHG savings for both the agriculture and energy sectors, their estimates for the mitigation potential of Brazil were even higher than that of the government.