Dissertations and Theses

Summary

There is a growing need of the productive sectors in the development of techniques of mitigation of greenhouse gases (GHG) in order to reduce the additional greenhouse effect. However, the challenge for the agricultural sector is to reduce net GHG emissions while increasing production to meet growing demand for food, fiber and biofuels. In this study, the GHG balance in sugarcane production scenarios (S0, S1, S2 and S3) was estimated, and the manual harvest with burning (CQ) is converted to the mechanized without burning (CC, sugar cane taking into account the adoption of conservationist agricultural practices, such as reduced soil preparation and the introduction of crop rotation with Crotalaria juncea L. during cane field reform; and (ii) the potential for GHG mitigation in the period from 2012 to 2041 due to the conversion of the sugarcane areas harvested with burning (2010/2011 harvest) in the State of São Paulo to three management scenarios (S1, S2 and S3). Based on the IPCC methodologies (2006), the annual GHG emissions balance includes agricultural and mobile sources (machinery), according to the average annual consumption of diesel and agricultural inputs per hectare. In the scenarios involving raw harvesting, the potential for soil carbon accumulation was also considered. The results indicated that synthetic nitrogen fertilization and diesel consumption were responsible for higher emissions in the raw cane scenario, while the burning of residues in the pre-harvest of sugarcane resulted in the highest emission observed in the cane burned scenario. Total GHG emissions were 2,651.9 and 2,316.4 kg CO2eq ha-1ano-1 for CQ (S0) and CC (S1), respectively. Considering the average soil carbon accumulation rate of 888.1 kg CO2 ha-1ano-1 due to the conversion of CQ to CC, which results in the long-term deposition of plant residues, the balance of GHG emissions in scenario S1 was reduced to 1428.3 kg CO2eq ha-1ano-1. The second decrease occurred when considering the substitution of conventional soil preparation by the reduced preparation during the reforestation period in the raw cane (S2) scenario, which resulted in a reduction in the total balance of GHG emissions to 1,180.3 kg CO2eq ha- 1an-1. In addition, the conversion of CK to CC, with the introduction of crop rotation with Crotalaria juncea L. and reduced soil preparation during sugarcane reforestation (S3), resulted in the lowest GHG balance, with 1,064.6 kg CO2eq ha-1ano-1. Considering the conversion of sugarcane areas harvested with burning in the State of São Paulo to three management scenarios, this study pointed to the technical potential of GHG mitigation accumulated in 2041, ranging from 56.1 to 72.6 Mt CO2eq, depending on the management scenario adopted. The agricultural management strategies presented in this study can contribute substantially to the mitigation of GHG in the production of sugar and ethanol in Brazil.

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Greenhouse gas balance due to the conversion of sugarcane areas from burned to green harvest, considering other conservationist management practices