Life cycle greenhouse gas emissions from rice production systems in Brazil: A comparison between minimal tillage and organic farming

Flávia Aparecida Nunes, Marcus Seferin, Vinícius Gonçalves Maciel, Simone Hickmann Flôres, Marco Antônio Záchia Ayub

Biotechnology & Biochemical Engineering Laboratory (BiotecLab), Institute of Food Science & Technology, Federal University of Rio Grande do Sul, Av. Bento Gonçalves, 9500, P.O. Box 15090, 91501-970, Porto Alegre, RS, Brazil.

Abstract

Knowledge on the environmental impact caused by rice cultivation, the most consumed cereal in the world, is essential to assess agricultural impact on total global anthropogenic emissions of greenhouse gases. Using Life Cycle Assessment (LCA), we compared the Global Warming Potential (GWP) of white and brown rice from two different cultivation systems, minimal tillage and organic, under the practices and climate conditions prevailing in the south of Brazil, the most important rice-producer region in Latin America. The “Cradle to Gate” approach was used, including the stages of cultivation, grain drying, and processing, considering the functional unit of 1 kg of protein produced. The results were characterized using the IPCC 2013 method. The highest value of GWP 100 was observed for the organic white rice, equivalent to 35.53 kg CO2-eq/kg of protein, followed by the organic brown rice, equivalent to 26.50 kg CO2-eq/kg of protein, whereas the lowest GWP 100, equivalent to 15.80 kg CO2-eq/kg of protein, was observed for the minimal white rice. The minimal tillage brown rice, released 20.91 kg CO2-eq/kg of protein. Results clearly show that the cultivation stage is the hotspot for environmental impacts, caused by field emissions, which represented 91% in the organic farming and 61% in the minimal tillage system. The use of mineral fertilizers, in the case of the minimal tillage system, represented 34% of the emissions. This research might help in the elaboration of rice production inventories, as well as in trying to provide reliable information to stakeholders in order to choose sustainable products and processes.

Graphical abstract

Keywords: Life cycle assessment; GHG emissions; Rice cultivation; Minimal tillage system; Organic farming.