Water and energy use and greenhouse gas emissions for nixtamalised maize masa flour production

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Abstract In Mexico, >10 million tons of maize are annually processed into food products, primarily maize tortillas. About 40–46% of commercially-produced tortillas are from nixtamalised maize masa flour (NMMF), which use is increasing throughout the country largely because it simplifies tortilla making process. Nonetheless, little information exists about resource demand and environmental burdens of NMMF production. The present study estimated fresh water and energy inputs to and energy-related greenhouse gas (GHG) emissions from NMMF manufacturing based on a generic NMMF production process re-constructed using literature data. Unit operations included alkaline pre-cooking, pre-cooked kernels mechanical washing, pre-conditioning, first milling, drying, cooling, sieving, and second milling. Estimated specific water use, energy use, and GHG emissions per ton of NMMF were 3.16 m3, 5.76 GJ, and 334.66 kg-CO2e. Pre-cooked kernels mechanical washing accounted for ∼94% of fresh water supply while drying was responsible for ∼48% of total energy and ∼46% of total GHG. Specific water use was highly sensitive to total solids concentration in pre-cooking suspension and the maize:water ratio in the pre-cooker. Specific energy use and GHG emissions were very sensitive to pre-cooked kernels final moisture content and drying air inlet temperature. Results can help guide future efforts towards improving NMMF industry sustainability.