# Environmental Impact of Corn Tortilla Production: A Case Study
## 1 Introduction  
Soil conservation is one of the main sustainability goals in ensuring food security and environmental protection [1]. For this reason, the production of food with the minimum impact on the environment is a major challenge for agricultural production. Nitrogen (N) is a critical input for optimum crop production because it promotes rapid growth of corn plants, increases leaf size and quality, and promotes fruit and seed development [2]. Many grain legumes require limited doses of N fertilisers, but others, such as maize, are big consumers of N, and consequently of energy [3]. This is important because maize is the second largest crop worldwide, with a production of 615,533,645 Mton (millions of tons) [4]. Moreover, in corn production the use of herbicides for the chemical control of weeds is intensive [5]; its high water requirements and the associated nutrient runoff contribute to severalimpacts on the environment such as eutrophication, algal growth and hypoxia in downstream water bodies [6]. Other corn production-associated environmental impacts are the unsustainable use of water for irrigation, the expansion of genetically modified corn, soil erosion and biodiversity loss [4]. This situation is unsustainable in the long term. Research on the environmental impacts of corn has been mainly on cultivation techniques [3; 5; 7; 8] and the production of biofuels [6; 9; 10], so there is limited information on the impacts produced by the transformation of corn for human consumption using life cycle analysis. The study by Grant and Beer [11] was conducted using life cycle assessment (LCA) for the determination of greenhouse gas (GHG) emissions from pre-agricultural activities on farms and post-farms in the manufacture of corn chips, taking as an indicator the CO\({}_{2}\) equivalent (CO\({}_{2}\) eq) and as a functional unit a box of ten 400 g packages of corn chips. They found that GHG emissions from obtaining raw materials comprises approximately 5% of the total throughout their life cycle; corn cultivation produces around 27%, and the manufacturing stage of corn fritters around 68%. The study showed that the most important source of GHG emission is the emission of nitrous oxide on the farm as a result of the application of fertilisers (0.12 kg of CO\({}_{2}\) eq per box). [PERSON] [12] took as a basis the ISO 14067:2013 standard to perform an analysis of the carbon footprint produced by ten nixtamal mills distributed in the Metropolitan Zone of the Valley of Mexico. His door-to-door study produced a result of 43.38 kg CO\({}_{2}\) eq t\({}^{-1}\) of processed nixtamal mass. Corn has many food uses, among which is its use for making tortillas. This is a millennial product which is part of the culinary tradition that continues to lift generations and cultures. Historically it was considered as the \"bread of life\" and there is a connection between Mesoamericans of around 2500 years ago and today's international tortilla marketplace [13]. Nowadays there is a great demand in North America and some countries in Central America; in the United States, the tortilla market is projected to reach USD 29.39 billion at a Compound Annual Growth Rate (CAGR) of 5.50% over the forecast period. North America alone captures 59.06% of the global market share in the year 2017 [14]. The tortilla is a food in circular and flattened form, with diameters ranging from 160 to 300 mm and is 2 to 6 mm thick. It is made with the mass of cooked corn that is obtained through the process of nixtamalisation [15]. In Mexico, half of the corn produced goes to the production of nixtamalised corn tortillas, while 11.3% of corn production is used to make flour for tortillas [16; 17]. The National Council for the Evaluation of Social Development Policy (CONEVAL) estimates that in the urban environment the annual per capita consumption of tortillas is 56.7 kg, and in rural areas, 79.5 kg [18].