**4. Conclusions**

The balance of energy and matter indicates that for each ton of harvested wheat in the Mexicali Valley, 1,130.03 kg of wheat straw are generated, of which 169.50 kg are used in diverse applications and 960.53 kg are burnt in open air. The incineration of this waste implies that 13,927.63 MJ are wasted without any use, as well as pollutant emissions. In the headfire burning, 73.96 kg of pollutants, composed of 10.57 kg PM, 61.47 kg CO, and 1.92 kg CH4, are generated. As for the backfire burning, 58.88 kg of contaminants, composed of 5.76 kg PM,

, are generated.

51.87 kg CO, and 1.25 kg CH4

**Figure 7.** Accumulated emissions by backfire burning.

**Figure 6.** Accumulated emissions by headfire burning.

74 Global Wheat Production

Wheat cultivation is an intensive activity of great importance for the economic development of Baja California, Mexico. It also means the generation of vast amounts of wheat straw that is burnt *in situ* and emits large quantities of PM, CO, and CH4 annually, contaminants that affect the air quality of Mexicali and its valley.

Since 1987 until 2015, the sown surface of wheat has incremented in the Mexicali Valley, resulting in an increase in the polluting emissions and the wasted energy.

Also, the total available energy estimated, draw from wheat straw incineration, for the 1987– 2015 period is 188.81 PJ, which represents a high energy potential that can be exploited in productive processes.

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Wheat Straw Open Burning: Emissions and Impact on Climate Change

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rys.2008.43.a494

Through the development of the model on iThink®, the emissions and the wasted energy, as a result of wheat straw burning, were estimated in the period under study. It demonstrates the severity of the problem and justifies the necessity of promoting sustainable alternatives for the disposal of wheat straw, with a lower environmental impact, among the farmers of the region.

According to the model of headfire burning, the results of the simulation indicate that the annual emission increased from 25,370 t (1987) to 43,292 t (2015), while for the backfire burning from 20,197 t (1987) to 34,465 t (2015), which represents a rise of 71%.

The balance of matter and energy results, developed in the current work, for 1 hectare of wheat harvested in the Mexicali Valley shows that 6.46 t of wheat are produced and 7.3 t of straw are generated; 6.205 t are burnt *in situ* in open fire, which generates 89,972.50 MJ and 477.78 kg of contaminants by the headfire burning and 380.37 kg of pollutants through backfire burning.
