Consider the following:

1. Carbon monoxide

2. Methane

3. Ozone

4. Sulphur dioxide

Which of the above are released into atmosphere due to the burning of crop/biomass residue?

Correct Answer: The correct option is 1, 2, 3 and 4.

Biomass and crop residue burning is a significant source of air pollution and greenhouse gas emissions. The combustion of agricultural residue releases several pollutants into the atmosphere:

1. Carbon monoxide (CO): Incomplete combustion of organic matter during crop burning leads to the release of significant amounts of carbon monoxide.
2. Methane (CH₄): Smoldering crop residues under oxygen-limited conditions produce methane, a potent greenhouse gas.
3. Ozone (O₃): While ozone is not emitted directly from burning biomass, it is formed in the atmosphere as a secondary pollutant. The precursors required for tropospheric ozone formation—such as volatile organic compounds (VOCs), nitrogen oxides (NO_x), and carbon monoxide (CO)—are released in large quantities during crop residue burning in the presence of sunlight.
4. Sulphur dioxide (SO₂): Plant biomass contains trace amounts of sulphur. Burning crop residues oxidizes sulphur to form sulphur dioxide.

Therefore, all four gases (Carbon monoxide, Methane, Ozone, and Sulphur dioxide) are released into the atmosphere directly or formed as a direct consequence of crop/biomass residue burning.