Stubble Burning and Pollution

Stubble Burning and Pollution

• According to a recent study, Delhi’s meteorology and the quantity of chaff (crop residue or stubble) burnt in Punjab and Haryana play a more important role in worsening air quality than the time chosen by farmers to start stubble burning.

Crop Burning:

• It is a traditional practice in Punjab and Haryana to clean off the rice chaff to prepare the fields for winter sowing.
• It begins around October and peaks in November, coinciding with the withdrawal of southwest monsoon.
• The pollutants and the particulate matter (PM) from the chaff, along with other sources of pollution in Delhi, get stuck in the lower atmosphere worsening the winter pollution.

Reasons:

• Subsidies and assured procurement of rice have led to a rise in the rice acreage.
• Increased and modernized farm mechanization extract the rice grains only and leave large quantities of rice stubble behind.
• Punjab Preservation of Subsoil Water Act 2009:
• This mandated farmers to delay sowing of paddy to late June to discourage groundwater extraction.
• This led to a delay of an average of 10 days compared to 2002-2008 and now due to the delayed harvesting, rice chaff burning coincides perfectly with the withdrawal of southwest monsoon.

Findings of the Study:

• Crop burning contributed nearly 40% of the near-surface PM 2.5 in Delhi in 2016, which saw one of Delhi’s severest pollution episodes.
• The study largely relies on mathematical modeling.
• Data on the number of crop burning episodes and levels of PM were plugged into a mathematical model.
• In results, it emerged that crop residue contribution to PM over Delhi in 2016, increased only marginally (1%) when compared to a hypothetical scenario of crops being burned 10 days earlier.
• Early burning while reducing PM burning by 20g/m3, did not reduce the number of days of significant PM exposure in Delhi, which hovered around 55 days.
• However, the study showed that delaying rice burning 10 days beyond what is currently practiced could be harmful leading to an increase in peak PM emissions as well as increase the number of pollution days.
• Stopping crop residue burning will aid the National Clean Air Programme (NCAP), which aims to reduce pollution by 20-30% in annual PM concentration by 2024.

Source: The Hindu