Farmers – time to clear the air?

A battle is being joined between farmers and those of us who need cleaner air.

As a cardiac patient now living in an urban area, I am on the alert for any news of how harmful particulates in the air can be reduced. Ammonia (NH3) is not a greenhouse gas, but it harms the environment. This occurs when it falls on the land and gets into water courses and also when it reacts with air to form killer particulates (PM2.5) that travel into populated areas.

Ammonia emissions

Unfortunately, farming generates 87 per cent of ammonia emissions, of which 8 per cent is from urea. Ammonia emissions from the agricultural sector give rise to numerous environmental and societal concerns, but they also represent an economic challenge in crop farming, causing a loss of fertilizer nitrogen.

The ammonia emissions originate from manure slurry (livestock housing, storage, and fertilization of fields) as well as urea-based mineral fertilizers. Consequently, regulations of ammonia emissions have been implemented in several countries.

The molecular cause of the emission is the enzyme urease, which catalyses the hydrolysis of urea to ammonia and carbonic acid. Urease is present in many different organisms, encompassing bacteria, fungi, and plants. In agriculture, microorganisms found in animal faecal matter and soil are responsible for urea hydrolysis.

Is a urea ban on the cards?

The Department for Environment, Food and Rural Affairs (DEFRA) is proposing to ban the use of solid urea on UK farms. This may hit farmers with an extra bill of £125 million. On the other hand, health economists have estimated the costs of air pollution to the NHS of between £1.54 and £2.81 billion. So how to decide? 

DEFRA has issued a consultation paper for farmers and fertiliser traders (closing date 20 January 2021).  One compromise might be to restrict urea spreading to certain seasons.

If solid urea is banned, most inorganic farmers will switch to ammonium nitrate (which caused the recent explosion in the port of Beirut). Therefore, it is closely regulated in the UK for both transport and storage, leading to increased costs for farmers, as storage and transport have to be upgraded.

Urease inhibitors

One strategy to reduce ammonia emissions is the application of urease inhibitors as additives to urea-based synthetic fertilizers and manure slurry to block the formation of ammonia. However, treatment of the manure slurry with urease inhibitors is associated with increased livestock production costs and has not yet been commercialised. Germany has been trying this but has found farmers use too many loopholes.

Last June, NFU (the National Farmers Union) issued a questionnaire “Urea user? Help us keep it in use.” 

Who is collecting the views of heart patients and asthma sufferers?

Reference: The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture. Jens Jakob Sigurdarson et al. Reviews in Environmental Science and Bio/Technology volume 17, pp 241–258(2018)