Patterns: © Shutterstock – Graham Corney, © Shutterstock – eNjoy iStyle, © Shutterstock – jeagun lee

Three easy apples to pick

Some types of change require long-term planning, new institutions, educating a new generation etc. Other things are so easy to do that they should have been implemented yesterday.

In the report “Measures to address air pollution from agricultural sources”, the International Institute for Applied Systems Analysis (IIASA) points at three areas where EU member states can achieve quick and cheap results to reduce ammonia and PM emissions from agriculture: the open burning of agricultural residues, mineral fertiliser application, and manure management.

1. Agricultural waste burning

Remote-sensing data shows that the burning of stubble and other agricultural residues is still common practice in parts of the European Union. Setting a field on fire is a quick way to remove crop residues, but depletes the soil of carbon and causes massive emissions of particles. In Bulgaria, Cyprus, the Czech Republic, Greece, Malta and Romania, the burning of agricultural waste contributed to more than 10 per cent of total fine particulate matter (PM2.5) emissions in 2015.

This despite the fact that the practice is banned under Good Agricultural and Environmental Condition (GAEC) standards in most EU countries. This means that farmers who persist in burning their fields under the Common Agricultural Policy regulations should lose some of their direct payments. In view of this, it is likely that member states need to improve their training of farmers, as well as monitoring and law enforcement. The study points out that the cost of implementing a ban is close to zero or may even be profitable, because of the increased soil fertility that follows.

2. Mineral fertiliser application

Mineral fertilisers contribute to almost one-fifth of EU ammonia emissions. Two main types of nitrogen mineral fertilisers are used in Europe: ammonium‐ or nitrate-based salts, and urea. The latter causes 50 per cent of all ammonia emissions from fertilisers, but only provides farming with 18 per cent of the fertiliser nitrogen. The use of urea varies between member states, from none at all in Sweden, Denmark and Belgium, while southern and eastern European countries, as well as Germany and the UK, have higher shares of urea in their fertiliser mix. In Germany it is even reported that the use of urea is growing. The report does not suggest a ban on urea, but two more moderate approaches:

Increased nitrogen use efficiency. There has been a 20 per cent reduction in fertiliser use in the European Union since the peak in 1988. A wider adoption of precision farming is suggested as a tool to increase nitrogen efficiency by 10–15 per cent without impact on crop yields. Automatic guidance systems for farmers offer a cheaper and increasingly popular technique for optimising the use of fertilisers.

Urease inhibitors. Urease is an enzyme that catalyses the hydrolysis of urea into carbon dioxide and ammonia. There are urea fertilisers coated with certain chemicals that suppress the activity of urease. The slower release will result in less excess ammonia that can escape in gas form. The urease inhibitors can reduce ammonia emissions from urea application by as much as 95 per cent.

3. Manure management

Livestock farming, including manure management, contributes to around 70 per cent of the ammonia emissions in the European Union. The dominance of this source is seen across all member states, even though the types and structures of animal farming are very varied. The number of animals, method of housing and manure systems, land availability, soil type etc. all affect which measures are practical to implement.

  • Extended grazing. Provided that there is enough land, ammonia emissions are much lower in a 24-hour grazing system than for animals that are kept indoors.
  • Optimised animal feeding. Adjusting the protein content of animal feed at different stages of growth is a technique that is already widely used. It is appealing to many farmers since it can reduce costs for feed.
  • Treatment of exhaust air (ventilation). In the Netherlands, scrubbers that remove PM10, ammonia and odour are required for animal housing close to Natura 2000 areas. The most advanced systems can remove up to 90 per cent of the ammonia emissions. These systems are expensive to install. The cost is tougher for small farms to bear and if it is made mandatory it could contribute to structural changes.
  • Storage of manure. In the European Union 18 per cent of ammonia emissions are emitted during manure storage. Different types of cover can reduce these emissions. The most effective, but also the most expensive, are airtight lids. Straw, woodchips or just allowing the formation of a crust are inexpensive techniques that could be implemented everywhere.
  • Manure injection. There are several techniques to reduce air contact while applying manure to a field. Deep injection (5–20 cm depth) is the most efficient, reducing emissions by up to 95 per cent. Diluting manure with water and direct incorporation through ploughing are techniques that do not require specialised equipment and can be effective.
  • Slurry acidification. This a common technique in Denmark when applying cattle manure. Higher acidity inhibits bacterial urease formation, which reduces the conversion rate to ammonia (NH3), and any ammonia formed is converted to the less volatile ammonium (NH4+). Emissions are reduced by 50–60 per cent. One drawback is that it requires the potentially hazardous handling of strong acids.

Besides these specific practices the report recommends that countries develop national strategies that aim at an integrated approach for managing emissions from livestock farming. They highlight examples from Germany, the Netherlands and Switzerland that include tightening of regulations and investment support for low-emission techniques.

Kajsa Pira

Measures to address air pollution from agricultural sources, IIASA, December 2017,



In this issue