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Fertiliser production - emissions, effects and solutions

23rd May 2014

So as the month of blogs looking at fertilisers and fertility draws to an end, it seemed like a good time to look at emissions associated with fertiliser production.  Now before some of you switch your computers off in horror at the thought of a chemistry lesson, I must confess that I’m not an expert in this field at all.  This won’t be a blog explaining all of the new techniques that are being developed in terms of reducing emissions, but just a summary of what’s going on.

Here at FCCT we have written blogs in the past about fertiliser use efficiency and bandied the statistics around that 50% of the greenhouse gas emissions associated with fertilisers are attributable to the production process.  Therefore management of cropping patterns, maintenance and use of precision equipment, nutrient management planning, and taking account of any manure and slurry applied to avoid over application will all have a significant effect on emissions from your farm.  For more information on how to minimise emissions from fertiliser application please click here.

Unfortunately there are yield implications when we stop using Nitrogen fertiliser.  Nitrogen fertiliser has played a key role in enhancing food production and keeping half of the world’s population adequately fed.   Decades of fertiliser overuse in many parts of the world have contributed to soil, water and air pollution, reducing excessive Nitrogen losses and emissions in a central environmental challenge in the 21st Century.

The process of manufacturing fertiliser

N fertiliser is produced using the Haber Bosch process.  This involves combining Hydrogen (from steam reforming) with Nitrogen (from the air) to create ammonia.  The process is very energy intensive, needing high pressure and high temperature to be most effective, and this comes with a large carbon footprint attached to it. 

Work by the International Fertiliser Industry Association (IFA) showed that fertiliser manufacture accounts for approximately 1% of global greenhouse gas emissions.  If associated Nitrous Oxide emissions from applying the fertiliser are taken account of as well, the total increases to 2.5% of the global total.

New technologies for reducing emissions.

There are long term solutions that are in development to reduce the emissions associated with fertiliser production.  These include carbon capture and storage, renewable electrolysis (to produce the hydrogen rather than the very energy intensive steam process), or the use of biomass gasification.  Biomass gasification uses a biomass based feedstock to produce a gas mix which is high in Hydrogen, which can be used to create the ammonia needed.  This ammonia is then combined with nitric acid to produce Nitrogen fertiliser (ammonium nitrate).  Studies looking at biomass gasification have found that the GWP can be reduced by 52% through using this production method.

As well as the process being energy dense, the other emission associated with fertiliser production is nitrous oxide emissisons which is a by-product of the production of nitric acid.  With improvements in best available techniques, the IPCC estimate that nitrous oxide emissions can be reduced to approximately 0.12 kg/tonne nitric acid.

Experiences in China

China’s participation is essential in global efforts in reducing nitrogen related greenhouse gas emissions because China is the largest producer and consumer of fertiliser N, accounting for about 30% of global manufacture.

A project developed by Rothamsted Research and China Agricultural University (alongside other colleagues in the UK and China) have been researching different options for reducing the environmental impacts of fertiliser use.  They found during the course of the project, that a combination of technical innovations in manufacturing, and changes in how the fertiliser is applied could help to reduce the GHG emissions by between 2-6% of China’s overall greenhouse gas emissions.  This is a significant reduction.

 Innovation in the UK

One company in the UK who is looking at minimising losses and emissions from production of fertiliser is Yara.  The European Union has defined “best available techniques” for the processes associated with fertiliser production.  Yara have worked on measuring the carbon footprint from fertiliser production and through the use of new technologies.  One example of this is their catalytic cleansing technology with abates about 90% of nitrous oxide emissions associated in the production of nitric acid.

For more information on the work done by Yara click here to visit their website.

What can we do?

In terms of practical measures that we can do at home, the only real option for anyone seriously interested in the emissions from fertiliser production is to ask questions and buy from producers who are minimising emissions.  Moving forward more innovations will lead to a more streamlined process and fertiliser manufacturers will become streamlined in their environmental credentials.

 The best way to minimise losses from fertiliser on the farm is to make sure that they are applied in the most efficient way possible.  This will mean that the proportion of the emissions that arises from application is reduced, and also that more of the Nitrogen is used to grow profitable crops rather than lost into the environment.