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Reducing emissions from farming: Green ammonia is vital

The UK Government announced its aim to bring all greenhouse gas emissions to net zero by 2050 back in June 2019 and many industries rose to the challenge with their own commitments to emissions reduction.

Agriculture was no exception, with the publication of the NFU’s net zero by 2040 pledge.

Commentators agree the net zero by 2040 pledge is an ambitious one and will require all farming sectors and ancillary industries to play their part in reducing emissions.

The production and use of nitrogen fertiliser is recognised as a significant contributory factor to the industry total, so the fertiliser production industry is working hard to meet its own reduction targets.

Anke Kwast, vice-president of Yara’s Climate Neutral Roadmap states that fertiliser production accounts for 1.5% of global emissions and a further 1.5% comes from the application and use of fertiliser.

She says: “When looking at greenhouse gas emissions for the production of wheat, we can see that one-quarter of emissions come from the farming element of the supply chain.

Of this proportion, 30-40% of emissions are from the soil, and 25-30% is related to fertiliser production.

“So both problems must be addressed.

Yara has developed emissions abatement technology which reduces the nitrous oxide emissions of its fertiliser production by more than 90%.

This means fertilisers produced using this process have less than half the carbon footprint of other fertilisers.

“There is scope to reduce the carbon footprint of making ammonia, the precursor of AN and urea by switching to green ammonia.

“This technique is carbon neutral and is in fact turning the clock back to 1905, when the first fertilisers were manufactured in this way

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“Electrolysis of water was used until 1991, when it became cheaper to extract the hydrogen from natural gas.

“Green ammonia is not compatible with urea production because urea is made by reacting ammonia with carbon dioxide and because green ammonia is fossil fuel free, there is no carbon dioxide available.

“This process is powered by renewable energy sources and the nitrogen obtained from the air using an air separation unit.

Green ammonia is then synthesised from nitrogen and hydrogen via the Haber-Bosch process.

“Yara is now working with partners to invest in this pioneering process and is establishing a 100MW wind power electrolysis green ammonia manufacturing plant, which will save 100,000 tonnes of carbon dioxide each year and has the potential to make enough green ammonia to fertilise an area of 0.5 million hectares.” Ms Kwast says improving nitrogen use efficiency is also vital if net zero targets for agriculture are to be met.

Yara is developing a range of tools for farmers to help them produce more food per unit of nitrogen applied.

Improving nitrogen use efficiency on grassland

Stage 1: Complete a nutrient management plan

  1. a) Carrying out a comprehensive soil analysis on every field at least every five years – selecting a number of fields each year and sampling on rotation makes this a more manageable task
  2. b) A FACTS-qualified adviser will provide fertiliser recommendations based on the results of the soil analysis, the available slurries and manures to be applied and the planned use for the field – multi-cut silage, traditional silage cuts and/or grazing c) Correct soil pH – the optimum pH range for perennial ryegrass and clover is 6.3-6.5

Stage 2: The importance of quality product a) Purchase a high quality fertiliser product – this will be entirely uniform and thorough screening of the product will ensure the same physical characteristics throughout to facilitate even spreading b) When buying a multinutrient fertiliser, consider buying a multi-nutrient compound rather than a blend.

Choosing a true uniform compound is one way of achieving the correct balance of nitrogen, phosphorus, potassium and sulphur in a form which can be spread consistently and accurately


Stage 3: Apply the correct amount of fertiliser evenly and at the right time a) Calibrate the fertiliser spreader accurately and repeat each time a different type of fertiliser is used to ensure the product is applied evenly b) Do not apply fertiliser when soils are waterlogged or heavy rain is forecast c) Fertiliser should only be applied when the soil temperature reaches a minimum of 5-6degC for a few days to ensure grass is growing and roots will actively take up the nutrients



She says: “If farmers can use nitrogen more efficiently, in terms of the rate and the timing they apply it, using variable rate management, this will help to reduce the emissions of ammonia and nitrous oxide.

“Yara has developed technologies which predict the nitrogen demand of crops more precisely and can also improve the accuracy of the variable fertiliser application methods.

“We are making a digital platform available which will enable farmers to download crop specific nutrient management plans, together with local weather data.

“Using this alongside crop monitoring technology should allow the farmer to reduce nitrogen losses to the environment by up to a half.

“Currently, the average nitrogen use efficiency across farms in Europe is 60%.

Our evidence shows this figure can be increased to 80% by adopting these approaches.”


Supplying essential nutrients to the soil improves grass production and animal health

Phillip Cosgrave, country grassland agronomist with Yara, says many grassland farmers could improve their nutrient use efficiency substantially and as a consequence lower their emissions.

He says: “A comprehensive soil analysis will highlight any nutrient and trace element deficiencies within the soil.

When one or more of the key elements for growth are limiting grass growth potential will be compromised.

“For example, a high percentage of grass tissue samples received at our lab in Pocklington had low sulphur levels last year.

Similar results are seen with soil analysis.

Sulphur is a key nutrient for plant growth because it is required for the formation of plant protein and can improve silage quality by lowering grass nitrate concentration at harvest.



“If growing more high quality forage on farms is the objective from both an environmental and economic sustainability perspective then it’ll be important that we look more carefully at the type of fertiliser we use and how it’s made.

“Applying fertilisers containing sulphur can boost dry matter yields by between 10 and 20% using the same amount of nitrogen, because sulphur removes the bottleneck in the assimilation of plant proteins.

“Selenium is also an essential trace element for all animals and humans.

Selenium deficiency occurs at herbage concentrations below 0.1mg/kg dry matter and results indicate that up to 88% of herbage samples are deficient.

“Deficiency in livestock causes still birth and retention of afterbirth in livestock, increased milk cell count and increased levels of clinical mastitis.

In calves, deficiency is associated with ‘white muscle disease’, also known as nutritional myopathy.

“Using fertiliser fortified with selenium is an effective way to increase grass selenium from a level of deficiency to sufficiency for grazed grass or grass silage.

Where herds are grazing predominantly, fortifying grass with selenium really makes sense.”

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