Gødningens livscyklus og Carbon Footprint

Production, transportation and use of mineral fertilizers contribute directly and indirectly to emissions of greenhouse gases, notably carbon dioxide (CO2) and nitrous oxide (N2O). Fertilizers also enhance agricultural productivity and stimulate CO2 uptake by the crop. They increase yield and reduce the necessity to cultivate new land, thus avoiding GHG emissions from land use change.

Optimizing Fertilizer Production

Carbon Emissions Catalyst prills. Catalytic cleansing technology developed by Yara abates about 90% of N2O emissions. Ammonium nitrate (AN) is used as an example, the most common used source of nitrogen in European agriculture, made up of ammonia and nitric acid. Its carbon footprint depends on the energy consumption, the feedstock used in the ammonia production and the N2O emissions from nitric acid production. EU has defined “best available techniques” (BAT) for these processes. Using BAT results in a total emission of 3.6 kg CO2-eqv per kg N for fertilizers that use ammonium nitrate as the nitrogen source. This is 50% less than the emissions of an average European plant not operating with BAT. Plants outside Europe generally have even higher footprints than average European. Yara’s plants are rated amongst the most energy efficient in the world. We have also developed and implemented catalyst technology reducing N2O emissions from nitric acid plants by as much as 90%. As a result, Yara’s fertilizers sold in Nordic countries have a low carbon footprint, below the European BAT level, and are fulfilling the emission standard set by the Swedish food industry for climate branding (4 kg CO2 per kg N).

Optimizing Fertilizer Use

The overall impact and mitigation potential of fertilizer management with regard to GHG emissions is important. The average 100% carbon footprint from using AN fertilizer is 5.6 kg CO2-eqv per kg applied N. Improved nitrogen management can reduce the emissions significantly, depending on soil and weather conditions. Growers need to ensure that the form, type, the amount and timing of nitrogen being applied will not result in significant losses due to denitrification, volatilization or leaching. A good soil structure increases N-use efficiency and reduces N2O losses. Optimizing N efficiency is key to maintaining and even increasing productivity and profitability. Crop nutrition programs developed by Yara help you choose the right product and apply it in the most efficient way. An array of management without BAT technology and tools such as the N-Sensor™ and the N-Tester™ and software applications such as the Internet based Megalab™ , assist farmers in keeping profitability up and environmental impact down.

A field study conducted on multiple farms in Germany examined the effect of fertilizer application using the N-Sensor. The findings demonstrated that use of the N-Sensor increased yields by 6%, reducing N fertilizer use by 12% and reducing the carbon footprint by 10 to 30%.

Avoiding Land Use Change

Arable land is a scarce resource that needs to be used in the most appropriate way to ensure food security without further land use change. Clearing of native vegetation, such as rain forest, accounts for up to 20% of world GHG emissions. Stopping land use change and deforestation is therefore a primary objective in climate protection.

Cropland has the lowest carbon content of all land types, except for deserts and semi-deserts. Intensification of arable production can save rainforests, grassland savannahs and wetlands from being converted into croplands. It therefore has a positive effect on carbon balance.

Which fertilizer to use?

In many regions of the world, urea is used as a source of nitrogen. Under European climate and soil conditions though, ammonium nitrate based fertilizers (such as AN, CAN, ammonium nitrate based NPKs) have proved to be the most efficient for farmers and more environmentally friendly than urea. Urea has a lower carbon footprint at the production stage of the fertilizer life cycle than ammonium nitrate.

Mainly due to the fact that part of the CO2 generated in ammonia production is captured in the urea. However, the CO2 is released as soon as the urea is spread on the field. In addition, more N2O is emitted from urea by the nitrification process.

Urea also emits more ammonia to the atmosphere during farming than AN, increasing the risk of not meeting the national limits on emissions of acidifying substances defined by the Gothenburg Protocol. The loss of ammonia from urea also requires higher dosage to compensate for higher losses. In conclusion, the actual life cycle carbon footprint of urea is higher than that of ammonium nitrate.