Optimize nutrient recycling on agricultural businesses

What's the problem?

Since the recycling rate of nutrients in agricultural businesses is currently very low, huge amounts of nutrients have to be added and this amount gets imported. Here, by the production of the imported input, as well as by transporting it,  greenhouse gas emissions are generated.

An example: Nitrogen (N) is a limiting nutrient for the growth of plants. Therefore, fertilizers must often be used to ensure sufficient plant growth and thus sufficient crop yields. In → conventional agriculture, mainly synthetically produced fertilizers are used. Their production is energy-intensive and causes large amounts of GHG emissions (roughly two tons of crude oil are used to produce one ton of nitrogen fertilizer).

What's the measure?

In agricultural businesses, nutrients should be recycled better and to a higher amount.

How can this be implemented?

In order to recycle the nutrients of the own farm, organic fertilizers (e.g. manure, compost and biogas digestion), as well as plant residues (e.g. mulches or N-fixing legumes) can be used in the crop rotation. These are materials that usually already exist on the farm.

Composting: Farmers composted various materials, such as farmyard manure, grass clover and/or other materials, such as residues from wine and olive processing. Regular turning, either with a special turning device of a contractor (rental machines) or with own agricultural machinery (e.g. tractor with forklift truck), as well as covering the compost rental with fleece blankets and the use of a solid underground help to optimize the process.

Biogas production and - utilisation from liquid waste: Ferment the farmyard manure in our own biogas plant.

Mobile animal husbandry: The cattle can be kept in mobile stables on the arable land and so the straw bedding and excrements of cattle, pigs, sheep and chickens can be used directly as fertiliser for the arable land.

How does this work against climate change?

• The production and transport of fertilisers emits fewer GHG emissions than synthetic fertilisers.
• Composting can efficiently reduce GHG emissions, especially methane, compared to storing manure in an open manure heap or pit.
• Methane emissions can be reduced by fermenting farmyard manure for biogas production. In addition, the produced biogas can be used for heating and thus emissions from fossil fuels can be avoided. In addition, farmyard manure can be used on one's own fields, which reduces the need for imported fertilizers.
• By using the straw deposits and excrements of the cattle as fertiliser, the need for imported fertilisers is reduced.

Which other effects does the measure have?

• Organic fertilisers also have an impact on global warming through direct and indirect N₂O emissions during storage and use, as well as on air pollution through leaching/emissions of NH3) and on groundwater contamination through nutrient leaching. In addition, farmyard manure causes CH₄ and N₂O emissions.
• Compared to the spreading of mineral fertilisers, the spreading of compost in the field improves the soil structure and therefore the resistance of the farm to extreme weather conditions (droughts, heavy rainfall). At the same time, compost carries fewer hygienic risks than fresh manure - which can be important in vegetable gardening or on grassland.
• Mobile animal husbandry produces far less animal suffering than industrial mass livestock farming. Furthermore, it limits the total number of animals, as they are directly bound to the arable land.

Further literature, sources