Ways to reduce greenhouse gas emissions from livestock farming in France

After transport, agriculture is the second source of greenhouse gas emissions in France, almost on par with industry and construction. With its 18 million cattle, 14 million pigs and 158 million poultry, the livestock sector represents 59% of these emissions. Reducing these emissions is an important challenge to achieve the objective of carbon neutrality by 2050. Inrae has just published a document in which it lists, among other things, all the research projects and the avenues developed to reduce these emissions. emissions.

And first, those of methane, the second contributor to the greenhouse effect in France after CO2 and whose warming power is 80 times higher. Agriculture represents 71% of these emissions in France and livestock production is the main source, particularly ruminants due to their biological digestion process, called methanogenesis. Microorganisms housed in the rumen of cattle produce methane, a by-product of food fermentation.

The most studied approach to reducing emissions from cattle consists of modifying the composition of their rations. If cattle grazing represents an important lever to contribute to this, the distribution of fodder supplemented with a concentrate rich in cereals and oilseeds is also a solution to consider and can reduce methane emissions by up to 20%. The researchers went further and calculated that the intake of certain food supplements based on red algae or fatty acids from oilseeds such as flax could reduce emissions by up to 40%.

Reduce the unproductive periods of animals

Genetics is another area currently being studied, as it represents an estimated share of around 15% in the variability of methane emissions from cattle. Scientists have managed to predict this genetic component based in particular on the analysis of the milk of each cow. From next year, breeding organizations will be able to include the methane production criterion in their animal selection schemes. By assigning a weight of 20% to this criterion in the selection scheme, it would be possible to reduce methane emissions by around 10% in 10 years of selection and by 30% in 30 years.

Another area of ​​research, this time indirect: herd management. The idea here is to reduce the unproductive periods of animals, for example by starting reproduction earlier, with births at two years of age. By avoiding feeding heifers that are not yet producing milk for too long, this approach could reduce cows' methane emissions by around 10%. Another solution is to extend the number of lactations of cows, rather than replacing them as soon as the next generation matures.

Nearly 300 times more warming than CO2, nitrous oxide (N2O) is another greenhouse gas emitted by livestock, the third contributor in France. Agriculture is the main emitter, since around 86% of national emissions come in particular from the fertilization of soils with nitrogen fertilizers, whether mineral or from livestock effluent. In addition to N2O, these fertilization processes are also the main sources of ammonia (NH3) emissions, a precursor gas for fine particles.

Certain spreading techniques have been identified as being able to cause massive emissions of nitrous oxide and ammonia, among other things when the effluents are in contact with the air. In particular, the one called splashing, which consists of using a paddle nozzle to project effluent over a long distance into the fields. Researchers now recommend their direct deposition on the ground using danglers or their burial by injection into the ground; two techniques that can reduce ammonia emissions by up to 90%.

Replace soybean meal with synthetic amino acids

Representing between 65 and 95% of the environmental impact of a farmed animal, food manufacturing is another area in which to intervene to limit its effects. To understand this impact, it is enough to analyze the pigs' ration, made up of 70% cereals (wheat, corn, barley, triticale), but also 15% oilcake (rapeseed, soya, sunflower). However, the latter are frequently imported and come from deforested areas, as is the case with soybean meal from Brazil.

During an experiment, scientists replaced this soybean meal with synthetic amino acids. Result: even if the growth of the animals slowed down, they observed better use of nitrogen. This change in formulation also made it possible to reduce the impact on climate change by around 20%. This gain could be calculated using a database called ECOALIM, which INRAE ​​has been publishing for around ten years, and which assesses the environmental impacts of raw materials used in food formulation.

A final lever consists of improving the feed efficiency of pigs, that is to say their ability to convert the feed they consume into weight gain. It can be obtained through genetic selection of animals exhibiting this trait as well as nutritional optimization of rations according to the individual nutritional needs of the animals. Thanks to the provision of foods adjusted to their specific needs and optimized in terms of environmental impacts, scientists have calculated that it would be possible to reduce the environmental impact of animals by 5% to 9% depending on their profile. genetic.