Better manure management could help egg farmers to respond to the pressure from NGOs, governments and consumers to reduce their environmental impact.
The egg sector may only be a low contributor to the animal production value chain’s emissions – ~ 300 million metric tons of CO2 equivalent in 2019 or <3 percent of the total emissions – yet it still faces pressure to adopt best practices to further reduce its impact.
Act where possible
Egg farmers have only limited influence on the emissions generated during the culture, harvesting and processing of crops used in layer rations.
However, they do have direct control over manure emissions, which at 20 percent of total emissions, are the egg sector’s second largest source.
The goal of optimum manure management is to reduce anaerobic bacteria’s fermentation processes before the application of the manure onto fields.
The rations fed to birds have a direct impact on manure chemistry and, therefore, on greenhouse gas emission intensity during storage and after application on the soil. Any condition decreasing nutrient digestibility of feeds will increase the concentration of fermentable organic matter in the manure, which, in turn, increases emissions.
Mitigation strategies typically focus on two areas – manure composition and storage.
The composition of manure needs to be considered, in particular, its pH, humidity, the presence of undigested organic substances and its nitrogen content.
The use of feed ingredients or supplements that enhance gut absorption, or that promote digestive system health, not only improve feed conversion and profitability but also reduce the amount of organic matter favored by micro-organisms in the manure.
The second strategy should focus on storage, particularly the type and length of storage, temperature and the time to soil application.
Wet or dry?
Manure is typically stored in one of two ways, either dry or wet.
Dry storage is more common. Regularly collected from the layer house, manure is stored in a dedicated shed and left to dry for several months.
However, it can also be stored outside in tanks or lagoons and mixed with used water. Storing liquid manure is more convenient as it can subsequently be sprayed onto fields as a fertilizer. However, in uncovered lagoons, there are significantly higher greenhouse gas emissions.
Finally, the timing of the manure application to match crops’ demands for extra nutrients can effectively reduce greenhouse gases such as nitrous oxide.
Manure analysis will reveal how much nitrogen is present. What birds are not digesting is not only money wasted, but food for micro-organisms.
