A study identifies the key technologies and strategies for reducing greenhouse gas emissions significantly along the livestock waste management chain.

One of the main challenges of manure management on livestock farms is reducing greenhouse gas (GHG) emissions and air pollutants. However, a recent study identified advanced technologies and effective strategies that can significantly reduce emissions throughout the entire manure management process.

The study analysed numerous mitigation practices applicable to each phase in detail, offering concrete solutions for more sustainable livestock farming. The manure management chain comprises three main phases: animal housing, manure storage and treatment, and field application.

The main mitigation measures

Key mitigation measures include storage technologies, such as closed or covered systems, to limit methane and ammonia emissions; biological treatments to reduce greenhouse gas production during manure decomposition; and optimised manure application techniques, such as the use of injectors or immediate soil incorporation, to minimise gas losses.

Solid-liquid separation can reduce methane emissions by up to 46% and ammonia emissions by 21%. If properly managed, impermeable covers for wastewater storage (e.g. plastic sheeting) can achieve emission mitigation efficiency of up to 99.5%. Air scrubbers, which are systems installed at the outlet of livestock ventilation systems and pass air through filter material or a liquid solution (water or chemical reagents), can reduce ammonia emissions by up to 99% (chemical) and 92% (biological), albeit at different costs and with different technical requirements.

Effects of diet and manure removal

The practices examined include feed formulation, which can directly influence methane production, and frequent manure removal to reduce gas build-up. Reducing dietary crude protein by 2% can cut ammonia emissions by up to 46%. Depending on the technology used, removing manure three times a week or daily can reduce methane emissions by up to 89%, ammonia by 25–30%, and nitrous oxide by up to 50%.

Treatment technologies

Techniques such as solid-liquid separation are employed during the storage and treatment process, allowing waste to be treated more efficiently and reducing greenhouse gas emissions. Anaerobic digestion reduces methane emissions by an average of 59%, transforming the effluent into useful biogas.

Acidification can reduce ammonia emissions by between 33% and 93%, methane by between 67% and 87%, and nitrous oxide by up to 90% if lactic acid is used.

Application phase

Finally, during the application phase of wastewater (or rather, digestate), various techniques are employed to optimise nutrient release into the soil and minimise gas loss. These include the use of injectors and low-emission distribution systems. Although surface injection reduces ammonia emissions by 62–70%, it can also lead to a 259% increase in nitrous oxide emissions. Therefore, it is essential to evaluate the trade-offs between gases, as reducing one can lead to an increase in another.

This study confirms that a combination of targeted management practices and innovative technologies can effectively reduce emissions throughout the livestock waste management chain. When selecting technologies, it is essential to consider not only their effectiveness in reducing emissions but also factors such as cost, technical feasibility, scalability, local regulations, and climate conditions. An integrated approach is essential to avoid pollution swapping and ensure effective emissions reduction throughout all stages of the supply chain.