Manure Manager

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Livestock emissions lower than previously thought: new research


May 7, 2020
By Manure Manager

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Research conducted in Ireland has found that emissions from livestock manure patches are lower than previously thought.

Teagasc, the state agency in the Republic of Ireland responsible for research and development, training and advisory services in the agri-food sector, recently ran a study focused on measuring nitrous oxide (N2O) from animal urine and dung patches during spring, summer and autumn on three types of pasture soils: well-drained; moderately-drained; and poorly drained.

Conducted by Teagasc researcher Dominika Krol, the project established that the average emission factors of nitrous oxide were “substantially lower” than the default emission factors of the Intergovernmental Panel on Climate Change (IPCC) – which estimated the “excreta-derived nitrous oxide” figure at two percent.

This, Krol says, means that two percent of nitrogen in the dung and urine patches was believed to be lost as nitrous oxide – a form of greenhouse gas (GHG). This latest project, however, has found those emission factors to be at a lower rate – 0.31 percent for cattle dung and 1.18 percent for cattle urine.

Krol said that the losses to the atmosphere were driven by factors including rainfall, temperature and soil moisture. The highest emissions were emitted in autumn, from the “imperfectly-drained soil,” she added.

Krol also noted that the original GHG inventory showed that up to 41 percent of nitrous oxide produced from Irish agriculture comes from urine and dung deposited by grazing animals. However, based on the new research, this fraction is reduced to approximately 23 percent.

This “clearly shows that our grass-based system has lower emissions than originally expected,” Krol said.

In addition, she noticed large differences between excreta, soils and weather, which she maintains can help to mitigate emissions.

Krol said that, going forward, changes in animal diet can be further investigated in a bid to reduce nitrogen in urine or move it towards dung. Grazing times can also be adjusted to extend grazing on well-drained soils but restrict grazing on poorly-drained soils when wet, she added.