Risk to rely on soil carbon sequestration to offset global ruminant emissions.

Area of Science:

• Agricultural Science
• Climate Science
• Environmental Science

Background:

• Grassland carbon sequestration is proposed to mitigate greenhouse gas emissions from ruminant agriculture.
• Understanding the limitations of soil carbon sequestration, including its time-limited benefits and differences between greenhouse gases, is crucial.

Purpose of the Study:

• To quantify the potential of grassland carbon sequestration to offset methane and nitrous oxide emissions from ruminant systems.
• To assess the feasibility of relying solely on grassland carbon sequestration to counteract the warming impact of current ruminant emissions.

Main Methods:

• Calculated the amount of carbon sequestration required to offset radiative forcing from methane and nitrous oxide emissions over 100 years.
• Compared the required carbon sequestration amounts with current global carbon stocks in managed grasslands and projected regional increases needed.

Main Results:

• One tonne of sequestered carbon can offset 0.99 kg of methane or 0.1 kg of nitrous oxide annually over 100 years.
• Approximately 135 gigatonnes of carbon are needed to offset global ruminant emissions, nearly double the current grassland carbon stock.
• Regional grassland carbon stocks would require increases of 25% to 2,000%.

Conclusions:

• Solely relying on carbon sequestration in grasslands is not a feasible strategy to offset warming from current ruminant emissions.
• The time-limited nature of carbon sequestration and the potency of greenhouse gases necessitate diverse mitigation approaches.
• Significant expansion of carbon storage in grasslands is required, highlighting the scale of the challenge.