For decades, methane from cattle has drawn attention as a major driver of global warming. Free-range grazing itself is not the core issue; the problem grows with the number of farms housing hundreds of cattle, creating a multiplier effect that makes livestock a dominant source of this greenhouse gas.
Globally, livestock releases about 3.1 billion metric tons of methane each year. Because methane traps heat far more efficiently than carbon dioxide, the issue is highly significant when considering climate impact.
Methane can retain atmospheric heat roughly 80 times more effectively than CO2 and contributes about 30% of the warming effect attributed to greenhouse gases. On this basis, livestock accounts for roughly one third of all methane emissions worldwide. By comparison, a small cow can be as impactful as a small car in terms of emissions.
The digestion process in cattle generates substantial methane, underscoring why it is such a focal point in climate discussions.
The European Union has targeted substantial reductions, aiming for an 80% to 95% cut in methane emissions from livestock by 2050, which has spurred calls for innovative solutions to reach those targets.
Algae, unexpected allies
In recent years, researchers have identified algae as a surprising ally in the battle against methane. In 2016, Australian researchers first demonstrated the potential of certain seaweeds to reduce methane production. The red alga Asparagopsis taxiformis, once considered invasive in parts of the Mediterranean, showed natural properties that could curb methane emissions in ruminant livestock.
Specifically, the compound bromoform in this algae interferes with the methane-producing pathway in the rumen. By 2019, studies showed that including less than 0.2% algae in cattle feed could yield methane reductions ranging from 40% to 98%. A University of California study later confirmed its effectiveness: seaweeds in livestock diets can reduce greenhouse gases without diminishing benefits over time, with reductions reported up to about 82% in certain conditions. These findings attracted attention and investment from prominent figures and firms, including Bill Gates, who backed ventures like an Australian startup developing seaweed-based feed; Rumin8. Other companies, such as DSM, have pursued similar feed additives since late 2021.
Another approach: algae in the manure mix
Recently, researchers explored a different avenue: introducing the same red algae into the manure itself. A study titled Boundaries in Sustainable Food Systems reported promising outcomes when the algae were present in the feces, suggesting an alternative pathway to cut methane emissions from waste streams.
In trials where the algae were added to cow dung, methane production dropped by about 44% for animals receiving both feed and manure supplements. Experts note that numerous factors influence emission outcomes, including storage conditions and climate. For instance, manure stored in cool, temperate environments—common in Europe—accounts for a portion of dairy sector methane emissions but can vary with management practices.
As researchers continue to gather evidence, the potential for seaweed-based additives and manure-focused strategies remains a central thread in efforts to reduce livestock-related methane. Researchers like Mohammad Ramin of the Swedish University of Agricultural Sciences emphasize the need for broader studies to confirm the real-world impact across dairy systems and manure management. Emission contributions depend on many factors, and ongoing work seeks to translate lab findings into practical, scalable solutions for farms of different sizes and regions.
Reference work: Frontiers in Sustainable Food Systems, 2023, 1187838. Attribution: this study and related reports compile findings on seaweed-based feed and manure interventions. (Frontiers in Sustainable Food Systems, 2023)
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