Recent research has shown that feeding cattle on different food sources can lead to reductions in methane emissions. Robson Peisley asks whether this could be enough to tackle the ever-growing problem of greenhouse gas emissions from the agricultural industry.
Cows are infamous for contributing to the climate crisis, but could a change in diet be the key to reversing this? Photo Credit: Robson Peisley
The Scale of the Problem
It has been widely published that the agricultural industry causes large amounts of greenhouse gas emissions. In fact, the IPCC (International Panel of Climate Change) state that, as of a 2019 report, around 20% of annual greenhouse gas emissions internationally are a direct result of agriculture. The UK government’s Agric-climate Report in 2023 found that agriculture accounted for 11% of total greenhouse gas emissions, 49% of methane emissions, and a staggering 71% of nitrous oxide emissions.
Cattle are widely regarded as part of this due to the methane emissions associated with producing beef and dairy. Research from University of California, Davis has revealed one cow can release 220 pounds (equivalent to almost 100kg) of methane into the environment.
Experts say that tackling agricultural emissions is key to reaching net zero and limiting global warming to 1.5°C, as set out in the Paris Agreement. Activists claim that reducing meat intake is the key to this, but growing evidence from scientists suggests that it is possible to reduce emissions of greenhouse gases from livestock. But is this enough to reach net zero, or is it a tool to reduce emissions in the intermediary period?
Red Seaweed
Asparagopsis seaweeds have been found to reduce the methane emissions of cattle when included in their diet. Photo Credit: Jean-Pascal Quod via Wikimedia Commons
A team of Australian scientists found that feeding red seaweed (Asparagopsis spp.) as a dietary supplement resulted in a reduction in methane emissions of cattle, goats, and sheep by over 80%. Red seaweed contains a compound known as bromoform, and this inhibits the enzyme which forms methane during cattle digestion.
When most people think of global warming, they think of carbon dioxide emissions. However, a range of greenhouse gases exist within our atmosphere. According to the US Environmental Protection Agency, methane is 28 times more potent than carbon dioxide as a greenhouse gas. A reduction in methane emissions is hence vital in tackling the climate crisis.
Red seaweed grows abundantly off the Australian coastline and therefore, with the right management, could be a source of sustainable cattle feed in such areas. Not all parts of the world have nearby coastal systems however, nor do all coastal systems have such an environment for red seaweed to be abundant.
Leucaena
Leucaena has also been found to reduce the methane emissions of cattle, due to it having a high concentration of tannins. Photo Credit: Tauʻolunga via Wikimedia Commons
Another potential food source for reducing livestock emissions is leucaena (Leucaena sp.), which can lead to a 20-30% reduction in methane emissions from rumination. Rumination is the process whereby ruminants, such as cows and sheep, digest their food. This produces large amounts of methane, and so biological solutions to alter this process could be beneficial in the climate crisis.
Another benefit of Leucaena is that it is leguminous, and therefore fixes nitrogen into the soil. This has knock-on benefits for soil ecology and improves soil quality - soils worldwide are becoming degraded, and this has led to an interest in regenerative farming processes such as rotational crop management involving legumes.
Local Sustainable Solutions
One of the barriers to adopting these species as food sources is that they require specific environmental conditions. The trials conducted on red seaweed and Leucaena occurred in regions where these species naturally grew. For areas such as the UK and Ireland, focus has therefore shifted to resources naturally occuring in our environment that could replicate this methane reducing process.
Another benefit of using local sustainable solutions is that they can reduce the need to ship resources via aircraft and boats. There are many positives to this, primarily that lowering transport distances will lead to a reduction in shipping emissions. The global shipping industry has also been associated with the spread of several invasive species including in the UK. The Wildlife and Countryside link found that 43% of invasive invertebrates in the UK may have or could in the future be brought to the UK via the shipping industry.
Willows
Willows are a native to the UK and Ireland which also contain the high concentrations of tannins found in Leucaena. Photo Credit: Kate Jewell via Wikimedia Commons
Willows (Salix spp.) are naturally abundant in the UK and have long been used as a sustainable timber source. Through coppicing, wood can be harvested from willow trees every 2-5 years due to their fast growing nature.
Willows are high in condensed tannins which have been found to interrupt the formation of methane in the rumen of cows. In 2022, Queen’s University Belfast decided to trial willow as a form of cattle feed after promising evidence in the laboratory from sampling over 200 different Irish plant species. The scientists found varying evidence in their livestock-based trials and experiments. Whilst willow reduced gross emissions, it appeared to lead to higher emissions per live weight gain, which is deemed the more important metric. Despite this, the scientists noted that it was only a pilot project, and that a more robust long-term study is currently underway. However, there is promising evidence that willows may be able to play a role in reducing cattle methane emissions. As well as this, sheep are also ruminants and so studies are underway to trial willow feed in sheep as well.
Nitrous oxides are another type of greenhouse gas which have been found to be 265 times as potent as carbon dioxide. Research which fed sheep willow trees found significant reductions in both nitrous oxide and carbon dioxide emissions, evidencing that willow could be key to reducing the emission of various greenhouse gases by ruminants.
The Future
Whilst there is some promising evidence from sheep that alternative livestock diets can reduce greenhouse gas emissions, the big question is whether it is enough in light of the climate crisis. Photo Credit: Robson Peisley
There are already synthetic supplements for livestock, particularly ruminants, to reduce greenhouse gas emissions. Research is now starting to find natural food sources which will be key in creating sustainable solutions.
Current research has largely focused on reducing greenhouse gas emissions from ruminants, and these solutions will not work with other livestock such as pigs and poultry. A reduction in animal product intake, and a consequential reduction in livestock numbers, is also therefore likely to be necessary to reduce agricultural emissions. Natural solutions are also still being researched to fully understand their effectiveness.
To meet climate targets, a reduction in livestock numbers will be necessary. However, there are signs that we could make remaining livestock agriculture more climate friendly by shifting their feed.
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