Olive By-Products Show Promise for Cutting Cattle Methane

Methane’s Outsized Role in the Climate Equation

Methane doesn’t linger in the atmosphere anywhere near as long as carbon dioxide — roughly 12 years compared to CO2’s centuries, but pound for pound it traps far more heat while it’s there, on the order of 25 times CO2’s warming effect.¹ That combination of short lifespan and high potency is exactly why methane has become a priority target under climate frameworks like the Paris Agreement: cut it now, and you get a genuine near-term dent in warming, unlike CO2 reductions which take decades to show up in the temperature record. ^2,3

Roughly a quarter of all human-caused methane comes from enteric fermentation, the digestive process in cattle, sheep, and other ruminants — putting it in the same league as the oil and gas industry as a source of the gas. ⁴ That’s pushed feed formulators and animal nutritionists to look hard at what happens inside a cow’s rumen, and whether it can be nudged toward producing less methane without hurting the animal’s performance.

Inside the Rumen: Where Methane Actually Comes From

Enteric methane isn’t a flaw in digestion — it’s a normal by-product of it. Microbes in the rumen break down feed into volatile fatty acids, mainly acetate and propionate, which the animal then uses for energy. Along the way, methanogenic archaea consume hydrogen and carbon dioxide generated during fermentation and convert them into methane.^5,6

The balance between acetate and propionate production turns out to matter a lot. Propionate formation actually consumes hydrogen, starving the methanogens of the raw material they need. Acetate and butyrate pathways, by contrast, release extra hydrogen that methanogens can use. ^7,8 So diets or additives that shift fermentation toward propionate tend to lower methane output — and often improve the animal’s energy efficiency at the same time, since propionate is a particularly useful energy source. ^9,10

This has opened the door to a range of mitigation strategies: reformulated diets, feed additives, and plant-derived bioactive compounds. Triterpenes, a class of plant secondary metabolites with known antimicrobial activity, are one of the more promising candidates because of their ability to influence the rumen’s microbial population directly.

Testing Olive Triterpenes on Rumen Fermentation

A 2022 in vitro study looked specifically at triterpenes extracted from olives (Olea europaea) to see whether they could shift ruminal fermentation in the same direction. Researchers, including teams from Natac Biotech, ran two linked experiments: ¹¹

• Experiment one tested increasing doses of olive triterpenes (up to 100 mg/L of inoculum) in batch culture to establish a dose-response pattern.
• Experiment two narrowed in on oleanolic acid specifically — one of the most abundant triterpenes in olive by-products — comparing it against an oleanolic acid derivative at 200 mg/L.

Both experiments used a no-additive control and sodium monensin (a widely used ionophore antibiotic) as a benchmark comparison. Rumen fluid came from crossbred steers fed either a forage-based or a highly fermentable by-product diet, and a fiber-rich substrate was used to test how oleanolic acid performed in its most bioavailable form.

The findings: Less methane, more efficient fermentation:

• Oleanolic acid reduced total gas production, methane included
• The drop in methane tracked with a shift in the acetate-to-propionate ratio, in favor of propionate
• More propionate meant less free hydrogen available for methanogens to work with — the same mechanism seen with other propionate-favoring interventions

The Bigger Picture for Livestock Producers

The appeal of a compound like oleanolic acid isn’t just the methane number. Experimental results suggest that under certain conditions, oleanolic acid can shift some ruminal fermentation parameters, like methane or acetate: propionate ratio, in the same direction as monensin, an ionophore antibiotic.¹¹ These in vitro results could fit into a broader push toward reducing antibiotic use in animal agriculture – a priority, separate from climate goals. And because olive triterpenes can be sourced from olive processing by-products, there’s a valorization angle too: turning what would otherwise be waste from olive oil production into a functional feed ingredient.

There’s also a welfare dimension worth flagging. More efficient fermentation generally means less digestive stress on the animal, which can translate into better feed conversion and productivity — the kind of outcome that benefits both animal wellbeing and the environmental footprint.

None of this replaces the need for further work but it’s a reasonable illustration of where enteric methane research is headed: available propionate-favoring formulations, plant bioactives, and feed efficiency gains — that can be combined to bring livestock emissions down.

Sources

1. European Commission — Methane emissions
2. UNEP, Global Methane Assessment, 2021
3. UNFCCC — The Paris Agreement
4. IPCC AR6, Mitigation of Climate Change, 2022
5. Knapp, J.R. et al. (2014), Journal of Dairy Science, 97, 3231–3261
6. Beauchemin, K.A. et al. (2009), Journal of Dairy Science, 92, 2118–2127
7. Mitsumori, M. et al. (2008), Animal Science Journal, 79(3), 257–267
8. Moss, A.R. (2000), Annales de Zootechnie, 49(3), 231–253
9. Hristov, A. et al. (2013), Journal of Animal Science, 91(11), 5045–5069
10. Króliczewska, B. et al. (2023), Agriculture, 13(3), 602
11. Cangiano, L. et al. (2022), Translational Animal Science, 6(2), txac056

About the Author

Dr. Luis Antonio Serrano Gonzalez

Chemist with an MSc in Food Quality, Hygiene and Safety, and a PhD in Organic Chemistry. Since 2021, he has worked as a Senior Scientific Researcher at Natac, contributing to the translation of scientific knowledge into practical and market-ready solutions.