Breath: it’s time to rationalise respiration in livestock emissions

The contribution of livestock to climate change is now well-established, and showing growing awareness in the average consumer. The FAO estimates that livestock alone contribute approximately 15-20% of global greenhouse gas (GHG) emissions. That’s a lot, especially when we consider that in contrast to other key contributors such as energy and road transport, there are fewer “clean” options for mitigation (besides eating less meat, of course).

As someone who spends their days researching and analysing the interactions between agriculture, nutrition and sustainability, I’ve come to know the relative carbon intensities of different foods by heart. Around three kilograms of CO2e (carbon dioxide equivalents—the measure of GHG emissions) are emitted for every kilogram of chicken meat; pork is a little worse at 4.5-5 kilograms; beef worse still, ranging anywhere from 12-30 kilograms; and in some systems, lamb comes out worst at 14+ kilograms per kilo [shown a little further down]. I’ve gotten used to quoting these numbers for years, and perhaps out of habit (or ignorance?) taken the methodologies by which they’re calculated for granted. They were, after all, set by the UN’s Food and Agriculture Organisation (FAO).

It wasn’t until I had to carry out a carbon intensity assessment for a food product myself, that I started to question whether these numbers capture the full picture of the global impact of livestock. I’m Sustainability and Business Development Manager for 3f bio, a spin-out company developing a novel and patented zero-waste technology for the production of Food, Fuel and Feed. The technology aims to make the meat-free food product mycoprotein (you may know it more commonly by its brand name Quorn™) through integration within existing biorefineries which already produce bioethanol (fuel) and animal feed (DDGS). Long story short: we’re developing a zero-waste process which can make healthy, low-cost, sustainable protein.

So I crunched the numbers on the GHG emissions, and our mycoprotein comes out at about 1.05kg/kg (shown below versus other protein). A good result: much lower-carbon than meat alternatives, and significant reductions on the existing process for mycoprotein production. However, there was still one key difference between the methodology for calculating our emissions, and that of livestock products. We included emissions from respiration in our estimates; a source of emissions left out of livestock numbers.

co2-intensity-imagesRespiration (i.e. breathing) isn’t simply an oversight—we didn’t just happen to forget that livestock breath out carbon dioxide. The FAO explicitly excludes respiration emissions on the basis that:
Respiration by livestock is not a net source of CO2…. Emissions from livestock respiration are part of a rapidly cycling biological system, where the plant matter consumed was itself created through the conversion of atmospheric CO2 into organic compounds. Since the emitted and absorbed quantities are considered to be equivalent, livestock respiration is not considered to be a net source under the Kyoto Protocol.

In other words: animals are part of a short cyclic system with the natural environment such that respiration is not a net source of emissions. In practice, this is right. To grow, crops (it could be grass, cereals, pulses—any crop an animal would eat) essentially capture CO2, removing it from the atmosphere. Then when an animal eats the crop, this CO2 is emitted back to the atmosphere through respiration (breathing). In a balanced natural system, this can continue over and over with no change in atmospheric emissions. Crop captures CO2 –> animal eats crop –> animal exhales CO2 –>crop captures CO2 –> animal eats crop –> animal exhales CO2. And repeat.

So it’s true: in a balanced biological system, respiration is not a net source of emissions. And since the FAO sets the guidelines for how to report on agricultural emissions, no one includes respiration in livestock footprints. But is there a valid case for us doing so?

There’s one fundamental driver of the need to have a focus on environmental sustainability at all: the very fact that humans are rapidly shifting Earth’s biological systems out of equilibrium. If our systems were in equilibrium—which is the rationale for not including respiration in our calculations—then there’d actually be no need for us to discuss climate change at all. The rapid rate of change through which we are altering our biological systems (which includes the carbon cycle) means that they are now out of balance.

Now, going back to the assessment that triggered this discussion in the first place: calculating the footprint of mycoprotein (a type of fungi). The very nature of the process is almost identical to that of livestock. It works like this: we feed a carbohydrate-rich crop into a fermenter, add some nutrients and oxygen –> fungi/mycoprotein grows –> as it grows, it respires–> this CO2 is emitted to the atmosphere. There’s actually very little difference between this and a livestock system; the only difference being that mycoprotein is grown in a fermenter rather than a barn or field, and the CO2 is emitted through a pipe rather than an animal’s mouth. In both processes, the CO2 was initially captured by the feed crop as part of a cyclic loop.

We included respiration in our calculations, because it didn’t make sense—and there is no credible case—for us not to. The process essentially emits CO2 through a pipe/vent/column to the atmosphere. It is therefore a source of atmospheric CO2 emissions. When compared in this way, it throws up the question of whether we should be doing the same for livestock.

Just how much of a difference would respiration make to these numbers? I crunched some of the numbers on respiration emissions based on published respiration rates[1], and animal growth/lifespan figures. You can see the end result below as dashed columns. For mycoprotein figures, I have subtracted respiration emissions to show the difference it makes.

[I should note that I’m providing these as an estimate only—there can be variability based on factors such as the lifespan and size of an animal, and its feed intake. Although not perfect, they should still give a feel for the magnitude of difference].


Makes a big difference, right? Some studies [although they have received some criticism on underlying figures, and are somewhat ideologically motivated] estimate that with respiration emissions, livestock would account for 51% of total global GHG emissions[2]. I suspect that’s not wholly accurate, but it’s still significantly larger than the figures we currently report.

However, the purpose of this discussion wasn’t to try to demonstrate or emphasise how bad or carbon-intensive meat is. With or without respiration emissions, it’s already obvious. It was in fact to raise a wider question of how we account for our GHG sources and sinks. As I mentioned above, we’ve shifted our natural systems—including the carbon cycle—out of balance. Now, in the Paris climate agreement, the world has [I should technically say “will” because it hasn’t come into force yet] pledged to restore this balance in the carbon cycle. In technical terms, we’ve pledged to achieve “net-zero” emissions. All this means is that our sources and sinks of GHGs balance i.e. the amount of GHGs we emit is exactly the same as the amount that the Earth’s natural systems can capture. Theoretically, if these balance then GHGs do not accumulate in the atmosphere.

What’s fundamental in ensuring that our sources and sinks balance? Knowing what they are and how much they contribute. There’s an old business mantra: “you can’t manage what you can’t measure”, and it lies at the core of what we’re trying to do. If you’re not measuring your sources and sinks, how will you ever be able to track progress in ensuring they balance?

The discussion around livestock respiration has been closed for a while now. But perhaps it’s time (considering the Paris commitment that the world is signing on to), to open it back up again. Yet it should be done through an intent on furthering understanding and progress rather than an underlying agenda to prove or disprove how bad/good our livestock systems are. It’s easy for such discussions to be taken over by groups at either extremes of the spectrum. The end result is usually a drowning out of voices in the middle, until everyone loses patience and we end up no further forward than when we started.

[1] Pedersen, S., Blanes-Vidal, V., Jørgensen, H., Chwalibog, A., Haeussermann, A., Heetkamp, M.J.W. and Aarnink, A.J.A., 2008. Carbon dioxide production in animal houses: A literature review. Agricultural Engineering International: CIGR Journal.