Cattle eating hay

Beef Basics: (ii)

 

The complexities of beef’s carbon footprints.

 

In the first article in this series, published last week, I touched on the central conundrum of good science communication, namely how complicated do we make our explanations of complex science? When considering questions linked to the carbon footprint and sustainability of beef, matters soon become very complex.

VetSalus recently published a summary of carbon footprints of various food products as part of our fact sheet, which is free to download from our website, www.vetsalus.com - UK version; NZ Version. I reproduce the table below.

Global Greenhouse Gas Emissions per 100 grams of Protein

Firstly, let me clarify that I intend no direct criticism of this graph which is a very useful summary of a complex picture; it is designed to stimulate interest and discussion, and it has!

What concerns me is that it presents a narrow slice of that complex situation, one which a non-scientist can easily comprehend; they may even decide to change their eating (and food buying) behaviours on the basis of this graph. Would a more in-depth analysis of the information presented lead them, inevitably, to the same conclusion?

The graph indicates that for every 100 grams of beef protein produced by beef cattle, around 34 Kg of CO2 is emitted. The graph does not actually define the unit of the x axis, but a little additional research corrects this omission. (1)

Immediately some questions emerge:

Are we discussing Kg of beef or beef protein?

It is clear that this graph has defined 100 grams of protein and as beef is approximately 25% protein, the 34 Kg of CO2e referred to relates to around 400 grams of actual beef.

Is CO2e the best measure of the carbon footprint?

There has been considerable debate about this, especially when methane is the greenhouse gas under investigation. Methane is a short lived but very potent greenhouse gas. Some authors have suggested that a different metric, GWP*, which recognises the short-term impact of gas such as methane, should be utilised (2). Conversion between the two metrics is not straightforward but the Kgs of methane emitted would be considerably reduced should GWP* be utilised.

If 34Kgs is the average, what is the variation around that number?

The range is wide. A large number of factors will impact the carbon footprint of beef production. These include the size, age and breed of animal involved, the diet fed and its source, the production system utilised and the distance and method of transportation used in transporting the product to slaughter and on to the consumer. There is also considerable variation in the actual carbon footprint figures quoted for beef production, with one paper reporting a range of 9 to 129 KgCO2e per Kg of beef, depending on production practice and geographical location. (3)

In a detailed report, which compares three common beef production systems in the USA; Judith Capper reported a range from 16Kg Co2e per Kg of beef for a ‘conventional’ system, finished in a feedlot, to 27Kg CO2e for grass fed. (4) But this is based on hot carcase weights, when valid comparisons between food types can surely only be made on a dry matter basis.

In the case of breed, for example, a growing amount of work has been done on genetic selection. One group has reported on the use of genomics, the identification and selection of genetic markers, to identify lower methane producing animals and suggests that genetic selection can be a powerful tool in the mitigation of methane emissions.(6)

Beef diets vary in constituents. Some natural grazing systems rely on 100% pasture consumption with minimal management of faeces, whereas more intensive systems involve carefully balanced diets, with complex, energy intensive management of faeces being required. The increase in methane emissions from intensive faecal storage systems, when compared to pasture systems, is considerable, with one source stating that grazing produces 7x less methane from manure. (1)

And then there is the sequestration of carbon from faecal material into the soil to be considered - how much faecal material will be sequestered into soil, and for how long? This figure will again vary; one report from Beef and Lamb New Zealand suggests many farms in that country are already close to carbon zero, when offsetting for trees and bush is included. (5) And of course, in many poorer countries, manure from cattle and buffalo are the only fertiliser that is economically viable.

Is 100 grams of wheat protein the same as 100 grams of beef protein?

The exact sequences of amino acids will differ and so will the nutritional value. In addition beef will contain micronutrients not present in plant species. At least one author, Professor Michael Lee, of Harper Adams University, has argued against comparisons based simply on mass, like 100 grams of protein; he is in favour of a more complex metric, which better accounts for the varying constituents and the nutritional value of the food products being compared. (7)

What about the by-products?

In the case of beef there are additional products, leather, bones, offal which are difficult to account for in simple, mass based metrics but which add to the overall value of the animal, against which its carbon footprint should be compared.

It is soon easy to see why a simple graphic has considerable attraction! The diagram would become rapidly cluttered if every item were accounted for. But the development of this list of questions soon begins to look like a biased argument in favour of beef, when in reality it should be viewed as an attempt to widen the discussion and bring more evidence into the debate. It would require a book to fully investigate the background story of beef emissions; for a review of one such tome, see the VetSalus website, (8) where we reviewed ‘Defending Beef” by Nicolette Niman.

But the fundamentals for veterinarians engaged in assisting their clients to reduce their carbon footprints remain unchanged: beef is a valuable human nutrient and methane is a potent greenhouse gas; systems exist which can significantly reduce methane output per Kg of beef and as veterinarians we are well placed to advise on these.

The next article will examine some of the methods of reducing the carbon footprint of beef in more detail, keep an eye out for this next week.

 

References:

  1. Livestock's Long Shadow, FAO: https://www.fao.org/4/a0701e/a0701e03.pdf
  2. Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants Lynch JM, Cain M, Pierrehumbert RT, Allen MJournal:Environmental Research LettersVolume:15 Issue:4
  3. Poore,J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science 360(6392) 987-992.
  4. Capper, J.L. (2012) Is the grass greener? Animals 2(2), 127-143
  5. New Zealand sheep and beef farms close to being carbon neutral – new research | Beef + Lamb New Zealand (beeflambnz.com)
  6. Berg, P.L., Lassen,J., & Litauer,M., (2013) Genomic Selection for methane traits in beef cattle. Proceedings of the Association of Animal breeding and Genetics, 20,403-406
  7. News - New research shows how temperate grassland beef provides key nutrients for human health – and could help reassess its environmental impact | Harper Adams University (harper-adams.ac.uk)
  8. Vet Salus Book Review: Defending Beef: The Ecological and Nutritional Case for Meat: Nicolette Niman | VetSalus

 

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