Monday, 9 September 2013

Eatology forum : pseudo-science of sustainable eating

The Eatology panel discussion staged by the Canberra Environment Centre was promoted as giving a definitive answer as to the most sustainable diet for Canberra. Disappointingly, the audience was not allowed to engage with the panel. The only questions asked were a selection of those submitted by email to the Canberra Environment Centre prior to the forum, carefully moderated by Richard Denniss from the Australia Institute.

Of the six-member panel, the one standout contribution was from the Choku Bai Jo organic vegetable farm owner, who made a refreshingly quantitative assessment of things.

Other panel members included a beef cattle farmer and a PhD student looking at the carbon impact of grazing systems. These panel members seemed to sense the pressure that was on them to justify the significant carbon impact of grazing that has been documented by the National Greenhouse Gas Inventory (1), United Nations Food and Agriculture Organization (2), United Nations Environment Programme (3) and others. They made a number of vague statements and unsubstantiated claims around meat production that deserve a response. Indeed, some of the claims they made were astonishing.

The student suggested that methane is not a problem because it is “all part of the natural carbon cycle”. This argument is not so different to that used by the fossil fuel polluters to claim that more CO2 is creating a greener earth (4). In fact, there are more introduced cattle than people in Australia – it is hardly a natural situation. And methane has a much higher global warming potential than CO2.

The student also made a bold claim that cattle grazing systems are a net methane sink, due to organisms in the soil consuming the methane as it is burped out by the animals. Then the student let slip that "there isn't the full research to back it up". On the contrary, measurements of all kinds, including at the pasture level, have confirmed that grazing systems are a net methane source (5). Although soils do absorb some methane, this is a rather minor effect. It has been estimated that it takes between 45 and 213 hectares of soil to offset the methane produced by one animal (6).

The cattle farmer argued that we should perform a full life cycle analysis in order to decide the most sustainable diet. It turns out that when people have done that, vegan diets come out best, whether organically grown or not (7,8). Credit must go to the cattle farmer for recognising the environmental damage that occurs through feedlot systems (i.e. in the production of almost all eggs, chickens, pigs and much of Australia's cattle).

It was suggested that Australia is different to other western nations because we don't have much feedlot production. This claim is not supported by the data. The grain harvest fluctuates from year to year, but on average, animals consume about one-third of it. Of this amount, beef cattle consume 21%, similar to the amount eaten by broiler chickens. This is shown in the following two figures taken from a report published by the Stock Feed Manufacturers' Council (9). In fact, it's not too difficult to demonstrate that animals consume more wheat than all of Australia's population.

Feed use in tonnes (dark blue) as proportion of annual grain harvest (light blue)

Grain use by animals in 2010-11

To have so much of Australia's fertile arable land devoted to feeding animals is an incredible waste of agricultural resources. There is more than enough arable land to feed the population with plant foods, with plenty left over for export. We heard much about consumer food wastage at the Eatology forum. The waste in our agricultural system due to feeding animals deserves equal consideration.

But—what if you purchase flesh that has come from local grass-fed animals? It is widely accepted that the greenhouse gas impact of the methane is around 20 kg CO2-equivalent per kg of cattle carcass (11, 12). There may be some limited opportunities for soil carbon sequestration, however this is highly uncertain and can only be verified by detailed long-term scientific monitoring at each farm (10). One review paper has suggested that this might offset about 43% of the methane emissions for a few years – with the sequestration diminishing over time as the soil reaches equilibrium (11).

Even in the optimistic scenario that the soil carbon could offset the methane by 43% (and you had scientific measurements from the farm to verify this), that leaves 11.4 kg CO2-equivalent per kg of carcass. That is still significant. If your family members eat up to the 65 gram daily red meat limit suggested by the dietary guidelines, that will consume a sizeable chunk of your solar panel carbon credits (if you have solar panels). This cost is inescapable for those who insist on being organic beef eating locavores.

Further, any carbon that does go into the soil is really just replacing the massive carbon losses that occurred through extensive land clearing by graziers. Earlier versions of the National Greenhouse Gas Inventory took this into account, with animal products having an extremely large land-clearing component (even larger than the methane impact) (12). These days the land-clearing accounts have been reset to zero, but this doesn't remedy the losses that actually occurred. The image below, produced using the ABARES MCAS-S tool (13), shows in yellow the extent of land clearing that has occurred across NSW in order to graze ruminants.

Grazing on cleared pasture (yellow) and on native vegetation (red). Source: ABARES MCAS-S tool

As people become more and more aware of meat eating’s environmental burden, perhaps it was inevitable that we would be sold a repackaged green-washed picture of eating meat by those with a vested interest in animal farming. Well, we didn’t buy it, and you don’t have to either. There is an alternative vision: soil carbon can be improved by restoration of native vegetation on former grazing lands, and conversion of plant agriculture to organic methods, without the huge risk that methane poses. Land is released from having to produce animal feed. Instead, some cropping land is kept spare and improved using rotation methods (14). In the meantime, a vegan diet has the lowest environmental impact. For example, the National Greenhouse Gas Inventory showed that the greenhouse gas impact of 1 kg legumes to be just 0.5 kg CO2-equivalent (12).

In the closing comments of the forum, the student on the panel left the audience with the not-so-subtle impression that vegans and vegetarians are causing deforestation in Brazil and contributing to global poverty because of soybean production. Yet, the vast majority of soybean worldwide is used to feed livestock (15) so that the relatively wealthy can “express their consumer preferences” for more animal products. Even in Australia, the demand for animal feed is so high that we have to import over half a million tonnes of additional soybean per year (16).  We produce enough soybean to meet a strong local demand in the human food supply, such as tofu and flour products.

And let's not forget about the cruelty aspect of meat. Even the "best" meat operations involve gaining animals' trust and then betraying it, sending them to a horrific end; separation of mother and baby causing intense emotional distress; and painful surgery without anesthesia (castration, etc).

People who choose to turn a blind eye to the environmental damage of meat eating and to animal cruelty might be interested in the salami making workshops that were promoted at the forum—rather incongruously we’d have thought—by the Canberra Environment Centre. However, they’d be taking a gamble with their own health—which is quite another matter.


(1) Australian National Greenhouse Accounts, National Inventory Report 2011, Volume 1. The Australian Government Submission to the United Nations Framework Convention on Climate Change, April 2013.
(2) Livestock a major threat to environment - remedies urgently needed. FAO Newsroom, 29 November 2006.
(3) UN urges global move to meat and dairy-free diet. The Guardian, 3 June 2010.
(4) CO2 Is Green (web site)
(5) Wang, Z-P. et al. (2009). China's grazed temperate grasslands are a net source of atmospheric methane. Atmospheric Environment, 43, 2148-2153.
(6) Johnson J. M.-F. et al. (2007). Agricultural opportunities to mitigate greenhouse gas emissions, Environmental Pollution, 150 (1),  107-124.
(7) Marlow, H.J. et al. (2009). Diet and the environment: does what you eat matter? American Journal of Clinical Nutrition 89 (5), 1699S-1703S.
(8) Baroni, L. et al. (2007). Evaluating the environmental impact of various dietary patterns combined with different food production systems, European Journal of Clinical Nutrition 61, 279–286.
(9) JCS Solutions (2010). Feed Grain 2010 Update Report: a report for the Feedgrain Partnership.
(10) Chan K.Y. et al. (2010). Soil carbon stocks under different pastures and pasture management in the higher rainfall areas of south-eastern Australia. Soil Research 48, 7–15.
(11) Crosson P. et al. (2011). A review of whole farm systems models of greenhouse gas emissions from beef and dairy cattle production systems. Animal Feed Science and Technology, 166, 29-45.
(12) Australia's National Greenhouse Gas Inventory 1990, 1995, and 1999 end use allocation of emissions : report to the Australian Greenhouse Office, 2002.
(14) Anderson, Will. "This is hope : Green vegans and the new human ecology." Earth Books, 2012.
(15) Nierenberg, D. 2005. ‘Happier meals – rethinking the global meat industry’, Worldwatch paper 171.
(16) AWB inaugural soybean production program. AWB Media release, 30 Aug 2012.

1 comment:

  1. I also attended this form and thank you putting the above data together. It certainly puts a more rounded perspective on the topic. After sitting through most of the discussion, I actually walked when the Choku Bai Jo organic vegetable farm owner mentioned that he was disappointed that his daughter had become a vegetarian. Robyn