What if the US Went Vegan Overnight? Part 2: Greenhouse Gas Emissions

In part 1 of this two-part series, I responded to Robin R. White and Mary Beth Hall’s concerns about the nutritional inadequacy that might result from a sudden change to a vegan diet. But the report also drastically minimizes the environmental impact of a shift away from animal agriculture. The authors argue that – contrary to much popular scientific opinion – ending animal agriculture in the US will produce a mere 2.6% reduction in total Greenhouse gas emissions. Today I will be examining their claims regarding changes in greenhouse gas emissions and animal agriculture. In particular, I’ll be challenging their implied assumption that all greenhouse gases are equal, that incineration is the best and only way to dispose of agricultural waste, and that animal manure can only be replaced directly with chemical fertilizers.

Are Greenhouse Gas Emissions More or Less the Same Without Animals?

In their paper, Robin R. White and Mary Beth Hall assert that an animal-free agricultural system will result in what appears a minuscule 2.6% reduction in GHG emissions.

There are a number of serious problems with this number. Firstly, not all greenhouse gas emissions are created equal. We know, for example, that methane gas has anywhere from 30-86 times the global warming potential (GWP) compared to carbon dioxide (the smaller number is over an one-hundred year period, the larger over a twenty-year time frame). This is a bit of a lie by omission, as the authors make no mention of this fact.

Methane is one of the most  potent greenhouse gases, particularly over the short-term. Over a 20 year time-frame, methane  has 86 times the heating potential of CO2. This fact is  critical given current concerns over rapid climate change.

Why is this such a vital distinction? Scientists argue that without major intervention, we will have irreversible global warming by 2036. This is a critical time period, and methane, with its GWP of 86 times C02 represents an existential threat. Once again, either White and Hall are ignorant of the GWP of methane, or they are deliberately misleading readers.

Agricultural Waste: Options for Disposal Aside from Incineration?

The authors assume all plant materials currently fed to livestock will be incinerated in an animal-free scenario. This obviously increases the perceived greenhouse gas emissions of plant-based agriculture. It also helps explain how the authors showed a mere 2.6% reduction in overall GHG emissions after removing animal agriculture.

Of course, there are alternative ways to handle agricultural waste products.  Burning is only one possible solution. One important option would be expanding biofuel production and selling the products overseas or reducing – with the goal of eventually eliminating – dependence on fossil fuels.


Composting also goes unmentioned in the White and Hall study. This is in spite of the fact that the EPA reports composting improves crop yield and can help reduce dependence on chemical fertilizers. This solves several problems at once: agricultural waste can be composted (after the usable portion has been turned into biofuel), reducing the need for chemical fertilizer, while simultaneously eliminating the need to incinerate waste. In other words, yet another “win-win” animal-free scenario that the study’s authors’ all too conveniently chose to ignore.

Another Solution: Night Soil or Biosolids

Another factor influencing the increase in GHG emissions projected in the study was the assumption all animal waste used as fertilizer would be replaced with chemical fertilizers. Of course, this is far from the case. Although it might seem less tasteful to some, human fertilizer (referred to more pleasantly as “biosolids”) is already approved for agricultural use. 

Although people in the organic community decry this as ‘sewage sludge’ it’s worth remembering that animal sewage is still sewage. Animals carry many of the same pathogens that humans do, and regulation around animal fertilizer is not nearly as strict. And of course, since we’re pretending that the US would be entirely vegan at this point in time, there would be no worries about prion contamination.

The US is only currently applying 50% of biosolids produced to land. Only about 1% of US agricultural land makes use of biosolids, thanks to consumer distaste for the practice. Advocates for organic farming are particularly vociferous in their opposition to using biosolids to grow food. And some mainstream companies, such as Dole and Heinz refuse to use biosolids, fearing a consumer backlash.

Closing thoughts

Overall, it seems clear professors White and Hall carefully constructed a scenario where shifting to plant-based agriculture displayed little or no benefit. As we saw previously, their assessment of the nutritional aspects of animal-free agriculture betrays significant bias. Likewise, their conclusion that eliminating animal agriculture would result in a mere 2.6% reduction in greenhouse gases is – at best – myopic. At worst it is intentionally misleading. It is disappointing indeed to see this study parroted throughout the news media. Particularly since the authors failed to consider basic questions critical to the accuracy of their work.

I realize the impossibility of accounting for all variables. But failure to address the tremendous impact of highly potent greenhouse gases like methane is deceptive. And this remains true whether or not that was the authors’ deliberate intention. Moreover, assuming that any additional agricultural waste would be incinerated helped artificially bolster the animal agriculture scenario. Considering other reasonable scenarios, such as composting, biofuel development, and utilization of biosolids paints a very different picture.

What would happen if the US went vegan overnight? Well, it’s unlikely to happen. But if it did, there is reason to assume things would go far better than in the purposefully apocalyptic scenarios designed by White and Hall. A vegan diet won’t destroy our health. And it is still one of the best ways to save the planet. 

What do you think? Join the conversation!

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