I agree with everything here. In particular: a lot of animals are farmed directly for pets, and ~3 billion sounds like a reasonable guess (I think Knight is double counting with ~7 billion). This was an update for me when I looked into this because I had thought almost all pet food was byproducts.
And I might be understating the scale case because I’m bugged by the methodology. But I don’t think the scale case is compelling when we think in terms of animals who could reasonably be taken out of the food system by vegan pet food, instead of number of animals farmed for pet food. This is something that motivates my (stray) thought that promoting beef > chicken/fish for companion animals could be high impact.
I like the Alexander paper but I think economic allocation makes more sense when you’re trying to attribute environmental harms than when you’re trying to reason about the number of animals killed in a counter factual scenario. Looking at the tools from LCA, I’d like to see somebody try a system expansion model here!
Please share the draft with me, I’d like to read it!
Thanks Ben and Seth for these thoughts, and Alistair for this post!
On scale — I’ve also recently realised that the scale as presented in Knight (2023) is inflated based on his ABP calcs it’s also my opinion, based on similar arguments to Ben’s, that the scale of this cause area is probably lower than Andrew suggests. [Based on Andrew’s response, I’ve rephrased the above sentence]. However, it’s worth remembering that ABP use in pet food is a declining trend, at least in the US. Premiumisation has already pushed animal-based ingredient use in pet food to have a roughly 50⁄50 split of ABP vs human consumable ingredients. And the ABP proportion is declining further—I’ll be publishing updated data on this in the next few months hopefully.
On tractability, I agree more with @Denkenberger🔸 that there’s more potential here than most people are assuming. Compared to humans, where taste/texture replication is v important and v difficult, and diet habits change regularly, it’s much easier to create palatable plant-based diets, and to keep dogs on exactly the same diet for a long period of time.
It may well be that transitioning dogs to plant-based diets is easier than for humans. The key is how they’re marketed—as in the human space, labelling the food as “vegan dog food” will badly damage uptake, but marketing as “hypoallergenic”/”clean”/”sensitive diet” can be more effective (see Omni, the UK’s leading plant-based dog food company, which is v quiet on vegan messaging, but is growing in mainstream appeal).
I’d also point those interested towards a new study (co-authored by Peter Alexander) by Harvey et al. (2026), which compares different ABP allocation methods. Their range for global impacts of dog food consumption is 469-1332Mt CO2eq annually. Knight’s 2023 estimate was 759Mt. So, while v likely still an overestimate, it’s roughly in range of this study too, which I think was well conducted (the lower range is using economic allocation, the higher fig is using a form of mass allocation that definitely overestimates impacts).
I’m interested in looking more into the marginal impact of ABPs in pet food (e.g. via system expansion modelling), and am interested to chat this through with anyone who has thoughts on this!
[Edit: I make a further case for tractability on another post on this topic here. Would encourage those sceptical of vegan pet diets on tractability grounds to read!]
Thanks Seth (good to hear from you)!
I agree with everything here. In particular: a lot of animals are farmed directly for pets, and ~3 billion sounds like a reasonable guess (I think Knight is double counting with ~7 billion). This was an update for me when I looked into this because I had thought almost all pet food was byproducts.
And I might be understating the scale case because I’m bugged by the methodology. But I don’t think the scale case is compelling when we think in terms of animals who could reasonably be taken out of the food system by vegan pet food, instead of number of animals farmed for pet food. This is something that motivates my (stray) thought that promoting beef > chicken/fish for companion animals could be high impact.
I like the Alexander paper but I think economic allocation makes more sense when you’re trying to attribute environmental harms than when you’re trying to reason about the number of animals killed in a counter factual scenario. Looking at the tools from LCA, I’d like to see somebody try a system expansion model here!
Please share the draft with me, I’d like to read it!
Thanks Ben and Seth for these thoughts, and Alistair for this post!
On scale —
I’ve also recently realised that the scale as presented in Knight (2023) is inflated based on his ABP calcsit’s also my opinion, based on similar arguments to Ben’s, that the scale of this cause area is probably lower than Andrew suggests. [Based on Andrew’s response, I’ve rephrased the above sentence]. However, it’s worth remembering that ABP use in pet food is a declining trend, at least in the US. Premiumisation has already pushed animal-based ingredient use in pet food to have a roughly 50⁄50 split of ABP vs human consumable ingredients. And the ABP proportion is declining further—I’ll be publishing updated data on this in the next few months hopefully.On tractability, I agree more with @Denkenberger🔸 that there’s more potential here than most people are assuming. Compared to humans, where taste/texture replication is v important and v difficult, and diet habits change regularly, it’s much easier to create palatable plant-based diets, and to keep dogs on exactly the same diet for a long period of time.
It may well be that transitioning dogs to plant-based diets is easier than for humans. The key is how they’re marketed—as in the human space, labelling the food as “vegan dog food” will badly damage uptake, but marketing as “hypoallergenic”/”clean”/”sensitive diet” can be more effective (see Omni, the UK’s leading plant-based dog food company, which is v quiet on vegan messaging, but is growing in mainstream appeal).
I’d also point those interested towards a new study (co-authored by Peter Alexander) by Harvey et al. (2026), which compares different ABP allocation methods. Their range for global impacts of dog food consumption is 469-1332Mt CO2eq annually. Knight’s 2023 estimate was 759Mt. So, while v likely still an overestimate, it’s roughly in range of this study too, which I think was well conducted (the lower range is using economic allocation, the higher fig is using a form of mass allocation that definitely overestimates impacts).
I’m interested in looking more into the marginal impact of ABPs in pet food (e.g. via system expansion modelling), and am interested to chat this through with anyone who has thoughts on this!
[Edit: I make a further case for tractability on another post on this topic here. Would encourage those sceptical of vegan pet diets on tractability grounds to read!]
re: “the scale as presented in Knight (2023) is inflated based on his ABP calcs”
Readers should be aware that this is an unsubstantiated claim. My recent post has more information on this topic.