It's largely (heh) about their size and that they're not really as optimized for meat as e.g. pigs. They breed comparatively slowly and take longer to grow.
Moreover the weight of a cow carcass is no higher than 60% that of the animal, while for pigs the lower bound is ~78%. Poultry is also very efficient in this regard, especially turkey yielding 80%+.
Where I'm from domestically consumed beef comes mostly from dairy cows so it's not particularly good, but it appears to be the more environmentally sound choice than growing them just for the meat(not that this was the aim - it's just cheaper).
The sooner we can get lab grown beef the better. I don't care if it's more expensive or even if it isn't as efficient in terms of energy input as growing, raising, and slaughtering actual cows. It'd still come with tons of benefits like reducing antibiotic use, taking up less land, causing less suffering, eliminating illnesses, etc.
We're not about to run out of land. My recommendation is to use nuclear power to desalinate seawater and turn the Sahara Desert into a vast grassland on which we can raise a couple of billion cattle in order to feed the world. I think the same should be done in the Australian Desert.
Current enourmous land use by meat industries has many negative effects. We should individually switch to plant based (if you haven't already) and in public policy rapidly remove all subsidies from meat and animal industries and fully price in all negative externalities (GHG, antibiotics risks, pandemic risks, air and water pollution). At the same time subsidize plant based alternatives. As a result plant based alternatives would be several times lower in cost than the meat versions, which in turn would drive consumption changes.
The problem with only reducing meat from cows and sheep is that other meat sources are still worse than plant based with regard to climate change and we're at a juncture where climate policy need to shift into full gear on all fronts. Not a time for half measures. Meat from chicken is also likely even worse than beef in terms of pandemic risk and perhaps also antibiotics resistance risk. In addition to that chicken meat industries cause much more animal suffering than all other land based animal meat industries combined which I think is a very strong argument to phase out chicken meat production - that industry wouldn't last a week if the type of animal protection regulation people in general think already exists for it would in fact be enacted, applied and enforced.
The idea that negative externalities should be priced in is the standard view in economics. I think most people, if provided the reasoning for it, would accept such pricing in when it comes to such serious global problems as climate change, antibiotics resistance, pandemic risk and air and water pollution.
The seaweed/algea story is pushed strongly by meat industry greenwashing efforts. It isn't large scale deployed anywhere and the potential benefits are overblows.
https://www.wired.com/story/carbon-neutral-cows-algae/
"What’s more, feeding cattle algae is really only practical where it’s least needed: on feedlots. This is where most cattle are crowded in the final months of their 1.5- to 2-year lives to rapidly put on weight before slaughter. There, algae feed additives can be churned into the cows’ grain and soy feed. But on feedlots, cattle already belch less methane—only 11 percent of their lifetime output. ... This means that even if algae diets on feedlots worked perfectly, it wouldn’t help with the 89 percent of cows’ belches that occur earlier in their lives."
Seaweed, garlic, etc. has shown to reduce methane. Yet at the same time creates uncertainty around more nitrous oxide, which might makes it even worse.
I find the methane issue quite dubious: as it gets oxidized over time, the quantity of methane from cattle in the atmosphere is more or less proportional to the number of heads. The problem with CO2 otoh is that it keeps increasing because we create it from fossil sources.
There are two problems with methane: for one, while it is "sitting" in the atmosphere, its greenhouse effect is much stronger than CO2's. After that somewhat short-lived period, it oxidizes to CO2 and water, so it still at best ends up as bad as CO2.
So even if we stopped producing CO2 from fossil fuels today, we would still be increasing the amount of CO2 in the atmosphere though breeding cows and other livestock, moving through a CH4 phase that does even more harm. Livestock are releasing the C trapped in plant bodies.
That carbon in cow farts & burps was grass yesterday, which was atmospheric CO2 last week. Cows are not fed petroleum products, though some petroleum may be used in the production of industrial feed (but not or much less for pasture feeding).
Atmospheric CH4 does not "do harm" as such, it's indeed a greenhouse gas that contributes to global warming in proportion to its prevalence. Said prevalence, as I'm trying to point out, is proportional to the number of heads of cattle. As such, if we don't increase the number of heads significantly, the impact will be constant.
Contrast with fossil fuels for, say, transportation: their impact on greenhouse effect is constantly increasing at a rate proportional to the number of cars/planes/trips.
Or put another way: we have to stop using ICE cars and planes altogether to stop increasing greenhouse effect; we only have to keep eating the same amount of beef and cheese to stop their impact.
But the C trapped in plant bodies comes from sequestered atmospheric CO2, no? It's not possible to permanently increase atmospheric CO2 purely through livestock, only "temporarily" increase methane (permanently, if we keep the livestock industry running forever).
There is only one place that actual surplus carbon comes from, and that is fossil fuels. Everything else is part of the closed-loop carbon cycle.
There's also what they're being fed, which apparently is mostly soy and corn... and require a lot of land, water (and chemicals) at this scale. As far as I understand, it'd be much more efficient to grow calories and proteins that we can directly consume instead.
Maybe beef is bad largely due to their sheer volume (c.f. China's per capita emission is much lower than North America or Europe, but their aggregate impact is still enormous due to their large population).
Moreover the weight of a cow carcass is no higher than 60% that of the animal, while for pigs the lower bound is ~78%. Poultry is also very efficient in this regard, especially turkey yielding 80%+.
Where I'm from domestically consumed beef comes mostly from dairy cows so it's not particularly good, but it appears to be the more environmentally sound choice than growing them just for the meat(not that this was the aim - it's just cheaper).