According to this[0] Our World In Data article, which is based on 2018 data, livestock (including fisheries) produces about 15% of all emissions, assuming that animal-based products account for about a third of the supply chain costs of the food industry:
Total food emissions: 26%
Direct livestock + fish: 31% of that 26%
Due to livestock land use: 16% of that 26%
Due to crops for animal feed: 6% of that 26%
Due to supply chain (1/3 of total): (18/3)% of that 26%
Total: ((31+16+6+(18/3))/100)*0.26 = 15.34%
And according to this[1] Our World in Data article, transport makes up about 16.2% of emissions.
The analyses can differ depending on how far you "travel up the chain" of production, but it appears that transportation and animal agriculture are within the same ball-park, plus or minus 5% perhaps.
> Most of the food livestock consume are leftovers of human-grade crops.
This is incorrect. Most livestock feed is soy, and humans can and do eat soybean meal. About 98% of soybean meal is used for animal feed and only 1% is used to produce food for people.[2] For soybeans as a whole, only about 6% grown worldwide are turned directly into food products for human consumption.[3]
I would like to see where that 98% really comes from, the links you posted talk about 70% (and most of that being consumed by poultry, not cattle). And even that seems excessive [1]. I would love to see a clear separation between the soybean. meal (leftover from oil and soybean grinding) and explicit feed grade soybeans.
Total food emissions: 26%
Direct livestock + fish: 31% of that 26%
Due to livestock land use: 16% of that 26%
Due to crops for animal feed: 6% of that 26%
Due to supply chain (1/3 of total): (18/3)% of that 26%
Total: ((31+16+6+(18/3))/100)*0.26 = 15.34%
And according to this[1] Our World in Data article, transport makes up about 16.2% of emissions.
The analyses can differ depending on how far you "travel up the chain" of production, but it appears that transportation and animal agriculture are within the same ball-park, plus or minus 5% perhaps.
> Most of the food livestock consume are leftovers of human-grade crops.
This is incorrect. Most livestock feed is soy, and humans can and do eat soybean meal. About 98% of soybean meal is used for animal feed and only 1% is used to produce food for people.[2] For soybeans as a whole, only about 6% grown worldwide are turned directly into food products for human consumption.[3]
[0] https://ourworldindata.org/emissions-by-sector
[1] https://ourworldindata.org/emissions-by-sector
[2] https://www.canr.msu.edu/news/where_do_all_these_soybeans_go
[3] https://www.ucsusa.org/resources/soybeans