As a very rough first approximation, a person consumes 1 million food calories (kilocalories) per year. As carbohydrate, that's 4 cal/gram. Total population is about 8 billion.
8 billion cal * 1 million / (4 cal/g) / 1 million g / tonne = 2 billion tonnes net carbohydrate
That's a rough estimate (carbohydrate is neither pure carbon nor CO2, there is a humidity content) and undercounts total ag production (animal protein consumes a large amount of input feed for a much smaller amount of protein) , but gives a rough order-of-magnitude sense: 1e9 tonnes food vs. 1e11 tonnes net emissions.
FWIW, Our World in Data gives 2.7 billion tonnes net cereal production in 2018:
That does put it into perspective, thanks. To be clear though I meant CO2 used as gas in (for example) food processing, rather than somehow converting it back into other carbon forms and ultimately carbohydrates in the foods themselves.
Keep in mind that a gas is roughly 1000x larger than an equivalent solid mass.
So take all the food grown on Earth in a year, multiply it 100x, and multiply that 1,000x, to come up with the volume of gas you'd be dealing with sequestering somehow.
Gas doesn't like being sequestered, less so for hundreds or thousands of years. (Natural gas formations are interesting accidents of geological history in which sufficient source material, methane conversion of that material, and a geological substrate in which that gas is trapped in the earth, all coincide.) There's also the fact that eventually re-introducing that gas to the biosphere is probably beneficial (on the order of tens to hundreds of millions of years), as biologically-active carbon is weathered out of the system (though solar irradiance will also be increasing over this period, and by various accounts, the happy music stops in about 800 million to 1 billion years).
It really is difficult to convey the volumes of resources humans use on an annual basis. Vaclav Smil's books on the topics of energy and material resource uilisation are highly recommended, especially Making the Modern World:
