The biggest polluters are
- Transport 28%
- Electricity 25%
- Industry 23%
- Commercial & residential 13%
- Agriculture 10%
Agriculture (fertiliser, wild rodents, diesel, animals, rotting plants, not including plants wasted by consumers) is only 10%
We're making the best inroads into electricity. It is clearly possible and economical to convert all electrical grids to carbon neutral technology
We're starting to convert residential and commercial to entirely electric (except for the carbon and methane emissions from humans and pets, especially ones that eat beans) so that 13% is solvable
So at the moment 38% of greenhouse gases are easy, just needing political will
Another 23% is harder, industry needs some inventions, especially a green steel making process, and a green concrete making process. Both are years away and probably possible
Transport is hard. 6% is personal transport. That's easy to electrify. Trucking is harder, planes are harder still. I don't know how feasible wind power is for shipping, at least the trade winds blow the right way for Asia to America
The best bet for transport was a green liquid fuel, but the company trying to grow diesel from bacteria folded several years ago.
We are never going to decarbonise agriculture by abandoning any part of it. We can do a bit by practicing permaculture - that keeps more carbon in the ground; we can clean up animal agriculture by not feeding cattle human food, let them eat grass, and there is promising technology for reducing their (and other ruminants') methane emissions by feeding them seaweed
If we waved a wand and removed all farm animals from the world it wouldn't make a dent in carbon emissions or methane, cows would be replaced by deer which also make methane in exactly the same way cows do, but with no one feeding them seaweed
Uneaten grass would rot and be turned into methane (it's the same bacteria that work in cow and deer guts to break down grass). No one's treating rotting grass with seaweed.
Our best bet is to keep the marginal lands occupied by cattle and regulating people running cattle, requiring them to minimise their animals' emissions, or offset them
*Edited to fix typos