I've read a lot of papers about negative emissions. My main take-away was: 1. It will be necessary 2. We can solve part of the problem with cheaper/easier solutions like trees and ocean farming, but we will need more technological solutions.

I think BECSS are difficult since it's still uncertain how the actual net carbon negativity changes when we change land to grow 'BECSS' crops/grasses. Also BECCS cost a land and water, something which will be a luxury when we are going from 7.5 billion to 10 billion people in 2050. With DAC we can actually set an upper boundary of the total cost of the negative emissions, which will only go down due to technological improvements.

What I do agree on is that we need to stop using fossil fuels where possible. I don't think every sector will be ready in time (airplanes and boats for example). However we can make synthetic fuels using direct air capture which are almost carbon neutral (look at the super work David Keith is doing with Carbon Engineering: http://carbonengineering.com/ )