"Estimates suggest that 8-10% of global greenhouse gas emissions are associated with food that is not consumed." (page 20, note that it's just a reference to another paper)
"This suggests that 17 per cent of total global food production may be wasted" (page 8)
That would imply food is responsible for 47-59% of global greenhouse gas emissions which seems unrealistic.
Take into account that they are measuring how much food emits when it rots, but not how much food captures when it grows. The net effect might be smaller.
Another thing that might be happening is that they take into account the emissions of its transportation via intercontinental ships, trucks, etc.
I'm not claiming this as fact, but it seems sensible enough that those products which have the shortest shelf life (meat, dairy etc) also have the highest greenhouse gas emissions.
"This suggests that 17 per cent of total global food production may be wasted" (page 8)
That would imply food is responsible for 47-59% of global greenhouse gas emissions which seems unrealistic.
https://ourworldindata.org/food-ghg-emissions
"Food is responsible for approximately 26% of global GHG emissions."
Working backwards from that number: Food waste (17%) would be responsible for 4.4% of global GHG emissions.