You have to account for: - all the meat and diary your child is going to consume in those 18 years - all diapers that are going to be produced and disposed.

You have to account for: - all the meat and diary your child is going to consume in those 18 years - all diapers that are going to be produced and disposed. - all methane and CO2 you child produced on an a daily basis for those 18 years (exhaling, digesting/pooping/farting) - concrete used for building this extra room for your child ... just to name a few.