Fossil fueled GA is a very non environmentally friendly pastime relative to its benefit to society on the whole.
Why? What is wrong with individual benefits?
I made the calculation more than once and I really do not see any difference to using a car. My aircraft runs on Autofuel and I had to do the comparison for several business trips for tax reasons. Total used fuel A to B was almost the same (environmental impact with the aircraft is less, as it only needs 1/2 mile for take off and landing, instead of the miles road the car needs) and total cost was to the Pound equal. The benefit was time saved, typically 2/3 of total, and taking the aircraft for business avoided overnight stays in these cases. As in these cases the saved time could also be charged to the customer, it was an individual benefit (be home again at evening) and a business benefit (saved hotel costs and gained hours charged at customer). I still hope they start separating the business related part of GA in statistics, no clue how big the percentage of real business use in GA is.