As drone deliveries have gone from wild idea to reality in the past couple of years, the question has remained as to whether there will be any environmental benefit from having these flying robots drop off our packages at our front doors.
On the surface, the battery-powered craft would seem to be the greener alternative to energy-hungry, exhaust-producing delivery trucks, but delivery trucks have the benefit of density -- they can carry several packages and heavy loads across the same distance. The University of Washington decided to figure out which one, drones or delivery trucks, were responsible for less carbon pollution and the answer is: it depends.
The researchers found that drones do carry an advantage over trucks when the distances are short and when there are fewer delivery stops along the way. Trucks on the other hand, win out when the distance to be traveled is long and there are more stops on the route.
“Flight is so much more energy-intensive — getting yourself airborne takes a huge amount of effort. So I initially thought there was no way drones could compete with trucks on carbon dioxide emissions,” said senior author Anne Goodchild, a UW associate professor of civil and environmental engineering. “In the end, I was amazed at how energy-efficient drones are in some contexts. Trucks compete better on heavier loads, but for really light packages, drones are awesome.”
The study was carried out by comparing carbon dioxide emissions and vehicle miles between drone and truck deliveries in Los Angeles. A model was created using real-world scenarios that involved 330 service zones and recipients numbering from 50 to 500. The model used real data from a previous study on grocery delivery services. The study also assumed that each drone delivery consisted of a single package and that the drone would have to return to a base to before completing another delivery.
The drone energy demand was estimated by using the energy consumption of 10 different hypothetical drones in the model and carbon emissions were calculated using an average fuel mix for the state of California.
After running the models, the researchers concluded that drones could be a greener alternative in certain scenarios like short trips in communities, on campuses or military bases. Another arrangement would be having trucks carry large packages and covering the long distances to a central hub where drones then took care of the last-mile deliveries to homes and businesses.
In the meantime, the researchers suggest that the same zeal that saw people inventing lightweight drones that were robust enough to perform these types of tasks should be applied to making trucks lighter and more fuel efficient too.