The COVID-19 pandemic boosted interest in automated transport technologies as a contactless way to help customers get their purchases. However, there hasn’t been an assessment of how robots and automated vehicles impact the already energy-intensive process of transporting packages from local distribution centers to customers’ front doors.

Now, researchers from the University of Michigan and Ford report in an open-access paper in ACS’ Environmental Science & Technology that automating residential package transport doesn’t influence the greenhouse gas footprint as much as the delivery van’s size and type.

We evaluate life cycle greenhouse gas (GHG) emissions for automated suburban ground delivery systems consisting of a vehicle (last-mile) and a robot (final-50-feet). Small and large cargo vans (125 and 350 cubic feet; V125 and V350) with an internal combustion engine (ICEV) and battery electric (BEV) powertrains were assessed for three delivery scenarios: (i) conventional, human-driven vehicle with human delivery; (ii) partially automated, human-driven vehicle with robot delivery; and (iii) fully automated, connected automated vehicle (CAV) with robot delivery.

—Li et al.

The researchers looked at 12 scenarios, ranging from a human-operated delivery process to a totally automated system, along a typical suburban route where one package is dropped off every half mile. In each scenario, they calculated the greenhouse gas emissions, or the carbon footprint, for each package delivered.

To do this, they added up emissions data from production and lifetime operation for a commercial walking robot and different cargo vans, including human-driven and self-driving models, gasoline- and battery-powered models and two cargo sizes.

Among their findings:

• The robot’s contribution to life cycle GHG emissions is small (2–6%).

• Compared to the conventional scenario, full automation results in similar GHG emissions for the V350-ICEV but 10% higher for the V125-BEV.

• Conventional delivery with a V125-BEV provides the lowest GHG emissions, 167 g CO₂e/package, while partially automated delivery with a V350-ICEV generates the most at 486 g CO₂e/package.

• Fuel economy and delivery density are key parameters, and electrification of the vehicle and carbon intensity of the electricity have a large impact.

• CAV power requirements and efficiency benefits largely offset each other, and automation has a moderate impact on life cycle GHG emissions.

GHG emissions versus delivery density for fully automated scenarios (curves) for V125 (green) and V350 (orange) with internal combustion engine (solid) or battery electric (dashed) powertrains compared to results from previous studies by Stolaroff et al. (red symbols) for the US average cases and Edwards et al. (blue symbol). The ICEV results from Stolaroff et al. and Edwards et al. are operational only (WTW), while battery production is included for BEVs and drones. Use of warehouse is not included. Li et al.

The results indicate that robots and vehicle automation account for a relatively small percentage (<20%) of a package’s footprint. Instead, the delivery vehicle’s size and fuel source had very large impacts on the overall greenhouse gas emissions.

The authors acknowledge funding from the Ford University of Michigan Alliance Program and the Ford University Research Program.

Resources

• Luyao Li, Xiaoyi He, Gregory A. Keoleian, Hyung Chul Kim, Robert De Kleine, Timothy J. Wallington, and Nicholas J. Kemp (2021) “Life Cycle Greenhouse Gas Emissions for Last-Mile Parcel Delivery by Automated Vehicles and Robots” Environmental Science & Technology 55 (16), 11360-11367 doi: 10.1021/acs.est.0c08213