By Mark Sisson, PE
As environmental awareness of port operations has steadily increased in recent years, air emissions have emerged as one of the most serious negative impacts from operations. More and more ports worldwide are implementing policies that aim to reduce air emissions with a “zero emission” terminal being hailed as the holy grail of the industry.
Efforts to reduce air emissions typically fall into three broad categories:
• Do everything possible with electric power
• Generate as much renewable power on site as possible
• Make the terminal, especially the non-electric parts, as efficient as possible
Electric power is compelling for many reasons. Equipment running on electric power generates zero local emissions. The emissions of health risk related pollutants such as nitrogen oxides and hydrocarbons are far lower at stationary power plants, even coal fired power plants, than from mobile sources like ship engines, so switching to electric power results in a large net reduction in these types of pollutants.
Electric powered machines use far less energy for the same amount of work than diesel machines because they do not use power to idle, and they can regenerate power when braking, or when lowering a container. The chart below describes the electrification potential of many elements of marine container terminals and their landside connections.
Although dockside cranes, yard gantry cranes, and ships are all powered by either cables or bus bar type power transfer systems, other elements will have to depend on battery power. Yard tractors have a relatively easy duty cycle that consists of a confined operating area with low speed, little to no gradients to climb, and high fraction of idle time. This duty cycle lends itself to battery power very easily and prototype electric tractors are already in place at the port of Los Angeles.
Other types of duty cycles involving heavier loads, steeper grades, and longer distances mean that battery power for things like street trucks, or reachstackers, is still some way off. A great deal of time and money is currently being invested in improving battery performance, so this story may change quickly if there are significant breakthroughs in battery technology in the years to come.
Although the greenhouse gas emissions from electric power depend on the source fuels for the local grid, the long term trend in most places is for the grids to evolve into ever lower carbon content so electric equipment will automatically become “greener” over time in most locations. Ports are not waiting for power grids to become greener in many cases. They are taking matters into their own hands developing renewable energy on port property.
Solar power is the most common option for ports, as photovoltaic panels can be added to everything from building rooftops to parking shade canopies to electric cranes and even ships to generate clean power from the sun. Some terminals, such as the YTI terminal at the Port of Los Angeles, even post real time solar power generation data on their websites (http://live.deckmonitor
Wind turbines can generate a great deal of power, with a single turbine capable of producing more than a megawatt of power, if the local wind conditions are favorable. Many ports in northern Europe make extensive use of wind power generation on or near port property. Ports are great places for turbine placement because winds are often stronger at the water’s edge than they are inland, and there are already many large steel structures on the horizon so there may be less aesthetic objection to wind turbines in a port than on a ridgeline in undeveloped countryside.
Although less developed than solar or wind power, clean energy can also potentially be derived from tidal and wave power, and from fuel cells powered by hydrogen or natural gas.
Increasing efficiency on terminals can be accomplished in many ways, but the main focus is typically on longer hours of operation in order to smooth out the peaks in demand, and on better, earlier, transfer of information to allow the terminal operator to make better decisions.
Up until 2005, truck gates at terminals in the ports of Los Angeles and Long Beach, the two largest ports in the US, were typically only open from 8-5 on weekdays. This work schedule was used to minimize labor cost on the terminals but it resulted in substantial queues of street trucks waiting to enter the terminals.
In 2005, operators in southern California created the PierPASS organization to implement a daytime fee scheme to fund longer gate hours. Terminals stayed open for twice as long each day and trucks that picked up containers on the day shift were charged a fee to subsidize the costs of operating night gates. Approximately 40 percent of traffic shifted to night gates almost immediately. This resulted in a dramatic decline in truck queuing time and related emissions from idling trucks.
Some ports, such as the Port of Vancouver Canada, have implemented appointment systems to spread out the demand for truck service evenly throughout the day. As these systems get more sophisticated, operators may be able to rehandle containers in advance so that the containers to be picked up each day are nearly always on the top of the stack. This will further reduce truck delay and related emissions.
Ports and trucking companies are also working to develop “virtual container yards” so that when an import container is unloaded at a warehouse, it can be picked up at that warehouse by an exporter who needs an empty container to fill with cargo as opposed to being drayed back to the container terminal as an empty. Trucking companies are always working to maximize the number of double moves, i.e. driving with a container in both directions, that are done at ports. This results in fewer emissions per container moved.
Shifting cargo movement from trucks to rail or barge is an effective way to reduce emissions per ton-mile of cargo moved. The Port of Rotterdam has written into its newest terminal leases that container terminal operators must shift from the current 60 percent of cargo moved via truck to a future goal of only 35 percent of cargo moved via truck, with the remainder moved by rail or barge.
There are a great many tools in the toolbox for motivated port authorities and terminal operators to use to transform their operations in the direction of zero emissions. By taking advantage of global best practice from both a policy and technology perspective, ports can make steady progress toward a long-term goal of zero emission operations.
Mark Sisson leads AECOM’s marine analysis group, and is responsible for business development, project execution, and oversight of research and development of simulation models. He holds a BS in civil engineering from California State Polytechnic University and an MS in civil engineering from Northwestern University, and is a registered professional engineer in the state of California.