Introduction

Air Pollutant Reduction Strategies in Clean Air Plans and Their Effect on Greenhouse Gases

GHG Co-Benefits from Air Pollutant Reduction Strategies

This Tool Box is constructed with two main sections: air quality and greenhouse gases.  These topics are accessible from tabs on the main page.  The additional tab, “Integration,” describes how and when strategies from each of the toolboxes create “co-benefits;” strategies that accomplish the goals of both subjects.  Links embedded among many of the strategies in each toolbox also provide a path for understanding co-benefits

Integration 

Air Pollutant Reduction Strategies in Clean Air Plans and Their Effect on Greenhouse Gases

Many strategies to reduce emissions under Port clean air plans also affect emissions of greenhouse gases (GHGs).   Often, the effect is to decrease the amount of GHGs emitted in addition to reducing air pollutant emissions.   These are referred to as strategies that have “co-benefits.”   In some cases, however, clean-air strategies may result in an increase to GHGs, either directly from the operation, or indirectly through increased energy or material use – a “co-disbenefit.”  This section of the toolbox describes general circumstances leading to co-benefits and disbenefits to GHG emissions that arise from implementation of air pollution reduction strategies.  

Because they are more common, and desirable, this section focuses on co-benefits.  It begins with a general discussion of circumstances leading to co-benefits and follows with a description of four general clean air strategies that also have distinct GHG benefits.  Brief discussions of co-disbenefits and cases where benefits may be uncertain are included in some of the co-benefit discussions.   For a quick-reference, all of the strategies listed in the Air Pollutant Toolbox have been put into a table at the end of this section that succinctly describes their effect, if any, on GHG emissions.

 

GHG Co-Benefits from Air Pollutant Reduction Strategies

Although air pollution reduction strategies are primarily designed to achieve reductions in diesel emissions and other toxic pollutants that are detrimental to public health, some of these strategies also result in concurrent GHG emission benefits.  These strategies should play a key role in achieving the goals for both clean air and climate protection plans.  Well understood examples of clean air plan strategies with GHG co-benefits include the use of shore power for hotelling operations and reduced cruising speed for ocean-going vessels.  GHG emission benefits associated with these strategies have already been quantified and reported in many ports’ clean air plans.  So for a climate protection plan, these same strategies may only need minimal revision to focus on GHG benefits. 

Other clean air strategies may provide slight reductions in GHG emissions that may require in-depth investigation to discern if a GHG co-benefit exists.  For example, requiring the use of low sulfur fuel in OGV engines and boilers may result in slightly decreased CO2 emissions because of the higher energy to carbon content of the distillate fuel compared to heavy fuel oil.  However, there may also be small increases in fuel-cycle CO2 emissions because of the increased energy at the refining stage to produce the distillate fuels which may offset the small CO2 benefits.  Discerning GHG effects for measures like these are dependent on local supplies and conditions, requiring significant research and effort to calculate.  While the most intensive study may seek to discern such details, strategies being developed with limited resources may find it more prudent to focus on only the measures that have clearest and most significant co-benefits associated with them.

The single most prominent mechanism for co-benefits from clean air plan strategies is reducing fuel consumption.  This can be accomplished through a wide variety of methods, most of which fall into one of four categories:

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These four categories are described in the following sections: 

Co-Benefit Strategy #1) 
Improve Vehicle Efficiency with Newer, Cleaner Vehicles

While most port equipment and vehicles will last ten to twenty years or more before they need to be replaced, a program to hasten the turnover can greatly reduce both air pollutant and GHG emissions.  Such programs may achieve their goals through financial incentives for operators or performance mandates, but their underlying motivation is to take advantage of significant technology improvements that have occurred in recent years (and continue to occur) that have resulted in cleaner, more efficient vehicles and equipment.   A fleet of newer equipment that is replaced more frequently has significant operational benefits including reduced down-time, but it can be capital-intensive to undertake. 

Example:  Truck Fleet Modernization
In the United States, requiring that all trucks servicing a port meet national 2007 standards will significantly reduce NOx and PM because of improved vehicles emissions technologies that are required to be present on all new vehicles of that year.   For most ports in the US, the age of trucks bringing containers to and from terminals is greater than 10 years, meaning that post-2007 technologies could reduce emissions of both NOx and PM by at least 90% for most trucks.   Technology that removes NOx will also reduce N2O, a potent greenhouse gas.  The main GHG reduction, though, comes from these newer trucks being more fuel efficient, translating to an equivalent reduction in CO2 emissions. 

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Co-Benefit Strategy #2)
Operational Improvements to Reduce Energy Use

Operational improvements are adjustments made to a given system that result in the functions of that system being accomplished with fewer overall emissions.  Any system that consists of vehicles or equipment engaged in repeated tasks likely has some potential to increase the efficiency with which those tasks are accomplished.  There may also be opportunities to reduce emissions from equipment operating in the system that have minimal effect on the function and efficiency of the system as a whole but greatly reduce pollutants.  Looking at a port and its related operations as a series of distinct, interacting systems is common practice in the industry because it allows for optimal coordination of logistics functions.  The same approach can also be a robust strategy for identifying opportunities to reduce emissions. 

For instance, container terminals are designed to optimize the movement, organization, and dwell of containers as they transition from water-side vessels to land-side transportation.  Optimal terminal layouts use the least amount of space and energy to accomplish this transition.  Likewise, a terminal optimized for emissions reductions may seek to accomplish the transition with minimal equipment acceleration and deceleration.  It also may position electrification infrastructure and choose sub-systems that allow for maximum electrification of operations.  Overall, a systems approach to reduce emissions of both air pollutants and GHGs will seek to minimize need for speed and frequent acceleration, minimize distance traveled, and maximize availability of electrification infrastructure.  The following example illustrates these concepts applied to vessels as they come to berth. 

Example:  Vessel Speed Reduction
A Vessel Speed Reduction (VSR) program requires participant vessels to slow down as they approach or depart a port.  The primary objective of the VSR program is to reduce emissions from OGVs during vessel transit near a port.  When ships slow down, the load on the main engines decreases considerably, compared to the engine load at higher speeds, leading to a decrease in the total energy required to move the ship through the water.  This energy reduction in turn reduces emissions for this segment of the transit.  Since the load on the main engines affects power demand and fuel consumption, this strategy significantly reduces all pollutants including PM, NOx, SOx, and GHG emissions.  Though VSR reduces fuel consumption and may save operating costs, these savings and the emission reduction benefits must be balanced by the increase in time it will take for a vessel to reach the port and the costs associated with that delay.

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Co-Benefit Strategy #3:
Reducing Emissions with Cleaner Energy

Fuel and energy costs are among the highest costs associated with operating vessels and ports.  Therefore, discussions about the best energy source have been fundamental to the industry throughout its history.  The incentive to reduce energy costs drove the industry to use the cheapest form of fuel available to power the ships that move millions of containers around the world.  Up until recently, shore-side equipment around the world was also using some of the least refined fuels that would allow their modern engines to function with sufficient power.   Development of targeted regulations are forcing changes to how and when vessels and equipment burn various types of fuel, but significant progress can be made beyond even the most stringent regulations to reduce emissions of both air pollutants and GHGs even further. 

In many cases, key air pollutants can be reduced through the use of more refined, desulfurized, or plant-derived fuels.  These options often have minimal or unclear effects on GHG emissions because their GHG impacts require investigation of “life-cycle” emissions that can vary significantly with source and process.  While these types of fuel may be desirable for other reasons, incorporating them into a climate protection plan should be done with caution.  To alleviate this problem, “low-carbon fuel” standards are currently being developed to help rigorously and uniformly identify the potential GHG benefits associated with alternative fuels.  Switching to natural gas has the advantage that reductions to both air pollutant and GHG emissions are well understood.

The ideal approach to reducing both air emissions and GHGs with cleaner energy is to switch from hydrocarbon-powered engines to electric power.   Even in the worst case scenario, where electricity is sourced from minimally controlled coal-fired power, electric power offers significant benefits over hydrocarbon-based power:

Example A:  Shore Power for At-Berth OGV Emission Reductions
Based on the above description of the benefits of electrification, the preferred approach for reducing at-berth emissions is shore-power -- transferring the electrical generation needs for OGVs while at berth from onboard diesel-electric generators to the cleaner shore-side power grid, which generates power through regulated/controlled stationary sources.  Reducing emissions occurring during dwelling (hotelling) from OGVs while at berth has significant air quality and GHG emission co-benefits because it eliminates almost of all of the ships’ direct emissions.  The shore-power approach is generally best suited for vessels that make multiple calls per year, require a significant power demand while at berth (a function of dwelling load and time at berth), and will continue to call at the same terminal for multiple years.  The most common ship types that are good candidates for shore-power are large string-service containerships, cruise ships, reefer ships, and specially designed crude tankers that have diesel-electric powered pumps. 

Shore-power requires extensive infrastructure improvements onboard vessels that would use the system, as well as on the terminal side for supplying the appropriate level of conditioned electrical power.  The onboard infrastructure costs are dependent upon the candidate vessel’s current configuration, conduit space, and electrical panel space.  Despite the broad range of applications and complex technical concerns, working groups and standardization efforts over the last 3 years have led to draft guidelines that have been finalized by the ISO and are now being reviewed by the International Electrotechnical Commission (IEC).  The draft report is expected to be publically available by mid-2009.

Example B:  Electric Trucks
Trucks that move containers in and around terminals are ubiquitous and generate significant GHG and air pollutant emissions over thousands of hours they each operate in a given year.  They represent an ideal target for emissions reductions both for this reason and because they fit within an operational profile that corresponds to the capabilities of current electric vehicle technology.  During their short range of travel, they are required to stop and start frequently and idle about 50% of the time.  Electric trucks eliminate idle emissions and will regenerate electricity every time the truck stops.  On acceleration, electric motors deliver starting power much more efficiently than diesel engines.  By switching to electric trucks, not only is the fuel cleaner, but the overall process is much more energy efficient.  Prototypes of electric trucks are currently being tested in real-life terminal operations.  Several types of hybrid trucks, including a plug-in serial hybrid, have also been announced by manufacturers.

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Co-Benefit Strategy #4:
Add-on Technology to Increase Efficiency and Reduce Emissions

Any equipment or process that can be added to existing equipment that improves the efficiency of that equipment is likely to result in co-benefit emission reductions.  Most add-on equipment for air-quality improvement, however, adds additional engine loads or external power requirements that may lead to a co-disbenefit for GHGs.  This is because things like pumps, heaters, and blowers add a parasitic load to an engine that reduces the power available to the engine’s primary function.  With these additional loads, the engine has to work harder to accomplish the same task and operate these systems or energy has to be introduced externally to power them.  In either case, additional load implies additional emissions either directly from the engine or indirectly through power generation. 

In some cases, the add-on equipment can make up for inefficiencies in the original system.  These inefficiencies could exist because the more efficient technology was not available at the time of the original design or because the capital cost of the technology exceeded the perceived future benefits at the time of purchase.  A clear example of this type of add-on technology is a hybridization package for rubber-tired gantry cranes (RTGs).  In this case, a basic hybrid system, consisting of electric motor, battery, and control equipment, is refit to the existing RTG and functions to capture power generated by containers as they are lowered.  The electric motor, then, is used to supplement power for raising containers and other movements where the diesel engine is less efficient.  By recapturing energy and allowing the diesel engine to operate more efficiently, manufacturers have claimed a ~70% reduction in fuel use and related air pollutant and GHG emissions.  Increasing interest in electrification and rapid improvement of battery and other energy storage systems will make such hybrid and electrification refit options even more cost effective. 

Example: OGV Engine Retrofits
Numerous technologies for reducing vessel engine emissions are currently under development and testing.  Much of the focus has been placed on reducing NOx emissions. Technologies such as selective catalytic reduction (SCR), sea-water scrubbers, dry low NOx combustion, humid air injection, water fuel emulsion, direct water injection, exhaust gas recirculation, electronic engine controls, etc. can be used for NOx, but none of these also contribute to significant decreases in GHG emissions.  Slide-valves, on the other hand, are relatively new, more efficient types of fuel injectors that reduce emissions of NOx and PM by minimizing the sac volume in the fuel-valve nozzle tip.  Slide-valve technology was introduced in 2002 and today most MAN Diesel main engines are delivered with this technology. Slide-valves can also be retrofit in to existing MAN Diesel main engines.  Because slide valves increase the combustion efficiency, they also reduce GHG emissions.


Source Category

General Strategy / Specific Strategy

Co-Benefit

Co-disbenefit or Uncertainty
Ocean Going Vessels      
  • Vessel Speed Reduction GHG Benefit due to reduced overall emissions  
  • Operational Improvements Likely GHG Benefit, but depends on specific strategy  
    Reconfigure Terminals Likely, if overall operation is more efficient or favors lower fuel use  
    Deepen Channels, Improve Access, On-dock Rail Larger ship capacity and direct rail transfers can reduce emissions  
    Speed Up Vessel Load/Unload Reduce Vessel Dwell Time Likely, due to increased efficiency, less ship hoteling time  
    Improve Electrical Infrastructure for AMP, Regen Cranes, Etc. Not dierctly, but facilitates strategies that bring co-benefits  
  • Clean Fuels Depends on fuel  
    LNG Yes, due to lower intrinsic GHG production in combustion  
    Low-Sulfur Fuel Higher energy density may enhance combustion efficiency Low S fuel processing adds emissions, may not enchance combustion
  • Emission Control Technologies Depends on Technology.    
    Slide Valves Likely, due to enhanced combustion  
    Seawater Scrubbing Adds parasitic load to operate system
    Engine Upgrades, Repower Likely, due to increased efficiency and enhanced combustion control  
  • Shore Power GHG Benefit  
Harbor Craft     Co-Benefit Co-disbenefit or Uncertainty
  • Engine Replacement with Engines Meeting Cleaner Standards
Likely GHG benefit, but depends on  technology   
  • Clean Fuels Depends on fuel  
    O2diesel/Bio-Fuels Benefits possible through life-cycle production, but  varies with source Biodiesel has higher direct emissions due to lower fuel density.  
    Low-Sulfur Fuel Higher energy density may enhance combustion efficiency Low S fuel processing adds emissions, may not enchance combustion
    Emulsified Fuels Can reduce efficiency by reducing overall fuel energy content
  • Emission Control Technologies Controls that improve combustion will reduce GHG emissions Treatment retrofits may add load to the engine, decreasing efficiency
  • Electrification (including Shore Power and Hybridization GHG Benefit  
Cargo Handling
Equipment
  Co-Benefit Co-disbenefit or Uncertainty
  • Equipment Replacement with Engines Meeting Cleaner Standards
 
GHG Benefit most likely  
  •  Clean Fuels Depends on fuel  
    LNG/CNG Yes, due to lower intrinsic GHG production in combustion  
    O2diesel/Bio-Fuels Benefits possible through life-cycle production, but  varies with source Biodiesel has higher direct emissions due to lower fuel density.  
    Low-Sulfur Fuel Higher energy density may enhance combustion efficiency Low S fuel processing adds emissions, may not enchance combustion
    Emulsified Fuels Can reduce efficiency by reducing overall fuel energy content
  •  Emission Control Technologies  Technologies that improve engine efficiency will bring co-benefit  DPF's, DOC, SCR, etc. may cause minor additional engine loads
Heavy Duty Vehicles – Trucks Co-Benefit Co-disbenefit or Uncertainty
  •  Equipment Replacement Benefit likely, newer equipment will have maximum efficiency Important to account for emissions from vehicle disposal or re-use
  •  Operational Improvements RFID/OCR Systes and gate flexibility reduce truck idling  
  •  Clean Fuels Depends on fuel, See CHE Section  
  •  Emission Control Technologies Controls that improve combustion will reduce GHG emissions Treatment retrofits may add load to the engine, decreasing efficiency
  •  Idle-Reduction Technologies Yes, due to eliminating unnecessary engine operation  
Light Duty Vehicles   Co-Benefit Co-disbenefit or Uncertainty
  •  Equipment Replacement, maintenance Benefit likely, newer equipment will have maximum efficiency Important to account for emissions from vehicle disposal or re-use
  •  Operational Improvements Benefit Likely, through optimal fleet use and maintenance plans  
  •  Clean Fuels Depends on fuel, See CHE Section, Also Electric Vehicles soon available  
  •  Emission Control Technologies Controls that improve combustion will reduce GHG emissions Treatment retrofits may add load to the engine, decreasing efficiency
  •  Idle-Reduction Technologies  Stop/Start Systems, driver education, and idle reduction yield co-benefits  
Locomotives and Rail   Co-Benefit Co-disbenefit or Uncertainty
  •  Equipment Replacement Benefit Likely, newer engines are more efficient, hybrids available Important to account for emissions from vehicle disposal or re-use
  •  Operational Improvements On-dock rail and reduction of system bottlenecks reduce idling  
  •  Clean Fuels Depends on fuel, See CHE Section  
  •  Emission Control Technologies Controls that improve combustion will reduce GHG emissions Treatment retrofits may add load to the engine, decreasing efficiency
  •  Idle-Reduction Technologies  AESS, APU's, DDHS, & Plug-ins shut down main engines during lulls  
Construction Equipment   Co-Benefit Co-disbenefit or Uncertainty
  •  Equipment Replacement Benefit Likely, newer engines are more efficient Important to account for emissions from vehicle disposal or re-use
  •  Operational Improvements Benefit Likely due to Reduced Operating Times  
  •  Clean Fuels Depends on fuel, See CHE Section  
  •  Emission Control Technologies Controls that improve combustion will reduce GHG emissions Treatment retrofits may add load to the engine, decreasing efficiency
  •  Idle-Reduction Technologies  Stop/Start Systems, driver education, and idle reduction yield co-benefits  

 

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Idle reduction will reduce greenhouse gas emissions by eliminating fuel combustion.
TEmission control technologies that improve combustion or reduce fuel use will tend to reduce GHG emissions. Technologies that introduce additional power demands or restrictions on combustion may lead to slight increases in GHG emissions.
Using alternative fuels may also reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions while L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
Improvements that eliminate energy use or improve energy efficiency will also reduce GHG emissions.
GHG emission reductions are likely with engine or equipment replacement due to fuel savings from improved electronic controls and advanced designs.
Idle reduction will reduce greenhouse gas emissions by eliminating fuel combustion.
Emission control technologies that improve combustion or reduce fuel use will tend to reduce GHG emissions. Technologies that introduce additional power demands or restrictions on combustion may lead to slight increases in GHG emissions.
Using alternative fuels may also reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions while L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
Improvements that eliminate energy use or improve energy efficiency will also reduce GHG emissions. .
GHG emission reductions are likely with engine or locomotive replacement due to improved fuel efficiency of newer designs. Options such as hybrid and electric locomotives will produce even greater GHG benefits.
Idle reduction will reduce greenhouse gas emissions by eliminating fuel combustion.
Emission control technologies that improve combustion or reduce fuel use will tend to reduce GHG emissions. Technologies that introduce additional power demands or restrictions on combustion may lead to slight increases in GHG emissions.
TUsing alternative fuels may also reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions while L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
Improvements that eliminate energy use or improve energy efficiency will also reduce GHG emissions. Rigorous fleet maintenance will optimize vehicle fuel efficiency.
GHG emission reductions are likely with vehicle replacement due to improved designs and options for hybrid, electric, and other emerging low-emission technologies. .
Idle reduction will reduce greenhouse gas emissions by eliminating fuel combustion.
Emission control technologies that improve combustion or reduce fuel use will tend to reduce GHG emissions. Technologies that introduce additional power demands or restrictions on combustion may lead to slight increases in GHG emissions.
Using alternative fuels may also reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions. L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
Improvements that eliminate energy use or improve energy efficiency will also reduce GHG emissions. Gate efficiency measures reduce fuel consumption by reducing idling time for trucks and shortening their overall transaction time.
GHG emission reductions are likely with engine or vehicle replacement due to the improved fuel efficiency of newer designs.
Using alternative fuels may also reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions. L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
Using alternative fuels may also reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions. L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
GHG emission reductions are likely with engine or equipment replacement due to improved electronic controls and advanced vehicle designs that improve efficiency.
Meeting energy needs by using grid power in place of fossil fuel combustion will result in a net reduction of GHG emissions.
Emission control technologies that improve combustion or reduce fuel use will tend to reduce GHG emissions. Technologies that introduce additional power demands or restrictions on combustion may lead to slight increases in GHG emissions.
Using alternative fuels may reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions while L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
GHG emission reductions are likely with engine replacement due to improved electronic controls and advanced engine designs. Recent development of diesel electric tugs offers another option of fuel efficiency and GHG emission reductions.
Meeting energy needs by using grid power in place of fossil fuel combustion will result in a net reduction of GHG emissions.
Emission control technologies that improve combustion, like slide valves and engine repowering, will likely reduce GHG emission. Technologies that indtroduce additional power demands, like seawater scrubbing, are likely to increase GHG emissions.
Using alternative fuels may reduce direct or indirect GHG emissions. Low sulfur fuels have minimal impact on GHG emissions. L/CNG produces less GHG's per unit of energy when burned. Biofuels, such as ethanol and biodiesel, may or may not lead to overall GHG emissions reductions depending on the fuel lifecycle.
Improvements that eliminate energy use or improve energy efficiency will also reduce GHG emissions -- either directly from reduced fuel use in operations or indirectly from fuels used to generate electricity for operations.
GHG Emissions will also be reduced through improved combustion efficiency at lower speeds.