Additional Resources
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Q & A - Diesel Retrofit Technologies
Diesel Retrofit Technologies – Availability, Performance and Cost
Q: Has biodiesel (B20) been demonstrated on 2007 trucks and does it help with regenerating the trap?
A: Several of the engine OEs have approved use of B20 in their 2007 engines. Others have approved lower blends such as B5 or B10. Use of biodiesel does not impact the regeneration characteristics of the 2007 active filters to any great extent. There may be a slight decrease in the formation of PM which indirectly helps regeneration in that there is not as much PM (~ 5% less) to deal with.
Q: Is the CO2 exhaust component increased or decreased by DOCs or DPFs? How can the change be calculated?
A: There is essentially no increase in CO2 emissions with the use of either DOCs or DPFs. Traditionally, CO2 is measured during FTP testing of the baseline engine and compared to the engine fitted with the aftertreatment system.
Q: With regards to the 90% PM reduction of a DPF, is PM2.5 reduced 90% also?
A: Wall flow filters that reduce PM by 90% or more will reduce PM by the same percentages across all particle sizes.
Q: Please say again what "LNT" stands for?
A: LNT stands for “Lean NOx Trap” otherwise known as a NOx adsorber. It is potential NOx reduction technology for use with diesel engines to meet the EPA’s 2010 on-road NOx levels of 0.2g/bhp-hr.
Q: Where are the top retrofit opportunities (i.e., on-road, off-road, marine, etc.), or where are the priorities?
A: All the markets mentioned here are target markets for retrofit. The most experience and largest number of retrofits have taken place in the on-road sector. There are many millions of on-road vehicles that remain good retrofit candidates. Off-road is also a prime target since these machines have emissions levels higher than on-road vehicles and many of them operate in sensitive areas. And as more retrofits are completed and the new 2007/2010 and Tier 4 engine come on line, reduction of marine and locomotive emissions will become more and more important.
Q: Any issues with soot release during acceleration?
A: Wall flow filters have no issues with soot release during acceleration.
Q: What are the maintenance requirements for each type of device (DOC, Partial Filter, DPF, EGR, SCR)?
A: Both DOCs and partial filters essentially require no maintenance except for a periodic visual inspection of brackets and hangers. DPFs, due to their reliance of wall flow filters, will capture all of the lube oil ash that would normally go out the tailpipe as lube oil is consumed. As such, a periodic cleaning of the filter is necessary as the backpressure of the system increases. Visual inspections of hangers, bolts, backpressure monitors are also recommended. For either low pressure, cooled EGR or high pressure EGR, inspection of the system components as well as annual cleaning of secondary filters is recommended. If coupled with a DPF, the same requirements for the DPF are again recommended. For SCR periodic visual inspections and potential cleaning of the catalyst and urea nozzle may be required. And if coupled with a DPF, the same types of requirements are again recommended.
Q: Who are the technology leaders in partial filters and DPFs?
A: Most of the technology companies that have verified product with the EPA and/or CARB for retrofit are leaders. Amongst these are Johnson Matthey, Donaldson, Caterpillar, Cummins, ECS and Cleaire. For OE first fit (new engines, both 2007, 2010, Tier 4, Johnson Matthey, BASF and Umicore are the leaders.
Q: On the active DPF, does the vehicle operation have to be ceased during the burn-off?
A: For the three systems that are currently verified by either EPA or CARB, the vehicle operation must cease. The 2007 OE active systems as well as active systems yet to be verified for retrofit will not require vehicle operation to cease.
Q: Does the United States have the infrastructure to support broad implementation of SCR?
A: While there were concerns early on about a urea infrastructure, a urea stakeholder group was formed and has made significant progress towards putting a system in place. Amongst the stakeholders are EPA, engine OEs, vehicle OEs, technology companies, truck stop association, etc.
Q: With the use of a lean NOx catalyst is there an effect on the system efficiency due to extra weight and energy needed to operate it. Is there a fuel penalty?
A: While it is true that combined filters and NOx systems add weight to the vehicle, system efficiency is not impacted. In fact in certain cases, the engines can be calibrated for fuel economy (increase in NOx) since these increases in NOx can be eliminated with the NOx reduction aftertreatment.
Q: The slide that shows "verified" technologies - what CARB levels are these technologies verified to?
A: CARB has verified Level 1 (DOCs), Level 2 (partial filters) and Level 3 (active and passive filters) technologies. They have also verified Level 3 filter technology with low pressure cooled EGR for 40% NOx reduction and a lean NOx catalyst with a filter for 25% NOx reduction.
Q: What are the byproducts of an SCR system? What is the disposal plan for the byproduct/s?
A: There are no “byproducts” with the use of SCR. In some cases there may be a small amount of ammonia slip (unused ammonia) that will be controlled or eliminated with an ammonia slip catalyst.
Q: Are catalytic based filters in common use - have they been found to be practical?
A: There are well over 250,000 catalyst based filters that have been retrofitted on HDD vehicles around the world. In addition there are several million HDD vehicles in North America, Europe and the Far East that were supplied with catalyst based filter systems as original equipment. There are also well over 5,000,000 catalyst based filter systems operating in Europe on several LDD automotive platforms.
Q: What is the cost impact ($/hp roughly) for emission upgrade groups? Is there a cutoff age between repowering and retrofitting?
A: Approximate costs for retrofit are $1k-$2k for DOCs, $4k - $5k for partial filters, $7k - $10k for passive filters and $13k to $40k for active filters. Typically, another $10k would be added to the cost of a filter system for NOx control. The cutoff between repowering and retrofitting is largely dependent upon specific cases and the goals trying to be achieved. Repowering may not be an attractive option if other systems (cooling, hydraulics, transmission) need to be upgraded or modified. However, retrofit may not be an attractive option if the technology options are limited, i.e. no Level 3 filter verified for the application.
Q: The Eco-System Fuel Line Device has been used successfully to reduce fuel use in the Houston Ship Channel area on certain barges. www.ecofuelsystems.org
Q: For the off-road equipment, is engineering for each make and model still an issue or are we getting to the point where one device fits multiple makes/models?
A: Due to the broad variety in off-road applications, engine sizes and duty-cycles, some level of engineering will be necessary. However, concepts such as “universal design” with multiple inlet and outlet heads and bracketry will help to minimize the amount of individual engineering needed.
Q: The fact is that you can retrofit 20 school buses versus one $20,000 engine upgrade. How do you overcome the more is better mindset?
A: To a large degree, technology choices are driven by two things, the goals for reduction (Level 1, 2 or 3) and the money that is available to meet these goals. For the example cited, if your goal is to retrofit with Level 1 devices that get 25% PM reduction you can probably retrofit 10 – 20 buses for your $20k. If the school buses operate with low exhaust temperatures (<200C) but you need Level 3 filters (~90% PM reduction) you might only be able to retrofit 1 or may 2 buses for your $20k.
Q: When the turbo fails on a medium duty CAT engine will the ATD be unusable due to oil saturation?
A: If there is a turbo failure on any diesel engine fitted with an aftertreatment device, there is a potential to damage either the oxidation catalyst or filter. In some cases the DOC and/or DPF may be recoverable.
Q: Verified NOx reducing retrofits seem to be limited in the range of engines they are applicable to, and are all quite expensive. Is anything in the works to expand the range of candidate engines and to bring the cost way down?
A: Additional NOx retrofit products are in the process of being verified with both EPA and CARB for a broad range of engines and applications. Unlike the reduction of PM, HC and CO, reducing NOx requires the use of a catalyst that needs either urea (ammonia) or diesel fuel to be injected across the catalyst thereby increasing the complexity of the system required for NOx control and thus the cost. With a increase in volume (# of systems sold) we would expect the cost of the systems to come down a bit.
Q: How does long-term idling of heavy-duty trucks, such as that needed for Hour-Of-Service requirements, affect OC and DPF operation?
A: Idling is not the optimum mode of operation for the functionality of DOCs and DPFs since they rely on exhaust temperature to reduce PM, HC and CO. The good news is that at idle, the formation of PM is not that significant and DOCs and DPFs will tolerate a certain amount of idling. However in very cold weather, extensive idling has been known to cause fouling of DOCs and DPFs. As more states institute anti-idling statutes and use of APUs and electrification of truckstops increase, the issue of extended idling should become less.
Q: What is the effect of biodiesel 2.5 or 15% on exhaust aftertreatment systems?
A: Many of the engine OEs have approved the use of biodiesel blends up to B20 (20% blend) and in most cases there are no negative effects on the aftertreatment systems. One cautionary note here, the biodiesel that is used MUST be made to strict ASTM standards. If the biodiesel is not made properly, i.e. you processed used vegetable cooking oil in your garage, there may be a negative impact not only on the aftertreatment system, but on the engine as well.
Q: What are the typical lifespans of the various retrofit devices?
A: Typically DOCs and DPFs will last for 5 – 10 years and provide several hundred thousand miles of effective service. There are many system operating in Europe that have reached 1,000,000 miles and there are numerous examples of filters on Class 8 trucks operating in California having reached 500,000 miles of service, the truck was retired and the DPF was transferred to the replacement truck. Of course proper maintenance of the engine is critical to the ultimate life of these retrofit systems.
Q: Do you have an estimate for how many retrofits (how many vehicles) will be performed over the next 5-10 years in the US?
A: It is EPA’s goal to see every one of the 12,000,000+ diesel engines operating in the US to be retrofit at some point in their lifecycle. It is relatively easy to expect that some significant portion of these engines will be retrofit as more and more states move to mandate emission reductions from both on- and off-road engines to meet their emission reduction targets for their SIPs.
Q: Has CAT, Cummins and/or their company association lobbied the federal government to increase funding to the EPA or to states for nonroad retrofits?
A: All of the companies involved in retrofit, as well as their trade associations have been very active in promoting an increase in the levels of funding from Federal, State and Local levels. In fact, the Diesel Emission Reduction Act (DERA) signed into law by Congress in 2005 and which earmarked $1 billion over 5 years, was promoted and supported by over 137 different stakeholders. In fact it was one of the broadest and most varied coalitions of stakeholders ever to coalesce around an issue.
Q: Are there devices particularly suited to electrification and are there any advantages to overall operation, device life, and life cycle costs to having electrification capabilities?
A: Active systems that require periodic electric regeneration have a role to play for those applications that are too cold and potentially too dirty for passive (catalyst based) systems. However electrically regenerated systems typically have a cost premium over passive systems, require dedicated infrastructure and have an ongoing operating cost associated with the use of electricity. Additionally, since these electrically regenerated systems do not contain a catalyst, there is no reduction in the amount of CO and HC from the engine.
Q: Not all DPF systems require temperature data logging. There are several which are verified by CARB for all duty cycles, regardless of exhaust temperature.
A: All passive DPFs require that temperature profiles be understood. Active systems, either electrically regenerated or regenerated with a fuel burner, do not require temperature datalogging. However, these active systems are considerably more expensive than passive systems.
Q: Clean School Bus EPA grants recommend that DOC projects be put out to bid to multiple suppliers of the hardware. Is this practical, or are there a limited number of suppliers in any region? Most engines in our project are International DT 466.
A: There are several manufacturers that have verified DOCs with both CARB and EPA. In most cases these manufacturers operate on a national basis. A list of verified technologies as well as contact information can be found at http://www.epa.gov/otaq/retrofit/contacts.htm and http://www.epa.gov/otaq/retrofit/verif-list.htm.
Q: What are the regulatory or voluntary state/local measures driving the move toward retrofits? I thought that reductions in emissions of HC, PM, and NOx were preempted by federal regs?
A: The bottom line driving retrofit is that the states need to reduce inventories of ozone (NOx and HC) and PM in order to reach attainment as directed by the Clean Air Act (CAA). The federal government has the authority through the CAA to set federal standards for new engines. California and a handful of other states have had the ability to set their own standards for new engines under the CAA of 1970. The CAA does not give the federal government the authority to mandate retrofit programs nationally. However, the states through legislative authority can set mandates for retrofit, and as in the case of California, these mandates are broad and all encompassing so that the state of California can meet the goals of the CAA through its State Implementation Program which can target both NOx and PM nonattainment areas.
Q: There seems to be a lot of concern regarding the impact of liquid urea within SCR devices. What is your experience on whether or not this is a realistic concern?
A: For an SCR system to work properly, urea must be injected into the exhaust stream at temperatures above 200° - 250° C. This is a requirement of the SCR catalyst itself since the catalyst does not reduce NOx below this temperature. The urea is actually injected as a liquid through a nozzle and is atomized as it enters the exhaust.
Q: What impact does biodiesel have on the various retrofit devices? Is one device more beneficial that another when using biodiesel?
A: Biodiesel blends of up to B20 have been approved for use in several manufacturers' engines. Use of biodiesel essentially has no impact on any of the retrofit products that have been verified.
Q: What are the impacts on burning ULSD vs. biodiesel (B10)?
A: In today’s on-road market, any biodiesel blend should be made with ULSD and particularly if it is to be used with n aftertreatment system. Use of ULSD by itself will give PM reductions of about 10%. An additional 5% PM reduction may be seen when using a biodiesel blend.
Q: What is the biggest challenge the panelists see to get more funding and the biggest challenge to getting more fleets to "volunteer" for retrofit?
A: Today, there is more state and local funding available than ever before. It actually approaches hundreds of millions of dollars annually, but it is geographically in the West, TX, OH, NY, NJ and the Northeast. And it’s a good thing for the states to step up and devise creative ways to fund retrofit. On the federal level, funding dollars will remain scarce based on the budgetary issues we face with the war in Iraq, and a host of other issues. As far as expanding retrofits, education, information, workshops, etc. to get the message out there that there are solutions for retrofit, that clean air is good, and we can all benefit from it.
Q: For a pilot project to retrofit 200 school buses with DPFs, what would be the best way to screen our bus fleet to determine which buses to retrofit?
A: The best way forward is to put together an inventory list of all your buses including the engine model, model year and approximate mileage on each bus. Then distribute the list to the verified manufacturers on either EPA’s or CARB’s website at http://www.epa.gov/otaq/retrofit/verif-list.htm or http://www.arb.ca.gov/diesel/verdev/level3/level3.htm. The manufacturers have a great deal of experience with school buses, and to a large degree may be able to tell which bus engines are good candidates for passive filters, active filters or if temperature traces need to be done. Then apply for funding (federal, state, local, bake sale, car wash, etc.) and put out an RFP.
Q: The comment was made that DPFs cost from $10K to $40K and up. What size engines use the $10k solution?
A: The vast majority of 1994 and newer model year engines with horsepower rating less than 450HP would likely be candidates for passive filters at a cost of $10k or less. This assumes that the exhaust temperatures average at least 200° C. If temperatures are less than 200° C, it is likely that the more costly active systems will be needed.
Q: Given that DOCs and DPFs remove different parts of PM, why use a DOC when it doesn't remove the solid carbon core of PM?
A: DOCs are often supplied on engines older than 1994. The amount of PM was about six times higher that engines that are newer than 1994. As a result, a lot of PM mass can be reduced with a DOC. While it is true that a DOC gets only a small amount of carbon (~ 2-3%), the SOF (soluble organic fraction) is largely made up of hydrocarbons, some of which are very toxic, i.e. benzene, formaldehyde, etc. so reductions of the SOF are important.
Q: How many miles/service hours is a retrofit after-treatment device supposed to last before its warranty expires?
A: Depending upon its weight class, LHD, MHD or HHD, CARB requires a 5 year, or 60,000, 100,000 or 150,000 mile warranty for verified devices. The EPA requires that verified devices come with a warranty, but they do not dictate the terms of the warranty expecting that the marketplace will set the terms.
Q: Is there one web site that would direct applicants to all funding sources available for their state?
A: Funding for retrofits is an extraordinarily complex and convoluted business. The most comprehensive sites are the EPA’s voluntary website, CARB’s website, TERP’s (Texas) website, local MPO (Metropolitan Planning Organization) websites, plus other state websites as well as verified device manufacturers, consultants, trade associations, etc.
Q: How do you suggest getting CO reduction on landfill gas? Are there certain components in the gas that can damage a catalyst? And what are they?
A: Is it CO you’re trying to destroy, or is it methane? If it’s methane, there are methods of capturing it and burning it in a natural gas engine. It is likely that there will be some contaminants that will be entrained as well, things like phenols from plastics.
Q: In our fleet we also use biodiesel. We use B-99 in 20 of our buses. 16 of the buses are Crowns with the L6-71 engines. The fuel we is soy based. Have any test been done with B-99 using the passive filters?
A: To my knowledge, no testing has been done with B99 and passive filters. Testing has been done with blends up to B20 with no ill effects. Most engine manufacturers would not agree with the use of B99. Whatever level of biodiesel that is being used, it is critical that the biodiesel meet the ASTM standards for quality and content.
Q: How does retrofit technology, particularly one using EGR, but also other technology, interact with engine durability/maintenance? Do retrofit kits offered take responsibility of NOT damaging the engine?
A: One provision of the CARB warranty for verified products is that device manufacturers must offer warranty coverage for consequential engine damage if that damage is caused by the verified device. EPA’s warranty requirement is not specific, but most reputable suppliers will be willing to work with customers if there are issues with the technology.
Q: What are the benefits of burning biodiesel (B10) vs. ULSD- emission wise?
A: Today’s on-road biodiesel blends should be mixed with ULSD especially if aftertreatment is used. ULSD can get you up to 10% PM reduction while biodiesel blends will yield about 5% PM reduction.
Q: Are engine upgrades subject to verification by EPA or CARB like other retrofits are?
A: Yes.
Q: Urea freezes at -10 deg C. What are the EPA guidelines for heating up urea?
A: The EPA has issued guidance documents dealing with Urea SCR certification. The EPA’s 27 March 2007 document refers to freeze protection as follows: B. Freeze Protection The reducing agent should not be adversely affected by extreme climatic conditions, particularly freezing temperatures. Some reducing agents freeze at temperatures that occur seasonally in certain parts of the U.S. Urea, for example, freezes at 11°F. Manufacturers need to either use a reducing agent that will not freeze at low temperatures, or design their SCR system to prevent freezing (e.g., use of heater elements in or around the storage tank and heated lines). Manufacturers who use a heated SCR system need to ensure that minimal “thaw” time is required to melt enough reducing agent to recharge the system, should the reducing agent freeze due to extensive exposure to low temperatures.
Q: If educating the customer is the catalyst for more voluntary retrofits, what's currently being done alone those lines?
A: There are a number of different activities that are taking place on an ongoing basis. For example, the DTF’s webinar, federal, state, local conferences and seminars, “Ride and Drives”, websites, advertising, direct sales calls, etc.
Q: What is your expectation related to marine applications, especially in California? Who will be responsible to certify the after-treatment system?
A: Any manufacturer that wishes to participate in CARB’s Diesel Risk Reduction Program would have to verify any aftertreatment system it wanted to offer as a solution to reduce primarily PM, but also NOx, CO and HC. SCR and filter systems have already been fitted to tugs, ferries, freighters in the U.S. and in Europe.
Q: Are there repair/maintenance cost data available for the retrofit kits that have been in use since 1990?
A: There is no central database where this type of data is accumulated and analyzed. Anecdotally, filter cleaning (removal of ash) has been occurring every 60,000 to 150,000 miles or every 1 – 2 years depending on the application (heavy transient vs. over the road) at a cost of $300 to $400 per cleaning event.
Q: Are any closed crankcase ventilation systems verified as standalone technology?
A: No. Neither the EPA nor CARB verify technologies that reduce PM by less than 20 – 25%.
Q: Wouldn’t using biodiesel in a vehicle with an ATD be the similar to using leaded gas in a car with a converter?
A: Today’s on-road biodiesel blends need to be made using ULSD and biodiesel that meet the ASTM quality standards. If these two conditions are met and the biodiesel bled is limited to B20 or less, there is no impact on the aftertreatment device.
Q: Do locomotive and marine retrofits qualify for CMAQ funding?
A: Retrofits of locomotives and marine vessels can qualify for CMAQ funding since they do provide reductions of emissions – mitigation as well as potentially take trucks off the road – congestion. Projects involving marine and locomotive components would need to submit the proper paperwork to the ruling MPO.
Q: I understand that the use of ULSD drops the engine efficiency by about 33%; if you have to burn more fuel to get the same mileage, how much reduction do you really get for CO or NOx?
A: There is no validity to the statement that use of ULSD reduces the efficiency of diesel engines by 33%. To my knowledge there is no impact on engine efficiency with the use of ULSD.
Q: If you are using biodiesel (B10) with 5ppm ULSD (CAN blend), is there a need for a retrofit device?
A: The use of a B10 blend with ULSD will provide some minimal reduction in PM, potentially 10% or so. With retrofit of DPFs on these same engines, reductions of PM by 90% or more are quite attainable.
Q: Does the panel have any thoughts or experience with Catalyst borne fuels?
A: Fuel borne catalysts (FBC) have been used in Europe to provide improvements in operating requirements for filter systems, such as exhaust temperatures. FBC have not received wide acceptance by either EPA or CARB. Some of the by-products from use of FBC can be quite toxic. A case in point is one copper based FBC that resulted in formation of dioxins and furans at the tailpipe. Both EPA and CARB require that any FBC that requests verification must go through multimedia testing to ascertain if there is any impact to air, water and land from the use of the FBC. Multimedia testing is a multi-million dollar ($3 - $5 million) and multi year (3 – 5 years) endeavor and as a result has not been widely considered for use in the US.
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