CO2e Benefits of Reducing Black Carbon Emissions from U.S. Class 8 Trucks with Diesel Particulate Filters: A Preliminary Analysis

Transcription

1 CO2e Benefits of Reducing Black Carbon Emissions from U.S. Class 8 Trucks with Diesel Particulate Filters: A Preliminary Analysis Air and Waste Management Association Conference Session Vd #6: Strategies for Controlling Black Carbon. Paper #409, Xi an China May 12, 2010 L. Bruce Hill, Ph.D. Senior Scientist Clean Air Task Force, 18 Tremont St. Suite 530, Boston, MA 02108

2 Problem: Sensitive regions face short-term risk that will be difficult to address with CO2 strategies.

3 Short atmospheric lifetime of black carbon means reductions can have near-term benefit Bice et al, 2008

4 Questions: 1. Which diesel retrofit devices can reduce BC? 2. What is the net carbon dioxide equivalent (CO 2 e) reduction, based on GWP, from a diesel truck equipped with a filter? 3. What would the CO2e benefits be of a U.S. Class 8 truck rebuild rule in the United States?

5 Level 1. Diesel Oxidation Catalyst (DOC) CARB Level 1 Device < 25% PM reduction. Fits most engines, easy to install muffler replacement. No operational issues. Inexpensive. (~$1000 installed) Relatively ineffective. Many DOCs get <20% particulate reduction. Strips organic carbon via oxidation, does not reduce black carbon.

6 Level 2. Flow Thru Filter (FTF) (e.g. Donaldson DMF) Level 2 Device ~50% PM mass reduction. Up to 70% under optimal duty cycle and T. Wider range than DPF: fit to engines with exhaust T >210 deg C 40% of duty cycle. Mid range cost ~$U.S $7000 Removes both organic and black carbon via oxidation and trapping by a metal fleece. Black carbon reduction appx same as overall reduction ~50%). Back pressure potential if clogged by excessive lube oil burn. More tolerant of higher fuel sulfur content reportedly to 350 ppm.

7 Field Test: Level 3 DMF: ~40-70% Black Carbon Reduction Magee Sci AE91 Black Carbon Monitor

8 Level 3. Diesel Particulate Filter (DPF). Most effective. Level 3 Device >85% PM mass reduction. Up to 99% under optimal duty cycle and T. Fit to engines with exhaust T >240 deg C 40% of the duty cycle. Passive (doubly catalytic) and active (regeneration via injected fuel or electric.) Cost US $6000-$10,000 (passive) Virtually eliminates all black carbon via honeycomb wall-flow filter. Back pressure potential if clogged by excessive lube oil burn. 15 ppm S ULSD requirement

9 Field Test: DPF 95+% Black Carbon Reduction Magee Sci AE91 Black Carbon Monitor Conventional 1114 ug/m3 Black Carbon DPF-equipped 5 ug/m3 Black Carbon

10 Uncontrolled DPF Retrofit Chase Studies: DPFs Virtually Eliminate PM Video at: iesel/videos/

11 Do DPFs Cause a Fuel Penalty? A DPF could create back-pressure which could theoretically impact fuel economy and therefore create excess CO2 & BC offsetting BC reductions. Therefore, the CO2e reductions from the BC must overcome the increment of CO2e (CO2 + BC) associated with any additional fuel consumption. If there is no fuel penalty, there is no long term downside to retrofit-related BC reductions. A review of the literature finds that fuel penalties associated with retrofit DPF applications range from zero to a few percent. A field study of 20 retrofit tractor-trailer trucks in the U.S. that travelled approximately 150,000 miles a year/vehicle suggests no measurable fuel penalty associated with the DPF. Four years worth of fueling records, covering 1.28 million fleet miles, for 10 MTA New York City transit buses that were retrofit with a DPF suggest no statistically significant fuel penalty. Nonetheless we assume a 2 percent fuel penalty in our calculations.

12 Is there a BC-Related Net CO2e Benefit from Diesel Filters? Method I: This approach is a simple stoichiometric and GWP-based calculation combined with engine emissions assumptions including a 2% fuel penalty. See: DPF-Climate.pdf Method II: Olivier Boucher, Hadley Centre, UK, modeled our U.S. fleet scenario based on Boucher and Reddy (2008).

13 Constants/Assumptions Based on U.S. Class 8 Heavy Duty Onroad Diesel) Two principal assumptions simplify the analysis: 1) DPFs are readily available off the shelf and, 2) ULSD is universally required, as it is in the United States.

14 Two Carbon Dioxide Equivalency Metrics Used in the Estimates: GWP: Adopted as a part of the Kyoto Protocol, Global Warming Potential or GWP, was established to create a common CO 2 -equivalent scale for comparing the potential effects of different greenhouse gases in meeting each country s reduction commitments. GTP: An alternative to GWP proposed by Shine et al (2007), Global Temperature Potential (GTP), is a temperature-change based metric recently highlighted as potentially a more practical approach to CO 2 - equivalency.

15 Method I Results Based on a best estimate GWP 20 of 2,200, the installation of a DPF on a Class 8 truck results in a CO2e benefit of about 2,286 g/gal CO2e. Total climate forcing of a gallon of diesel fuel burned in a US Class 8 truck (uncontrolled) is approximately 12,586 g/gal, or more simply a DPF reduces approximately 18% of the total CO2e. Use of a 50% efficient ARB level 2 FTF would be approximately half the benefit. Incorporating a 2 percent fuel penalty yields a net climate benefit of approximately 2,080 g/gal CO 2 e per gallon of diesel fuel (2,080 g/gal) for US Class 8 trucks and reduces approximately total CO2e by 17%.

16 CO 2 e / Gal ULSD DPF benefits for Published GWP/GTP Metrics (2% Fuel Penalty) Source of GWP/GTP Metrics: Excellent Summary Paper Fuglesvedt et al (2009)

17 Hypothetical DPF-based Class 8 Engine Rebuild Rule CO 2 e Benefits

18 Method 2: GTP-based Temperature Change from Hypothetical U.S. Class 8 Rebuild Rule w/ 2% FP. (Courtesy, Olivier Boucher, Hadley Centre, UK)

19 Diesel Particulate Filters: leapfrogging to near term climate forcing reductions.

20 For More Information: L. Bruce Hill, Ph.D. Senior Scientist Clean Air Task Force 18 Tremont St., Ste 530 Boston, MA USA (603) Reports at: Video at: