Comparison of Clean Diesel and Natural Gas HD Vehicles Tim Johnson Corning Incorporated May 24, 1999

Agenda Objectives Approach To inform ARB of the potential benefits of Clean Diesel technologies as they compare to CNG vehicles. Approach 1) Show progress in diesel engine and aftertreatment technologies. 2) Look at recent results on CNG vs. diesel 3) Compare emission levels of clean diesel to CNG 4) Relate actual real-life vehicle results from the UK. 5) Compare economics.

Emerging Regulations and Health Concerns Market Drivers for Clean Diesel

Tighter regulations are driving diesel to become very clean 4.0/0.05 1/0.05 1.58/0.026 2.0/0.1 3.8/0.04 4.0/0.1 5.56/0.177 g/ bhp-hr Adjusted for test differences Tightest tests are assumed (steady state or transient) Euro IV/V is the Council proposal HDD: 65% NOx and 50% PM efficiencies will be needed to hit the Euro IV/V standards; 75% NOx will be needed to hit the US2007 assumed standards

Diesel engines are coming under much scrutiny regarding toxins PM2.5, and particularly particles less than 100 nm, deposit in the respiratory tract Carcinogens and other toxins from Diesel, or general motor vehicle, exhaust are becoming a concern

Engine technologies and emissions Diesel is getting very clean

Fuel injection is getting increasingly sophisticated There is much work on using injection shape control to reduce PM and NOx and improve fuel economy. 30% reductions in NOx and PM and 5% reductions in fuel consumption due to pilot injections and rate shaping.

Fine particle number distributions from a common rail HDD engine vary with increasing injection pressure At high load greater injection pressure keeps distribution the same, but decreases the numbers at low RPM and increase them at high RPM. At low load, increased injection pressure creates more fine particulates. EPA SAE 1999-01-1141 7.9 liter, 144 kW engine Scanning mobility particle sizes (SMPS) showed minimal effects of dilution ratio from 50:1 to 560:1.

Variable Geometry Turbocharging (VGT) and EGR Cut NOx 10-40% under low load conditions in a 1.8 l Euro III engine Low Load: VGT drops NOx 45% at baseline fuel consumption. High Load: VGT/EGR could not be optimized, no NOx reductions Ford SAE 1999-01-0835

EGR drops NOx about 40%, regardless of what else is added 12.7 L Heavy Duty Engine Detroit Diesel Series 60

Cooled EGR or SCR, and Traps will be Needed Euro IV Euro 3 HDD engines will have “common rail”, high-pressure fuel injection with rate shaping VGT, and electronic engine controls 60% NOx and PM reductions will be necessary to hit the corner of Euro 4 Cooled EGR with Traps hits corner, but has 3% fuel penalty vs. Euro 3 SCR hits NOx, but may require 40%PM reduction

Advancements in Diesel Particulate Traps 2+ orders of magnitude reductions in particulate numbers

Retrofitting Off-Road Diesel Equipment with Catalysts & Filters Significantly Reduced Emissions PM -3 to 50% 80-95% 20% typ. NOx 0-17% 2-15% 12% typ. Nescaum SAE 1999-01-0110 Emissions reductions from DPF and oxidation catalysts depend on the equipment 25% of Big Dig off-road (Boston tunnel) will be equipped with DOCs and passive DPFs.

The VERT Study on LDD & Off Road HDD Showed Filters Significantly Reduce PM and Gaseous Emissions Filters reduced PM by 99%+ by number, but only 70% by mass EC: elemental C OC: organic C Filters reduced PM by more than 99% by number at all load points Sponsors: Swiss & Austrian Accident Insurance Agencies, German Association of Construction Professionals, Swiss EPA Considering reform fuel and fuel additives, filters had the greatest impact on reducing PAHs. New lubricants, catalysts, and engine controls are also effective in curtailing PM Filters reduced CO by 40%, HCs by 85%, and NOx by 25%. No secondary emissions were formed VERT SAE 1999-01-0116

Diesel particulate filters are very effective in reducing particulates These two studies and several more have shown that DPFs remove 95+% of ultrafine particulates, bringing emissions down to gasoline levels

Continuous Regenerating Trap One of the new technologies that reduces toxins and particulates is the CRT system Continuous Regenerating Trap NO is first oxidized to NO2: NO + 1/2 O2 = NO2 The NO2 then oxidizes the soot: 2NO2 + 2C = 2CO2 + N2 Net: one pollutant eliminates the other NOx/soot ratios are important

JMI CRT System is very effective, but requires low-S fuel and min JMI CRT System is very effective, but requires low-S fuel and min. NOx/C AVL SAE 980190 A minimum NOx/PM ratio of 8:1 was determined to be needed for CRT operation. It is generally available over most of the operating range.

Advanced diesel aftertreatment systems are very effective in reducing pollutants The CRT reduces hydrocarbons and CO by >90% under the conditions of the study The soluble organic fraction (SOF) of the PM was reduced by >70% The two aldehyde toxins were significantly reduced NOx was not affected

70+% reductions in NOx and toxins NOx and HC Treatment 70+% reductions in NOx and toxins

SCR drops NOx levels 70 to 75% 12.7 L Heavy Duty Engine Detroit Diesel Series 60

NOx Traps are Evolving for Diesel 91% NOx eff. at 2000 rpm/2 bar Very low sulfur levels are needed (<10 ppm) Diesel engines can be run rich enough to desorb NOx traps, with only 2% penalties in smoke & fuel efficiency FEV SAE 1999-01-0108

Catalysts Performance on Toxic Emissions mg/bhp-hr Toxic Hydrocarbon Compounds Reduced by 58% with 368 ppm S Fuel MECA: API Diesel Issues Forum 4/99

Increased catalyst loading will reduce toxins by 80%, but 50ppm sulfur fuel is needed to keep SO4 down Higher catalyst loadings are effective for reducing all non-PM emissions. Low - S fuel (50ppm) is needed to control PM emissions, especially at the high Pt loading that is most beneficial for toxin reductions Pt loadings: A 0 g/l B 0.02 C 0.2 D 2.0 Hino SAE 1999-01-0471

Clean diesel technologies are effective for both new and retrofits PM Traps will take out 99+% of particles Traps will take out 70 to 95% of PM mass soluble organic fraction gives lower percentages engines can be tuned to minimize SOF NOx EGR gets 40% reductions SCR gets 70%+ NOx Traps are emerging at 70 to 90% HC and Toxins 60 to 95% reductions with catalysts or traps depends on sulfur

Compressed Natural Gas Emissions CNG emissions are low

CNG vehicles emit 60 to 95% less PM and 0 to 30% less NOx than equivalent diesel vehicles Buses and airport vehicles Colorado School of Mines SAE 1999-01-1507

Choice of CNG Engine management technique is critical to controlling emissions High CNG NOx due to insufficient lean operation at high load. Early mixer type engines High CNG NOx due to insufficient lean operation or ignition retard. Depending on CNG engine management strategies, CNG may have higher NOx levels or fuel consumption then diesel. Closed-loop stoichiometric TWC reduces CNG emissions. Fuel economy suffers WVU SAE 982456

Relative emissions depend on driving behavior With non-aggressive driving in CBD cycle, CNG NMHC emissions are double, NOx is 50% less, and PM is 97% less than diesel With aggressive driving in CBD cycle, CNG NMHC emissions are 10X, NOx is 30% less, and PM is 97% less than diesel WVU, Colorado School of Mines, NREL SAE 1999-01-1469

CNG with catalysts have reduced emissions vs CNG with catalysts have reduced emissions vs. diesel, but advanced aftertreatment can make them similar

In the critical sub-100 nm range, CNG particulate numbers may not be much different from diesel ELPI used for measurements Millbrook Proving Ground SAE 1999-01-0470

The U. K. City Diesel Experience City buses and refuse trucks are going to clean diesel instead of CNG

“Diesel buses are becoming very clean indeed” Simon Brown, Principle Engineer, London Transport Buses Two years ago, only one supplier of “City Diesel”. Now, the UK is going low-sulfur across the country. Price differential is 1.4p/liter. On old engines, City Diesel and Oxidation catalysts go a long way. On newer engines, City Diesel and the CRT were very clean. Euro 2 Engine Pre-Euro 1 Engine

London Diesel buses are cleaner and more fuel efficient than CNG or LPG buses “it is beginning to look as if the most beneficial and cost effective solution is high quality, fully reformulated Diesel combined with exhaust aftertreatment. We will have 50% of our bus miles on City Diesel by December 1997.” Simon Brown No deNOx technologies

“For refuse collection vehicles, the lowest cost and cleanest alternatives were City Diesel and a CRT” Alison Simmons, Principle Pollution Control Officer, Walsall Metro. Borough Council Emissions are roughly equivalent to a catalyzed CNG truck CNG truck lost 7% of payload Annual operating cost of CRT was -11% vs. CNG and +18% vs. std. Diesel Capital cost of CNG buses was 7 to 20% higher than CRT (BP127,000 base)

Economics - Diesel is $20,000/yr/bus cheaper No CNG retrofits are feasible need to replace significant numbers of vehicles to see impact two fuel services will be needed Infrastructure costs are high $40,000 to $60,000 per CNG bus incremental difference; clean diesel may be $2000 to $5000 $500,000 (10 buses, 2-3/hr refueled) to $5,000,000 (200 buses, 30/hr refueled); clean diesel requires low-sulfur fuel - marginal infrastructure Operating costs are higher -10% vs. +50% more equivalent energy; +35% typical +15% more maintenance $50,000/yr/bus for CNG vs. $30,000/yr/bus for diesel; amortization and overhead Source NYC MTA private communication

Summary Diesel engine technologies have come a long way, and have significant potential Diesel after-treatment technologies can make diesels as clean or cleaner than CNG Clean diesel technologies are much cheaper than CNG and can be retrofit or purchased new California is well-positioned to take advantage of clean diesel technologies, with emerging supply of low-sulfur fuel