NO emissions from CNG taxis will eventually oxidize in the atmosphere to NO2, but by that time it is dilute and dispersed. NO2 emissions direct from the tailpipe of a DPF equipped diesel create roadside exposure of the population at large to a recognized toxic component. NO2 creates lung inflammation, and reduces resistance to respiratory disease. A study recently carried by Environment Canada in cooperation with Health Canada exposed exhaust from DPF equipped diesels to laboratory rats and found evidence of inflammatory lung response relative to a control group. While this was done using a heavy duty diesel engine, the same mechanism will occur in light duty diesels. A report has been issued entitled “Treatment of Diesel Exhaust with a Diesel Particulate Filter enhances lung inflammation” (1) The report indicates that the enhanced inflammatory and oxidative stress response to diesel exhaust treated with a diesel particulate filter is in line with a 4 fold increase in NO2 emissions. The Euro 4 diesel taxis may therefore be creating an additional hazardous air pollutant in the process of reducing PM. This does not occur with the CNG taxis.
Continuing to use CNG taxis in their present form saves 16 kilotonnes CO2 per year compared to what the Crown diesels produce, and if the new Toyota Wish CNG taxi is used in place of the Epica diesel taxi, the savings can be 20 kiltonnes CO2 per year.
Gilbert Von - C.Melchers GmbH & Co - CNG Presentation
C. Melchers GmbH & Co. CNG presentationSingapore International Energy Week Natural Gas Uses in Transportation: Liquid? Gas? Electric? 25th Oct 2012
C. Melchers CNG References• Melchers opened the first dedicated conversion workshop in Singapore• About 60% market share in converted vehicles using Italian conversion technology• >1600 Taxis passed the 200,000 km mark.• First company to introduce Type 4 (light-weight) cylinders for mass conversion• Engineered and built world’s largest CNG station at Toh Tuck• Currently supplying of CNG systems to Malaysia, Vietnam, Indonesia, Myanmar.
Singapore – CNG study As of Sep 2012: 25,192 Diesel Taxis, 2,643 CNG Taxis Study undertaken in 2011 to illustrate environmental benefits of CNG taxis vs. diesel taxis. Cost of CNG: ~ USD 0.85/litre equivalent (incl USD 0.16 government duty). Cost of Diesel: ~ USD 1.30/litre Types of taxis compared: Toyota Wish 1800cc CNG/Petrol Toyota Wish 2000cc CNG/Petrol Toyota Crown Euro 2 Diesel Chevrolet Epica Euro 4 Diesel Hyundai Sonata Euro 4 Diesel
Comparison of Toxic EmissionsVehicle PM Emissions PM Emissions from 1000 taxis PM emissions from 1000 taxis on annual basis g/km g/km at 208,000 km/Annum Kg/AnnumToyota Crown Euro 2 diesel 0.1 - 0.2 100 - 200 20,800 - 41,600Chevrolet Epica Euro 4 diesel 0.001 1 208Toyota Wish CNG Not detectable 0 0Note: Even though Particulate Matter (PM) emissions from Euro 4 vehicles has been reduced considerably by the DPF, it can create new toxic emissions in the process by creating NO2: PM accumulates in DPF → Passive regeneration by oxidizing NO to NO2 → NO2 reacts with carbon to burn off as CO2. If NO2 slip occurs, excess NO2 emission results.
CO2 comparison between Diesel & CNG TaxisVehicle Description F.E. Fuel CO2 CO2 if 20% petrol CO2 for 1000 taxis CO2 Savings by L/100 km g/km and 80% CNG g/km on annual basis Using CNG Kilotonnes/Annum Kilotonnes/AnnumToyota Crown Diesel 10 Diesel 260 54.08Toyota Wish CNG 1800cc v1 9.73 Petrol 49 CNG 131 180 37.44 16.64Toyota Epica Euro 4 diesel, 6 spd auto 7.6 Diesel 210 43.68Toyota Wish CNG 2000cc v2 6.25 Petrol 31 CNG 85 116 24.13 19.55Hyundai Sonata Euro 4 diesel auto 7.3 Diesel 191 39.73Hyundai Sonata CNG 4 spd auto - not taxi 7.9 Petrol 39 CNG 106 145 30.16 9.57