GHG and CNG versus diesel fuel

[dieselcruiserhead]

Hi guys,
I've been looking into converting our local fleet to CNG from our current diesel/small biodiesel percentage (5%-20% depending on temps). I'm having a lot of trouble finding good comprehensive GHG information for the purposes of the conversion and to give to public officials. I've heard everything from 0% difference to even 90%. I am aware of the molecular structure of methane and this is supposedly the argument I've heard for the high GHG drop but that a portion of the unburnt fuel is methane so it's 21 times stronger a GHG so that mitigates any GHG solutions.

Can anyone speak to this? I've been looking on the NREL and DOE sites trying to find a report about this but so far nothing...

Also I understand the new ISL-G engines get about 1gg to 1 gallon of diesel equivalency in terms of fuel consumption. So this would in effect double and former numbers where it was formerly two GGs of CNG to match 1 gallon of diesel, which I imaging would help a lot...

thanks,
Andre in Park City, Utah

[dieselcruiserhead]

Re: GHG and CNG versus diesel fuel

Top - Thanks guys...

My research has been the CNG "is usually" GHG neutral in terms of emissions compared to diesel vehicles. However, in 2007 it appears the ISL-G Cummins engine came out (that everyone rants and raves about) and despite that CNG has 25% of the energy content of diesel it amazingly gets about the same mileage. The CNG emissions of CO2 are about 70% that of diesel but the unburnt methane emissions (methane is 21 times more potent than CO2 as a greenhouse gas) bring it back to about a "no discernible difference."

In my mind I was thinking a post-combustion catalyst or reaction chamber, much like what is installed into Ford pickups recently, should be able to burn that unburnt methane which should universally increase emissions but specifically consume that methane. The ISL-G takes a similar approach where it uses EGR - exhaust gas recycling - which routes portions of the exhaust back into the combustion process for reburning. The question is if that is generic exhaust or if there is somehow a higher percentage of methane.

It is interesting to me to mess with one of the most potent GHG's to possibly lower GHG emissions...

Please let me know your thoughts!

Here are the links to the ISL-G. This is now considered the universal 'awesome' application for CNG in buses, dump trucks, etc...

It's saying I can't post links until I have 15 posts so cut and paste these links:

bit.ly/cpuV3
bit.ly/2F0Yq5
bit.ly/2zhed9

It has been out for a couple years and every fleet manager I talk to rants and raves about them...

thanks,
Andre

[Curtis]

Re: GHG and CNG versus diesel fuel

Andre, you can contact Cummings Westport directly. Their info is posted in my Clean Cities forum here; http://www.cngchat.com/forum/showthread.php?t=3410

They can most likely give you emissions data on the ISL-G to assist you. They claim a 23% reduction in GHG over deisel, however you're running a blend which may change the numbers a bit.

You may also find some helpful info here: http://www.google.com/search?q=ISL-G...rlz=1I7SUNA_en

I would certainly join your local Clean Cities Coalition. That is their main function in life, to assist fleets with data, funding and resources to assist you in doing exactly what you're doing. Contact your local AQMD as well to see what resources they can offer.

All the best.

[CraziFuzzy]

Re: GHG and CNG versus diesel fuel

Something you also have to realize is, that even though CH4 has a higher GHG impact, it is a short term impact. In the upper atmosphere, solar radiation will break the CH4 down to CO2 and H2O (same reaction as combustion). This will limit the 'advertised' 21x impact.

[Curtis]

Re: GHG and CNG versus diesel fuel

Remember guys, many fleets, particularly in CA, are operating under mandates to lower GHG outputs, idle reduction, carbon footprints of their fleets, etc. under new regulations that are, or soon to be in effect. It's a smart move to do what Andre is doing and looking for a cost effective way to be proactive. Money is always a consideration, but there are incentives for this type of conversion.

Andre, send me a PM. I have another thought I'd like to cover with you that might be a big help.

[dieselcruiserhead]

Re: GHG and CNG versus diesel fuel

Thank you Curtis, will do.

Appreciated,
Andre

[Gerben]

Re: GHG and CNG versus diesel fuel

Methane may have a 21 times stronger GHG potential than CO2, but the emission quantities are negligable. We're talking about ppm levels if the car is converted properly. The difference to diesel is very small overall in terms of CO2. (Unless you have biogas ofc.) The main difference is in other emissions like NOx. CNG is better for local air quality. Another aspect is the emissions of methane during transport. In Europe we use a lot of Russian gas from Siberia. During transport to the EU a significant amount of methane is lost. Without those losses CNG would be a lot cleaner. Finally engine efficiency is crucial. A CNG/diesel dual fuel reaches better effficiency than a CNG gasoline bifuel. Newer OEM CNG vehicles with turbo engines are also better than aftermarket conversions.