Molecular Bioengineering for Biofuels
Update on the Mercedes F 500 MIND Diesel Hybrid: Surprise!

Hybrid Fuel Diesel Retrofit System

Hybrid Fuel Systems is a small company with a product by the same name that converts medium- and heavy-duty diesel engines to a “dual fuel” mode that replaces about 80% of the diesel fuel with Compressed Natural Gas (CNG) or Liquefied Natural Gas (LNG).

HFS systems start the engine with diesel fuel and then inject an increasing amount of natural gas, cutting back on the diesel, as the engine speed and load increases. Engine modifications are not required, and the company claims that vehicles retain the diesel engine qualities of performance, torque, power, and efficiency. When operating with natural gas, Hybrid’s system reduces NOx emissions by at least 30% and PM emissions by 80–90%.

The system consists of a set of parts that can be installed on most medium- and heavy-duty diesel engines within a day by a trained technician. Components include:

  • The ECU programmed to meter a precise mixture of natural gas and diesel in response to engine speed, load, temperature and other operating conditions

  • A gas regulation system that maintains a smooth fuel supply under all conditions

  • A gas injection system that allows precise metering under rapidly changing engine conditions

  • Sensors, wiring harnesses, and all other parts

The cost of the conversion kits range from $3,500–$4,500, not including the natural gas tanks and lines. Still, it sounds like a pretty good deal dollar-wise.

Hybrid Fuel Systems has installed 1,400 kits to date.


Steve Spence

I'm scratching my head "Why?" on this one. Sure, lets replace one fossil fuel with another that has less BTU, and costs more. Of course, the smart thing to do is replace the fossil fuel with a biofuel that is renewable, burns cleaner, and doesn't require any conversion $$$. BIODIESEL.

John Norris

I'm with Steve on this one. Especially as natural gas is about to go off a cliff in the USA. I assume the CO2 would be about the same (as dino diesel that is).



That’s a really good point, and it’s right from a GHG and energy use point of view. (And on supply.) CNG is close to diesel (big variations based on origination, etc.) on energy use, and can be slightly worse on the GHG. From a PM and NOx view, it’s cleaner than diesel.

Good comparisons in the Argonne Lab document Mike Briggs pointed to in the comments on fuel comparisons: Well-to-Wheel Energy Use and GHG Emissions...

Biofuels make tons of sense to me. But if you don’t have access or sufficient supplies—or haven’t figured it out yet—isn’t it still better from a PM/NOx urban health perspective to do a quick conversion—particularly since those vehicles that would be converted are probably older, with fewer emissions/combustion controls, etc? Improve for a few years and then bring in a newer vehicle.

However, since from a well-to-wheels energy use and GHG perspective it could be worse to go to should a public organization decide?

I think we will end up seeing a pragmatic focus on CNG in concentrated urban areas with big air problems. (Like Tokyo or Indian cities.) They’ll take the immediate improvement in PM and NOx reduction.

Brett Jarman - NGV Network

It's not an either/or argument.

There are some situations more suited for biodiesel, some more suited for natural gas and some for neither.

Large scale biodiesel adoption would put massive stress on an already overstressed agricultural sector. And if demand for agricultural crops for transport use increases, there will almost certainly be an impact on the price of basic food stuffs on our supermarket shelves. (i.e. increase demand = increase in prices).

That's not to say biodiesel shouldn't be used though. If the fuel can be supplied at the right place, in the right amount and for the right price then by all means it should be used.

Why bother with Natural Gas? Apart from enjoying the immediate air quality benefits outlined above, some parts of the world don't have the same supply restraints or price mechanisms that you have in the US. The Hybrid Fuel Systems product mentioned above is finding markets in Brazil and other South American nations where they have an abundance of natural gas. In Australia, where I live, we have vast supplies of natural gas which is available relatively cheaply. And despite your supply and price restraints, there are applications in the US where natural gas makes more sense than other alternatives.

Natural gas vehicles have also provided valuable learning curves on the path to hydrogen vehicles. Much of what we know from working with high pressure gaseous fuels such as natural gas is now being applied to hydrogen vehicles, both internal combustion and fuel cell applications.

Infrastructure for natural gas vehicles will also support hydrogen vehicles as they become more prevalent (compression & liquefaction facilites) - this alone is a valuable reason to support natural gas vehicles now.

There's still a way to go before we eliminate our dependence on fossil fuels. In the meantime, solutions can be found in existing crude based fuels, expanding use of gaseous fuels, adopting hybrid vehicles, and indeed the use of biofuels. (I'd put 'using less' at the head of the list of solutions though).

To use Mike's words above, a 'pragmatic focus' for particular applications will help determine the best fuels to apply in particular situations.

Brett Jarman

Forgot to mention. Bear in mind that natural gas can also be obtained from renewable sources. Biomass facilities, digesters and methane capture at garbage facilities are becoming more common place and are often viable for providing fuel for transport use.

A dual-fuel system such as the Hybrid system can provide the best of all three worlds. Biodiesel and natural gas (either biomass or fossil fuel derived) when available or straight diesel when they are not.

John Norris

Brett, Mike, I enjoyed your perspectives. CO2 certainly isn't the only game in town. Clean air is worth having. I live in a small European town and the air quality is atrocious due to the preponderance of diesel vehicles. Maybe we need plug-in bio-CNG hybrids! Pre-hydrogen, that is :)

Tye Grewal

Brett you are right on the mark with your explanation regarding the technological transition and progress taking place in the energy sector and energy complimentary sector. It is small new ideas that will allow the human race to progress to later use hydrogen and other renewable fuels.

These new technology allows consumers to have a choice against having to consume a monopoly regulated fuel like oil from which most diesel is derived. Over the long-term, these new ideas will be used to innovate new techniques of usage and newer technology will be developed that will build on the previous ideas. I (and I believe most consumers) would love to be at the stage where we could be already using hydrogen, polluting less, and having endless supplies of energ. A world without monopolies such as OPEC and so on… (Perfect Utopia). This will all take time. After all, look how long it took to get from the first flight of the Wright brothers to the modern age of the supersonic jets…...

We should encourage new ideas that help consumers to reduce fuel consumption (which will also reduction pollution), gives choices other than fossil fuels, and develops technology that gets us closer and closer to the future that everyone envisions in a Utopian perspective. This is all assuming that a “Utopian” state actually exists.


We need to get it through our heads that putting a demand on any natural product will cause a shortage which will give them reason to raise cost's. Same as oil natural gas may look good today but start demanding more and more and it will return you right back to the same problem, increase cost's to the consumer. Best I have researched and found is the water or HHO conversion, cheap and cheap to operate, 300 miles on a gallon of water. Everyone knows Hydrogen is the cheapest conversion and there are some really good systems out there. Look at the guy from Glendale, AZ, even welds and generates electricity with HHO using water. Just pop in Water fuel in your search engine and examine all the choices and rating pages of testing the systems, you will be shocked. I want to see the commercial haulers able to stay in business they are a valuable asset to our economy. I drive a 2004 Duramax and it sets more than drive now because of fuel so keep looking and find the best and cheapest for now to keep em rolling.

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