Swedish truck maker Volvo Trucks regards gas as the most viable alternative to oil as a fuel for diesel engines.
Above all, it offers considerable potential as a bridge to greater use of climate-neutral biogas. “This allows us to deal suitably with the most pressing problem – reducing carbon dioxide emissions,” says Lars Mårtensson, Volvo Trucks’ Environmental Director.
Oil and coal, the two fossil fuels that today power most of the planet’s industries, heat homes and get vehicles on the move, will dry up one day, although that day may be some time off yet. What is a more acute problem, however, is the emission of carbon dioxide, nitrogen, sulphur and particles from oil and coal.
For the transport industry, which is 97 per cent dependent on oil, the pressure is now on to find alternative fuels. One of the alternatives that many insiders regard as most promising is natural gas.
“Natural gas is one of several alternatives. And natural gas can be better than oil since it produces lower carbon dioxide emissions,” says Magnus Swahn, President of consultancy firm Conlogic which works on the development of sustainable logistics solutions.
Natural gas consists primarily of methane, which upon combustion releases 30 to 50 per cent less carbon dioxide than oil does and about 40 per cent less nitrogen oxide. And unlike oil, natural gas does not release sulphur, heavy metals or ash into the air.
Not all the Earth’s natural gas reserves have been fully charted, but those that have been discovered are very large compared with the planet’s known oil reserves.
A switch to natural gas in the transport industry could be one way out of oil dependency and would result in a considerably lower environmental impact.
“However, if combustion takes place with the Otto cycle’s poorer efficiency rating, this benefit is erased,” warns Magnus Swahn.
This is a fact about which Swedish commercial vehicle manufacturer Volvo Trucks is fully aware.
“The diesel engine’s efficiency rating is a massive 30 to 40 percent higher than that of today’s gas-powered vehicles using spark plug technology according to the Otto cycle,” explains Lars Mårtensson, Environmental Director of Volvo Trucks.
One energy technology in which Magnus Swahn has considerable faith is methane-diesel, where gas and diesel are used in combination. The main power comes from methane gas but a smaller quantity of diesel serves as a sort of “liquid spark plug” to ignite the gas. If liquefied gas is used instead of compressed gas, the result is a far longer operating range.
“This is a highly elegant solution. It delivers the diesel engine’s high energy efficiency combined with the low emissions of methane gas. I really like that combination,” he says.
Three years ago Volvo Trucks presented no less than seven trucks each tailored to run on a different alternative fuel. Methane-diesel technology was one of the approaches that Volvo Trucks decided to focus on in its ongoing development work.
“A gas-powered truck harnessing the methane-diesel engine’s energy efficiency is a natural advantage since it can also be run solely on diesel,” says Lars Mårtensson. “This is both practical and reassuring since the gas filling station infrastructure has not yet been fully expanded.”
However, even natural gas is a finite fossil fuel and replacing one fossil fuel with another is not the most forward-thinking of strategies, according to critics.
He responds that we must see natural gas as a bridge to fully expanded production of biogas, which is a non-fossil fuel that can be extracted from household refuse, for instance.
“The production of biogas is beginning to get under way in many countries. We are currently living in a transition period, we are shifting from decades of oil dependency to a society structured around renewable fuels,” he explains.
During 2010 Volvo Trucks has been carrying out field tests with methane-diesel engines running on up to 70 percent gas in the fuel. The rest is bio-blend diesel, that is to say fossil diesel mixed with green diesel produced from renewable raw materials.
“The aim is that we should run on 80 percent green biogas and 20 percent green biodiesel as the combustion agent. This will make carbon dioxide emissions 80 percent lower than with conventional diesel power,” concludes Lars Mårtensson.
Facts about natural gas and biogas:
Natural gas is extracted either from separate wells in the Earth’s crust or at the same time as oil is pumped out. There are major reserves in many places the world over, among them Russia, Iran, Algeria and the North Sea.
Biogas is a non-fossil fuel that is formed when organic waste such as food scraps, manure, by-products of the food industry and agricultural waste, are broken down in an oxygen-poor atmosphere and transformed into methane gas and carbon dioxide. When biogas is upgraded to gas for powering vehicles, the carbon dioxide, hydrogen sulphide and water are extracted.
Both natural gas and biogas consist mainly of methane, so the two gases are totally compatible with each other and can be mixed entirely freely with each other. The big difference is that biogas is virtually climate-neutral, that is to say those emissions of carbon dioxide that result from combustion come from the carbon dioxide in the surrounding air that has been trapped in plants via the natural process of photosynthesis. The combustion of biogas therefore does not increase the amount of carbon dioxide already in the air.
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Source: Volvo Trucks