Compressed natual gas (CNG)

Contrary to liquefied propane/butane mixtures, or autogas (LPG), CNG is compressed natural gas. It consists of about 98% methane (CH4) and so causes substantially fewer pollutants than gasoline or diesel.

Advantages for consumers and environment

• Less pollutant and CO2 production
• Contrary to LPG, CNG is lighter than air and does not form explosive vapors; use of underground parking is possible (not with LPG)
• Particularly secure pressure containers are made of steel (recently also aluminium or bonded materials) and have a closure valve and overpressure protection.
• Operating costs compared with diesel are about a third less, compared with gasoline over up to 50 per cent
• Trouble-free and quiet running
• High anti-knock rating

Possible problems

• Not a renewable fuel; however, supplies will last for two centuries (based on present consumption)

Since the operating costs of CNG are substantially lower, natural gas vehicles pay off above all if you drive high mileage annually. Some Austrian power suppliers promote the purchase or the retrofitting of CNG. Vehicle models equipped for use with CNG will cost 500 to 2000 euros more than diesel models.

Car gas (LPG)

LPG (liquefied petroleum gas) is also frequently called autogas. It is a liquid gas that consists of propane and butane and is obtained as by-product of crude oil refining. The composition varies depending upon region: The warmer the average temperature is, the higher is the butane portion of the mixture. Autogas is characterised by a high energy content and a high degree of purity and is esspecially clean burning.

Advantages for consumers and environment

• High anti-knock rating (octane number mostly over 100 RON)
• Less environmental impact due to nearly complete combustion
• Quieter running
• Operation is comparatively economical

Possible Problems

• Not a renewable fuel (availability similar to oil)
• Different composition (international) affects anti-knock rating, energy content, fuel consumption and so fuel costs

Bio fuels

There are several concepts for using renewable resources to drive vehicles: fermentation/bio gas, bio diesel and bio ethanol.

Fermentation gas

Fermentation gas generally is a mixture of the main components methane and carbon dioxide, which is produced by decomposition processes in special biological gas facilities. Sometimes equivalent gases developed as by-products (dump gas, sewer gas) are also included under this term. Fermentation gas production uses sewage sludge, bio waste, leftovers, liquid manure, muck, or special energy plants.

Methane contained in the fermentation gas serves as the source of energy serves; the higher the portion, the higher the energy level in the gas.

Advantages for consumers and environment

• Prepared fermentation gas (bio methane) is unrestricted as a replacement for natural gas.
• Fermentation gas produced to the quality level of natural gas has the best ecological balance among the alternative fuels.
• Considerable CO2 savings due to renewable resources and, depending upon raw material, up to 70% less CO2

Possible problems

• The targeted cultivation of energy plants can cause ecological problems (monoculture, intensive agriculture).
• Ecology and/or CO2 balance depends strongly on the basic materials used.

Biodiesel

As replacement for the fossil diesel, bio diesel is manufactured from vegetable oils (fresh oils like rape seed oil, possibly supplemented by old food oils). The oil is mixed and estrified with methanol. Also untreated vegetable oils can be used as sources of energy, but these are not called bio diesel. The use of untreated vegetable oils requires special engines.

Important: Before you use pure bio diesel, obtain technical clearance from the manufacturer; an admixture of up to 5% is problem-free with all diesel engines.

Advantages for consumers and environment

• Less polluting in case of leakage
• Sustainability due to the use of renewable resources
• Bio diesel significantly lowers the soot emission (up to approx. 50%)
• Better CO2 balance than diesel
• Bio diesel contains neither benzene nor other poisonous aromatics
• High cetane numbers and better burning than diesel

Possible problems

• Relatively high energy expenditure for production
• Reduction of the cultivated areas that are available for food production
• The available farming surface is by far not sufficient in order to replace conventional diesel with bio fuel
• The use of nitrogenous fertilizer releases the greenhouse gas laughing gas in the production
• Up to approx. 40% higher hydrocarbon emission
• Sometimes higher nitrogen oxide emissions

Bio-ethanol

Bio-ethanol (also agrarian alcohol) is an ethanol that is made exclusively from biomass (regenerating carbon carriers) or the biologically degradable portions of wastes and is intended for the use as bio fuel. Ethanol is used as fuel in gas cells and combustion engines, whereby the latter mixture with gasoline is usual. 5% admixture (= E5) is not a problem for most engines. Flexible fuel vehicles (FFV) can use bio-ethanol as well as gasoline.

Advantages for consumers and environment

• Engine performance can be clearly increased by the higher anti-knock rating by partially added water-free ethanol.

Possible Problems

• Bio-ethanol is frequently produced from foods and animal feeds (corn, rape, sugar beets), which has led to discussions about its ethical compatibility (rising food prices). There is hope for bbio-ethanol of the second generation from vegetable waste materials or special energy plants.