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Gasoline and diesel can be improved by chemical reformulation that can lead to decrease in ozone-forming pollutants and carbon monoxide emissions per km travelled, but will be greater for non-catalyst controlled vehicles (IEA/OECD, 1998). Performance problems, cold-start ability, smooth operation and avoidance of vapour lock are disadvantages of using reformulated fuels. Alternative fuels to petroleum include compressed natural gas (CNG); liquefied petroleum gas (LPG); methanol from natural gas, coal or biomass; ethanol from biomass; electricity and hydrogen. The use of these options in reducing GHGs will depend on ease of use, performance and cost, however, CNG, LPG and ethanol are now used in niche markets (high mileage and urban travel) in both developed and developing countries (Sanwar et al., 1999). On a full-cycle basis, use of LPG can result in 20-25% reduction in GHG emissions as compared to petrol, while emission benefits from CNG are smaller - about 15%. Although CNG emits less CO than petrol, gains from CNG depend on the amount of associated methane emissions from gas recovery, transmission, distribution, and use. Life cycle GHG emissions from alcohol fuels, such as methanol and ethanol, depend on the source and conversion technology (DeLuchi, 1993; IEA, 1993). GHG emissions from methanol made from coal will be double that of petrol, whereas methanol from natural gas will be the same, and from wood will be lower. Ethanol from maize, wheat and sugar beet will result in GHG emissions of 20-110% of that of petrol depending on fertiliser inputs and fuel used for conversion. Ethanol from sugar yields 80% GHG emission benefits in comparison to petrol, and almost 100% if baggase is used instead of coal in conversion (Goldemberg and Macedo, 1994). The use of ethanol and CNG as transport fuel is shown in Boxes 8.1 and 8.2.
| Box 8.1 Compressed natural gas as a transport fuel | ||||
| Compressed natural gas (CNG) can be an attractive alternative transport fuel to gasoline because of its environmental benefits including reduction of GHGs. It is more useful for countries with natural gas resources and a relatively good gas distribution system. The use of CNG as a transport fuel started in the 1930s but failed to increase its share because, as with most alternatives, petroleum was a preferred fuel due to cost advantages. However, the current threat of climate change has increased the focus on alternative transport fuels including CNG. Countries with programmes on the use of CNG as a transport fuel include the USA, Canada, UK, Thailand, New Zealand, Argentina and Pakistan. CNG is used in both private vehicles and transport fleets. It is estimated that about 250 million vehicles are using this fuel worldwide, and its use is on the increase, representing 2% of total global transport fuel use. The advantages to using CNG, beyond environmental ones, include reduced engine maintenance cost, and improved engine and fuel efficiency. Disadvantages include power loss, limited range of storage (100-150 km), and high cost of conversion. The environmental benefits relating to climate change are given in the Table below: | ||||
| EMISSIONS | CNG | REG. GASOLINE | SUPER GASOLINE | DIESEL |
| CO | 1 | 10.4 | 9.0 | 1.2 |
| Unburned HC | 1 | 2.0 | 1.4 | 1.2 |
| NOx | 1 | 1.2 | 1.4 | 1.1 |
| Particulates | neg. | present | present | very high |
| SO2 | neg. | neg. | neg. | very high |
| Lead | nil | declining | declining | nil |
| A case is given below to illustrate transfer of CNG technology
between Pakistan and New Zealand. Pakistan has proven reserves of natural gas in excess of approximately 850 billion m3 (90% methane, sp. gr. of 0.56, and octane of 130). The country embarked on using CNG as a transport fuel in 1980 with officials of the Hydrocarbon Development Institute of Pakistan (HDIP) visiting Italy and New Zealand for two years to gain experience with CNG technology. A pilot phase was first introduced in 1982 in Karachi, and all the compressors and conversion equipment was purchased in Italy and New Zealand. In 1992, the government, through the Ministry of Petroleum and Natural Resources, promulgated the CNG Rules of 1992 that have commercialised CNG as a transport fuel in Pakistan. Six years later, 25 CNG stations became operational and another 25 were at various stages of completion. Along with the Rules of 1992, the Gazette of Pakistan Extra of July 28, 1992 provided guidelines for the safe practices of CNG relating to storage, filing and distribution. Under a UNDP/ESCAP programme in 1991, HDIP in collaboration with Liquid Fuels Management Group (LFMG) of New Zealand undertook a detailed six-month field test of completely retrofitted buses, partially converted buses and diesel buses. The results revealed that CNG is environmentally better, because it was lead free, had no particulate matter, and very low smoke density, but the levels of CO and NOx emitted were higher than that of diesel. It was found that CNG is more economically and technically suitable for conversion from spark ignition engines, but will require major modifications for high compression diesel engines. Originally, all conversions were done in New Zealand, but now Pakistan only receives kits from there and the conversions are done by local technicians. Though the cost differential between CNG and gasoline is small, it is estimated that about 25,000 gasoline vehicles have been converted to CNG. Source: (Sarwar et al., 1999). |
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| Box 8.2 Ethanol as a transport fuel in developing countries (Source: Goldemberg, and Macedo, 1994) |
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Ethanol can be important in helping to reduce GHG emissions. The energy derived from biomass, and in this case, from a renewable, "clean" source, i.e., from sugar cane, has the unquestionable advantage of permitting the almost complete re-absorption of CO2 emitted through the combustion of ethanol. This closed cycle allows, in principle, to increase the global energy supply, essential for sustained economic growth, without creating hazards for the environment. The relevance of fuel alcohol in connection with the global efforts for reducing CO2 emissions is singled out as one of the major contributors to the reduction of the greenhouse effect. It is important to note that, with technological advances and research, the price of alcohol can be made competitive with gasoline in the long run, but with the added advantage of providing a clean and renewable source of energy. Ethanol in Brazil The programme benefited from a combination of favourable circumstances: the availability of adequate technology for the production of alcohol; the ability of the sugar sector to adjust quickly to the production of alcohol; the expansion of the distilleries; and the low international price for sugar, due to the general crisis of the sector, in part caused by overproduction. Until 1979, the first phase of the Programme, alcohol production concentrated on anhydrous alcohol (99.33% ethanol) for blending with gasoline. The proportions of the mixtures varied. During this period, the programme benefited greatly from the expanded installed capacity of the distilleries annexed to the sugar mills. The second phase began with the second oil crisis (1979), placing considerably more ambitious goals before PROALCOOL. A change occurred, resulting in the predominance of hydrated alcohol, used in pure form as car fuel. The car factories in Brazil began to design vehicles using fuel alcohol exclusively. The industry appeared to welcome the new fuel and invested in research and development of alcohol-run cars; given the high oil prices, fuel alcohol would permit increasing production. The first cars run solely on fuel alcohol were produced in 1979. By December 1984, the number of cars run on pure hydrated alcohol reached 1,800,000, i.e., 17% of the country's car fleet. Fuel alcohol is a "clean" fuel because the local effects of
gas emissions are less damaging to the environment, generally speaking.
On the average, alcohol-run vehicles emit less carbon monoxide, hydrocarbons
and sulphur. Another advantage of alcohol over gasoline is that alcohol
replaces tetraethyl lead, which is hazardous to health and the environment,
and is used as an additive to increase gasoline octane level. In fact,
in the United States, alcohol is added to gasoline to diminish the high
index of environmental pollution. In 1975, The Triangle, a private enterprise, decided to use surplus molasses from up to 40,000 tonnes of sugar for ethanol production and started production in 1979. The German Company Gebr. Hermman supplied the plant design and was willing to provide a "turn-key" project. The Zimbabwean firm only purchased the plants (at a reduced price) while the German firm supervised its activities. Adaptation was necessary and involved discarding many automatic controls in favour of manual operation to suit the capabilities of the local workforce. Local material was utilized up to 60%, substituting stainless steel used in the distillation columns with approval of and supervision by the German firm. The final cost was US$ 6.4 million for a plant capable of 40 million litres a year. The ethanol produced is sold to National Oil Corporation of Zimbabwe and they resell it to various oil companies. Ethanol as a fuel with 13% blend was the only petrol available for a long period in Zimbabwe, with very few modifications. The plant has been operating for over 18 years with a lot of environmental benefits, skill transfer and technological adaptation as well. |
Electric vehicles have the potential of having significant life-cycle GHG reductions depending on the primary energy source; the vehicle technology and method of use (DeLuchi, 1993; ETSU, 1994; Martin and Michaelis, 1992). Its widespread use will depend on battery charge/discharge efficiencies at high current, motor and controller efficiencies at high load, and improvements in vehicle design. Also, electric powered systems can be costly and inflexible. Hydrogen is a clean transport fuel but requires high energy input and has serious storage and cost problems. Development of alternative aviation fuel, such as liquefied natural gas (LNG) and liquid hydrogen, is going on and can result in up to 20% lower carbon emissions than kerosene for LNG, but is not expected to be commercial in the next 10 years. Details of alternative fuels are in Table 8.4.
| Table 8.4 Technical and potential transport fuel technologies | ||||||
| TECHNOLOGY | EXAMPLES | STATUS | TECHNICAL FEASIBILITY | CONVERSION EFFICIENCY | ENVIRONMENTAL IMPACT | MARKET POTENTIAL TIME FRAME |
| FUEL SUBSTITUTION | ||||||
| 1. Improved Gasoline and Diesel Fuel |
Reformulated gasoline Reduced Reid vapour pressure (RVP) |
Within current refining techniques |
Chemistry available Refinery balance and the need to produce more light ends |
<2% gain for vehicles increase in refinery energy efficiency |
Significant VOC reduction Limitations on fuel additives |
0-10 years |
| 2. Natural Gas and LPG |
On-board storage System integration |
Demonstration fleets Field trials Fuels commercially available |
Range extension needed System cost abatement |
Close to gasoline with engine adaptation | VOC, CO2 and particulate reduction | 0-15 years |
| 3. Alcohol Fuels (in an ICE) |
Neat methanol Neat ethanol M85 |
Demonstration fleets Field trials in large vehicles Commercial availability of blends |
Supply limitation and cost needs Change in OEM design Low-cost emissions control option Multiple feedstocks |
15% improvement | VOC and CO2 reductions | 0-20 years |
| 4. Hydrogen (in an ICE) | Neat H2 in ICE storage systems | R&D and prototypes |
Renewable source of supply Distillation & production hurdles |
Dependent on feedstock and storage system | Substantial reductions in all pollutants | 30 years |
| Energy Regeneration |
Hydraulic and kinetic storage Engine management and electric storage |
R&D and prototypes Large vehicles with electric trains Demonstration bus fleets |
Energy storage systems Transmission of power requires availability of CVT to blend power |
Dependent on mission profile but 15-20% improvement possible | Reduction of all emissions in proportion to efficiency gain | 10-20 years |
| Electric and Hybrid Vehicles |
Electric batteries Fuel cells Solar photovoltaic cells Hybrid systems |
Demonstration fleets Field trials in niche markets |
Range and cost limitations may limit market Adopting hybrid drives may increase use options |
Dependent on base fuel with 20-40% gain possible |
Reduction to zero of all vehicle emissions Environmental benefit to be gauged against overall fuel cycle |
10 years |
Recent increasing interest in the development of hybrid vehicles (combination of gasoline engine and battery-motor system) is yielding positive results that can have a positive impact on GHG reduction. Making optimum use of the different power supply system to suit the demand, and with an engine switch-off system during short breaks, up to 30% fuel efficiency gains can be achieved, as has been shown for models by Mitsubishi and Toyota (Tsuchiya, 1997). However, there are some disadvantages such as higher weight and slightly higher cost, but current declining cost could assist its commercial success. Use of hybrid vehicles with fuel cells and batteries is actively being considered by many manufacturers, but the cost is still very high for commercial application and may be in market early next century (OECD, 1997).
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