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Green Fuels And Vehicles
Most fuels can be used for heating, lighting, cooking and electricity production, and some fuels can provide motive power for transport vehicles. Most transportation fuels are liquids or gases, because most transport vehicles require the high energy density of some liquids, gases and solids. Liquids and gases are generally easier to handle and store, are more portable, and burn cleaner than solids.

Walking, biking, car pooling, public transportation, increasing gas mileage of private transport vehicles and other methods of reducing fuel consumption, reduces the ecological footprint and fuel costs. Saving fuel means saving money, which could be used to buy, convert or build a more fuel efficient vehicle, or one that uses only green fuel that you could produce for yourself, green energy storage methods (such as compressed air or ultracapacitor batteries instead of toxic chemical batteries) for starting and running electronic devices, and can be constructed using common, low-tech, eco-friendly, widely available parts. Again this would result in reducing fuel consumption, reducing your ecological footprint, and saving money.

Petroleum Gas Powered Vehicles

About 95% of all public and private transport vehicles currently use petroleum based fuels for motive power, and petroleum based oils for lubrication. In the US, about 2% of all crude oil is used for electricity production, 4% is used for general residential and commercial purposes, and 24% is used for industrial purposes to produce nearly every product on the market.

Crude oil is used for example, to produce adhesives, artificial sweeteners, asphalt, carpets, caulking, CDs, chemicals, contact lenses, dentures, disposable diapers, dyes, electronics, enamels, epoxies, fabrics, fertilizers, food preservatives, furniture, glycerin, hair products, inks, linoleum, medicinal/nutritional capsules, nail polish, paints, perfumes, pesticides, petroleum jelly, pharmaceuticals, plastics, PVC, rubber, rubbing alcohol, shoe polish, skin products, soaps, solvents, tar, toothpaste, waxes ... and the list goes on. Yet it is well known that biofuels, or even common vegetable oils can be used instead of crude oil to produce such products.

The remaining 70% of US oil is refined to produce fuels such as gasoline, butane, petrol, diesel fuel, jet fuel, kerosene, fuel oil and lubricants (i.e., machine and motor oils, greases, etc.). Extracting, burning, producing, using and disposing of petroleum products is however an expensive, major source of environmental pollution such as VOCs (volatile organic compounds), heavy metals, particulate matter, radioactive materials (such as uranium and thorium), greenhouse gases (such as CO2), sulfur dioxide, nitrogen oxides, sulfuric acid, carbonic acid, nitric acid, and other pollutants that contribute to acid rain, climate change, global warming and adverse health effects.

Methane and Propane Powered Vehicles

Methane and propane gases are produced by the anaerobic digestion of biomass, and are usually compressed into gas or liquid form, such as natural gas or propane fuel. Methane and propane can be used for heating, cooling, lighting, cooking, and biofuel. Methane is a far worse greenhouse gas than CO2 however, and both methane and propane emit CO2 and other pollutants similar to gasoline when burned. Producing methane and propane also requires a significant amount of space and biomass, which is too impractical and expensive for most individuals to setup and maintain.

Biofuel Powered Vehicles

Biofuels such as biodiesels, bioalcohols, biogas, syngas, solid biofuels, and second generation biofuels, are fuels derived from biomass conversion, solid biomass, liquid fuels and various biogases. Most biofuels can be burned for heating, lighting, cooking, transportation, and other purposes.

Biodiesels
Biodiesel is a liquid fuel made by transesterification of vegetable oils or animal fats. Many diesel engines can run on biodiesel, and the parts needed to build and repair them are widely available. Peanut oil for example, was used as fuel in the first diesel engine. Electronic 'common rail' and 'unit injector' type diesel engines made since the late 1990s however, have finely metered and atomized multi-stage injection systems that are very sensitive to the viscosity of fuel, and because biodiesel may become more viscous at lower temperatures (depending on the feedstock used), they can only use biodiesel that is blended with conventional diesel fuel. If mixed with mineral diesel, biodiesel can be used instead of petroleum based diesel in most diesel engines made from 1994 to present. Pure biodiesel (B100) is the lowest emission diesel fuel, which is most often used as a diesel additive to help reduce emissions of carbon monoxide, hydrocarbons and particulate matter from modern diesel powered vehicles. B100 may be used alone as fuel in most current diesel engines without any modifications (depending on the fuel rail design), but must be heated with electric coils or heat exchangers to reduce its viscosity to that of diesel for efficient combustion, which is easier to do in warmer climates.

'Green biodiesel' is produced by the fractional distillation or hydrogenation (rather than transesterification) of fats or oils. Unlike most forms of biodiesel, hydrogenated fats and oils generally tend to perform better at low temperatures, have better storage stability and are not susceptible to microbial attack.

Straight, unmodified, and even used vegetable oils can be used as biofuel, but like B100, must be heated with electric coils or heat exchangers to reduce its viscosity to that of diesel for efficient combustion. Straight vegetable oils can be used in many older diesel engines that do not have common rail or indirect electronic diesel injection systems, as well as most modern indirect injection diesel engines.

Most biodiesels are nontoxic, biodegradable, oxygenated (i.e., contains less carbon, but more hydrogen and oxygen than fossil diesel, thus improving fuel combustion and reducing particulate emissions from un-burnt carbon), burn more efficiently than gasoline or hydrogen, and serve as an effective solvent, which helps to maintain efficiency by cleaning residues deposited by mineral diesel and cleaning the engine combustion chamber of carbon deposits. Unlike most diesel fuels, which are produced from fossil fuel based feedstocks, biodiesel is produced from renewable feedstocks, which can be grown almost anywhere in the world, are safe to handle and transport. Biodiesel can even be produced from plants such as sea algae, without displacing lands or crops that could be used for producing plant based foods, medicines, fabrics and other goods. Biodiesel is also considered a 'carbon neutral' biofuel, because the CO2 released from burning biodiesel was previously absorbed by plants grown to produce it. The CO2 released by land use changes and deforestation was likewise previously absorbed by the plants removed, and can be re-absorbed by more plant growth ... eventually.

Any form of biodiesel however, requires an immense amount of energy, land and water to produce. Biodiesel production consumes up to twice the energy it produces, while burning it as fuel destroys ecosystems, and emits environmental pollutants such as greenhouse gases, hydrocarbons (such as benzofluoroanthene and benzopyrenes) and particulate matter.

Bioalcohols
Most bioalcohols can be used in most engines, without modification. The first Model T Fords for example, ran on straight ethanol. Ethanol is a bioalcohol produced by the fermentation, enzymatic digestion, distillation or drying of plants rich in sugars, starches and/or cellulose, such as corn, wheat, sugar cane, sugar beets, fruit or potatoes. Ethanol is often used as a gasoline additive to increase octane (and thereby thermal efficiency) and reduce vehicle emissions, but can also be used alone as a gasoline alternative in many engines. Like biodiesels however, the production of bioalcohols requires a considerable amount of energy, land and water, consumes as much or more energy than it yields, reduces supply and thereby increases the prices of plant based foods, medicines and other goods, while some of the by-products of ethanol production and combustion pollutes the environment and our bodies (albeit much less so than the production and combustion of fossil fuels). Ethanol also has a 16% lower energy density than gasoline, so it would take more ethanol and larger, heavier fuel tanks to produce the same amount of work as gasoline, and travel the same distance.

Methanol, or 'biomethanol', is usually produced from biomass, natural gas (a non-renewable fossil fuel) or methane. Methanol is biodegradable in anaerobic and aerobic conditions, with a half-life of only 1-7 days, as opposed to the 10-700 day half-life of gasoline. Accumulation of methanol in soil, water or air is therefore unlikely. Methanol, or rather its metabolites formaldehyde and formic acid, are highly toxic and potentially fatal to humans however, as they can cause permanent blindness, hypoxia, metabolic acidosis and/or death if methanol is ingested, inhaled or absorbed. Methanol does not produce a visible flame when burned either, so it would be more difficult to detect and could be more of a fire hazard than fuels that produce visible flames if burned. Methanol also has a 26% lower energy density than gasoline, so like ethanol, would take more fuel and larger, heavier fuel tanks to do the same amount of work, and travel the same distance.

Butanol is another, less common bioalcohol, which is produced by the fermentation of corn, grass, leaves, agricultural waste and other forms of biomass. Straight butanol is sometimes used as fuel for fuel cells, can be used as fuel in gasoline engines without any modification, has a higher energy output than ethanol, is less corrosive and less water soluble than ethanol. The energy density of butanol however, is about 10% less than that of gasoline, engines using it as fuel are less fuel efficient than those using ethanol or methanol, and the combustion of butanol emits higher levels of CO (carbon monoxide), CO2 (carbon dioxide), SOx (sulfur oxides), NOx (nitrogen oxides) and other environmental pollutants, than ethanol or methanol do. Like many alcohols, butanol is also considered toxic. Exposure to butanol can damage DNA, cause eye and skin irritation. Repeated overexposure can depress the nervous system. Prolonged exposure can cause severe depression of the nervous system, cancer and/or death.

While the emissions from vehicles using bioalcohols as fuel may be less than emissions from fossil fuels, such fuels do nevertheless, contribute to the ecological footprint, climate change, global warming, smog, acid rain, and adverse health effects. The cost of most bioalcohols is also comparable to that of gasoline.

Biogas
Biogas is methane produced by anaerobic organisms via the anaerobic digestion of organic material, such as biodegradable waste, landfill gas, human or animal feces, or energy crops. Anaerobic digesters are used to produce biogas, solid biofuels, fertilizers, and to help manage waste. Landfill gas is the least clean form of biogas due to the VOCs it contains but all forms of biogas are essentially methane, which is a far more potent greenhouse gas than CO2, and likewise contributes to environmental pollution.

Syngas
Syngas is a mixture of hydrogen, CO (carbon monoxide) and CO2, which is produced by partial combustion of coal, biomass or municipal waste. Syngas (alone, with other alcohols and/or gasoline), may be burned in most internal combustion engines, turbines, and high temperature fuel cells. Syngas is also used for producing ammonia, methanol, DME, SNG (synthetic natural gas), synthetic petroleum, biochar, hydrogen, chemicals, and may serve as a diesel substitute. Like other biofuels however, the production and combustion of syngas contributes to environmental pollution, can be a fire and health hazard.

Solid Biofuels
Solid biofuel (digestate) is basically dry biomass, such as wood, saw dust, grass trimmings, charcoal, energy crops, hog fuel (i.e., densified biomass that is concentrated into a fuel product, such as wood pellets, cubes or pucks), and agricultural, human or animal waste. Solid biofuels are burned directly as a heat source for space and water heating, producing steam, electricity, or biochar (a wood charcoal substitute, which can reduce deforestation due to charcoal production). Because solid biofuels can be made from the by-products of other processes, such as farming, agriculture and forestry, competition between those producing fuel with those producing food, medicine, fabrics and other plant based products, can be minimized or even eliminated. The combustion of raw biomass is far less polluting than burning fossil fuels, but burning biomass still emits a considerable amount of pollutants, including PAHs (polycyclic aromatic hydrocarbons), CO2, particulates, dioxins, and chlorophenols. Modern pellet broilers actually generate much more pollutants than crude oil or natural gas boilers do.

Second Generation Biofuels
Second generation biofuels are produced from sustainable feedstocks, such as waste gases, and plants that can be grown almost anywhere, are not normally used in the production of foods, medicines and other much needed goods. Second generation biofuels do not contribute to higher prices for such goods, result in the least amount of GHG (greenhouse gases), and require the least amount of land, water, energy and other resources to grow. Some second generation fuels currently being developed include algae and microbe based fuels, cellulosic ethanol, biohydrogen, biomethanol, DMF, BioDMF, Fischer-Tropsch diesel, biohydrogen diesel, myco-diesel, mixed alcohols and wood diesel. Algae and a number of certain microbes can be grown sustainably, without requiring the use of land or water needed for other purposes. Developing biofuel crops best suited to various regions worldwide would also increase the availability of biofuels in more areas, which would increase energy security and reduce the need for fuels to transport, process and distribute fuels from few to many places. While most biofuels emit 20-70% less GHG than fossil fuels, second generation biofuels such as lignocellulosic biofuels emit up to 90% less GHG than their fossil fuel counterparts.

The combustion of any biofuel however, even second generation biofuel, emits greenhouse gases, aldehydes (i.e., formaldehye, acetaldehyde, etc.) and other environmental pollutants. Biofuels that are not made from waste biomass or crops grown on abandoned agricultural lands can take 3 to 1000 years to re-absorb the CO2 released due to land use changes. Nitrate fertilizers made from biofuels emit so much nitrous oxide, they produce more greenhouse gases than the fossil fuels they replace. Biofuels made from crops normally used for the production of foods, medicines, fabrics and other plant based goods, reduce available space for buildings and production of such goods, resulting in increased prices for real estate and plant based goods. Biofuel production also takes more energy than it yields when the energy, water and land needed to produce biofuels could in many cases be put to better use.

Compressed Air Cars

Compressed air powered vehicles produce zero emissions, are eco-friendly, and because they do not typically require a cooling system, fuel tank, spark plugs, silencers, or even a transmission, compressed air vehicles are usually more affordable than conventional vehicles to buy and repair. It may be possible to use an engine's pistons or vehicle shocks to compress air for a compressed air battery (although likely not many of them) instead of a chemical battery, to start a vehicle, and possibly to power other electrical devices in vehicles powered by fuel sources other than compressed air or electricity. But it takes more energy to compress air than to charge a battery, compressed air has a very low energy density so it stores much less energy in the same amount of space as chemical batteries do, compressed air cars have a very limited range due to tank technology, usually take longer to refill than gas powered cars, and are less efficient than electric vehicles.

Electric Vehicles

Electric vehicles such as electric cars, motorbikes, bicycles, trains, trams and buses, use electricity (in the form of AC or DC power) as fuel, which can be produced from green, renewable energy sources and does not emit pollutants when consumed. Even if electricity used as fuel is not derived from renewable energy sources, electric vehicles produce about 97% less pollution than petroleum dependent vehicles. Electric motors and parts are already widely available and affordable, and electric motors, such as that in the Tesla Roadster, can produce up to 288hp (215kW). Electric vehicles are quiet and cost about the same as conventional gasoline powered vehicles, typically have fewer parts and last longer than gas powered vehicles, require little maintenance, can be at least as powerful and go at least as fast in as short a time as their gas powered counterparts, and some electric vehicles can travel up to 120 miles on a single charge.

Energy storage however, seems to be the biggest financial and environmental hurdle to electric vehicles becoming one of, if not the mainstream form of public and private transport. Electric vehicles require a constant source of electricity, and most use a total of about 20-50kW at 50-300V of electricity per charge, which requires some way to store electricity. Currently, the most common form of energy storage in electric vehicles is chemical batteries. The average battery array in electric vehicles consists of one large, heavy, expensive sodium or lithium ion battery, 12 (12V) to 20 (6V) smaller lead-acid batteries, or a number of other chemical batteries, which store 12-15kW or 50-300V of electricity. Chemical batteries take 4-10 hours to recharge however, are toxic and expensive, limited in range to about 50 miles or so per charge, and must be replaced every 15,000-100,000 miles. Compressed air batteries, super or ultra capacitor batteries are eco-friendly, nontoxic, usually outlast whatever they are used in, and may be used in place of a battery for starting electric vehicles. Super and ultra capacitor batteries can be charged in a fraction of the time it takes to charge conventional batteries, and can quickly recapture and release energy for regenerative braking to increase energy efficiency. It may even be possible to use thermocouples to convert waste heat from a vehicle's motor into electricity to further improve efficiency. Compressed air batteries, super and ultracapacitor batteries only have a fraction of the energy density and storage capacity that typical chemical batteries do however, and thermocouples are only about 4-10% energy efficient.

Hydrogen Powered Vehicles

Hydrogen fuel can be burned as a gasoline alternative, a heat source for space and water heating, cooking, lighting or distillation, as fuel in fuel cells to produce electricity to use directly, or as fuel for electric vehicles. Hydrogen can be made from natural gas, as a by-product of butanol fermentation, or by electrolysis of water (which can be done using green, renewable energy sources and methods). Production of hydrogen fuel via the electrolysis of water is the only well known eco-friendly and sustainable method, but is not very energy efficient or affordable. The conversion of hydrogen fuel to electricity using fuel cells can be eco-friendly, sustainable and energy efficient, but fuel cells available to the general public typically use toxic chemicals as electrolytes and fuels other than hydrogen for power, which contribute to environmental pollution and may pose significant health risks. Burning hydrogen outside the earth or in a vacuum produces only heat and light, but hydrogen burned within the atmosphere under normal pressure reacts with oxygen to produce water, as well as nitrogen oxides, which contribute to environmental pollution. Hydrogen fuel also takes as much or more energy to produce than it yields, fuel cells are fragile, have a low service life, and are still quite expensive. It takes about 10,000 times the storage space to provide the same amount of power as gasoline, which limits the range of hydrogen powered vehicles. Even compressed hydrogen gas takes about 60 times more storage space than gasoline to provide the same amount of power as gasoline, and it adds an extra 6,000 pounds of weight, further reducing gas mileage and efficiency. As of yet, hydrogen fuel is one of the least efficient, most expensive options for alternative fuels.

Steam Powered Vehicles

Steam has been used as a clean energy source for electricity production, mechanical and motive power for much longer than vehicles powered by fossil fuels, biofuels or electricity. Steam turbines, generators, engines, and the parts to build or repair them, are thus generally widely available and affordable. VW and Enginion have already developed several fully functional, energy efficient, eco-friendly, affordable steam powered vehicles, such as the EZEE03, that produce steam almost instantly without an open flame, take only 30 seconds to reach maximum power from a cold start, produce up to 220hp (164kW) with a 1000cc (61cu in) oilless engine, using ceramic cylinder linings and steam instead of oil as the lubricant. Unfortunately these steam cars and others like them are not yet available to the general public, but Enginion does offer other steam powered products, such as the SteamCell Power Generator and Heating system. Steam engines usually use water as fuel, can recycle and reuse the same water in a closed system, are eco-friendly, and affordable. On the other hand, steam engines typically require a lot of heat to produce the amount of power needed for transportation, so some method of producing or collecting and storing a lot of heat would be necessary for most steam engines. Yet low temperature steam engines, such as those manufactured by Cyclone Power Technologies, can operate on temperatures as low as 225°F. Thus, it may be possible to use a solar evacuated tube water heating system or something similar for heat collection and storage, and if necessary, an electric heating system that plugs into any electrical outlet for quick backup water heating. In time, steam powered vehicles may turn out to be one of, if not the most common, eco-friendly, affordable option for sustainable travel.

Hybrid Vehicles

Hybrid vehicles combine more than one method of producing, distributing and/or storing energy for motive power. There are for example, hybrid vehicles powered by gasoline and methane or propane, gasoline and biofuel, gasoline and electricity, gasoline and hydrogen, electricity and hydrogen, hydrogen and biofuel, etc. Most hybrid vehicles are more fuel efficient and earth friendly than gasoline powered vehicles, but some also require two motors, which increases the cost to build, buy and repair them.
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