Sustainable fuels

Sustainable fuels are important in Australia and many other countries because electric vehicles are not yet capable of travelling the long distances required in a large rural country. What sustainable fuels are practical today?

Hydrogen

Hydrogen is a favourite fuel in science fiction and among people seeking to get their face on television at any cost. There are hydrogen based systems in a small selection of German and Californian cities. A hydrogen atom supplies only a quarter of the energy supplied by a carbon atom. Pure hydrogen is hard to store. Your hydrogen powered vehicle will be practical for the same uses as electric cars, short inner city commuting.

Hydrogen is liquid below -252.87°C (-423.17°F) making liquid hydrogen impractical for everything except the space shuttle launch. Hydrogen requires massive pressure to liquefy it at room temperature so give up on storing hydrogen the way we store liquefied petroleum gas. Hydrogen can be stored in special tanks containing a special metallic sponge that absorbs hydrogen but the sponge is expensive to produce and is practical only for Arnold Schwarzenegger when he is trying to attract votes. Arnold has two Hummers converted to alternative fuels and only one converted to hydrogen. The other, the more practical one, uses biodiesel.

The best way to store hydrogen is to combine hydrogen with carbon. You get a massive increase in hydrogen density by adding small amounts of carbon. Fuel cells convert hydrogen to electricity by combining two hydrogen atoms with one oxygen atom to form H₂O, commonly known as water. The carbon in from hydrocarbon fuels is used to strip the oxygen from the water to produce more hydrogen for the fuel cell. One carbon atom produces four hydrogen atoms. Ethanol is the favourite fuel for fuel cells because ethanol is readily available, cheap, and convenient.

Ethanol as a hydrogen source

Ethanol is C₂H₅OH indicating there are two carbon atoms in the middle with five hydrogen and one oxygen atom attached plus an extra hydrogen atom hanging off the oxygen atom. Fuel cells can split the ethanol into two carbon atoms, five hydrogen atoms, and one hydroxyl molecule (the bit with one oxygen and one hydrogen atom). One hydrogen atom should combine with the hydroxyl to produce one unit of energy. The remaining four hydrogen atoms combine with two oxygen atoms to release four more units of energy. Each carbon atom can strip the oxygen from two water molecules to release four hydrogen atoms. The two carbon atoms produce a total of eight free hydrogen atoms that are combined with four oxygen atoms to release eight units of energy. You end up with thirteen units of energy from one ethanol molecule and the ethanol molecule uses a tiny amount of space compared to storing thirteen hydrogen atoms.

Ethanol and methanol are natural fuels high in hydrogen. The original petrol engine was first demonstrated using ethanol and ethanol was an important ingredient in fuel mixes until the 1930s. Australia and many other countries sell an E10 mix using 10 percent ethanol mixed with conventional fuel. Some countries are moving to E20 and E25. Brazil is converting to 100 percent ethanol for cars.

Methane as a hydrogen source

Methane, CH₄, is a gas produced by waste rotting in land fill sites and is collected, using underground pipes, to produce electricity. In a fuel cell, the carbon atom can produce four hydrogen atoms giving you a total of eight hydrogen atoms to produce eight units of energy. The poor quality of the gas from landfill often results in the gas being burnt in low technology heating applications. Methane is not practical for use in vehicles because of the high pressure required to store a useful amount of fuel.

Methane is also produced from petroleum products as a by-product of refining the petroleum. Currently there is no system for labelling methane based on the source. If you are buying pure methane in quantity then you are almost always receiving methane from petroleum.

Liquefied petroleum gas as a temporary hydrogen source

Liquefied Petroleum Gas, LPG, is a lot of hydrogen combined with a small amount of carbon, and is in common use in Australia for long distance commuting and for commercial vehicles that are not big enough to benefit from diesel. Fuel cells can work with LPG. You could convert a lot of cars to fuel cells today and use LPG as a temporary fuel until production of ethanol and alternatives reaches the point where you can stop buying LPG.

LPG is butane (C₄H₁₀), propane (C₃H₈), or a mixture of the two.

Biodiesel

The world is running out of diesel. Diesel is artificially created from other petroleum products and the conversion wastes energy. We need an alternative.

Diesel engines work beautifully on vegetable oil with very little work on the oil. When Rudolph Diesel invented the diesel engine, he demonstrated the engine using peanut oil. Today a a huge number of cars worldwide run on rapeseed oil (including canola), palm oil, and soy oil.

You combine vegetable oil with a small amount of methane to produce biodiesel. Methane can be collected from rotting food waste. Food waste can be fermented to produce ethanol then fermented further to produce methane then used as fertiliser and mulch to help produce more food. Used vegetable oil from cooking can be recycled as biodiesel in the same plant that produces methane.

Rapeseed is one of the most common seeds grown for oil and food. Canola is the name for a variety of rapeseed developed in Canada. Rapeseed oil has the advantage that it is thinner than palm oil based diesel and works in the colder parts of the world.

Palm oil production is common in tropical regions and produces a slightly thicker diesel that works in the warmer parts of the world. Some parts of some tropical countries do suffer deforestation to increase palm oil production and it is a political issue to solve. If the source of palm oil could be traced, we could ban imports of oil from new deforestation areas.

Asian countries produce huge amounts of soybeans and could use lower quality soy for biodiesel. Soybeans are used for human food and stock feed. Replacing diesel with soy oil will cut into the use of soybean for stock feed and push up the price of feed lot fattened meat. Healthy lean meat will not increase in price because it is not fattened in feed lots. After you squeeze out the oil, the left over soybean mash can be used as food for animals or fermented to produce ethanol then used as fertiliser and mulch for production of more food. Some parts of Brazil suffer deforestation to increase soybean production and it is a political issue to solve before buying soybean based diesel from Brazil.

Petroleum oil prices rose rapidly from 2001 until 2007 then dropped back to 2004 prices. In 2004 low vegetable oil prices made biodiesel economical. In 2007 some vegetable oils jumped in price when petroleum oil prices were starting to fall. Biodiesel will fluctuate in economic value and in some years will need subsidies.

Fuel efficiency tests

You read about the fuel efficiency of new cars and it looks excellent compared to existing cars. Perhaps we could reduce petroleum use by replacing our cars?

No. The fuel efficiency tests are useless for most people. Most car journeys in Australia, Canada, USA, and similar suburban oriented countries, start with a commute to work in the morning when the car engine is cold. The fuel efficiency tests start with a car warmed up to the laboratory temperature. That warm up period chews an extra couple of litres of fuel that is never counted in the official figures. The batteries in hybrid cars are not effective until warm. If you want to achieve the official figures you have to start by burning fuel to heat your garage overnight, if you have a garage. More than half of Australia cars are parked outside or in open car parks and drop 10 to 20 degrees overnight.

In a real world test around Sydney conducted by the NRMA, the Toyota Prius was the most efficient and used 18 percent more fuel than the official figures. A Suzuki Alto used 46 percent more than the official figures. A Ford Fiesta Econetic is advertised as the most fuel efficient car based on official figures but did not come close to the advertised figures, using a massive 30 percent more than the official figures, and more than the Toyota Prius despite being a smaller car.

There might be small crowded cities where everyone parks in heated garages and drives only short stop/start trips. For the rest of us, the official figures are useless. Measurements of real fuel economy show you do not gain much when replacing a three year old car with a similar new car and the massive burning of fuel required to manufacture the new car will never be regained. You do not see worthwhile fuel gains until you replace a car that is 10 years or older or you replace a gas guzzling American car with with a Japanese, Korean, or European car, where higher fuel prices have always made car design more efficient.

The common Ford family car in Australia is the Falcon. The Toyota equivalent is the Camry. You might need the Falcon if you have to tow a very large boat. The Camry is sufficient for everything else. The Camry is AU$12,000 cheaper and uses 36 percent less fuel. The Camry hybrid is AU$7,000 cheaper and uses 60 percent less fuel. An upgrade from any Ford Falcon to either Toyota Camry would save you enough fuel to cover the fuel used for manufacture and then a lot more in subsequent years, a truly green upgrade.

Diesel or petrol?

European car brands push diesel as more efficient than petrol but individual petrol cars beat diesel. Why?

Diesel engines are made of iron instead of alloys and are heavier as a result. The weight difference is significant in small cars, giving petrol an advantage. The biggest increase in efficiency for modern engines comes from gearboxes containing more gears. The lighter petrol engines can have better gearboxes and still remain lighter.

Diesel produces more power per volume of fuel because diesel fuel contains a higher ratio of carbon atoms but is heavier and produces more carbon pollution for the same volume of fuel. When you compare diesel to petrol for a given weight of fuel, there is only a small difference and again it is from the extra carbon leading to higher pollution.

The most efficient diesel engines are stationary engines run at constant speed to pump water and for other industrial uses. Diesel engines used in vehicles around the city burn as much carbon as their petrol equivalents. Trucks cruising the interstate highways show better fuel consumption than trucks in the city but not as good as those stationary engines. Note that those big trucks cruising the highways can have 18 gears to keep their diesel engines running near constant speed.

Manufacture of biodiesel is more efficient than the manufacture of ethanol, making biodiesel a quicker replacement for existing fuels in big vehicles. Fuel cells already run on ethanol giving ethanol the advantage when powering anything small and anything based on electricity.

Temparature

Diesel clogs up in cold weather. Ethanol evaporates in hot weather. Australia is hotter than northern Europe and northern USA. A solution designed for Berlin winter (-3°C, 24°F) might not work in Oodnadatta summer (50.7°C, 123.26°F). When some expert prattles on about the perfect solution, find out where they live and compare their environment to your environment.

Flexibility

A stationary engine, where weight is not a problem, could be built to run on a blend of ethanol and diesel to use up whatever is produced locally. The local production could vary across the seasons with biodiesel produced from beans in summer and ethanol produced from root crops in winter. Instead of converting methane into hydrogen, the methane can be added to the ethanol/biodiesel mix. Stationary engines can have attachments to consume almost anything burnable as fuel.

The stationary engine can generate electricity to charge batteries in electric cars. When the car is charged, the electricity can switch to heating water and other uses. During the day, when your compost is heating up and producing more methane, you run the engine on methane. Overnight you add something else from your fuel mix. For city use, you get more flexibility by using natural fuels to generate electricity. Electricity is not practical for tractors and long distance trucks.

You can also use the natural fuels to supplement wind farms during windless days and solar panels overnight.

Hybrids

Hybrid vehicles are better around town no matter which fuel you use. A small battery can save the energy you waste when braking then return the energy when you need to accelerate. Highway cruising contains very little stop/start travel and does not benefit from hybrid technology. Inner city travel is almost all stop/start driving and benefits the most from hybrid power. The inner city commute to work should, of course, be replaced by travel on trains, buses, bicycles, or a pure electric car. Hybrids with current battery technology win on the commute through the suburbs where a pure electric car runs out of power.

Hybrids with large batteries can be charged at home or at work from solar electricity panels. Someone stupidly handed out a patent that stops people using the latest battery technology in cars. The patent applies only to large batteries used in cars. You can use the same batteries to power toys, iPods, and toasters but not cars. Cars are temporarily restricted to using older battery technology that makes large batteries too heavy for commuter vehicles.

The use of hybrids is completely separate from the use of vegetable based fuels and should be encouraged in larger countries, including Australia, where people travel longer distances.

Fuel cells could be used in conjunction with hybrids to top up the batteries when the engine is switched off. The engine is switched off when you are stopped at traffic lights but you still use your sound system and headlights. You could provide that low level of power direct from a fuel cell instead of draining the hybrid battery. Currently fuel cells have to run on ethanol. You could have two tanks, one for ethanol, and one for diesel.

Engine seal erosion

The people pushing petroleum products like to tell stories about ethanol eating away the rubber and plastic components of engines. Brazil runs cars on 100 percent ethanol with no problems. The car manufacturers simply replaced a few cheap plastics with slightly different plastic. All your government has to do is pass a law requiring all future petrol engines to be compatible with ethanol. A few years later, when there are lots of compatible cars on the road, you tell the petrol companies to switch a percentage of their pumps to 100 percent ethanol.

Hydrogen at home

This idea only works in country houses. It requires space and there are safety issues. You cannot use this in a city apartment.

The biggest problem with hydrogen is storage. Out in the country low pressure storage is practical and cost efficient. You can use excess electricity from solar panels in the middle of the day to electrolyse water into hydrogen. In the evening you cook using the low pressure hydrogen. Windy days can drive the electrolysis using the excess electricity from your wind farm. The hydrogen will fill a big plastic bag inside a metal shed with the metal protecting against static electricity and lightening. If a fire occurs, water sprinklers will control the heat from the fire until the hydrogen is consumed. The shed will consume space and there is usually plenty of space on farms. The roof of the shed will be covered with solar panels to drive the electrolysis.

The secret is the low pressure. You do not have to use expensive high pressure containers with special expensive treatments for hydrogen. Hydrogen destroys steel. Hydrogen leaks through almost everything. In the farm hydrogen storage shed, small leaks are acceptable and vent harmlessly through the roof.

Conclusion

Hydrogen is the cleanest fuel and is not practical outside of small cars in big cities or stationary use where the hydrogen is produced and consumed at the same location. Ethanol is currently the most efficient way to deliver hydrogen to fuel cells and is environmentally sound when produced from waste plant material instead of food. Ethanol is the best choice for a quick replacement of petrol imports. Biodiesel is currently more practical for large vehicles and long distances and in hot climates.