Alternative fuels are a hot topic right now. Apart from the main fossil fuels, there is also biodiesel, alcohol, wood gas and electricity to consider.

Here’s a table comparing the pros and cons of different biofuels to help decide which fuel to use.

wood gas

Wood gas or Producer gas is a very old type of fuel that is easy to produce and use. It consists of partially burning biomass followed by combustion of smoke and gas as fuel.

It sounds weirder than it actually is and can be done on a budget. In fact, most wood gas applications are driven by budget or fuel supply issues. Wood gas production includes a gasification unit (where incomplete combustion occurs), a filtration unit to filter tar and ashes from the gasifier, and delivery to an engine.

There are many types of gasifiers, depending on the fuel used and the desired effects. To fuel an engine, the gas needs to be very clean to prevent tar formation in the engine, and this is where Imbert-style downdraft works so well. Very little tar is produced with this design, so your filtering process is less complicated.

Additionally, a wide funnel rather than a long one as in the moderator design will allow the use of green or high moisture content fuel.

Once you have chosen a gasifier design, you will need to consider filtering the gas produced. Cyclone filters combined with a fabric or mesh filter will work well. Cooling the gas is also important because it precipitates tar and moisture in the gas. If so, run the coil through a pipe or a radiator.

It’s pretty easy to actually burn gas in an engine. Essentially, you create a gas carburetor that allows air and wood gas to mix before entering the engine. A solid butterfly valve will allow you to throttle the fuel supply. Most systems require a blower to pull gas through the system to reach the engine. The other alternative is to start the engine on gasoline and switch to wood gas when it warms up.

This is difficult to do, but once you get the hang of it it works well.

Wood gas is not a fill-and-go type of fuel. You need to start a small fire in the gasifier and then once that starts, close off the air intake to the gasifier and start the engine or blower. Your engine will lose about 20-40% of its power by running on wood gas, so you should keep this in mind. It works quite well for stationary applications such as generators or shredders.

Another great thing about gasification is that you can use any fuel source, from corn cobs to wood chips to paper, even plastic and tires! While some fuels may be easier, anything containing oxygen, hydrogen, and carbon will work.

biodiesel

Biodiesel is probably one of the most popular homemade fuels. It’s easy to build and use as long as you have a diesel engine.

Biodiesel is made from vegetable oils and mixed with an alcohol, then dried and filtered. Some diesel engines can use vegetable oil directly in SVO (Straight Vegetable Oil) installations, but some problems may occur.

A diesel engine is generally more efficient than a gasoline engine. Therefore, these engines are popular in countries with expensive gasoline or fuel delivery. Diesels also have higher torque at low speeds, making them the preferred alternative for work vehicles such as tractors and trucks.

Diesels are known to last a long time, and some stationary engines like Lister Clones or Changfas can last over 100,000 hours between overhauls. There are almost no gasoline engines today that can meet these specifications, or even half of them.

Biodiesel production starts at the factory. Since oil production is low per acre, high oil output is a major concern, so special care should be taken to select a high-yielding crop that is well-suited to your environment. Canola is often chosen due to its high output per acre, but several other crops are possible. Don’t expect more than 100-200 gallons of oil per acre.

The oil usually comes from the seed part of the plant, and these parts must be crushed, pressed and heated to extract the oils. Some oils will need pre-treatment to get rid of free fatty acids before biodiesel production.

Processing oil can be done in the backyard, but special care must be taken because it involves potentially lethal processes and chemicals. Home refiners are available at low cost, but most are easy to make yourself. Be sure to research your recipe well so you can obtain the chemicals needed, such as non-alcoholic water or methanol.

Most chemicals can technically be produced at home, but beginners are advised to start simply and work towards full production.

Once you refine your biodiesel, you can use it in almost any diesel engine. Many diesel fans swear that biodiesel is better for the engine and gives greater energy output, but these claims vary between techniques and recipes.

Biodiesel is the closest thing we have to an alternative fuel silver bullet. It is easy to produce and use. The problems lie in the fact that, in general, growing crops specifically for oil is not very efficient in space, due to the low oil content in crops. Efficiency can be increased in another biofuel system by using crop residues for animal feed or feedstock.

Many people argue that it is unethical to use cropland to grow fuel instead of food, and this is especially important for low-yielding crops such as oils. Care should be taken to avoid competition between energy and food resources.

Using waste oils from fast food restaurants, for example, increases the appeal of biodiesel because you are using the waste stream and therefore pushing this original oil further.

It’s a slight change to biodiesel, using things like waste motor oil. Some adaptations will be needed. However, if you mix this oil with some gasoline, it can be a very affordable option.

Butanol

Butanol is a higher energy alcohol than ethanol (105 kBtu, versus 70 kBtu per gallon), making it an attractive alternative to ethanol. However, it also has some disadvantages.

Because butanol is more potent than ethanol, it does not require engine modifications like ethanol, giving it an advantage. However, it is more difficult to do, requiring higher levels of distillation energy, because the maximum concentration for ethanol is 14% versus 2.5%.

Butanol can be made from all the same raw materials as ethanol, but it is made with 2 different bacteria, not yeast. One bacteria converts sugar and starch into butyric acid, then another takes over and turns it into butanol. This process has historically been called the ABE process as Acetone, butanol and Ethanol, but 2-3 times more butanol is produced than Acetone.

The problem with butanol has always been in the purification process. Since concentrations above 2.5% begin to kill butanol-producing bacteria, several methods are being investigated to increase output. One is genetic modification of bacteria, but for our DIY fans, absorption or molecular sieves seem to be the best bets.

There are several hydrophobic membranes in there that will allow butanol to pass through but prevent water from passing through. This is like a water filter and allows the production of a continuous flow. Absorbing butanol into an oil or solid material can also be very efficient. As of 2008, no open source butanol projects using these methods have been published. I hope someone out there makes this happen.

Using butanol is very easy. Put it in your car and go! People have taken cross-country trips on butanol and proven that the lower emissions and one-to-one gasoline replacement are completely affordable. If we can figure out the production side of butanol, it could be the next great fuel.

ethanol

Ethanol is a basic biofuel that can be made by almost anyone. But problems in making ethanol create problems even for professionals!

The trick is the quality of the finished product, or how much water is in the final output. Removing the water requires different “tricks” to separate the water-loving ethanol. On top of that, ethanol can corrode certain metals and eat away at plastics and some rubbers. Therefore, converting your vehicle or engine to use ethanol is a must.

Ethanol is basically alcohol made from sugar. We won’t go into detail about what ethanol actually is, but for now, think of it as a really strong liquor like infinity. In fact, most of the time ethanol needs to be 80% pure or better to work in your vehicle. If you’re mixing it with gasoline, it needs to be 98% pure or better, as is the case with E85 blends.

Ethanol can be made from anything that contains sugar. Of course it’s easier to make from something that contains a lot of sugar. Forget making it from corn, as it doesn’t contain as much starch (complex sugar) as other crops. Jerusalem Artichokes are considered the most productive per acre and the nice thing about them is that you get lots of extra biomass to feed your methane system!

Cattails can be another major feedstock, with production levels of more than 1,500 gallons per acre (five times higher than the average corn yield).

Once you have your feedstock, mix it with water and yeast to ferment for a few days. It is best to boil this “mash” before adding the yeast to kill any wild bacteria, fungi or yeast that may be present in it. Everything loves sugar, and you don’t want them to compete with your alcohol-producing yeast.

You can get up to 14% ethanol content if your feedstock has enough sugar (20-25%), but most beginners have success getting up to 8% ethanol. Filter the puree to remove any solids and you are ready to purify the puree.

Ethanol loves water, and that creates problems for us because water doesn’t burn very well. If you’re using ethanol directly, some water is sufficient, but more than 20% water probably won’t flow very well. There are several ways to get water from something. The most common is distillation, which involves heating the fermented mixture just beyond the boiling point of alcohol (lower than the boiling point of water) and then condensing the vapor back into a highly concentrated liquid.

This isn’t as difficult as it seems, but efficiency is low and you need to generate heat for it to work.

Another method to separate water and ethanol is to use a chemical or material to absorb ethanol from water. You will then need to separate the material in question from ethanol if it has a significantly higher boiling point than water; this may be easier than distillation. Sulfur and oils are usually used in this process, but you can also use special membranes and water absorbent materials.

So once you get your ethanol to a relatively pure state, you should be able to use it. This is rubbing with ethanol. It has a lower energy content than gasoline (70 kBtu versus 125 kBtu per gallon), so you need to burn more of it to get the same power from an engine. This includes changing the engine, increasing injector or port sizes, changing timing, and possibly even changing the compression ratio.

Of course, once you do all this to your engine, it won’t run the same as gasoline. Engines with computer-controlled fuel injection look much better in this regard, as the computer can change the behavior of engine components and then return them to gasoline standards when you fill the pump.

First of all, ethanol can eat some plastic and rubber, so you will need to replace those components as well. For this reason, ethanol is often mixed with gasoline. With the blend, the ethanol doesn’t eat anything and the engine mods aren’t as extensive. This can certainly reduce your dependence on fossil fuels, but it won’t replace it completely.

As you can see, making ethanol isn’t very complicated, but using it is tricky, to say the least. And this is true of most biofuels, you either spend time and money making them or you spend time and money running them.

Source: http://velacreations.com/articles/energy/fuels/