Biogas can come from a multitude of sources, from alcohol fermentation to using the natural process in the breakdown of organic materials that releases methane, which can be harnessed to provide a fuel as well.
Here we will go through the different types of Biogas production
Ethanol Fuel Production
Alcohol can be used for heating, lighting and as a motor fuel. Alcohol is relatively easy to make, after all lots of hillbillies have done it for years, but making fuel grade alcohol is a little more difficult. For use as a motor fuel alcohol needs to be 180 to 190 proof, that’s 90% to 95% pure alcohol with less than 5% to 10% water content. Ethyl alcohol is generally made by yeast, (as well as some newly genetically engineered bacteria), the yeast or bacteria make alcohol as a byproduct as they consume a mixture of corn, grain or other plant material, plus water and sugar. The yeast/bacteria can only convert a small percentage of the mixture to alcohol, requiring a distillation process to separate the alcohol from the water.
Ethanol is basically an extremely distilled version of alcohol,
YOU MAKE IT THE SAME WAY!
AND YES! IT IS 100% LEGAL
You have to apply for a free Federal permit to produce ethanol for fuel production, as long as you produce less than 10,000 gallons (which isnt an issue for home use).
Skipping ahead through the process you have to add 2% gasoline to the ethanol which thus renders it “undrinkable” and legal to have and used.
Premium Vodkas are triple distilled and then the alcohol is distilled with water to make them teh 80 proof that you buy on the shelf.
Ethanol is made the same way but distilled to nearly 100% alcohol.
You can ferment ethanol from, wheat, corn, sugar, wheat, potatoes, sawdust, compost, fruits and vegetables
Think of all the rotten fruit you throw out, or stores throw out in your town or nearby city!
I wont go over the distillation process, as it is not a specialty of mine, and it can be dangerous if you just “wing it”
So that being said, the best book i can reccomend is “I Make my own Gas” by Steven Harris (see i said more on him later!)
The book, supplies, starter kits and more information can be found at his site at
David Blumes book “Alcohol can be a Gas” is on Steven Harris’s website, and is the Bible of home ethanol production
Methane Anaerobic Digester
Methane digester – it’s not for everyone. Only the hardiest of homesteading souls determined to become completely self reliant even in their fuel use will want to try this. However, a methane digester is a great way of using the manure on your property and converting it into something highly useful. If you have a lot of cows – say about 150 or more, you would have enough manure and enough methane to cut back considerably on your energy costs. But even if you have the manure from a family cow, you could still convert that manure into enough methane gas for cooking or heating water.
What is Methane?
Anytime an organic substance – either from an animal or vegetable source – decomposes, it produces methane gas. Methane gas is a greenhouse gas that is supposed to be far more detrimental on our environment than carbon dioxide. A methane digester takes that gas and converts it into energy.
Plus, unlike oil, which is a finite resource, methane is constantly being produced on our planet. We’ll never run out of methane gas. Plus, once methane gas is produced, the waste substances left over – both solids and liquids – can be used as organic fertilizers.
How a Methane Digester Works
When matter breaks down and there is no oxygen, then the anaerobic bacteria break down the matter and produce biogas as a waste product. This happens naturally in swamps, rice fields, soils that are water-logged and the intestines of large animals, but can also be manufactured by storing waste in an airtight container and providing an exit valve for the resulting methane gas.
Can it Replace the Power Grid?
It couldif you had enough manure, preferably cow manure, which is one of the best sources of methane gas. If you have at least 150 cattle or more on your land, it would probably be worth the cost to invest in a large-scale, continuous feed methane digester. With that much manure – and the resulting methane – you could easily generate your own electricity.
But For the Rest of Us…
Most of us small-scale homesteaders would use a batch-type methane digester. They’re relatively easy to assemble – if you know welding. It involves getting two drums: one that is 50 gallons and the other 30 gallons. Cut the top off the 50-gallon drum and the bottom off the 30-gallon drum.
Install an exit valve onto the top of the 30-gallon drum. This is where you will tap off the methane gas. Then fill the 50-gallon drum with manure, shredded newspaper and lots of water. Stir it until it becomes slurry – a liquid with particles of manure and newspaper.
Put the smaller drum on top and hold it down with weights. The created gas will force the top drum to rise. Release this first gas into the air. It is crucial to do this because this first gas is highly flammable. When the top drum rises again, this gas should be usable methane gas.
Methane gas – like any gas – is highly flammable. You will want to research this thoroughly before you try this at home. Here’s a good resource to get you started.
Pros and Cons of Methane Generator Systems
• Makes good use of organic wastes. You can obtain fuel from sewage sludge and animal slurries first, and prevent runoff and methane emissions at the same time – and you still get fertiliser at the end of the process.
• Is a clean, easily controlled source of renewable energy.
• Uses up methane, a powerful greenhouse gas.
• Reduces pathogen (disease agent) levels in the waste.
• Residue provides valuable organic fertilizer.
• Simple to build and operate.
• Low maintenance requirements.
• Can be efficiently used to run cooking, heating, gas lighting, absorption refrigerators and gas powered engines.
• No smell (unless there’s a leak, which you’d want to know about and fix immediately anyway!).
• Most practical to be generated and used at the source of the waste. This is because the energy needed to compress the gas for transport, or convert it into electricity is excessive, reducing the efficiency of biogas energy production.
• For safety, basic precautions (see below) must be adhered to.
Small Scale Waste to Energy Methane Generator Systems
Each kilogram of biodegradable material yields around 0.4 m³ (400l) of gas.
So in practice, in small scale waste to energy systems, if you have some livestock, plus kitchen and human waste you can meet your cooking and lighting needs easily:
• 2 gas rings for a couple of hours a day will use between 1-2 m³
• Gas lights need around 0.1 m3 (100l) per hour.
Driving any kind of engine (eg a generator or a pump) is, however, way beyond the domestic-scale. (Better to go for algal biodiesel!)
What Size Methane Generator is Needed?
If generating methane from manure, collect dung for several days to determine average daily dung production. On this basis, the appropriate size biogas digester plant can be calculated.
For example, where 55 kg of dung a day is available a 8 m3 plant is warranted; where it’s only 6 kg of dung a day, a 1 m3 plant will suffice.
For a family of 8 with a few animals (say 8-10 cows), a 10m³ digester is a commonly used size in India, with 2 m³ gas storage.
Ideal Temperatures for Producing Methane from Manure
How long you leave the material in a batch digester depends on temperature (2 weeks at 50°C up to 2 months at 15°C). The average is around 1 month – so gauge how much material you will add each day, and multiply it by 30 to calculate the size of the digester.
While anaerobic digestion occurs between 32° F (0°C) and 150° F (65°C), the optimum temperature range for methane generating microbial activity is 85°F (29°C) to 95° F (35°C).
Little gas production occurs below 60°F (16°C). In colder climates placing the digester in a greenhouse, and perhaps using some of the methane to warm the system, are possible strategies.
Methane Generator Systems
• The biogas digester is the system component where the animal, human and other organic wastes are introduced, usually as a slurry with water, to break down anaerobically.
• A storage container is used to hold the gas produced, from which it is piped for burning as a fuel. Variable volume storage (i.e. flexible bag or floating drum) is easier, cheaper and more energy efficient than high pressure cylinders, regulators or compressors.
• When the digester is emptied, the spent effluent is dried for later reuse as a fertilizer.
Types of Biogas Digesters
The two main digester types of digesters are the continuous and the batch. Continuous digesters have a constant throughput of material, and batch digesters extract the gas from a contained batch of material, which is then emptied and a new batch added.
As firewood for cooking has become scarce, millions of small scale continuous digesters are in use in developing countries, especially India and China. Digesters tend to be larger-scale in developed countries, taking animal slurries and human sewage.
Methane Generator Design
The Indian cylindrical pit design has become a popular choice around the world due to its reliability and simplicity. It comprises two basic parts: a slurry tank and a covered by a gas cap or drum to capture the gas released from the slurry.
Domestic Scale Batch Biogas Digestor
Small experimental biogas digester at Redfield.Waste material is put into the oil drum, neoprene cover rises when full of gas, gas is tapped into container (upside-down plastic drum with water seal) which rises as more gas enters.When full, gas can be tapped off and used with the little gas ring.
Batch digesters based on a container (see photo, above) are feasible on the domestic scale.