A man pouring food waste into the biogas digester

How can I make a simple biogas digester at home?

The biogas digester is an efficient way to utilize biodegradable kitchen and garden waste. But, it’s expensive to buy. 

You can build a simple biogas digester at home yourself. Making a biogas digester at home can be a fun do-it-yourself project. It will turn your kitchen scraps and yard waste into free, carbon-neutral fuel.

Here is the easiest DIY project on how to make a biogas digester at home

Materials

  • Two drums (Drum A must be slightly smaller than drum B so that A can fit inside B.)
  • Manure that supports the bacteria needed to create anaerobic conditions.
  • Input pipe and funnel for adding processed food waste.
  • Fertilizer-drain pipe.
  • 3 unseals.
  • Valve for controlling gas outflow.
  • Pipe for connecting outflow valve to burner Gas Burner
  • Chicken wire & cable ties to make a cage for the biodigester.
  • For cold climates and winter: Black spray paint, aluminum tape, or other outdoor insulation materials.

Step 1

Make sure the drum is tight enough to keep oxygen out and methane in. Remember that it should be loose enough so that it doesn’t crack.

The smaller drum should still slide down on its own weight, creating pressure and allowing gas to flow.

Step 2

There are three holes that have to be cut into the two drums. One pipe for solid input and another for gas output must be placed at the top of the smaller drum. The third hole will allow you to drain excess digested mass as fertilizer. 

You will need to cut three appropriately sized holes in the lid of your jar and insert rubber stoppers. 

These stoppers should be made from a material that won’t let air pass through but still allows gas to escape during the digestion processes, such as plastic or cork. Generally, the input pipe for your biogas system would be larger than the outflow valve. 

This is because as food goes into your digestion tank it takes up more volume and makes for a smaller space to push through when exiting.

Make sure that the drum is thoroughly sealed by placing it in water. If gas leaks out and fills up the space around the drum, your measurements will be affected by air pressure.

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Lastly, the input pipe should have a closed valve installed so that it is not left open after manure, garbage or other material has been added.

Step 3

To prevent the top of your drum from popping off, create a cage made out of chicken wire that will allow the smaller drum to rise without coming into contact with other drums.

Don’t drill holes into the larger drum to secure it. That would allow oxygen in, and remember that your cage needs to have pipes for oxygen going in and out of it.

Step 4

To prepare the manure, dilute it with water at a 1:1 ratio and stir until you have a slurry consistency. Then pour this mixture into the bottom of your larger drum carefully.

Step 5

Once you have introduced the smaller drum into the larger one and given it time to settle, adding some cut grasses is a good way of building up your system.

Keep the amount of plant matter to a minimum, and avoid large amounts of sugar in your mixture.

The first step is to allow bacteria to establish themselves, as well as the correct pH level with plant matter that grazing animals can then turn into methane.

After an interval, any remaining vegetables and cut grass should be added as well. Manure is needed to maintain the bacteria count.

Step 6

If you live in a cold climate, adding insulation may be necessary to maintain the temperature inside your biogas digester system.

Bacteria grow best when the temperature is between 32 and 37 degrees Celsius or about 90 to 99 degrees Fahrenheit.

If the temperature drops below 15 degrees Celsius or 60 degrees Fahrenheit, the bacteria will no longer be active.

A few tips for keeping the container insulated would be:

  • Paint the container black to draw in as much heat from the sun as possible.
  • Place the container in the ground so that heat generated by bacterial activity will be absorbed.
  • Cover the container with aluminum foil or another material that will keep its contents insulated in bad weather.

Step 7

Connect your burner to the line you attached to the outflow valve and enjoy using your new gas supply.

Sources of Biogas Production

Livestock Waste

Livestock wastes, including manure from poultry, cattle, and pigs are all excellent sources of biomethane. These organic materials can be decomposed in a controlled environment to yield significant quantities of this renewable energy source.

Landfill Gas

Landfill gas is created from organic waste that has been deposited in landfills. This material breaks down and creates a combustible mixture of gases that can be used to power generators.

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Activated Sludge from Waste Treatment Plants

Sludge from wastewater treatment is a good source of organic materials, which promotes the generation of biogas.

The biologically de-constructed sludge left over from the water treatment process can be used to produce methane gas in special decomposition chambers.

Industrial, Institutional and Commercial Wastes

Industrial manufacturing processes often use organic raw materials in their production cycles.

Food and beverage manufacturing companies use large amounts of organic waste to make their products.

Biogas generation plants can be used to harness materials that would otherwise decompose and release methane, a greenhouse gas.

Types of Small-Scale Biogas Digesters

Fixed Dome Biogas Plants

A fixed-dome plant is made up of a gas holder and compensation tank, both of which are immovable. 

The gas holder is located above the compensator tank in the digester, where natural gas or biogas flows into it to be compressed by an expander and stored long-term until needed.

When gas production begins, the slurry is flushed into a compensating tank. The pressure of the stored gas increases as more volume is added—which happens when there’s an increase in height between two levels of slurry. So if there’s less gas in the holder than usual, its flow rate (and therefore average velocity) will be lower than normal.

Floating Drum Plants

A floating drum plant
Courtesy: Build a biogas plant

Floating-drum plants are made up of an underground digester and a floating gas holder. Gas is collected in the drum, which rises or falls depending on how much has been stored there.

Low-Cost Polyethylene Tube Digester

The model Low-Cost Tube Digester consists of tubular polyethylene film (two coats, each 300 microns thick) wrapped around a 6-inch PVC pipe and further secured with rubber straps made from recycled tire tubes.

Balloon Plants

Baloon digester buried shallowly under the ground
Courtesy: IndiaMART

A balloon plant, also known as a bubble-cap or transparent vessel digester (TCVD), consists of a heat-sealed plastic or rubber bag that combines the functions of an anaerobic digester with a gas holder. 

The gas is stored in the upper part of the balloon and it has two openings to connect directly with skin tubes.

Advantages of biogas

here are some of the benefits you can find from a biogas

Biogas is Eco-Friendly

Biogas generation reduces carbon dioxide emissions by converting methane into carbon dioxide, which can be used in agriculture and horticulture by adding it to the soil for better growth of plants. 

This reduces the greenhouse effect and helps in cooling down the earth’s temperature.

Additionally, biogas production reduces landfill waste by diverting organic material away from landfills where it would otherwise decompose releasing harmful methane into the atmosphere.

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Biogas Generation Reduces Soil and Water Pollution

Biogas generation reduces soil and water pollution by preventing the release of methane gas into the atmosphere. 

Methane gas is a powerful greenhouse gas that contributes to global warming by trapping heat on the earth’s surface. 

Methane is produced during the anaerobic decomposition of organic matter under anaerobic conditions (without the presence of oxygen). 

Biogas generation reduces soil pollution through the reduced use of chemical fertilizers as well as other contaminants like slurry and manure.

The best cooking alternative in developing areas

The use of biogas as an alternative to firewood is gaining popularity in many developing countries. 

Biogas is produced through anaerobic digestion, a process by which organic matter is broken down by bacteria in an oxygen-free environment. 

It is also safer than burning wood or coal since there are no open flames or sparks involved; therefore it requires less maintenance and safety precautions than traditional fuels like kerosene and LPG gas cylinders which need regular maintenance checks and refills at regular intervals.

It Is Cost-Effective

Biogas has many advantages over other types of energy sources such as oil, coal, natural gas and nuclear power. It does not contribute to global warming since it does not release any greenhouse gases during combustion like fossil fuels do. 

Also, biogas has no emissions which are harmful to human health like smoke from burning coal or wood. Biogas is also more cost-effective than other types of renewable energy sources.

It generation produces organic fertilizer

This is a renewable energy source that can be used for heating and cooking purposes. 

It is produced by the anaerobic digestion of organic waste material (usually animal manure) in an airtight container called a digester. 

The process involves breaking down this waste through bacterial action so that it releases methane gas which can then be collected for use as fuel. 

The remaining liquid from this process is called slurry which can be used as fertilizer on crops.

Conclusion

Making your own biogas digester at home can be a lot of fun for anyone. It is easy, whether you’re a novice or an advanced maker, and it opens up a whole new range of possibilities for you.

if you want to save some money on your energy bills and live off-the-grid, at least for a small portion of your household needs, why not try using a biogas digester?

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