Biogas: Definition, Types of Digester, and Uses

As we know, now cooking gas is in high demand. But considering the price, it does not seem affordable. Biogas has relevance. Biogas can produce by us and here we discuss what is biogas, the history, and the creation of biogas. Its benefits and drawbacks, types of biogas digestion, and the process of anaerobic digestion.

What is biogas?

Biogas refers to the fuel gas derived from the decay of organic matter. It is a mixture of methane and carbon dioxide produced by combustible gas sewage. Bacterial decomposition of garbage or plant crops, green manure in the absence of oxygen, and manure.

The division of organic materials in the absence of oxygen is called anaerobic digestion. It occurs in a large tank commonly known as a digester. The bacteria inside the digester convert biological waste into biogas. Thus, biogas is produced by anaerobic digestion by anaerobic bacteria or by fermentation of biodegradable wastes.

This renewable source of energy has evidence of ammonia, water, nitrogen, hydrogen sulfide, and hydrogen. When gases mentioned as hydrogen, methane, carbon monoxide oxidize with oxygen. The energy discharged in this process allows biogas to be used as fuel.

Bio gas

History of Biogas

In the early 17th century, Jan Baptita van Helmont found that flammable gases could develop from a decaying substance. By 1776, Count Alessandro Volta concluded a connection between decaying matter and gases.

In 1808, Sir Humphrey Davy laid out the methane traces in biogas. Therefore, in 1859, the first digestive plant was made in Mumbai. In 1895, biogas was utilized to fuel street lights in England. Finally, microbiology developed as a science, and by 1930.

Bushwell and several other scientists discovered anaerobic bacteria and suitable conditions that promote methane production. More and more countries in the modern world are using sophisticated systems in biogas.

Why chooses biogas?

Biogas plants depend on anaerobic digestion, a dissolving process in which waste is digested by microbes to generate methane gas (biogas). The waste can transform into a biofertilizer and be separated directly into fields. And biogas can utilize interchangeably with natural gas as a fuel.

Biogas can be particularly useful in rural or poor areas due to the low cost of set-up and availability of waste materials. Essentially any organic waste can utilize in this process, although factors such as pH and temperature affect gas production.

It has been cited as a renewable energy alternative due to the fact that it is a zero-emission process. By capturing methane emissions, biogas plants work to prevent the greenhouse effect and limit the number of harmful gases circulating in the atmosphere.

By adding and closing loops on earlier linear processes of sending organic waste into landfills, anaerobic digestion, and, says, anaerobic digestion. It is able to meet the challenges of waste, energy, sustainable food product, and nutrient recycling, “Biogas Association.

In addition, biogas generation relies on renewable, natural materials that can replicate or reproduced, thus becoming a sustainable method.

The by-product of the biogas generation process enriches biological digestion, which is a complete supplement, or substitute, for chemical fertilizers, which often have toxic and harmful effects. In contrast, organic digestion can increase plant growth and resilience to diseases.

Biogas End Uses

Raw Biogas and Digestate

With very little processing, biogas can lit on-site to heat buildings and power boilers or even digester. Biogas can use for mixed heat and power (CHP) operations, or biogas can be converted into electricity using a combustion engine, fuel cell, or gas turbine, resulting in the use of electricity on site. Or can sold on the electric grid.

The remaining nutrient-rich after the digestion process is solids or liquids; It contains all the recycled nutrients that were present in the original organic material but are more readily available for the manufacture of plants and soil.

The composition and nutrients of the digestion will depend on the feedstock added to the digester. Liquid digestion can easily spray into the fields as fertilizer, reducing the need for purchasing synthetic fertilizers.

Solid digestion can use as a livestock bed or compost with minimal processing. Recently, the biogas industry has taken steps to create a digestion certification program, to ensure digestive safety and quality control.

With biogas systems, dairies, farms, and industries can decrease operating costs by using their own organic waste to power their equipment and buildings. Fair Oaks Dairy in Indiana produces 1.2 million cubic feet of biogas each day with compost from 9,000 dairy cows.

Some of the biogas has updated to CNG and use electric trailers delivering milk to Fair Oaks processing plants. Decreasing the use of 1.5 million gallons of diesel fuel per year.

Renewable Natural Gas

Renewable natural gas (RNG), or biomethane, is a biogas that has been refined to remove carbon dioxide, water vapor, and other trace gases so that it meets natural gas industry standards.

RNG can inject into existing natural gas grids (including pipelines) and be used interchangeably with conventional natural gas. Natural gas (conventional and renewable) produces 26 percent of US electricity, and 40 percent of natural gas is used to generate electricity.

The remaining natural gas is used for commercial purposes (heating and cooking) and industrial ones. The RNG has the capacity to replace 10 percent of the natural gas used in the United States.

Compressed Natural Gas and Liquefied Natural Gas

Like conventional natural gas, RNG can use as a vehicle fuel because it is converted to compressed natural gas (CNG) or liquefied natural gas (LNG). The fuel economy of CNG-powered vehicles is comparable to conventional gasoline vehicles and can use in light to heavy-duty vehicles.

LNG is not wide use as CNG because it is expensive both to produce and store, although its high density makes LNG a better fuel for heavy-duty vehicles that travel long distances. To make the most investment in fuel infrastructure, CNG and LNG are best suited for fleet vehicles that return on a refueling basis.

The National Renewable Energy Laboratory estimates that RNG can account for five percent of natural gas used to produce electricity and 56 percent of natural gas used to produce vehicle fuel.

Average Maximum Biogas Production from Different Feedstocks

As we discussed above, what is mainly use for the production of biogas and place inside the fermenter (a special container) are:

  • Food scraps
  • Animal waste
  • Sludge from wastewater treatment plants
  • Animal compost and green biomass from agriculture
  • Other biodegradable waste by-products from industrial facilities such as slaughterhouse

Food Waste

About 30 percent of the global food supply is lost or wasted each year. In 2010 alone, the United States produced 133 billion pounds (66.5 million tons) of food waste, mainly from the residential and commercial food sectors.

To address this waste, EPA’s food recovery hierarchy first prioritizes source reduction, then uses additional food to address hunger; Animal feed or energy production is a low priority. Food should send to the landfill as a last resort.

Unfortunately, food waste makes up 21 percent of American landfills, with only 5 percent of food waste recycled into soil reforming or fertilizer.

This waste mostly sends to landfills, where it produces methane with breakdown. Although the landfill can capture the resulting biogas, landfilling organic waste provides no opportunity to recycle nutrients from the source organic material.

In 2015, the EPA and USDA set targets to reduce the amount of food waste sent to landfills by 50 percent by 2030. But even if this goal met, there will still additional food that will need to recycle.

Energy efficiency is important. As just one example, with 100 tons of food waste per day, anaerobic digestion can produce enough energy to power 800 to 1,400 households per year. Fats, oils, and oils raise from the foodservice industry can additionally combine in anaerobic digesters to increase biogas production.

Landfill Gas

Landfills are the third-largest reservoir of human-related methane discharges in the United States.

Landfills contain anaerobic bacteria present in a digester that break down organic materials to form biogas, in this case, landfill gas (LFG). Instead of allowing the LFG to escape into the atmosphere, it can collect and be used as energy.

Currently, LFG projects across the United States generate approximately 17 billion kilowatt-hours of electricity and distribute 98 billion cubic feet of LFG natural gas pipelines or directly to users each year.

For reference, in 2015 the average American household used about 10,812 kilowatt-hours of electricity per year.

Livestock Waste

A 1,000-pound dairy cow produces an average of 80 pounds of compost every day. This compost is often stored in tanks to be kept before planting not only does manure produce methane, as it decomposes, but it can also contribute to the extra nutrients in the waterway.

In 2015, livestock compost management provided about 10 percent of all methane effusions in the United States, yet only 3 percent of livestock waste was reused by anaerobic digesters.

When livestock manure is used to produce biogas, anaerobic digestion can reduce greenhouse gas emissions, reduce odors, and reduce compost pathogens by up to 99 percent.

And this EPA estimates a capacity of 8,241 livestock biogas systems, which can generate more than 13 million megawatts of energy each year.

Wastewater Treatment

Many wastewater treatments plants (WWTPs) already have on-site anaerobic digestion to treat sewage sludge, which segregates during the treatment process. However, many WWTPs do not have the equipment to use the biogas they manufacture and instead flare it.

Out of 1,269 wastewater treatment plants using anaerobic digesters, about 860 use their biogas. If all facilities that currently use anaerobic digestion – treating 5 million gallons each day – were to set up an energy recovery facility, the United States could reduce annual carbon dioxide emissions by 2.3 million metric tons – equivalent to annual emissions from 430,000 vehicles.

Crop residue

Crop residues may include stalk, straw, and plant pruning. Some residue is left on the ground to retain soil organic matter and moisture, as well as to prevent erosion. However, higher crop yield increased the amount of residue, and removal of a portion of these could be sustainable.

Crop yield rates vary depending on the crop, soil type, and climatic factors. Recognizing sustainable crop rates, the US Department of Energy expects that there are currently about 104 million tons of crop residues possible at a price of about $ 60 million per dry ton.

Crop residues are usually co-digested with other organic wastes because their high lignin content makes them difficult to break down.

Benefit or Advantages of Biogas

  • Ecofriendly: Biogas is developed through anaerobic digestion, meaning that oxygen is not required for its production. Technically this means that no form of combustion has developed, so no greenhouse gases have been released. Thus, biogas is environmentally friendly.
  • Renewable: Biogas is a renewable source of energy. All products like garbage, sewage, crop residues, manure, and green manure are used and will be available in plenty. Therefore, biogas can be produced on a regular basis.
  • Reduce soil pollution: All products used in biogas production are ecologically friendly and biodegradable. Mixed with soil, it becomes compostable and increases soil fertility thus reducing soil pollution.
  • Low Investment: Biogas can be developed at home with very low cost and investment. The raw material used can be obtained free of charge. Developed gases can be easily used for cooking and generating electricity. If biogas is compressed, natural gas can be obtained and used for automobiles.
  • Healthy generation: Biogas generation by-products can be used as organic manure (digestive) which is rich in nutrients. It can be used as an ideal supplement for chemical fertilizers and thus reduces health complications.
  • Employment: The biogas industry has produced a large number of employment openings in many countries. A number of people have been employed for the collection of raw materials and biogas manufacturing.
  • Healthy cooking option: Biogas is a healthy cooking option and is also economical. It helps women and children in firewood collection, especially in rural areas. Cooking on a gas stove is always a far better option than cooking on an open fire.
  • Improving water quality: Anaerobic digestion reduces and inactivates pathogens and parasites. This, in turn, reduces water pollution and water-borne diseases.
  • Reduces fossil fuel use: As the use of biogas increases, the use of fossil fuels such as oil, coal, and gas can be reduced to a great extent. This has helped countries like India and China because they have invested a lot in the biogas plant and its development.

Drawback or Disadvantage of Biogas

  • Contains impurities: Biofuels used for automobiles contain impurities that can cause erosion of metal parts. This raises the maintenance expense of the vehicles. It is more suitable for domestic purposes.
  • Cannot meet demand: Biogas is in great demand due to low cost. But unfortunately, technologies are no longer efficient enough to produce as much to meet requirements. In most countries, the government is not willing to invest much in these biogas plants.
  • Not suitable for all areas: Biogas can be utilized in areas where raw elements are available in lots. Mostly these are available in abundance in rural areas. Therefore, it is practical to build a biogas plant in rural areas.
  • Not economically attractive: Since the raw materials used are available cheaply, it is not economically attractive.
  • Weather-affected: Like most renewable sources of energy, biogas also has a temperature effect. The hot climate is the ideal condition for bacteria to function. Therefore, it is difficult to establish biogas in areas where the climate is cold.

Biochemical Process in Anaerobic Digestion

The method of anaerobic conversion can divided into 4 steps like

  • Hydrolysis,
  • Acidogenesis,
  • Acetogenesis and
  • Methanogenesis.
Biogas anaerobic Prosses

1. Hydrolysis

In this step, the organic compounds reduce to a simple form so that microorganisms can easily use them. The rate of hydrolysis depends on factors such as organic matter size, surface area, size, and biomass.

Biomass typically includes large organic polymer proteins, fats, and carbohydrates. These are broken down into small molecules like amino acids, fatty acids, and simple sugars.

This is the first step required in anaerobic fermentation; Fermenting bacteria hydrolyze complex organic matter into soluble molecules. Some products of hydrolysis, including hydrogen and acetate, can later be used by methanogens in the anaerobic digestion process.

Most molecules, which are still relatively large, must further break down in the acidification process. So that they can use to produce methane.

2. Acidogenesis

Acidogenesis is the next step of anaerobic digestion where acidogenic microorganisms break down biomass and organic products after hydrolysis.

These fermenting bacteria produce an acidic environment in the digestion tank by detecting the amount of ammonia, methane, carbon dioxide, hydrogen sulfide, low volatile fatty acids, and organic acids, as well as other byproducts.

The major acids produced are acetic acid, propionic acid, butyric acid, etc.

3. Acetogenesis

In common, acetogenesis in the production of acetate, a derivative of acetic acid from carbon and energy sources by acetogens. These microorganisms catalyze many products manufactured in acidic to acetic acid, carbon dioxide, and methane.

Acetogens break down biomass up to a point, allowing methane to use more of the remaining material to make methane.

4. Methanogenesis

Methanogenesis constitutes the final stage of anaerobic digestion in which methanogens form methane from the end products of acetogenesis as well as some intermediate products of hydrolysis and acidogenesis.

The two main products associated with the use of acetic acid and carbon dioxide are the two main products of the first three stages of anaerobic digestion to produce methane.

While carbon dioxide can be converted into methane and water through a reaction, the main mechanism of methane-making in methanogenesis is the pathway involving acetic acid.

In this phase, methane and carbon dioxide are produced, which are the two main products of anaerobic digestion.

Types of Biogas Digesters (Reactors)

There are various designs but two types of biogas reactors are common: Floating-dome plants and Fixed-dome plants.

1. Fixed dome biogas plants

The fixed-dome plant has a fixed digester combined with a non-movable gas holder, which is placed on top of the digester or gas collected in space at the top of the digester.

When gas production begins, the slurry is displaced into the compensation tank. The amount of the gas rises between the amount of the gas and the height among the slurry level in the digester and the slurry level in the compensation tank.

The price of fixed dome biogas plants is comparatively low.

The plant is simple because it has no moving parts and also no rusted steel parts and has a longer life (20 years or more) of plant than can be expected. A digesting tank is built underground which protects it from physical damage and saving space.

While covered digesters are shielded from low temperatures at night and in a cold climate, sunshine and warm weather take continued to heat the digester. No day/night temperature fluctuations in the digester positively affect bacterial processes.

The construction of stationary dome plants is labor-intensive, thus creating local employment. Fixed-dome plants are not easy to build.

They should only be made where construction can be monitored by experienced biogas technicians. Otherwise, the plants may not be gas-tight (holes and cracks).

2. Floating dome biogas plants

Floating-dome plants have an underground digester (cylindrical or dome-shaped) and a moving gasholder. The gas-holder floats above the fermentation solution.

The gas has collected the dome, which rises up and down according to the amount of gas stored. The gas dome is prevented from bending by a guiding frame. The position of the dome indicates the available volume/pressure of the gas.

Construction is relatively easy; However, steel domes cost more and in addition, steel parts are susceptible to corrosion. Floating dome plants have a shorter lifespan than fixed-dome plants. In addition, regular maintenance costs arise for the painting of domes.

Since the start of budget fixed-dome Chinese models, floating dome plants are becoming obsolete. Apart from the high investment and maintenance costs of floating dome plants, there are some design weaknesses as well.

3. Balloon Plant

It consists of a rubber bag or balloon and mixes the digester and the gasholder. The input and output connections to the skin of the rubber bag.

Conclusion

The biogas system converts waste management costs into revenue opportunities for America’s farms, dairies, and industries.

Transforming waste to electricity, heat, or vehicle fuel provides a renewable source of energy that can decrease dependency on imported oil, decrease greenhouse gas emissions, enhance environmental quality, and localize May boost jobs.

The biogas system gives an opportunity to reuse nutrients in the food supply, decreasing the need for both petrochemical and mining fertilizers.

The biogas system is a waste management solution that solves many problems and produces many benefits, including revenue streams.

The United States currently has the ability to add 13,500 new biogas systems, providing more than 335,000 construction works and 23,000 permanent jobs. However, to attain its full potential, the industry needs constant policy support.

Farm Bill Energy Title programs and reliable financing of a strong renewable fuel standard encourage investment and innovation in the biogas industry. If the United States expects to increase its fuel supply and take action in climate shift, it should fully consider the many benefits of biogas.