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FAQs about Biogas

Ross Group’s engineering division works on a wide variety of project types. One of the unique areas they are involved in is the design and engineering of biogas facilities. As a sustainable energy source, biogas is gaining a lot of traction in the United States and around the world. This week, we caught up with our resident biogas expert Alan Hill to discuss some frequently asked questions.

What is biogas?

Biogas is a gas that is produced from the natural degradation of organic material, such as food waste, plant matter, or animal waste. It’s a similar biological process to composting, where bacteria break down organic materials and produce carbon dioxide. The primary difference with biogas is that the environment lacks oxygen, so the kind of bacteria is different – anaerobic instead of aerobic. The anaerobic bacteria produce methane in addition to carbon dioxide. This combination of gases is referred to as biogas. Biogas generally also contains other gases, such as hydrogen sulfide, in smaller quantities depending on the feedstock.

How can biogas be used?

Since a main component of biogas is methane (natural gas), biogas can be used in most of the same ways natural gas is used. Three of the most common uses for biogas are:

  • Fuel for steam boilers

  • Fuel for electricity generation

  • Injection into the local natural gas utility pipeline

Depending on the application, biogas may need pre-processing to remove carbon dioxide and other gases. Steam boilers require little or no pre-processing since the gas is burned for heat. Injecting biogas into the local natural gas pipeline system, however, requires the most pre-processing since the utility supplies gas for all kinds of purposes.

When biogas is pre-processed (or upgraded) to “pipeline quality,” it is often referred to as Renewable Natural Gas (RNG). There are a variety of cost-effective ways to upgrade biogas to RNG, so that has become one of the more common uses for biogas over the past two years.

What is the process for producing biogas?

Biogas is produced at a variety of facilities, some of which include:

  • Landfills

  • Municipal Wastewater Treatment Plants

  • Dairy Farms

  • Food-Processing Facilities

At many of these facilities, biogas used to be considered an unwanted biproduct. However, with more focus being devoted to renewable energy, what was once an unwanted biproduct is now a valuable resource to be recovered.

What types of facilities are required for producing biogas?

The main piece of equipment where the action happens is called the Anaerobic Digester. There are many designs out there, but a large vertical tank is one of the more common. Solid and liquid waste enters the tank in batches and is mixed together. After a period of days to weeks, the organic material is digested and biogas is produced. The leftover solids and liquids are high in nutrients and can be applied as fertilizer for agriculture. The biogas from the Anaerobic Digester is often sent directly to a user on-site or to upgrading equipment for pipeline injection.

The digestion process sounds simple, but there is actually a lot to it. An Anaerobic Digester needs the right combination of waste or the bacteria won’t produce biogas as intended. It’s often compared to a human stomach. If we spend all day eating only cookies, then our stomach is going to become upset and not function as smoothly. The Anaerobic Digester is similar, in that it needs a balanced diet.

How does biogas compare to other energy sources?

Biogas is one of many renewable energy sources that are used to supply our world’s energy needs. While solar and wind power require favorable weather conditions, biogas does not. Because of this, the energy from biogas can be utilized to smooth the ups and downs of solar and wind power. Biogas does, however, favor warmer climates for quicker digestion and greater production.

What are the benefits of biogas?

Biogas puts our waste to good use. Waste is going to decompose and produce carbon dioxide and methane no matter what. Rather than letting the energy content of methane go to our atmosphere untapped (and at the same time negatively affect the climate), biogas technology allows us to capture that energy. The biogas process also produces valuable fertilizer from the organic waste, which helps farmers grow the food we need more efficiently.

What does the future look like for biogas?

The future is bright for biogas in the United States. More projects are developing, particularly in dairy waste where a much higher value is assigned to biogas due to its low carbon intensity. The technology has traditionally been applied to municipal wastewater treatment to process human waste; however, it has more recently been applied to process other organic waste, while purposefully producing energy. There is the potential for development of approximately 15,000 new sites across the country, which could add 103 trillion kilowatts an hour per year and reduce emissions by an equivalent of 117 million vehicles. Tapping into this technology could help reduce greenhouse gas emissions and improve environmental quality, ensuring this valuable alternative energy source will grow in the near future.

Visit the American Biogas Council’s website for more information and details on this interesting topic.



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