Archive: Oct 2023

Why Nitrogen Removal is Necessary for Upgrading Landfills to RNG

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We all know how important it is to prioritize recycling and composting, but what do we need to do with the waste that isn’t recyclable? Unfortunately, they end up in landfills. These places are often seen as a last resort for our refuse. However, there are innovative ways in which we can make them more sustainable. One is upgrading them into Renewable Natural Gas (RNG) through an effective landfill gas treatment, such as Nitrogen Removal.

Nitrogen removal

By removing nitrogen gas from landfill gasses, RNG is recycled as electricity or as fuel for heating or thermal applications. However, the question remains: Why is nitrogen removal essential to turn landfill gas into RNG?

If you’re ready, let’s discover its importance and the different landfill gas removal applications available!

Upgrading Landfill Gas to Renewable Natural Gas

Landfill gas is composed of many different gasses, which depend on the type of waste present. Methane and carbon dioxide are estimated to comprise 90 to 98% of landfill gas. On the other hand, the remaining 2 to 10% is made up of nitrogen, oxygen, and other trace gasses. 

These gasses can pose dangerous health risks once a person is exposed. Evidently, landfill gasses can also negatively impact the environment in multiple ways.

Some adverse effects of landfill gasses include:

  • Create smog if left uncontrolled
  • Contribute to climate change
  • Soil vapor intrusion
  • Bad odor
  • Short-term exposure: Breathing difficulties, nausea, coughing, irritation of the eyes, nose, and throat, and headaches.
  • Long-term exposure: Chest pain, nasal blockages, weight loss, sleeping difficulties, and asthma aggravation.
  • Explosion hazard due to high levels of methane gas in enclosed spaces

Listed are only some of the countless harmful effects landfill gasses can cause people and the environment. Landfill gas capture is highly recommended to effectively recycle these dangerous gasses as renewable natural gas instead of releasing them as emissions.

Standard Methods to Upgrade Landfill Gas to RNG

To produce RNG, landfill gas must be captured and upgraded to comply with pipeline specifications. Complying with pipeline requirements involves removing volatile organic compounds, sulfides, carbon dioxide, moisture, and nitrogen from landfill gas.

Numerous technologies and processes are used to achieve this feat. These are proven effective, but some factors must be considered to find the most optimal solution. For instance, professionals must consider equipment costs, methane recovery levels, and other expenses.

Methods that are used in landfill gas treatment:

  • Water Scrubbing: Also called water wash, this process involves compressing landfill gas to remove impurities through the dilution of water.
  • Solvent Scrubbing: This process uses a chemical solvent such as amine or a physical solvent such as Selexol. These will remove carbon dioxide and sulfides from biogas.
  • Membrane Systems: Employs moisture removal, compression, and hydrogen removal, then uses carbon and membranes to remove remaining volatile organic compounds and carbon dioxide.
  • Catalytic Reaction: Landfill gas is heated and passes through a catalytic bed where oxygen reacts with methane to create carbon dioxide and water.
  • Cryogenic Distillation: Separates oxygen and nitrogen by liquefying the landfill gas at very low temperatures. After that, high levels of methane can be recovered with ease.
  • Pressure Swing Adsorption (PSA): PSA uses two methods: First is the compression of landfill gas with moisture and sulfide removal. The second one involves nitrogen and methane attachment, allowing nitrogen to pass through.

Pressure Swing Adsorption and Cryogenic Distillation are two popular methods for removing or separating nitrogen. Nitrogen can easily attach to other landfill gasses, commonly oxygen, methane, and carbon dioxide. This fact facilitates landfill gas removal using a vapor-phase activated carbon and a molecular sieve for PSA and liquefaction at very low temperatures for Cryogenic Distillation.

The Nitrogen Removal Process

Nitrogen is present in landfill gasses. It’s an odorless, colorless, and tasteless gas that comprises around 78% of our air. It’s also plentiful in the Earth’s atmosphere. With that said, what is its role in landfill gas collection?

The simple answer is that removing nitrogen results in high BTU gas, which means more energy can be produced. High outputs of BTU gas are equal to higher heat intensity. Nitrogen removal is also necessary to comply with RNG specifications and requirements.

As mentioned above, nitrogen removal is achieved through two different methods: Cryogenic Distillation and Pressure Swing absorption (PSA). Let’s learn more about each one.

Pressure Swing Adsorption (PSA)

Under Pressure Swing Adsorption, gasses tend to be trapped or adsorbed under high pressure. It means the higher the pressure, the more gas is absorbed. Once the pressure drops, gas is released. The process is done with the help of a skid system called a gas separator membrane skid.

The goal of PSA is to separate gasses in a mixture since different gasses can be adsorbed onto a solid surface. In landfill gas removal applications, the gas is compressed under high pressure. After that, moisture and hydrogen sulfide are removed. The remaining gas will pass through a vessel, which results in the biogas being upgraded into a renewable natural gas.

Benefits of using Pressure Swing Adsorption:

  • Extremely clean operation
  • Quick return on investment
  • Cost-effective equipment that requires minimal maintenance
  • Low operating costs
  • Sustainable and reduces the CO2 footprint

Another method is when nitrogen attaches to methane. The process allows the nitrogen to pass through, and methane is extracted by depressurizing and pulling a vacuum through the vessel.

Cryogenic Distillation

The second method is Cryogenic Distillation. It’s when gaseous mixtures are separated through distillation at high and low temperatures. In the case of landfill gas capture applications, oxygen, and nitrogen are removed from landfill gas through simple distillation.

Distillation refers to the process of separating a gas mixture based on differences in their boiling points. In Cryogenic Distillation, landfill gas is exposed to very low temperatures until it liquefies.

Once it turns into liquid, oxygen and nitrogen are separated throughout the process due to their different boiling points. As a result, methane remains condensed, allowing for easy removal at high recovery rates.

Experience Successful Nitrogen Removal with the Proper Landfill Gas Treatment

Nitrogen removal is necessary for landfills to upgrade their gas into usable renewable natural gas. The methods used, namely Pressure Swing Adsorption and Cryogenic Distillation, are highly efficient in converting landfill gasses to RNG.

If you’re looking for quality skid systems that can aid in this process, it’s best to find experts in the field. Stark Compression, formerly Glauber Equipment, is a leader in manufacturing customized skid systems for the renewable natural gas industry, and we’re fully prepared to deliver unrivaled results.

Are you interested and want to know more about our capabilities and services? Feel free to contact us today! You can also request a free quote, and our team will find a solution designed and developed for your landfill gas utilization needs!