Biomethane is a gas with the same chemical-physical properties of Natural Gas (NG). Both are CH4 rich gases (up to 99.0%). Differently from the NG which is recovered from non renewable fossil sources, the biomethane is recovered from the biogas which is produced from several renewable sources like agricultural products, zootechnical and agricultural wastes, FORSU and algae. The Biogas has a content of CH4 in the range of 40-80% with the balance of CO2. By the GM upgrading process the CO2 is selectively removed from the Biogas producing the biomethane which can be utilized as a substitute of the NG. Biomethane production plants from Products and byproducts of agriculture and zootechnics Organic Fraction of Municipal Solid Waste (OFMSW) byproducts of the food industry Algae.
GM Technology for Biomethane Production?
- Total selective recovery of methane and CO2: GM technology allows for the complete and selective removal of CO2 from biogas, resulting in biomethane that is virtually pure methane (>99%). This is in contrast to other biogas upgrading technologies, which may leave some CO2 in the biomethane or require additional steps to remove it.
- Flexibility to treat biogas from different sources: GM upgrading units are very flexible and can be used to treat biogas produced from a variety of sources, including agricultural and zootechnical wastes, municipal solid waste (MSW), and food industry byproducts. This makes GM technology a good choice for a wide range of biogas producers.
- Close collaboration with the client: GM works closely with clients to ensure that their upgrading unit meets their specific needs and requirements. This includes providing support with feasibility studies, plant design, and plant management.
- Strong organization and structure: GM has a strong organization and structure that allows them to support clients throughout the entire biogas upgrading process, from start to finish.
The GM biogas upgrading process works as follows:
- The biogas is pretreated to remove any particulates or other impurities.
- The biogas is compressed to about 8 bar (g).
- The biogas enters a column where the CO2 is selectively absorbed by a backwashing process using an aqueous solution of potassium carbonate (K2CO3).
- The biomethane, purified from CO2, exits the top of the absorber at a pressure of about 8 bar (g).
- The biomethane is cooled, dried, and odorized before being injected into the natural gas grid or used as a biofuel.
The solution that has absorbed the CO2 leaves the bottom of the absorber and enters a regeneration column at atmospheric pressure where the CO2 is partially released due to the pressure drop and partially stripped by steam produced from the same solution using an external heat source. The CO2 can then be recovered and reused for a variety of purposes, such as food production or industrial applications.
3. Products and applications
Biomethane can be used in a variety of ways, including:
- Injection into the natural gas grid:? The Biomethane, after a final conditioning in order to meet the local grid specification (drying, odorization and Wobbe index), can be injected into the natural gas grid connected to the civil and/or industrial consumers;??can be injected into the natural gas grid and used as a renewable substitute for natural gas. This can help to reduce greenhouse gas emissions and improve energy security.?
- Vehicle fuel:?Biomethane after compression can be utilized?as a substitute of the natural?gas (Biofuel) for cars, trucks and tractors with a further benefit in reducing the greenhouse impact. Biomethane can be compressed and used as a vehicle fuel. This can help to reduce greenhouse gas emissions from the transportation sector.
- Cogeneration:? Biomethane can be utilized for high efficiency cogeneration units for combined heat/power production (CHP) owing to the higher energy value compared to the Biogas?and to the most efficient reutilization/integration?of the waste heat.? Biomethane can be used to generate electricity and heat in cogeneration units. This is a very efficient way to use biomethane, as it utilizes the waste heat from the electricity generation process.
- Other applications: Biomethane can also be used for a variety of other applications, such as heating and cooling buildings, producing industrial chemicals, and generating hydrogen.?
- Utilization of?removed CO2:?The CO2 removed by utilizing the GM process to upgrade the Biogas to Biomethane, can be totally recovered at high purity and reutilized as raw material for multiple uses (food?grade included).
Deep insight into GM technology
GM technology is a very efficient and flexible way to produce biomethane from biogas. It is based on a well-established absorption technology that has been used for many years in the chemical industry. GM technology has a number of advantages over other biogas upgrading technologies, including:
- High purity biomethane: GM technology can produce biomethane with a purity of up to 99.5%, which is higher than other biogas upgrading technologies.
- Flexibility: GM upgrading units can be used to treat biogas from a variety of sources, including agricultural and zootechnical wastes, MSW, and food industry byproducts.
- Efficiency: GM technology is a very efficient way to upgrade biogas to biomethane. It has a high methane recovery rate and low energy consumption.
- Scalability: GM upgrading units can be scaled to meet the needs of a wide range of biogas producers, from small farms to large industrial facilities.
- Comparing technologies:?
- CHEMICAL?ABSORPTION:?The solutions of Amines or K2CO3 utilized in Chemical Absorption are the most efficient and generate the purest Biomethane with high heating values. Due to the low solubility of methane in the absorption solutions, the processes do not require any post- treatment of the Off-gas, as the loss of Biomethane in the process is negligible. K2CO3 solution additionally is more stable (no degradation of the solution during the process) than an Amines solution and not dangerous to manipulate. K2CO3 also requires less regeneration heat and allows for a simpler more compact plant layout.
- PHYSICAL?ABSORPTION:?Physical absorption uses either Pressurized Water Scrubbing (PWS) or organic solvents. Water scrubbing when compared to chemical scrubbing absorbs less CO2 and requires larger columns with greater liquid circulation. The Methane recovery is also lower, as Methane partially dissolves in water, therefore the Off-gas requires post- treatment by thermal or catalytic oxidation before it can be released into the atmosphere.
- MEMBRANE?SEPARATION:?Membrane separation exploits the different molecular size of each component of Biogas to separate each other by a semi- permeable membrane. As the separation of the CO2 from the raw Biogas is only partial through each pass, the scrubbing process requires several stages of membranes to achieve an acceptable separation, increasing investment and operating costs. Membranes are very sensitive to impurities contained in the raw Biogas and periodical or emergency replacements are required during the normal operation.
- PRESSURE SWING?ADSORPTION:?In Pressure Swing Adsorption (PSA) CO2 is adsorbed in vessels filled with a molecular sieve made-up of activated carbon or zeolites. The adsorption takes place at an elevated pressure while the saturated vessels are regenerated by cyclical depressurization. The Off-gas however requires a post-treatment to oxidize the significant residual methane content prior to it being released to the atmosphere.
Overall, GM technology is a very promising technology for the production of biomethane from biogas. It offers a number of advantages over other biogas upgrading technologies, including high purity biomethane, flexibility, efficiency, and scalability.
