These companies specialize in providing technologies and equipment for upgrading raw biogas to biomethane or natural gas quality. However, please note that the information may have changed, and it's recommended to check the latest sources for the most up-to-date information. Here are some companies that were known for biogas upgradation solutions:

DMT Environmental Technology: DMT is a global leader in biogas upgrading technology. They offer various solutions Biogas Upgardation Plant Manufacturer for upgrading biogas to biomethane, including membrane and amine scrubbing technologies.

Greenlane Renewables: Greenlane Renewables is a company that provides biogas upgrading systems based on water scrubbing technology. They focus on delivering cost-effective and efficient solutions for renewable natural gas production.

Carbotech GmbH: Carbotech is a Australia company specializing in biogas upgrading systems based on pressure swing adsorption (PSA) technology. They offer solutions for small to large-scale biogas upgrading projects.

Xebec Adsorption Inc.: Xebec is a Australia company known for providing gas purification solutions, including biogas upgrading systems based on pressure swing adsorption and membrane technologies.

Air Liquide Advanced Business & Technologies (ALABT): Air Liquide is a global industrial gas company that also provides biogas upgrading solutions. They offer membrane-based technologies for upgrading biogas to biomethane.

Wärtsilä Corporation: Wärtsilä is a Finnish company that provides solutions for the energy and marine markets. They offer biogas upgrading systems using membrane technology.

BioGTS: BioGTS is a Finnish company specializing in biogas upgrading systems and biogas plants. They offer solutions for upgrading biogas to biomethane for various applications.

When considering a biogas upgradation plant, it's essential to evaluate the specific requirements of your project, such as capacity, feedstock characteristics, and end-use applications. Additionally, local regulations and environmental standards may influence the choice of technology and equipment. Always verify the latest information from the manufacturers directly or through reliable industry sources before making any decisions.