Weltec Biopower GmbH, a leading international anaerobic digestion (AD) technology provider, together with environmental services provider PreZero and Enagás Renovable, have announced the start of construction of a biomethane plant north of Madrid, Spain. Once operational, the plant in Colmenar Viejo will generate up to 60 GWh of green energy annually, equivalent to the energy requirements of approximately 11,700 households or 30,000 residents.
According to a statement, the Colmenar Viejo project has received all the urban planning and environmental permits required for construction.
In addition to planning approval and the construction licence granted by the municipality of Colmenar Viejo, the plant has received Integrated Environmental Authorisation from the Community of Madrid confirming that the project meets the comprehensive technical and environmental requirements applicable to this type of facility.
Strong partners
The plant is being developed by environmental services and waste management company PreZero Stiftung & Co. KG, and Enagás Renovable.
PreZero, part of the Schwarz Group, which also includes Lidl and Kaufland, has extensive expertise in waste management and the biomethane sector, and operates throughout Europe and manages waste generated by more than twelve million people in Spain and Portugal.
As the Spanish market leader, PreZero produced more than 53 percent of the country’s biomethane in 2025. Enagás Renovable is a leading independent energy producer in Spain, focused on the development of renewable gases and decarbonisation solutions.
The company currently has a portfolio of more than 20 projects across the country, positioning itself as a key player in the energy transition.
Treat household biowaste
The new facility will process up to 75,000 tonnes of organic waste annually. This will include separately collected household biowaste from the brown bin in Colmenar Viejo and surrounding municipalities.
Organic material currently accounts for around 40 percent of household waste by weight in the region. Instead of landfilling, these feedstock resources will be used to produce biomethane, aka renewable natural gas (RNG).
At the heart of the plant in Colmenar Viejo are three stainless-steel digesters from Weltec Biopower, each measuring 25.34 metres in diameter and 10.05 metres in height, with a volume of 5,067 m3.
The tall tank design enables high substrate throughput within a small footprint, thereby contributing significantly to the efficient use of the approximately 6,200 sq.m site.
A gas-tight pre-storage tank with a capacity of 1,177 m3 is situated upstream of the digestion process. It ensures a continuous supply of substrate and stable process conditions.
Hygienisation ensures compliance with the statutory requirements governing the treatment of organic waste streams.
Proven modular systems
All biogas digesters and storage tanks are made of high-quality stainless steel and manufactured by WELTEC BIOPOWER using its tried-and-tested modular construction system.
The components are industrially prefabricated and assembled on site, ensuring a consistently high level of production quality. The modular approach also enables efficient logistics and flexible scalability.
Stainless steel is particularly resistant to corrosion under the demanding biological and chemical conditions found in the digestion process. This gives the plant a long service life, high operational reliability and low maintenance requirements, emphasises Alain Priser, International Sales Manager at Weltec Biopower.
The facility will operate as a closed and sealed industrial system. Advanced biofilters and activated carbon systems are designed to remove up to 99 percent of odorous substances from the exhaust air.
The upgraded biogas will be injected directly and continuously into the gas grid, eliminating the need to store it at the plant.
With the biomethane plant in Colmenar Viejo, the municipality and the Community of Madrid are taking a pioneering role in sustainable waste management and the circular economy.
Support local, national and EU objectives
Currently, around 60 percent of the region’s waste is sent to landfill, leaving valuable resources unused. The new plant will help reverse this trend by converting regional organic waste into locally produced renewable energy.
It will also support the EU objective of reducing the proportion of municipal waste sent to landfill to no more than ten percent by 2035.
The project will also provide tangible benefits for Colmenar Viejo. A social agreement with the municipality provides for economic and community benefits.
These include energy to support heating of local public schools, treatment of residents’ separately collected organic waste at no charge, and priority consideration for residents when filling jobs created by the plant.
An environmental education centre will further strengthen environmental awareness in the municipality.
