Anaerobic Digestion Plant in Mafra

The specific objective of this project was to carry out civil construction work and to supply and assemble the electromechanical equipment, electrical installations, instrumentation and automation needed to build the anaerobic digestion plant. 

The work consisted of the following constructions: 

- Construction of industrial buildings for reception, pre-treatment, methanisation feed, methanisation, mixing, mixing of the vegetable fraction, composting, refining and storage and dispatch, with supply and assembly of the respective electromechanical equipment and electrical installations; 

- Construction of digesters, fermentation tunnels and biofilters; 

- Construction of the exploitation building, workshops, gatehouse, electrical installations and biogas buildings; 

- Leachate and domestic sewage networks including the construction of a small WWTP; 

- Water supply network including a water reservoir; 

- Industrial water network, rainwater drainage network and biogas network; 

- Auxiliary buildings, namely the fuel station, wheel wash and weighbridge; 

- Exterior arrangements, including roads, footpaths and landscaping. 

The main work carried out was as follows: 

- Deforestation and stripping of the intervention area; 

- Earth levelling works to allow the construction of platforms on which the plant was built; 

- Construction of external support walls to contain the land, where necessary, given its large unevenness; 

- Excavation for the installation of the reception building, namely the pit; 

- Construction of the reinforced concrete foundations consisting of footings and foundation beams; 

- Execution of the elevated reinforced concrete structure for digesters, fermentation tunnels, biofilters and buildings; 

- Construction of the metal structure and cladding for the façades and roof of the industrial buildings; 

- Execution of the underground constructions relating to the WWTP, water reservoir and equipment massifs; 

- Carrying out architectural work, including masonry, roofing and other finishing; 

- Water, irrigation, sewage and fire networks; 

- Electrical installations including switching and transformer stations and exterior lighting; 

- Energy production; 

- Telecommunications, including voice and data networks; 

- Supervision system; 

- Integrated security system, including safety signs, automatic fire and gas detection system and access control system; 

- Mechanical installations and equipment – HVAC, including the associated electrical installations; 

- Various infrastructures, namely access and car parking; 

- Landscaping. 

In addition to the above, other procedures had to be carried out: 

- Boreholes to assess the foundation capacity of the site; 

- Drawing up the ‘as-built’ project and the operating and maintenance instructions; 

- The operation and maintenance of the installation during the start-up and trial service periods, technical advice and the training of the client's operating team. 

As far as the construction process is concerned, most of the buildings have reinforced concrete foundations on which a metal structure rests while roof and façade are covered with metal sheet: 

- Pre-treatment hall, which has a floor area of 50x40m2 and a vertical clearance of 10m; 

- Biomethanisation feed building, which has a floor area of around 20x20m2; 

- Biomethanisation building, which has a floor area of 55x14.60m2; 

- Mixing building is 25.00x8.50m2; 

- Vegetable fraction building, with a floor area of about 80x30m2; 

- Composting buildings, with a floor area of around 70x30m2; 

- Compost reception and refining building, which has a floor area of around 110x30m2; 

The exceptions to this type of foundations are: the office building, composting tunnels, reception and biofilters area and other technical buildings that, due to the process requirements, have a traditional reinforced concrete structure.