Biogen, Merevale, Warwickshire

Every so often, a job presents itself which is a little unusual, and Biogen was definitely one of those.

In April 2014, Coles Grant & Jones were approached by a Main contractor in London, via word of mouth, asking if we would be interested in looking at a project in Merevale, Warwickshire, for the construction of an anaerobic digestion plant, the aim of which is to process 45,000 tonnes of food waste per year, and to generate 2MW of green electricity enough to power approximately 4,500 homes.

Anaerobic digestion is the process by which organic matter such as animal or food waste is broken down to produce biogas and biofertiliser. The word “anaerobic” actually means ‘in the absence of oxygen’, and the process happens in a sealed, oxygen-free tank called an anaerobic digester.

The biogas naturally created in the sealed tanks is used as a fuel in a CHP (combined heat and power) unit to generate renewable energy i.e. electricity and heat.
The by-product of anaerobic digestion is a nutrient rich biofertiliser. This is firstly pasteurised to kill any pathogens and then stored in large covered tanks ready to be applied twice a year on farmland in place of fossil fuel derived fertilisers.

Knowing that this is a relatively new and experimental technology, we had meetings with the main contractor on a similar project upon which they were close to completion in Baldock, Hertfordshire. Interestingly, the sites are relatively self-sufficient; a substantial rainwater harvesting facility was to be installed on site to make best use of natural resources, whilst heat and electricity is generated on site as part of the process works, with only incoming fresh water supplies being provided off site, together with peripheral electrical supplies.

Keen for the association with renewable technologies, CGJ developed costs in conjunction with the main contractor, and work began on site.

As the facility is sited in a green, rural area, works had to be carried out in a controlled manner, with due care and consideration being given to neighbouring farmland.

We are given to understand that the odour created by anaerobic digestion is somewhat unpleasant, and sticks to everything in the immediate facility, requiring site operatives to take numerous showers during the working day, especially prior to leaving site! To manage the odours, the main operating building is sealed to outside, presenting a challenge of providing a balanced pressure regime to the changing area lobby, via airlocked rooms, and to provide balanced, filtered ventilation to changing and shower areas for site operatives, whilst not allowing odours to enter the office facilities.

The project was completed at the beginning of 2016.