Minimising Effluent Treatment Impact

A large brewer wanted to reduce their Anaerobic Digestion Effluent Plant steam demand. The site was using 10% of their steam on the preheating demands of the plant worth £215k/year of natural gas.

The primary goal was to develop a solution to satisfy the effluent plant heating demand using alternative heat sources to reduce the site gas bill and CO2 emissions.

What we did

Several different technology options were reviewed based on fit of solution and financial viability:

  • Regenerative heat recovery from Effluent Plant outflow  
  • Heat recovery from new refrigeration plant cooling tower water or heat pump
  • Heat recovery from a pasteuriser cooling tower
  • Heat recovery from a steam boiler condensing economiser
  • Addition of  a biogas CHP to the Effluent Plant

The above were all analysed whilst taking into account:

  • Feasibility
  • Risk
  • Cost (CAPEX or financed)
  • Payback (ROI)
  • Lifetime Profitability (NPV)

How we did it

We completed in depth data analysis of the effluent plant heating demand vs potential heat sources. The half hourly profile of heat demands is often poorly understood leading to heat being dumped when demand is low or being in short supply during demand spikes. One of the key challenges was the effect on seasonal temperature variations affecting the capability and requirements of the plant.

The above technology options were specified and modelled to see their performance. This included variation of each type of technology such as: 

  • Heat exchanger suitability: Spiral, Corrugated Tubular and Wide Gap Plate
  • Biogas CHP modelling with various heat recovery options
  • Gas Boiler condensing economiser heat recovery system
  • Fridge plant heat pump vs straight recovery from existing heat rejection loop

With extensive knowledge on energy systems applied within the brewing industry we were able to successfully design several costed solutions to the problem. This included:

  • Identifying viable solutions through initial modelling
  • Carrying out site audits with plant operators and equipment suppliers
  • Specifying and costing the optimum solution and calculating financial metrics such as ROI and NPV.


The project showed a phased implementation of a condensing economiser and a Biogas CHP provided the optimal solution to offset the heating requirements of the effluent plant and maximise return on investment. Providing an ROI of 2.1 years and a NPV in excess of £3M over a ten year period.

The project is now being implemented with Carbon Architecture’s support.

The site’s Engineering Manager said:

Reducing site carbon emissions is key for us to meet our environmental targets. Carbon Architecture’s work has allowed us to make the best decision on how to tackle our Effluent Heating Requirements. We look forward to working with them on implementation.


  • Customer – Brewing
  • Plant – > 4.5M hl / Annum
  • Cost Saving –  £880k per annum
  • Return on Investment – 2.1 years
  • Lifetime Profitability (NPV): £3.2M over ten years