500kW Biomass Boiler

Companies House

Companies House is an executive agency of the Department of Business, Innovation and Skills (BIS). Its main functions are the incorporation, registering and dissolving of companies as well as the distribution of company information to the public.


In 2010 when we began working with the Environmental Management Team at Companies House, they had already implemented many energy efficiency measures across the 29,000 square metre Cardiff site. The time had come to replace the aging gas boiler plant and the client team wanted to investigate the viability of replacing the gas boilers with a biomass boiler in order to reduce energy costs and CO2 emissions in line with organisational carbon reduction targets.


Sustainable Energy undertook an initial feasibility study to assess a range of options available to Companies House in terms of plant type, specification, size and cost. This included comparing different heat supply scenarios such as new condensing gas boilers versus a biomass boiler with new high efficiency gas boilers as back up.

Sustainable Energy developed boiler house and fuel store layouts, fuel delivery strategy and logistics and completed detailed hydraulic design of all plant room equipment and the integration of the new biomass and auxiliary gas boilers with the existing low temperature hot water distribution system at the site. The engagement continued throughout implementation with support for planning approval, developing of Invitation to Tender documents, assisting with contractor appointment and technical support during construction and commissioning phases. Sustainable Energy managed the RHI accreditation process for the plant.


The biomass boiler solution comprises a 500kW wood pellet boiler with 50m³ pellet silo and 30,000litres thermal storage. Back up heat is provided by 2.3MW auxiliary gas boilers; the system design includes full integration of the biomass and gas boilers, aided by a comprehensive control and monitoring system.

The installation has now been operating successfully for over 4 years; the 500kW boiler has consistently supplied circa 87% of the site heat demand, previously met by 4MW of aged gas boilers. Ongoing monitoring confirms that the biomass boiler is meeting best practice guidelines by operating with a seasonal efficiency of over 84%.

“As a government agency we want to lead by example in meeting government carbon reduction targets.”

Gareth Leek, Environmental Manager at Companies House

Read more in the official DECC Case study