Burning biomass is a clean way of generating electricity and is often called "carbon neutral." Carbon released into the atmosphere when the material is burned is equivalent to the amount absorbed by the plant during its growth cycle.
This Steven's Croft biomass power project involves the use of various renewable wood-based fuels including forest wood and agricultural residues, urban wastes, and energy crops, all of which are readily available in the local area.
Over 480,000 metric tons of fuel is needed to power the station every year, made up of the following:
60% sawmill co-products and small roundwood
20% short rotation coppice (willow)
20% recycled fiber from wood product manufacture
We project-managed the £90M development, from design and construction supervision to commission and takeover. Construction included the power station in Steven’s Croft, a fuel processing facility, and 16 miles (26 kilometers) of underground electrical cable connecting the station to Chapel Cross substation. Scottish Power completed the installation, which incorporates a long directional drill beneath the M74 motorway.
The fuel processing facility was designed to store and blend all various fuel sources to provide an homogeneous fuel. It includes up to 14 days of round wood storage, a facility for reception of pre-chipped fuel, up to 212,000 cubic feet (6,000 cubic meters) of covered chipped fuel storage, a roundwood chipping facility, and fuel reclamation and forwarding equipment, with systems for final preparation of the fuel before delivery to the power plant.
Boiler conditions were designed to allow the best efficiency at 537°C, 137 Bar, and with a capacity to raise 126MWth of energy. The high steam conditions dictated the need for specialist corrosion resistant materials in the high temperature components and to control fuel quality.
The station is regulated by the Scottish Environmental Protection Agency. The main applicable legislation is the Waste Incineration Directive and the Large Combustion Plant Directive, which defines acceptable emission levels. These regulations demand state of the art equipment, which comply with Best Available Technique guidance. The power station’s emissions are therefore reduced to the minimum level achievable.
The site's surface water drainage system was designed around the sustainable urban drainage system (SUDS) guidance, to retain water on site and disperse through natural infiltration in the first instance.
Rainfall is captured in swales and is retained until the water disperses. On overflow, the surface water is sent through a wetland area, where it is naturally cleaned before flowing into a watercourse. Aqueous emissions are restricted to blowdown water from the boiler and water treatment effluent. Effluent is discharged at extremely low flow rates to ensure no adverse impact to local water quality.