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Pentland Plants commercial greenhouse

Pentland Plants wood fuel case study

  • Location: Loanhead, Midlothian
  • Wood fuel usage: heating for commercial horticultural glass houses
  • Installation date: November 2006

Reasons for changing to woodfuel

Pentland Plants was the first horticultural business in the UK to switch to woodfuel and, at the time, it was the biggest privately funded biomass project in Scotland.

Aided by the Carbon Trust, a business energy audit and evaluation of the site requirements was undertaken and a range of renewable technologies considered. Biomass was judged to be the easiest and most cost effective method of meeting the business energy needs. The decision to change to woodfuel was taken in an attempt to reduce the annual heating costs of £300,000.

The audit identified the need for a robust and simple system. The company directors undertook several site visits to Austria, Denmark and Germany to research and investigate European technologies that would be most suitable for their needs. They also sought advice from professional organisations which, combined with their personal research, has ensured a reliable installation.

System features and benefits

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A wood fuel boiler was connected to the existing heating system in the company's glass houses to supersede the existing oil boilers as the primary source of heating.

Although the oil boilers are not required for daily heating, space allowed their retention and they were in good serviceable condition, so it was sensible for them to be retained to provide extra capacity and security for the future.

The fuel storage shed contains a robust walking floor system that efficiently moves the large quantities of wood chip to the boiler.

Wood fuel supply

Pentland Plants sources and produces its woodfuel through its own wood fuel business, Pentland Biomass. Roundwood is purchased directly from local forests and stacked to dry for a year to bring down the moisture content before it is chipped into fuel.

The annual woodfuel consumption warranted the company's own investment in woodfuel processing equipment, which has been funded through the significant fuel cost savings and the Scottish Biomass Heat Scheme.

This self-supply fuel model further reduces the costs of their heating as well as creating a potential new income stream from sales of woodfuel to third parties.

Installation issues

Very little modification was required to the existing heat distribution system due to spare pipe work previously installed in advance of business expansion. This made the retention of the original oil boilers simple.

Lessons learned

  • Underground fuel storage would allow more space for storing roundwood on site
  • Dealing with the same boiler manufacturer representative throughout the installation process can smooth the process
  • A large area is required to produce and store a large volume of wood chip for self-supply
  • Large enough chip storage to run your system for a suitable time, in case of breaks in production, ensures continuous operation of your boiler
  • Plan for and allow the appropriate time to gain planning approval for your development, if required.
  • Planning issues should to be addressed at the earliest opportunity to reduce delays
  • Planning permission for the fuel storage shed and boiler house proceeded without delay, however the flue height requirement for the boiler slowed the process

Facts and figures

Note: figures are approximate

Building
Heated area 21,000 m2
Heated volume 75,000 m3
Fabric Glass and aluminium
Heating system
Boiler manufacturer Reka
Maximum boiler output 2,000 kW
Fuel type Wood chips
Fuel specification
  • Moisture content: <40% (M40)
  • Particle size: 80% of chips are <45 mm (P45)
Store capacity 180 tonnes (800 m3)
Back-up/top-up system Existing oil boilers (2 MW) retained
Fuel consumption, costs and savings
Weekly woodfuel use 270 tonnes (900 m3) at peak 45 tonnes (150 m3) during summer
Annual woodfuel use 2,500 tonnes
Annual energy consumption 8,000,000 kWh
Annual CO2 savings 2,500 tonnes
Wood fuel cost £125,000
Annual fuel cost saving at 2008/09 prices £256,000
Payback period 1 year (due to high oil prices during 2008)
Installation cost and funding
Boiler system £260,000
Funding source Private finance
Funding support rate n/a
  • Significant financial benefits over oil alternative
  • Secure fuel supply chain - self-reliant
  • Investment in woodfuel production machinery possible through fuel savings