During construction of the Human Impact Building, The Living Rainforest became the first tropical rainforest glasshouse to convert from fossil fuel to renewable biomass heating with the installation of a woodchip boiler (Froeling Turbomat), producing 220kW of heat. This enabled one of two oil-fired boilers (Strebel E500 400kW) to be replaced and the heating control system to be updated. The system now monitors all glasshouses and associated areas individually and when heat is required the woodchip boiler is programmed to kick in first, with the oil-fired boiler topping up as needed – generally during winter months and overnight. This has reduced the amount of carbon dioxide we produce from fossil fuels by around 220 tonnes each year. Further carbon dioxide reductions will follow installation of the Vertical Soil Heat Exchange (VSHE) system in 2008, and consequent phase out of the remaining oil-fired boiler.

8 view of building housing biomass boilerBiomass is a term used to describe all plant and animal material apart from fossil fuels. It can be burned to produce energy, as a renewable source, although current technological advances are also enabling us to convert biomass to liquid fuel and combustible gases.

The two main types of biomass are

  • Woody – waste from forestry, untreated wood, crops grown specifically for energy and short rotation coppice, such as willow.
  • Non-woody – animal, industrial and food processing products, and high energy crops, such as oilseed rape.

The key to renewable biomass energy is a plant’s ability to capture and store energy from the sun through photosynthesis. Burning the plants as biomass at a later date releases this energy as carbon dioxide, which can be reabsorbed by the cultivation of replacement crops, neatly placing it within the carbon cycle. It is the process of reabsorption which leads biomass to sometimes be classed as a carbon-neutral fuel. However, cultivation, harvest and transport of biomass all produce some carbon dioxide, so it cannot be classed as a truly carbon-neutral fuel, although it can be kept as close to carbon-neutral as possible through efficient production, transport and use.

Efficient production

For help and advice on installation and ongoing operation of our woodchip boiler, we teamed up with TV Energy which continues to arrange our woodchip provision. The Living Rainforest’s current supplier sources wood waste from sawmills and, in the future, may also collect waste from local tree surgeons. By sourcing waste products for biomass we do not contribute to the demand for land conversion to energy crops and also prevent additional carbon dioxide production from cultivation and harvest, as well as reducing landfill.

Efficient transportation

In order to reduce carbon emissions, biomass fuel should be sourced locally to minimise the amount of fuel used in transportation. The Living Rainforest’s supplier is based less than 10 miles away and the wood used is sourced from sawmills in West Berkshire and South Oxfordshire. In addition, waste wood is transported to our supplier in bulk so that it is denser and, therefore, more efficient to carry and, once transported to The Living Rainforest, the woodchips are placed in a sizeable storage area, accommodating one large delivery in place of several smaller ones.

Efficient use

Once chipped, the wood is dried (before transportation) to increase biomass density by removing water content, making the woodchip a more efficient energy source. In addition, The Living Rainforest’s woodchip boiler is highly efficient (’91-95% across the full output range’) and extremely clean, exceeding particulate emissions limits. It is also designed with easily replacable component parts to increase its service life, thus reducing the embodied energy of the installation.

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