Chris Franklin, MD at Ranheat Engineering – a leading UK manufacturer of wood combustion equipment – continues his series of articles exclusively for Furniture and Joinery Production. This issue, he looks at what to do with wood-waste in the summer. 

Some companies have seasonal variations in output of product, some don’t. If your output varies over the year, so will your wood-waste output.

With the current situation in Ukraine, it makes perfect sense to heat your factory using the wood-waste you produce. But what do you do with it in the summer?

Well, there are several options depending on the equipment you have. A simple warm air heater is supplied as standard with a summer winter diverter. In the winter the hot air is blown inside the building, while in the summer it blows into the atmosphere.

Some may feel this is a waste of energy and, well, yes it is, but it is still more environmentally friendly than sending it to landfill. 20 times more greenhouse gasses are emitted from decomposition than from combustion. So, it’s still better to burn and blow than drop and rot.

For boiler-based systems, you need a summer dissipator. A large heat exchanger is mounted externally to cool the water and blow the heat into the atmosphere. This enables the boiler to burn the waste, but not to use for heat again.

If the boiler is on the Renewable Heat Incentive, then this is a non-eligible use and will not qualify for RHI payments. It needs to be on your schematic and OFGEM need to be aware of its presence.

Another option is briquetting the wood-waste and placing it in storage for use in the winter. The problem is that the briquetting machine uses a lot of electrical power. So, conversion for storage is expensive. It all takes up a lot of space as the briquettes are bulky to store and some insurance companies see them as a fire risk.

One solution would be a bulk storage silo, which would allow fuel produced in the summer to be safely stored for use in the winter.

Alternatively, you can make use of the Organic Rankine cycle. Still under development, the Organic Rankine Cycle ORC is basically a way of producing electricity from hot water and is a well- documented Physics law.

It’s based on the refrigeration cycle: if you compress a gas, it gets hot, and if you expand a gas, it cools. Gas fuelled fridges, for example, were available in the 60s.

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