Chip

Wood chip is ideally delivered in bulk from a tipper trailer or walking floor lorry into an underground fuel store. Other delivery methods include tipping onto covered hard standing then using a tractor with front loader / tele-handler to load into an above ground fuel store. In some parts of the country, scissor lift (also known as high lift) trailers are available that can tip directly into above ground fuel stores, but this method of delivery can encounter difficulties and these vehicles are not widely available in the Southeast.
Three further alternatives are the construction of a shallow ramp allowing ordinary tipping vehicles to tip into above ground stores; the use of chip blowers; or the use of hook-lift bins which are filled off-site and simply unloaded at the site connecting into the fuel transfer system.
As wood chip is not a smooth, homogeneous material, blowing can be slow, noisy and add to the cost of delivery. In some situations, however, such as where access is limited, blowing can be the best and easiest option.

Wood chip fuel stores are usually either square with a rotating sweep arm agitator to move the chip into an auger, or square/rectangular with a walking floor mechanism to move the fuel onto an auger at the edge of the store. The auger then carries the fuel to the boiler. Walking floor fuel stores are more expensive but utilise space more efficiently (the circular motion of a sweep arm agitator will not reach the corners of a square fuel store). All wood chip storage areas should not allow water ingress or contamination of the fuel and should be well ventilated to allow continued drying and to prevent the growth of mould.

Pellet

In London and the Southeast, wood pellet is normally delivered pneumatically (i.e. blown directly from the vehicle) but it can also be tipped. Wood pellet is a much smoother and more even fuel than wood chip and thus delivery by blowing is much quicker and quieter than for wood chip.

Wood pellets are normally either stored in pre-fabricated hoppers or in stores with a V-shaped floor built to funnel pellets into the auger at the bottom of the V. If the slope has an angle of 45º this will happen naturally under gravity. Wood pellet stores must be completely impervious to water ingress as pellets expand and can reform as one hard lump if exposed to water.

• Always have at least two delivery pipes into the fuel store, to allow somewhere for air to exit while pellets are being delivered
• Avoid the build up of static electricity on delivery pipes by using metal pipes and connecting them to earth
• Avoid disintegration of pellets by using a good quality supplier, the right delivery vehicle, avoiding sharp bends in delivery pipework and installing impact mats to avoid pellets hitting hard surfaces in the fuel store
• Avoid creation of dust through point 3 and also by using a dust sock / filter on the air exit pipe

For more information about delivery and storage options, see the London Biomass Guide, which can be accessed through our ‘Past Work’ and ‘Downloads’ pages.

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