Life Cycle and Harvesting of SRWC

SRWC crops are generally harvested every 3-4 years. This takes place during the winter (November to March) when the trees are dormant. This is important for the moisture content of the woodchip produced and for the cycle of nutrients through the coppice cycle.

The methods employed during harvesting depend largely on the intended market for the crop.

The three methods of harvesting are:

Direct cut and chip harvesting – The crop is cut and chipped in one operation on site. The chipped product is immediately ready for storage. This is typically undertaken using a modified maize/forage harvester but can be difficult at wet sites where the size and weight of the machinery can cause soil rutting and compaction.

Rod harvesting – The crop is simply cut and bundled. For planting material or bundles of willow for crafts the rods can be cut again and bundled into uniform 2.5m lengths either on site or at another location. There are very few machines currently available to harvest willow in this manner, those that are available in the UK being able to handle small diameter willow only.

Billet harvesting – The crop is cut and cut again into 5-15cm lengths on site. These billets are then piled to dry at the side of the field before further processing for combustion. This is currently the most promising method of harvesting for willow allowing the billets to be milled into a fine dust for co-firing. The machinery typically used in this operation is a modified sugar cane harvester.

The average SRC plantation has a life expectancy of between 25 and 30 years, removal of willow coppice is relatively straightforward. The coppice is harvested and allowed to start growing then sprayed with a glyphosate herbicide. After a year, the stools can then be disc harrowed or ploughed to break up the root system.