Stump Harvesting for Biofuel

FEG Symposium 2009

Jack BarnesBiomass Manager

Scottish Woodlands Ltd.

University of Cumbria Newton Rigg

9th September 2009

Introduction:- Why Stumps

Scottish Government Targets

• 50% Renewable energy by 2020

• To substitute SRW and fossil fuels with an additional source of fibre.

Two companies based in south Scotland working together to provide AW Jenkinson with 120 000 tonnes of forest residue chip per annum for supply to the Eon Plant.

What Next?

• A source of non roundwood forest derived chip was required.

• Two pairs of stump shears were acquired by Dick Bros and a further four sets were purchased by SWL with SBSS grant assistance.

• These were mounted on 360 excavators.

Stump Shears

Stump Removal

• A protocol was developed for stump removal• UPM Tilhill, Euroforest and Scottish Woodlands

came together with the Forestry Commission to produce the industry protocol and operating procedure. This is the “Stump Harvesting Operational Control” document.

• Forest Research launched the finished document in April 2009.

The excavator mounted shears lift the stumps and present them for cleaning alongside the brash mat.

The excavator mounted cleaner lifts the stumps and drops them onto the Grid to clean them before presenting for

extraction to roadside.

A modified forwarder extracts the split stumps after a weathering period.

The modified forwarder has a solid tray in the base that can be tilted to remove soil, a rear headboard and extra

bolsters.

Following a further weathering period and possibly a secondary cleaning, which reduces the soil % from 20-30 to around 10 to 15%, the stumps are transported to the

processing facility at Lockerbie.

There has been a change in the haulage system to use dedicated self loading wagons specifically designed to haul

stumps.

Yet more pics

The processing facility

• This is an independent operation set up by a large local harvesting contractor with the assistance of SBSS grant aid.

The stumps are initially put through the cleaner….

and then through the shredder…..

to produce the hogfuel chips.

These are then collected from the processing facility for use at the power plant.

Site SelectionIt is vital that correct sites are selected for de-stumping. There are many factors determining this selection including:

• Soil type• Distance from the processing facility• Available stacking / storage space for stumps• Restocking timelines• Access restrictions• Slope• Environmental Factors, e.g. archaeology, riparian zones • Size of site (minimum of approx 6ha)

De-stumped Site

• If the correct sites are selected then it is possible to leave a site that will need minimal works to allow restocking.

• It is important to remember that some brash mats and stumps will remain, only about 60% of the site is de-stumped on average.

• Some additional drainage will still be required on most sites.

De-stumped and awaiting extraction.

Diagram of a Working Site

Potential Benefits to the Grower

• There should be some saving in ground preparation costs, depending on the site requirements post de-stumping.

• Further work into these costs is currently being undertaken.

• Easier access across the site for restocking, establishment operations and also sporting uses.

• Potentially reduced Hylobius activity due to removal of breeding sites.

• Possibly faster establishment due to increased site cultivation.

Potential Site issues post De-stumping.

• Higher weed growth, de-stumping operations tend to favour better site types.

• Potential soil erosion, following the protocol should minimise this, (max allowable slope is 20%)

• Possible larger carbon release than other ground preparation operations. Limited data at present, and we do not know the long term effects. The “big picture” approach needs to be taken. More mineral soils have less of a carbon issue.

• Embodied carbon in the operation, lots of large plant required to produce the fibre.

Current Position

• The south Scotland project has de-stumped a total of 500 ha since January 08, yielding approximately 100t per ha.

• In 2008 we delivered 59 000 tonnes on the contract, of which 22 000 tonnes came from forest residue chips.

• In 2009 to date we have delivered 61 000 tonnes on the contract, of which 14 000 tonnes came from forest residue chips.

In Conclusion

• Stump harvesting is producing a useful additional fibre source.

• The Industry has developed standard protocols for methods of operating and site selection.

• Soil % has been a major issue but operating developments have already reduced this by 50%.

• Specialist transport units have been developed and the processing infrastructure is in position to handle significant volumes.