Arriving on site one late September morning, we found co-director of
WoodForFuel.com, Gordon Mair, busy at the controls of the company’s recently delivered nine-tonne 56hp Volvo ECR88D reduced-swing compact excavator. The machine, fitted with a bespoke woodclip grab, was feeding 3m lengths of softwood into a heavy-duty chipper which was then discharging 25 tonnes an hour into a drying shed. “Feeding softwood into the chipper takes up most of the machine’s time since it’s vital to keep up a stock of fuel for our two CHP units,” explains Gordon. “The rest of the time we use the machine to load 3m lengths of softwood and hardwood at the start of our firewood production process.” We’ll come to the intriguing part of Wood for Fuel’s production process shortly but let’s start at the beginning. Soft and hardwood tree lengths are delivered to site where the ECR88D then places them from the stock piles onto the loading table. The machine has plenty of reach (7.3m) to carry out this operation from one position with the grab rotation function making the task of selecting, sorting and placing the logs an easy one. From there, the material is cut into various lengths ranging from 7 inches up to a maximum 20 inches, and then split and passed through a unique screening process. “Domestic woodburning stoves are becoming more popular and, of course, vary in size, so we are able to produce a whole range of different lengths of logs to fit most appliances,” comments Gordon. “We are quite fastidious in leaving little mess, so all of our logs are processed and then screened to remove loose bark and debris. Even the sawdust created by the processor is extracted by a suction process and deposited into a silo from where we then make briquettes, a very popular fuel for chimineas and barbeques.” Once the logs are bagged, they then await the final process before they are ready for sale where the very green part of Wood for Fuel’s production comes in. The shed that the machine was feeding softwood into via the heavy-duty chipper was used to store extra bags of logs and equipment. The notion of turning the inside of the shed into a unique drying facility for their woodfuel business was the brainchild of partners, Melvyn Percy and Gordon Mair. “Over the past 12 years our business has expanded and we were faced with not having the facility to turn around our logs quickly enough. Relying on the natural Scottish weather does not allow for consistently dry logs! Normally it takes a minimum of a year for hardwood logs to dry out naturally and make them suitable for burning in domestic log burners. The facility we’ve created using hot air to force-dry the material reduces this process to just days,” explains Gordon. “As our business is accredited by Woodsure, plus certified by HETAS as well as being BSL authorised, product quality assurance is our top priority. We started converting the barn at the end of March 2016 and were up and running just three months later with a fully integrated hot-air drying system with a large-capacity drying kiln and two bespoke CHP (Combined Heat and Power) units. The two CHP units generate all the heat and electricity needed to operate our production process and the remaining electricity is exported to the grid,” he continues. As mentioned, the process starts with the Volvo ECR88D feeding softwood logs into a
chipper. “The one thing that’s vital to our business – apart from the supply of the raw material – is the reliability of the machine loading the whole process, because if this lets us down then we are in pretty serious trouble,” continues Gordon. “We had experienced poor reliability with another make of machine when we started up last year and this consistently interrupted our production. We had had enough and decided to settle on the Volvo after having had good reports of the product’s reliability coupled with the proximity of SMT’s utility dealer, Rockbreakers UK, and their customer support centre at Stirling for complete peace of mind.”
The chipped material is stockpiled, then fed through a screening process with four sizes produced, these being dust (used for the production of briquettes), woodchip for biomass, woodchip for CHP, and oversize. The CHP units convert a single fuel – in this case the screened woodchip – into both electricity and heat in a single process at the point of use. Before the 70m³ feed hopper is loaded with the fuel for the CHP units, it has to be dried. Using two specially built drying floors, the woodchip is placed on the floor and hot air is forced through the underfloor vents. “By doing so, we can reduce the moisture content in 48 hours from around 38% to just 8% which is ideal for the burning process,” comments Gordon. “The fuel is placed into the feed hopper which lasts 6 days and then the production and drying process restarts, so again, it’s vital we have a high degree of reliability from the ECR88D to keep the operation running!”
...so the optimum size is used for fuel for CHP units CONTINUED OVERLEAF a THE VOICE MAGAZINE No32 2018 23
Logs screened prior to bagging
The ECR88D spends most of its time feeding a heavy duty chipper which...
...deposits material into storage bays within the shed
The woodchip is then screened...
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