Different levels of processing will be required for different fuel types. It’s vital to understand what skills, equipment, time and infrastructure are involved and be realistic about what you can do.
- Processing wood into fuel
- Processes involved
- Timber needs
- Equipment needs
- Infrastructure needs
- Professional input
- Planning requirements
- Quality control
- Woodfuel standards
- Renewable heat incentive
- Woodsure quality assurance scheme
- Preparing fuel for market
- Processing costs
- Risk, liability and H&S
There are various scenarios that may apply:
- you plan to harvest and process your own wood
- you plan to source wood from local woodland owners or contractors (and maybe tree surgeons) and want to process it yourselves
- you plan to harvest wood and you want it processed by someone else. In this case you need to identify and work with a woodfuel processor/supplier.
If you intend to process wood into woodfuel yourself then what happens at the processing stage is critical to the quality of the fuel you produce. Ensuring that the woodfuel you produce is of a reliable and consistent quality will lead to fewer issues down the line when using the fuel in your stove or boiler. Woodfuel quality is based on how wet the wood is (moisture content or mc), consistency of particle size, and ensuring that the woodfuel is free from contamination from other material, such as dust, soil and other fragments which impact upon the operation of your stove or boiler.
There are two main forms of forestry-derived woodfuel: logs and chips. Wood pellets are predominantly produced from sawmill or wood product processing plant residues and are made in large scale pellet mills and as such are unlikely to be appropriate for community scale production. Each wood heating system will have particular fuel requirements e.g. some boilers are designed for larger woodchip sizes than others. Before you take on the processing of your fuel you should be aware of the requirements and specifications further down the supply chain so that you are producing fuel of the appropriate type and standard for your biomass heating system.
Once harvested, wood needs to be cut to uniform lengths, stacked off the floor, in the woodland for drying and ultimately chopped into logs and transported off site for use in boilers or stoves.
Once harvested wood needs to be cut to uniform lengths, stacked for drying, transported to a processing site if outside the woodlands, chipped using a chipper and screen and transported to the woodchip boiler.
Wood pellets are produced on a factory scale by forcing dried sawdust and clean wood by-products (from sawmill or forestry activities) through holes in a rotating dye to form tight pellets.
Issue to consider
If you are processing your own wood you need to ensure that you know whether you are processing hardwood or softwood as they have different moisture contents and calorific values. If you are processing wood from a third party supplier ensure you have the correct certifications for the supply to ensure it is from a sustainable source.
If you intend to chip woodfuel yourself, you need to ensure that the wood is correctly prepared for chipping, according to the specification of the chipper being used. Your chipper provider will be able to give you the specification details.
Log processing equipment can be as straightforward as a chainsaw for which you will need training and a licence to operate. Woodchip processing requires more specialised equipment including a chipper and possibly screening equipment to provide a higher quality product. Chippers vary in size from small hand-fed chippers to machines that can chip large diameter roundwood and produce over 100 tonnes of chip per hour. It is essential to use equipment that will produce fuel to the correct specification for your boiler. Some general purpose chippers will not be suitable for producing high grade woodchip required by biomass heating systems. Buying a chipper could involve significant investment so look into the costs of buying a chipper versus hiring or leasing a chipper or contracting someone to chip your wood for you.
Review of small scale harvesting equipment (Biomass Energy centre) a provides information on types of equipment.
Log production will require space to cut, stack and dry lengths of wood. This can be done within a woodland setting, although you will need to ensure that there is somewhere dry and away from the tree drip line to stack and season logs.
Woodchip production and storage requires an area of clean hard-standing on which to site a chipper, and to store the chipped material prior to use within a boiler. This area may be on a site within the woodland or elsewhere. You will also need a covered store to put your chip when produced and before being transported to your biomass heating installation. In some cases, chip can be stored under a breathable membrane. Once wood has been seasoned and chipped, if it gets wet again, it tends not to dry out properly again so you need to keep your chips dry.
Chipping directly into a biomass boiler fuel store is not recommended as quality control procedures relating to moisture content, chip size and contaminants cannot be checked prior to use.
Consider the volume of chip that your heating system will require and hence the volume of storage needed for the woodchip prior to transportation to the heating system. If you are processing and storing away from the boiler site you will need to ensure good access for fuel delivery vehicles to collect the chip for delivery to the boiler.
If you are looking to produce woodchip, you may decide to use specialist contractors to help process your woodfuel. There are various lists of forestry professionals and contractors who may be able to offer processing services. For example, mobile chipper services may be available in your area. You should ensure that contractors have the appropriate qualifications and certifications necessary. Your local Forestry Commission rep should be able to help advise as to where to find lists of reputable local contractors. If using a contractor, you will need to consider where woodfuel processing will take place and how the woodfuel will then be delivered to your biomass heating installation.
Your local woodfuel supplier may also be happy to process your wood into woodchip for supply to your boiler. If you don’t have enough wood to meet your demand, this will be supplemented by additional woodchip from the supplier. They will agree a financial arrangement with you relating to the amount of wood, transportation requirements, moisture content/quality of timber and how much woodfuel you are buying from them.
If you don’t own or manage a woodland and you don’t want/aren’t able to process wood, it would be beneficial to contract an existing woodfuel supplier to supply your woodfuel rather than attempting to set up woodland management contracts for someone else’s woodland and then have another contractor process the wood into woodchip. This means that the risk associated with using the woodchip in your boiler sits with the woodfuel supplier rather than your community group. See the section below for more information about what you will need to think about if using a third party processor.
If you intend to work with a third party to help process your fuel, consider:
- Developing a specification of both the timber you have available and what woodfuel product you will need. Ensure you produce a clear specification based around the requirements of your boiler and that you understand what requirements your processor has for the timber they will be processing for you.
- What transportation is required for getting wood from the woodland to a processing site (if not in the woodlands) and then onto the biomass boiler. Access for large vehicles will be required at each site.
- Researching the financial implications of involving a third party processor compared to processing yourself. If you are using a third party to process your wood agree in advance and get in writing the terms and conditions of your financial arrangement whether you pay for processing and buy back fuel independently, or whether you link processing and fuel supply if both are being delivered by one party. Ensure transport is included if required.
- Who is liable for boiler fuel issues? If your fuel is being processed by a third party and your boiler breaks down subsequently due to problems with fuel quality you need to ensure you have adequately considered liability for fuel quality. Liability issues should be agreed in advance and included in any contractual agreement between you and a third party processor. Established woodfuel suppliers will have the necessary cover in place but woodland and processing contractors may not or may not be willing to take on the responsibility.
- If you supply timber to a woodfuel supplier for processing and supply back to your project, you should be aware that it may not be your actual wood that you get back – your wood will likely be combined with other feedstock at a depot and you will be supplied from the available chip supply.
If you are planning on erecting any structures or doing any processing on site, check with your local planning department to find out what permissions or permits you may need.
You must ensure that your fuel is processed to the right standard and specification for your boiler. Depending on your boiler you will need to ensure woodchip is of a consistent particle size (usually less than 5cm for small-medium sized boilers), and particular moisture content (usually less than 30% mc). Contaminated wood can cause a problem. Material such as slate, soil, grit, stones, metal, plastic and rubber can cause damage to processing machinery and if not screened out during processing can ultimately lead to boiler damage or failure. If you are sweeping up around your pile of woodfuel, dispose of your sweepings away from the woodfuel.
Woodfuel systems are designed to accept particular standards of fuel. It is vital to ensure that the fuel you produce is of the right standard to ensure the long-term operation and sustainability of the biomass heating systems you are supplying.
Woodfuel standards across Europe (EU Committee for Standardisation - Technical Committee 335) covers the physical and chemical characteristics of fuel and the source of the material.
If you are producing woodchip or logs for a biomass project that is, or will be, registered under the Renewable Heat Incentive, you will need to ensure that your woodfuel meets the new sustainability criteria due to come into force in Autumn 2015. Suppliers must comply with a greenhouse gas criteria and a sustainable forest management criteria. This will affect domestic and non-domestic RHI participants as well as producers and traders of biomass fuels.
Woodfuel Guidance sets out how suppliers may meet the sustainable forest management criteria.
Accrediting under the Biomass Suppliers List is one way smaller woodfuel suppliers can comply with the sustainability requirements.
The UK quality assurance scheme for assessing the quality of woodfuel. It is not necessary to be registered to meet the Renewable Heat Incentive sustainability criteria, but if you are supplying to biomass installations beyond your community heat project this scheme can demonstrate the quality of your fuel supply.
If you are producing logs, you will need to decide whether or not to bag your product and if so what size bags to use. If volunteers are taking logs home after a day working in the woods, bags may not be necessary. If you are selling logs or plan to offer a delivery service, bagging the logs will help with calculating costs per unit (e.g. a bag) and transporting your product to multiple customers. Larger operations may consider using 1m3 bags.
Costs will be incurred when transporting your wood between harvesting, processing and end user sites, buying/hiring equipment for processing, infrastructure costs such as hard standing and storage barns, and any third party contractor costs. The Forestry Commission provides outline standard costs of woodland management, timber extraction and processing costs:
Prior to embarking on your processing activities, you should conduct a thorough risk assessment based on the activities that will be taking place on your site/s. You will need to ensure you have the appropriate health and safety protocols and requirements in place for each stage of your processing operation. Much of the equipment involved needs specific training and is used under licence only. See the Forest Industry safety Accord (FISA) for more information on using forestry equipment. In addition, you will need to ensure you have the appropriate insurance cover to mitigate liability.