- Renewable Energy
Selecting fuel for your biomass installation
The type of biomass fuel selected impacts on all aspects of a project – design, specification and economics.
Fuel selection should therefore be considered from the very start of the planning process, and selected before progressing to boiler and equipment choice, site design and economic appraisal. When selecting a fuel, take the quantity, quality, and price into account. Consider the terms you require to make sure that you have good price stability for the long term. The best combination can sometimes be found from a source and supplier close to your site. The most likely options for a horticultural business are forest wood, straw, and wood waste.
Key factors governing choice of fuel:
- Reliability of supply: What fuel is available, where is it located geographically and are other users competing for it?
- Delivery: What is required to receive, offload and get the fuel into store quickly? An important factor in fuel cost is time taken for delivery, not the distance travelled. Ideally the fuel should be loaded straight into storage. Consideration needs to be given for access, vehicle manoeuvring, and height clearance required by different types of delivery vehicle.
- Storage: How much fuel does the store need to hold? There is a cost balance between the optimum size of store and the number and frequency of deliveries required. Consider how many hours of continuous full load operation you want to achieve and work back from there. The store should be able to take one full load on top of an already partially filled store. This avoids ordering part loads as most fuel suppliers charge a price premium for these.
Fuel prices vary significantly by type of fuel and there are also seasonal variations. For wood-based fuels there is a short term upward price trend. This is because supplier costs (especially transport) are increasing. Also the Renewable Heat Incentive (RHI) is set to increase demand, and this is likely to drive up prices as more customers compete for fuel supplies. Although demand may initially outstrip supply, increased demand and profits are expected to bring new suppliers and presently unused fuel materials onto the market, as well as encouraging investment in infrastructure. Taking all of these factors into consideration, the demand / supply situation is likely to balance out over the medium to long term.
Factors affecting fuel cost:
- Location in relation to raw material supply
- Delivery duration and distance
- Delivery volume (capacity & contract volume)
- Delivery vehicle
- Delivery frequency
- Seasonal factors
- Moisture content (%)
- Calorific value
- Form of delivered fuel — e.g. slabwood, woodchip, pellet (influences processing labour)
- Quality of woodchip / pellet (influences processing technology)
- Source type — virgin timber, reclaimed wood, arboriculture arisings, waste, etc.
- Contracting type — buying fuel by weight, volume, or energy
- Local demand compared to competing markets
There appears to be adequate wood in the UK to supply the present and short-term demand for biomass fuel in the UK. However, the biomass wood supply chain is complex and there are numerous potential sources of various grades of raw materials for both 'virgin' wood fuels and various grades of waste wood (both untreated and treated). Many current and planned biomass installations are committed to use virgin wood fuels derived from sustainable forestry sources due to permitting and consent issues.
The UK availability of raw materials for the production of virgin wood fuel is limited, and the most economically viable raw material here is small diameter round-wood (sometimes called chip-wood). The increased demand for this raw material has already resulted in significant price increases during 2010/11, with rises of up to 50% being experienced in some areas.
On the other hand there are still a large number of other potential wood-based fuel materials that are currently not commonly used for biomass fuel in the UK. These include forestry residues, sawmill residues and reclaimed material. Also, after oil and gas, wood is the largest traded commodity in the world with vast quantities of good quality chip available overseas. This is normally traded at a low price. Provided that plant health issues relating to the import of wood-chip can be overcome, the availability of this material is likely to moderate future price increases to some extent.
There is a lot less competition for straw as more specialist equipment is required to burn it. The existing market for straw centres around animal feed and bedding and producers and buyers are usually some distance apart. This means transport costs and delivery logistics limit its value. Biomass fuel project therefore represent a good opportunity for farmers to develop new, more local market for straw. Alternatively they could divert it to their own biomass installation and save on the handling and disposal costs they would otherwise incur.
Some biomass fuel suppliers are willing to enter into long-term supply contracts where prices are indexed linked to take account of inflation. In some cases the supplier may even offer a fixed price contract for a number of years – but you should be prepared to pay a higher than market price now in return for this price stability over time. Examples of this fixed price arrangement are particularly common at the moment for supplies of straw as a fuel.
It is also possible to negotiate lower rates if you are buying significant supplies outside of the peak heating season months when suppliers‘ cash flow is limited. However, to take advantage of this, a project will need to have the space to potentially store surplus fuel onsite and also to have a degree of fuel-flexibility in their biomass combustion equipment. Most biomass boilers need to be re-commissioned if a significantly different type of fuel is going to be used, so consider this before leaping on to a 'bargain' batch of cheap fuel.
You must base the project’s economic case on both a realistic, sustainable price and source of supply. It is important to include a fuel price sensitivity analysis and model both high and low fuel prices within the business case.
It is critical that the quality of the fuel is matched to the fuel feed and combustion equipment being installed. Equipment manufacturers specify the required fuel quality parameters required for efficient and reliable operation. Typically the European specifications are used which have been adopted by the UK as BS EN 14961:2010, although other standards such as the Austrian fuel standards are also frequently still used (although these have, technically, been superseded by the Euronorm standards).
The most important parameters to be taken into account are:
- The species / source
- Size of largest and smallest particles. Moisture content (this affects the net calorific value of the fuel)
- Ash content
- Ash melting point
- Levels of some elements such as Nitrogen and Chlorine
- Presence of fine materials
For wood fuels, particle size is very important. This does not usually apply to straw, as the fuel is usually fed in as de-stringed bales and a straw chopper is used. However, straw is prone to containing large physical contaminants such as stones which can impact on equipment reliability. Biomass fuel quality is a complex subject and full explanation is not in the scope of this publication. The main principle is that fuel quality needs to be considered throughout all phases of any biomass project. Failure to do so may result in lack of reliability and lower efficiency of the equipment as well as breach of equipment warranty and permitting conditions.