Split Logs vs. Pellets

The debate between pellets and more traditional split log fuel is one that has been discussed at length; both fuels have their advantages and disadvantages.
The main considerations for anyone choosing new heating systems are:

  • The cost of the fuel & availability of fuel
  • Ability to handle the fuel
  • Storage
  • Lifestyle

There are a number of factors that dictate the cost of fuel;

  • Supply & demand.
  • Location.
  • Quality of the fuel.

A good quality fuel needs to be seasoned until the moisture content is below 20%, this normally means for a minimum of 12 months, often longer depending on wood type and storage conditions.

Cost & Availability – Split Logs

Seasoning is required to reduce the moisture content of wood as a fuel, regardless of whether it is used in a boiler or not, even wood for a conventional open fire burns more efficiently if seasoned, unseasoned wood is very inefficient, the gases and acids released are harmful to the boiler and produce excessive smoke and ash. Seasoning involves storing cut timber for a period (>12 months) in dry well ventilated conditions to reduce the moisture content. If you are purchasing from a supplier, seasoned timber is a condition that is charged at a premium compared to freshly cut fuel. Freshly cut fuel is often available locally for purchase but this means you would need an area within your property for seasoning the freshly cut timber and storing the seasoned fuel. Whether you choose to purchase seasoned timber, freshly cut or choose to grow and season your own timber, Attack would highly recommend investing in a moisture meter. A moisture meter will confirm whether the fuel you are purchasing is as the supplier claims, or if you are seasoning your own fuel it will allow you to confirm when the moisture content is ideal for burning. Our suppliers will often provide moisture meters as part of their packages. With many companies and individuals offering timber for sale, there is a greater opportunity to bargain for the best price, and with the option of having your own coppice, split logs is by far the cheapest biomass fuel available.

Cost & Availability – Pellets

The material used to make Pellets should ideally have been seasoned before turning into pellets, variations in the quality of the material used to make the pellets often leads to variation in the quality of the pellets themselves, affecting efficiency and performance of the pellet burner. A reliable Pellet supplier should supply you with consistent quality pellet. The manufacturing of pellets has a higher carbon footprint than split logs. The processes involved from turning the raw material to pellets can  involve dryers to force the moisture from the raw material, then the pellets need to be formed and lastly delivered – this process increases their carbon footprint versus split logs. The fuel cost of the pellets is therefore likely to increase at the same rate as other forms of fuel. With little option but to purchase from a pellets supplier, pellets are the more expensive option.

Handling the fuel – Split Logs

Handling split logs is potentially one of the drawbacks of the fuel. If the split logs are purchased direct from the supplier then it may be possible to minimise the manual handling from the storage area to the boiler. However if you intend to harvest your own fuel then there may be much more handling and preparation involved. Whichever method you choose there is no denying the fact that you will need to load the boiler with fuel when it is required, put simply a split log boiler in it’s simplest form is not an automated system. There are ways of minimising the amount of times that you have to refuel the system, by choosing a larger accumulation tank, and possibly a larger boiler, as the fuel chamber increases with the kW rating of the boilers we offer.

Handling the fuel - Pellets

A well designed Pellet heating system will have zero handling. Pellets can be delivered in large quantities and blown into the hopper, ready for the auger to feed the boiler, this eliminates any need for handling. This service would normally be included as part of the pellet delivery charged at a weighted rate (normally per tonne). There is a possible alternative where you can get the pellets delivered in bags, however this would involve loading the bags into the hopper.

Storage – Split Logs

The amount of storage you require largely depends on how much heat you require, ideally an area large enough to minimise replenishing regularly, however should space be at a premium a smaller area is possible but will need replenishing more often. For the sake of convenience and minimal handling, the storage area should be as close to your boiler as possible. You will need to consider the access to your boiler more carefully as you may need to carry large volumes of logs over a prolonged period. The logs used for your boiler should be kept dry at all costs, as wet wood will detrimentally affect the system, not giving the required heat output, and costing you more due to poor efficiency.

Storage for seasoning

When seasoning wood the wood should be kept dry, however getting the wood rain wet doesn’t mean that it can not be used. When seasoning, it is the moisture deep within the wood that we are trying to extract, this will happen naturally in a well ventilated area over the course of 12-18 months. Surface water caused by rain can be dried, simply by keeping the wood dry for a few days undercover.
Storage – Pellets
Ideally the storage area should be as large as possible, this offers greater convenience by having to place fewer orders, and allowing you to bargain with the pellet supplier as they often offer a reduced rate for larger deliveries (some pellet suppliers even refuse to blow feed for orders under 3 tonne). Unlike split logs, keeping the pellets dry at all times is absolutely crucial. When pellets make contact with water they expand and turn into a slush, when this happens they can not be fed into the boiler, even if dried. The home owner has two options in terms of storage;
1. Keep minimal amount of pellets (approx 600kg), and have smaller quantities delivered, multiple 15kg bags or jumbo bags. These would then need to be emptied into a smaller hopper bin.
2. Have a large hopper which is capable of storing 3tonne or above of pellets and have the pellets blown fed upon delivery.

Lifestyle – Split Logs

When someone chooses to install a split log boiler it is likely that one of the main reasons is to reduce their dependency on fossil fuels, but this is also a lifestyle choice. With mains gas, LPG and Oil, we have grown used to flicking a switch and getting heat without any labour or thought as to where the fuel is coming from, this is not the case with a split log boiler. Whichever split log boiler you choose from Attack it will involve manually loading the boiler when it requires fuel. This frightens some people as they are used to the more conventional fossil fuel heating systems, however for some, who recognise the massive savings by adopting split log the manual labour element is negligible. Coupling the boiler with an accumulation tank means that there is a high level of convenience, allowing you to pull hot water from the accumulation tank when the boiler is out. Installing a split log boiler involves a little bit of foresight on behalf of the home owner to ensure they have heat when they require it.

Lifestyle – Pellets

Pellets are a convenient solution for those who require a hands off approach to their heating, but must be prepared to pay slightly more for their fuel. A pellet boiler will feed itself by using an automated auger feed. Like an LPG or Oil system, the customer does need to keep an eye on the level of fuel as the stored supply diminishes. The pellet silo, whether large or small will need to be replenished when deemed suitable by the homeowner, preferably before it runs empty. Pellet boilers offer the same level of automation and control offered by oil and gas boilers.


Welcome to Attack Biomass UK!

ATTACK offer a range of Biomass boilers, these include the split log boiler range DP, DPX and DPX Lambda and the 30S Pellet boiler. The ATTACK range of boilers offer:
  • Low running costs
  • High efficiency
  • Low maintenance and a low carbon footprint
The DP range of boilers is MCS accredited and eligible for the proposed Renewable Heat Incentive.