Wood as fuel: grow it, burn it

Nothing is as handy as oil. That’s why we got addicted to the stuff. But if you’re up for a challenge, planting trees is a much better option for the planet.

If you’re considering growing your own wood fuel know that it will require planning, suitable land, a storage area, labour, skill and appropriate equipment.
Having said that, wood fuel is probably the most sustainable, renewable and value for money source of energy suited to Irish conditions.  

Wood fuel types 
There are three main wood fuel types: firewood, wood chip and wood pellets. 
Firewood is often the most appropriate option if you wish to grow your own. It can be burned in a woodstove or a log boiler providing all your hot water and central heating requirements.  
One of the great advantages of firewood is the minimal handling and processing required producing a very good fuel. It is also cheap. A distinct disadvantage is that manual feeding is required so it may not suit people with mobility issues. 

Wood chip may be a suitable option if you have a (very) large heat requirement. If you have your own timber supply, the wood will need to be chipped. You can either buy your own or hire in a powerful wood chipper for a day.  
Making good quality wood chip is not as easy as it sounds as moisture content, dust content, size of particles, etc. all have a major bearing on the fuel quality produced. There is also the cost of the hire and fuel for the chipper.  

Wood pellets are highly compressed sawdust. But be warned: this is an industrial process and can’t be replicated successfully at home! 
 When buying, choose these products from companies that participate in a reliable quality assurance scheme. 

Before you start 
There is a wide range of both conifers and broadleaves that will make good fuel. You can start by having a look at what is doing well locally. This will ensure that they are suitable and will help the trees blend in with the surrounding area. 

Rather than getting fixated about a particular tree species, it is much more important to plant the right tree in the right place.  

What is the soil like – damp or dry, acidic or alkaline? Is it exposed or sheltered, is it a frost hollow? Are animals such as deer and rabbits likely to damage the young saplings? Your local Teagasc Forestry Adviser in ROI or DARD Forest Officer in NI can help you answer these questions. The adjoining tree species table may also help you choose the right tree for your site.  
Attractive forestry grants may be available to get you started (see info) but bear in mind that by establishing a woodland, you will be legally required to retain it. The financing available may be attractive but it is a one way street, so be forewarned!  
Another option is to purchase an existing woodland. Occasionally small woodlands come up for sale and present great wood fuel growing opportunities. However if you are planning to build a house within the woodland, it is essential to consult with all relevant authorities prior to getting into the planning phase as several limitations may arise. 

Plot size  
The amount of land required to grow some wood fuel can be surprisingly small but if you wish to be fully self-sufficient in central heating and hot water for an average-sized house then you will need about three hectares.  
If you will manage your woodland as a coppice (see Management section), divide this area in ten different annual sections (or coupes) so that a tenth is cut each year. This means that after ten years you’ll be back at the first coupe.  
These three hectares should give an annual production of about nine tonnes of well-dried firewood. This is the equivalent of about three thousand litres of home heating oil. 

Moisture content and storage 
Most tree species make good firewood. The crucial issue is moisture content.  

A cubic metre of freshly cut wood weighs roughly one tonne and (usually) has a moisture content of about 55 to 60 per cent. After one year of drying in appropriate conditions, it will lose 300kg of water. After drying for another year, it will have lost another 100kg of water. This will give a moisture content of about 30 per cent. 
For example, one tonne of spruce firewood with a moisture content of 20 per cent has a similar calorific value as one tonne of ash firewood with the same moisture content. However, because ash wood is denser, one tonne of well dried ash will result in a smaller volume and will therefore require less storage space. 
To give you an idea of the size of the shed you will need, a thousand litres of home heating oil has a volume of about one and a half cubic metres. Wood pellets replacing 1,000l of oil will require double this storage space; firewood logs four times this volume while wood chip will take up eight times the space! 

Management options 
As the trees grow, they will start crowding each other out. This process will start when the trees are between ten and twenty years of age and it’s only then that you will start getting free fuel. 

By removing poorer quality trees you will be providing more growing space for the remaining trees; this thinning process will provide substantial volumes of wood fuel and will encourage ground flora, benefiting wildlife and leading to a richer ecosystem.  

If you don’t want to generate wood fuel by thinning your woodland, regular coppicing is another great way to grow your own wood fuel. This process can start once the trees are ten to fifteen years old. Certain tree species will sprout producing multiple stems when cut at the very base of the tree. This operation can be repeated many times. Suitable species include ash, sycamore, willow, alder, hazel and oak. 
Coppicing takes place in winter and the new shoots will appear the following spring. The number of years between cuts depends on tree species and use but is usually every eight to twelve years in the case of wood fuel production. 
A modern take on coppice is short rotation forestry (SRF). Extremely fast growing willow varieties are grown on two to three year rotations. Large agricultural machinery is required and it’s therefore not a realistic option for homeowners. Harvesting willow on a small scale can be very difficult and is very time consuming but it can be done, for example when used in conjunction with zero discharge sewage treatment systems.  
In most cases, you will need a felling licence before you can cut down any trees (NI and ROI).  How to go about this, application forms and worked out examples are available from Teagasc and DARDNI.  

For specific queries in relation to felling regulations, contact your local Teagasc Forestry Adviser (ROI) or DARDNI Forest Officer (NI).

Harvesting and processing  
It is absolutely essential to dry wood thoroughly before burning, whether for fire wood or wood chip, as moisture content is directly related to calorific value (how much heat you get out of the fuel). That is why ash has an excellent reputation as a firewood because of its naturally low moisture content.  

It is necessary to remove the wood from the forest to dry it sufficiently. Crosscut (and split if necessary) the wood and stack in a highly ventilated area covering the top while leaving the sides open so that the wind can blow through it. Another great place to dry your wood fuel is by stacking it in an old fashioned hay shed. At least one and maybe two years of drying in good conditions will be required. 
Probably the most useful tool to have is a well maintained chainsaw. It is used to harvest your trees, crosscut the timber and even to process small amounts of firewood. However, firewood can be produced much more efficiently by using a mechanical firewood processor. You can either consider buying one or hire one for the day.  

There are several ways to extract timber from the forest. For the homeowner, either a quad bike with trailer or a small tractor are the handiest solutions. 

The above mentioned tools are very useful but they are also dangerous and accidents do happen. Make sure that you know how to use equipment safely and wear all necessary protective gear. 

It is clear that growing, harvesting and processing your own wood fuel is not for the fainthearted. It will require time, good health and skill. However, it can be very cost effective, benefits both the local and wider environment hugely and above all is deeply satisfying.

All photographs courtesy of Teagasc

Grants, felling licence and general advice: ROI grants apply to minimum 0.1 ha (1/4 acre) www.teagasc.ie/forestry – know that some requirements, e.g. for felling licenses, are due to change with implementation of the new Forestry Act; NI Forest Service www.dardni.gov.uk/forestry – know that grants for the 2015/2016 planting season are to be announced late autumn 2015. 

Quality assurance schemes: Önorm, DIN, WFQA 

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Steven Meyen

About Steven Meyen

Steven Meyen has worked in forestry since the mid-eighties with experience in Belgium, Nepal, Rwanda and Ireland. Since 1999, he has worked as a Forestry Adviser with Teagasc providing independent advisory and training services to forest owners. www.teagasc.ie/forestry

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