Wood pellets are a compacted type of bioenergy. They are typically made of timber waste, sawdust and agricultural waste that is dried and processed into a densely compressed cylindrical pellet measuring about 1cm long, resembling rabbit and chicken food. Because they have a low moisture and ash content pellets burn very efficiently to produce heat and electricity. As a result, wood pellets are generally used in direct burning devices such as domestic wood heaters and commercial furnaces and boilers.
The pellet market in Australia is still new but has been taken up by many consumers. Pellets are mainly used for residential heating, although there are an increasing number of commercial scale users – such as hospitals, swimming pools, retirement homes etc – using pellets to generate electricity. Pellets are also increasingly being used in large-scale coal power plants to help produce electricity in a more environmentally-friendly manner. Globally, the US, Canada and Europe are currently the biggest suppliers and consumers of pellets but significant demand is also anticipated from Japan and Korea.
Check out our blog post for more information. 6 things to know about pellets.
Source: Clean Energy Council
- Pellets can provide an economic and social boost for rural and regional communities by using local content, creating local employment and encouraging new and innovative farming techniques.
- Pellets can provide a use for wood by-products – such as sawdust – that would otherwise have no market value. As Australia is one of the top 20 producers of sawdust excess from forestry in the world, this presents opportunities for Australia to use sawdust for domestic renewable energy generation or for export. (A large global export market exists for wood pellets, with some 9 million tonnes of wood pellets traded annually.)
- Because pellets have consistent quality and size they are easy to transport, store and handle. This allows cost-efficient transportation and automatic operation for heat and power, for residential homes and large-scale power plants.
- Existing coal power plants can be modified to produce a percentage (typically 3 and 15%) of its electricity from pellets rather than coal (this is known as ‘co-firing’). Co-firing is a cost- effective way to reduce carbon emissions because it utilises existing infrastructure, such as power plants, ports and storage facilities. As a result, minimal capital expenditure is required. Co-firing using wood pellets is widely adopted globally and has been successfully piloted in Australia. Recent studies suggest that if Queensland were to substitute just 3% of coal used in its coal power stations with pellets, it would achieve carbon emission reductions in the order of 1.4 million tonnes per year.
Source: Clean Energy Council
The pellets emit far less carbon emissions than regular wood; they burn cleaner, longer and provide you with more heat. Our locally manufactured wood pellets are a compacted type of bioenergy. They are typically made of timber waste, sawdust and agricultural waste that is dried and processed into a densely compressed cylindrical pellet measuring about 1cm long, resembling rabbit and chicken food. Because they have a low moisture and ash content pellets burn very efficiently to produce heat and electricity.
THE FIRST CLEVER BIT IS THE BURNING OF THE PELLETS…
Wood pellets (around 6mm diameter and 10-20mm long) are augured from a hopper at the top of the heater into a fully enclosed burn chamber or “fire pot”. The first pellet is ignited using a small electric element to get it going. From there combustion process is fan forced to maximise burn temperature (700degC plus) ensuring an incredibly efficient process with almost zero smog or ash. Rather than a log, where most of it is smouldering away and the potential energy going up the chimney as smoke or settling as unburnt particle in ash, the pellets are fed in only as required and are always white hot. You can be pumping a beautiful radiant heat into your house in under ten minutes.
THE SECOND CLEVER BIT IS GETTING THE HEAT INTO YOUR HOME…
The heat from the burn chamber is fed through a high quality plate heat exchanger where almost every bit of energy is extracted and left in your room rather than going up the chimney.
The combination of the advanced burn chamber and heat exchanger make these pellet heaters the most efficient and clean method for using wood and bioenergy to heat your home.
THE THIRD CLEVER BIT IS THE SMART CONTROL….
The amount of heat produced is determined by the rate that the pellets are fed into the burn chamber. This is controlled by either setting the thermostat (set the temperature you want for your room), a manual switch to control pellet feed or even a remote where you can set temperatures and timing. Yes these can turn on 15min before you wake up so you can warm your toes while sipping your morning cup of tea.
An open fire place might run at about 10% efficiency which means that 90% of the potential energy in the log is either lost as heat through the chimney lost as smoke due to log not being burnt at high enough temperatures. There is a bit more to it than that but that describes it fairly well.
A “Pot Belly” might get up to 40% efficiency as it does a much better job than the open fire place in ensuring the log is burning at a good temperature and getting more the heat into the room rather than up the flue.
A modern slow combustion heater does an even better job and can get up to 60% efficiency with everything running really well.
That said you often find these heaters not being run at their optimum operating conditions with wood not being properly dry or sap free, manual feed of logs not being optimised and heaters being ‘choked down’ at night cutting out oxygen and causing more smoke. Further more, because it takes a while to get the heater going and you can’t just switch them off when you go to bed or leave the house; the over all efficiency of the process can be considerably less depending on how its used.
With a pellet heater they automatically control the pellets and oxygen feed to keep the heater burning at the optimum efficiency. The pellets themselves are very high in energy density, have low moisture (less than 10%) and are sap free. Furthermore they have efficient heat exchangers that ensure that almost all of the heat generated in the burning process ends up in your room rather than outside.
The other big benefit is that you can turn it on and off when you need it and keep the room at the right temperature rather than guessing. So not only is the heater more efficient, but the way you will use it will be more efficient.
Fossil fuels are also carbon sources that have been locked away for millions of years, whereas wood is part of the current carbon cycle. Burning wood is considered carbon neutral. Wood is also a relatively easily renewable resource.
However, the key to environmentally friendly wood heating comes down to three things:
- The efficiency of the heater
- The type and quality of the wood
- How the heater is operated
Type of wood heating
There are many factors that will influence efficiency and economy in comparison to fossil fuel counterparts. Wood heaters with high efficiency scores use less wood to generate the same amount of heat, therefore also creating less emissions – if the heater is operated correctly.
Radiant vs convective heating
Radiant wood heaters create the majority of their heat (66%) from the flames and heat people and objects directly rather than heating the air. A convection heater heats and circulates warm air around a room.
While an open fire is a joy to watch, fireplaces are generally very inefficient – only achieving around 5 – 10% efficiency. The fireplace itself is quite expensive to construct and requires a lot of materials. Additionally, an open fireplace only provides heat directly in front of the fire. Much of the heat can be lost not only through the flue, but through the rear wall which is usually outside the home.
An open fire’s efficiency can be greatly improved (up to 35%) by the use of a fireplace insert which is a hollow, metal structure built into fireplace, allowing for a greater degree of convection heating rather than relying purely on radiant heat.
Pot belly stove heater
Pot belly and similar wood heaters have an efficiency generally in the 25–40%; although according to the compliancy tag on mine, which is a relatively new model, it’s 47%.
A pot belly stove generates convective and radiant heat and are a good choice for heating small areas; particularly where space is an issue.
When I firstly installed my potbelly in a smallish area, the first night I was sweating even though the temperatures outside were below freezing. There is a bit of a learning curve in using them to get the right level of heat and particularly having them burn overnight. Pot bellies offer air flow controls which help control the rate the wood burns.
Slow combustion heaters.
Slow combustion heaters are a step up in efficiency – up to 70%. This is due to an airtight firebox, additional airflow controls and air inlets plus secondary combustion chambers to improve efficiency. They are the best option for heating large areas and can be fitted with a fan to help move heat more evenly around the room.
Wood pellet stoves
While not seen much in Australia yet, I understand that wood pellet stoves are very popular in other countries such as the USA. The wood pellets are usually made from sawdust waste from mills that has been compacted. Wood pellet stoves are reported to be incredibly efficient, offering combustion efficiencies of over 90%! Emissions are also said to be very low in comparison to other forms of combustion heating. Wood pellets can also be burned in normal slow combustion heaters and potbelly stoves, but without such high levels of efficiency.
Selecting a wood heater
A good wood heater for a large area can be quite an investment., so when choosing a wood heater, it’s best to consult an expert who can advise you based on issues such as climate, room size etc.
In my case, installing a slow combustion heater in such a small area wouldn’t have been effective as at medium and high burn settings, I would have sweltered. At low burn settings, too many emissions would have been created, so the pot belly was the best choice.
As a general guideline, aim for 1 to 1.5 kilowatts (kW) for each 10 m2 (108 square feet) of area needing to be heated. Always check the compliancy plate for efficiency ratings too. A slightly more efficient heater may cost a few bucks more, but will save you a ton of money (plus wood and emissions) in the long run. Also check and compare the compliancy label for emissions ratings.
Source: Michael Bloch
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More from the Clean Energy Council:
It is commonly thought that burning wood is bad for the environment. However, Australia has stringent controls on emissions from wood combustion. Furthermore, pellets are a highly refined heating fuel, which are dried to a uniform 4-6% moisture content. They are burned in well-controlled systems that run extremely hot and with sufficient airflow to ensure complete combustion. This is in contrast to normal wood which has a 20-40% moisture content that can prevent complete burning, resulting in smoke and emissions from wood particles that have failed to completely combust. As an example, about 2 million tonnes of pellets are burned annually in the US. However, particle emissions from wood pellets amount to less than 1% of the particle emissions caused by forest fires and less than 2% of the emissions from less well-controlled wood combustion, such as open fireplaces and wood stoves.
More from the Clean Energy Council:
Provided that wood pellets are supplied from forest resources that are managed and harvested in a sustainable manner – such as from the use of wood by-products from plantation timber – wood pellets offer a low-carbon, renewable energy source. It is estimated there is enough wood by-product from forest industry activities in Australia to supply 3000 gigawatt-hours of renewable energy per year without harvesting a single extra tree. Additionally, pellets from wood by-products are recognised as being carbon neutral under the Kyoto Protocol. This is because if wood by-products were left to decompose, they will return carbon to the atmosphere. When wood pellets are burned to produce heat or power, the same amount of carbon returns to the atmosphere. However, unlike an electric or oil heating system, no fossil fuels are used.
We have conducted a detailed Life Cycle Assessment to understand what the carbon impacts are with producing wood pellets from collecting waste biomass or harvesting plantation material, through to transport, processing and even including things like the impacts of making the plant equipment and running the business. For every tonne of wood pellets we make there is about 100kg of CO2e produced as a result. About 70% of this is in the energy used to run the plant which is why we will begin a transition to renewable energy for the factory. Another 25% is associated with the transport of the biomass to the factory and the pellets back to you and again this is why we have already started to run our vehicles on biofuels. Our goal is to turn 100kgCO2e/tonne into 20kgCO2e/tonne by 2015. Who knows we might even go better!
Even with the 100kg of CO2e per tonne of pellets you will have about 2% of the carbon footprint using a wood pellet heater when compared to an old electric bar heater and about 10% of the carbon footprint when compared to gas or a high efficiency reverse cycle unit.
Further to this we haven’t included all of the trees we have planted in the first place that sequester carbon into the roots and soil while continuing to regrow as we prune and thin. With this factored into the equation buying and using wood pellets from EnviroHeat will definitely result in a net carbon offset.
- The end of the flue needs to be 600mm above the roof line. It also needs to be 1500mm from any opening into the house.
- If the heater is going on carpet (or other flammable floor covering) you will need a hearth underneath. This needs to be minimum 6mm of non flammable material and depending on which model you have it will need to 300mm protruding from the front and 150mm on sides and back.
You will also need a standard 240V power supply to plug into. The heaters all come with about 1500mm of power cord.