Wood heaters currently sold on the Australian market must be tested to and comply with national emissions and efficiency standards, with a few exceptions such as cooking appliances. This is important because even though wood heating is a carbon neutral practice, which we will cover in depth in another article, it can contribute to air pollution if done poorly.

The current Australian Emissions Standard (AS/NZS4013:2025) states that solid fuel (wood) heaters must have tested emissions of no more than 1.0g/kg. This means that out of every kg of wood that you burn in your fireplace, no more than 1.0g of solid particle emissions can escape through the flue. This means that at the most, 0.10% of the wood you burn (by weight) is emitted as solid particle emissions.

But what does this mean in practical terms? Well, that’s what we’re here to find out.

Below I’m going to work up an example using one of our heaters, the Ribe Valencia Insert. The Ribe has an emissions factor of 0.4g/kg. This means that in the Ribe 0.04% of the wood burned is emitted as solid particle emissions.

In addition to the emissions factor (which is published by law for wood heaters sold on the Australian market), we also need to know the wood usage per hour statistic for the heater. This statistic is harder to come by. All tested wood heaters have this information available in the test report, but that information is only released at the discretion of the manufacturer, not required by law, so often this number is not readily available to you. Euro Fireplaces publish all their wood usage per hour statistics, to allow consumers to make an informed decision.

For the Ribe Insert this is 1.8kg/hour. Now this isn’t to say that you load 1.8kg every hour, in fact you load double the weight every 2-3 hours so a load size is 3.6kg.

We also need to know the heater’s extended burn time. This information is made available by most manufacturers, as it’s difficult to sell a wood heater without telling the end user how long it will burn for. The Ribe Insert’s extended burn time is approximately 6-7 hours. But this can be extended to approximately 7-8 hours if the optional heat bank is fitted. For the purpose of this exercise, we’re going to use heat bank so the number we’ll be using is 8 hours of overnight burning.

We also need to make some assumptions about how often the heater is used. In this scenario, let’s say that the Ribe Insert is the primary heat source in a home, meaning that it’s going to be run 24/7 throughout winter (from June to August, 14 weeks total) and intermittently for 3 weeks each at the end of autumn and the beginning of spring (6 weeks in total).

First let’s work out how much wood the Ribe will use in an intermittent week.

5:20pm – fire is lit – half a load of hardwood (1.8kg) and some soft kindling.

6pm – first load of wood goes on (3.6kg).

8pm – second load of wood goes on (3.6kg).

9:40pm – heater is shut down for overnight burning and the 3.6kg load burns until around 4:30am.

This totals 9kg for the day.

We can assume that there are at least 2 days in an intermittent week that the fire is not lit, due to weather, nobody being home, or just having an early night, so 9kg per day, burned 5 days out of the week:

9kg × 5 days = 45kg of wood per week

This applied to a 6 week period totals:

45kg × 6 weeks = 270kg

Now we need to know how much wood we will burn during peak heating season.

We’re going to negate the start up cycle in these calculations because it really will only happen once, assuming you are able to continuously burn.

Of the 24 hours in a day, 8 of these hours will be done using 1 x 3.6kg load of wood on an extended burn. This is one 3.6kg load burned over the full 8 hour period, rather than 3.6kg per hour.

We still have 16 hours of heating to do:

16 hours × 1.8kg per hour = 28.8kg

These numbers together (3.6 + 28.8 = 32.4) mean that when heating 24/7 you will use approximately 32.4kg per day or 226.8kg per week.

For a 14 week period this totals:

226.8kg × 14 weeks = 3,175.2kg

Adding both of our totals together we get:

3,175.2kg + 270kg = 3,445.2kg of firewood

So, under these assumptions, the Ribe Insert would burn approximately 3,445kg of firewood over the full heating season.

If the Ribe has an emissions factor of 0.4g/kg, this equates to:

3,445.2kg × 0.4g/kg = 1,378.08g

or approximately 1.38kg of particulate emissions over the entire heating season.

Now, to illustrate why the emissions statistic on its own doesn’t necessarily tell the whole story, let’s run the same calculation with a hypothetical fireplace that has a higher wood usage but the same emissions statistic of 0.4g/kg.

This is not a comparison with another specific product. It is simply an example to demonstrate what happens when two heaters have the same emissions rate but burn significantly different amounts of wood.

For this hypothetical fireplace, let’s assume that it uses 4kg of wood per hour during the normal burn period. Following the same loading principle as the Ribe, this means that each load would be 8kg.

This works out to be 7,656kg of firewood per year

At the same emissions factor of 0.4g/kg:

7,656kg × 0.4g/kg = 3,062.4g or approximately 3.06kg of particulate emissions over the entire heating season.

So, even though both heaters in this example have exactly the same emissions statistic of 0.4g/kg, the amount of wood they burn makes a significant difference to the total amount of particulate emissions produced over the heating season.

If we extend these same calculations over a 10 year period, the difference becomes even more significant. The Ribe would burn approximately 34,452kg (34.5 tonnes) of wood and produce around 13.8kg of particulate emissions, while the hypothetical higher-usage fireplace would burn approximately 76,560kg (76.6 tonnes) of wood and produce around 30.6kg of particulate emissions.

That is a difference of roughly 42.1 tonnes of wood burned and 16.8kg of particulate emissions over 10 years, despite both heaters having the same stated emissions rate of 0.4g/kg.

This is why looking at an emissions statistic in isolation can be misleading. The amount of wood a heater needs to burn to provide the required heat is also an important part of understanding the total amount of particulate emissions produced over the course of a heating season, and over a longer period of time.

A properly operated, lower wood usage heater, is always better for the environment.