You may have seen some bold claims recently about wood-burning stoves producing the same emissions as hundreds of heavy goods vehicles (HGVs). These attention-grabbing headlines certainly make you sit up and take notice. But how accurate are they? Let’s have a closer look at the facts behind the hype.

The controversial claim

First things first – where did this controversial claim originate? Well, it stems from a report published in 2021 by the European Environmental Bureau (EEB) titled “Where There’s Fire, There’s Smoke.” This report stated that one modern Eco design-rated wood-burning stove produces the same amount of fine particulate matter emissions as 750 Euro 6 HGVs over the same period.

That’s certainly an alarming statistic! No wonder it gained so much attention in the media. However, as we’ll discover, this comparison is not as clear-cut as it first appears.

Flawed comparisons

The EEB report bases its claim on a simple comparison of particulate emissions rates and stoves and HGVs when generating the same amount of energy – 1 gigajoule (GJ) worth. Converting between energy generated and emissions produced enabled a direct comparison between the two on the same scale.

However, as the Stove Industry Alliance points out, this approach overlooks some vital additional factors. Firstly, it only considers theoretical maximum emissions rates rather than real-world usage. Secondly, the emission measurement techniques and protocols vary enormously between stoves and HGVs.

So, in reality, this seemingly straightforward comparison is undermined by its simplicity. Not accounting for how stoves and HGVs operate daily produces a misleading picture.

In summary, we must be very careful comparing two completely dissimilar things, and this particular comparison is highly misleading – like comparing apples to oranges.

Real-world use

Credit: Stove Industry Alliance

To understand where the flaws lie in this comparison, we must delve into how stoves and HGVs are typically used. Let’s start with wood burners.

The latest government research shows that the average stove user has their appliance lit for around 29 hours per week during winter. That works out at between 3.7 and 4.5 hours of use per day.

Contrast this with HGVs, which can run up to 9 hours per day under driver-hour rules. That adds up to 63 hours of driving time per week – more than double that of a stove. And remember, HGVs operate year-round, not just seasonally like stoves.

So, the emission comparison made in the EEB report suddenly looks much less reasonable when considering real-world usage. An Ecodesign stove operating 29 hours a week will emit 20.16g of particulate matter. But a Euro 6 HGV running for 63 hours emits a vastly greater 271g – over 13 times more!

Emission heights

Brick chimney set against blue sky

Here’s another critical factor overlooked by the report – emission heights. Stoves typically vent emissions over 5 metres above ground level when installed correctly. But HGVs emit right now at ground level as they drive along.

Why does this matter? Scientific research shows this significantly impacts pollution dispersal and human exposure. Emissions from tall chimney stacks will disperse far quicker and broader, reducing ground-level concentrations. So, the health impacts per gram of emission can be expected to be lower for stoves than traffic.

Non-exhaust emissions

And there’s one final nail in the coffin for the EEB’s comparison. Their report only considered HGV exhaust emissions. It did not account for non-exhaust emissions like particulate matter stirred up from tyres and brakes.

However, experts estimate these non-exhaust emissions could more than double the particulate matter produced by HGVs. Yet the EEB figures only included emissions from the tailpipe. This overlooks a significant source of HGV air pollution.

A flawed report

When you boil it down, the comparisons made in the EEB report are dangerously flawed:

  • They don’t consider the real-world usage of stoves and vehicles.
  • They ignore the differences in emission heights.
  • They overlook non-exhaust emissions from HGVs.

On top of this, the report does not appear to have faced any independent peer review. So, its bold claims should undoubtedly be taken with a heavy pinch of salt.

Health impacts

When making comparisons between emission sources, it’s vital to consider the potential health impacts, too. 150 micrograms of particulate matter inhaled from a truck tailpipe is not necessarily equivalent to 150 micrograms from a chimney pot 10-11 metres overhead.

The dispersion, dilution and actual human exposure to the emissions can differ enormously depending on the source. So, simply comparing gross emission volumes does not paint an accurate picture.

As we’ve learned, the EEB study failed to account for these factors when making eye-catching claims. So, the suggested health impacts will likely be excessively skewed against wood-burning stoves.

Policy implications

These misleading comparisons also risk distorting air quality policymaking. If decision-makers believe wood burners are massively more damaging than the evidence supports, inappropriate measures could result.

Potential stove bans and punitive taxes on householders could be imposed without tackling broader air pollution issues. So it’s crucial environmental groups provide accurate, real-world emissions data rather than headline-grabbing sound bites.

Stove industry perspective

Credit: Stove Industry Alliance

Naturally, the stove industry itself has a vested interest, too. But they agree the lack of robust evidence is an issue on all sides of the debate.

The Stove Industry Alliance argues that finger-pointing at a single source, whether stoves, vehicles or others, is counterproductive. Instead, air quality policies should be based on thoroughly assessing all pollution sources and ‘real-world’ impacts.

They accept that burning wood contributes to PM2.5 emissions alongside many other activities. However, excessively strict stove curbs without similarly firm measures on vehicles, agriculture and other emitters could cripple rural households relying on wood fuel.

A more balanced approach is needed, recognising that panacea solutions rarely exist in complex policy areas. Emission sources must be compared like-for-like using real-world usage and exposure data rather than theoretical rates alone.

Wider pollution sources

While stoves and vehicles grab the headlines, major air pollution stems from myriad other sources, too. Household cleaning products, wood-burning pizza ovens, open fires and ageing coal power stations all play a part.

Agriculture is a huge contributor through ammonia emissions from fertiliser and livestock waste. Yet how often do we see introspective headlines about ‘barbecues producing the same fumes as 5000 cows’?

Plus, there is a vast array of industrial processes pumping out oxides of nitrogen and sulphur on a regular basis. Air pollution recognises no convenient boundaries.

So, singling out one minor emission source in isolation achieves little without a broader strategy. 

Clearing the air on emissions

As the Stove Industry Alliance rightly points out, none of this is to say wood burning doesn’t still impact air quality. The responsibility lies with all of us – from policymakers to corporations and individuals – to clean up the air cooperatively using sound evidence.

Experts suggest that in order to tackle poor air quality, we must be sure to fully understand the impact of all sources of emissions and not be selective. 

Only by building a complete picture of the causes and taking account of real-life emissions data, usage patterns, and more can sensible policies be developed. Relying on crude comparisons helps no one clean up the air we all breathe.

So next time you come across another attention-grabbing pollution headline, take a pause for thought. Check the sources, understand the assumptions made, and always question what real-world picture is being painted. The truth may not be quite so newsworthy after all.