Clean Air, Better Health - Climate Impacts

Burning wood is NOT climate neutral

Burning Wood Emits more CO2 than the same amount of coal or gas: as explained in the UK Clean Air Night video, wood heaters also emit more CO2 for the same amount of heat than coal or gas, so there will be more CO2 in the atmosphere after a night in front of the fire than if you'd used other forms of heating. Cutting down trees stop them absorbing CO2 from our atmosphere and it can take decades, or even as long as a century for forests to grow back and reabsorb the CO2 released when we burned wood.

Only about half of global warming comes from CO2 emissions. The other half is from non-CO2 climate pollutants, mainly short-lived climate pollutants (SLCP) such as methane, black carbon and carbon monoxide. Important research, published in 2022 in the Proceedings of the US National Academy of Science by Dreyfus and co-authors [1], shows that global temperatures are likely to exceed 2°C by 2050 unless we focus on reducing both CO2 emissions and SLCP.

Just one Sydney wood stove = health costs of thousands of dollars per year and as much global warming as 23 homes with gas central heating. Burning wood in an enclosed wood heater emits substantial quantities of SCLP. Over the next 20 years - the critical period if we are to keep global warming below 2°C - SLCP emissions from a wood stove will cause 4 times as much warming as the CO2 emitted by burning the wood. Consequently, a household burning Sydney's average of 3.43 tonnes of wood will cause as much global warming over the next 20 years as 23 similar households using gas central heating. Despite less than 5% of Sydney households using wood as main heating, the NSW Government's Greater Sydney Air Quality Study reported that wood heating is responsible for 42% of all man-made population-weighted exposure to PM2.5 pollution and a financial burden of over $2 billion per year, equivalent to several thousand dollars per heater per year.

Other countries are also taking action against false claims that burning wood is environmentally friendly or carbon neutral. In July 2023 the Danish Government charged 23 companies with violating that country’s Marketing Practices Act with their deceptive environmental claims about wood burning. Danish Consumer Ombudsman Christina Toftegaard Nielsen ruled that wood stoves, firewood, and wood pellets may no longer be marketed as environmentally friendly or carbon neutral, because they were considered false and misleading. “When companies market wood-burning stoves and firewood, they must not give consumers the mistaken impression that heating by burning wood is environmentally friendly. It is misleading and therefore contrary to the Marketing Act.”

Climate Impacts & Tipping Points

In December 2023, 200 scientists from around the world published the Global Tipping Points (GTP) Report at the COP28 UN climate talks in Dubai. Over 25 GTP were identified. The GTP report notes that human activities are already pushing us close to some tipping points. The exact thresholds are uncertain but, at warming of 1.2°C, the widespread loss of warm water coral reefs is already becoming likely, while tipping in another four vital climate systems is possible – Greenland and West Antarctic ice sheet collapses, North Atlantic circulation collapse, and widespread localised thaw of permafrost. Beyond 1.5°C several of these become likely … All the above highlight the importance of aiming for climate neutrality (no additional contribution to the global temperature rise) to reduce the risk of exceeding tipping points. We don’t have 100 years before passing tipping points it’s now critical to target all SLCP to slow global temperature rise.

Burning wood causes more climate damage because of its SLCP emissions than heating up to a dozen similar homes with modern, efficient, electric heating. Not burning wood is therefore the best and most sustainable action anyone currently burning wood can to to reduce their contribution to global warmng and help avoid the risk of passing dangerous climate tipping points.

It is really important to take urgent action, including not burning wood, now that Six leading international datasets collated to monitor global temperatures show the annual average global temperature was 1.45 ± 0.12 °C above pre-industrial levels in 2023 and likely to be even higher.

Rapid Climate Breakdown. Earth’s systems are breaking down at astonishing speed. Polar ice melting much faster than expected. Summer meltwater poured in torrents from Greenland's ice cap. Andrew Freedman and Jason Samenow’s Washington Post article reports that the melting on 31 July 2019 outpaced all data collected since records began in 1950. Daily losses are 50 years ahead of schedule; they were forecast in the climate models for 2070. A paper in Geophysical Research Letters reveals that the thawing of permafrost in the Canadian High Arctic now exceeds the melting scientists expected in 2090.

Huge wildfires burned across the Arctic, releasing more carbon dioxide in 2019 than in any year since satellite records began nearly two decades ago. According to the World Meteorological Organisation: "A recent study found Earth’s boreal forests are now burning at a rate unseen in at least 10,000 years.”

Climate change was a key factor in Australia's devastating 2019-20 fires that resulted in 417 premature deaths in Eastern Australia and released an estimated 830m tonnes of CO2, more than all except the 5 most polluting countries in the world.

Climate tipping points = irreversible warming. Current warming increases future warming - methane from permafrost and undersea ice add to future warming, as does CO2, methane and black carbon from burning forests. If this continues, even if we reduce our emissions to zero, we may pass a tipping point of irreversible climate change.

Share of non-CO2 pollutants contributing to global warming almost as much as carbon dioxide: Study

Best path to net zero = Cut Short-lived Climate Pollutants (SLCP) Three renown climate scientists (Molina, Ramanathan, Zaelke) warn: "the climate battle could be lost long before 2050; it might even be lost by 2035. ... it's time for fast climate mitigation, especially in the form of reductions of the short-lived so-called “super-pollutants”—black carbon, methane, tropospheric ozone, and hydrofluorocarbons, abbreviated as HFCs.

"Speed must become the key measure of all climate mitigation strategies: a speedy reduction of global warming before it leads to further, self-reinforcing climate change feedbacks (i.e. current warming increasing future warming)," say the 3 renown climate scientists.

Quickest way to reduce current warming. If we stop emitting SLCP, they dissipate much more rapidly from the atmosphere than CO2. The greatest reductions in SLCP emissions can be achieved by stopping fracking, tackling methane emissions from mines and gas pipelines and switching from wood and gas heating to efficient heat pumps (also called reverse cycle air-conditioning).

Evaluating the climate impact over the 20 years after emissions - the critical period if we are to keep global warming well below 2 degrees C - as well as over 100 years will identify the best strategies to avoid passing dangerous climate tipping points.

Serious Risk of Passing Tipping Points. The Arctic and Antarctic are warming faster than the global average rate. When polar ice melts, it absorbs radiation instead of reflecting it back into space. Methane traps 86 times as much heat in the first 20 years after emission as the same weight of CO2. It is released when permafrost and undersea ice melt, and this adds to future warming, as does CO2 from wildfires.

Huge wildfires and unexpectedly fast melting are just part of the mounting evidence (such as methane blow-holes in Siberia) that we need to take urgent action to tackle the Climate Emergency, or risk passing a tipping point (i.e. a point of no return). Berkley Earth's Global Temperature Report for 2020 predicts that global warming will exceed 1.5°C by 2037.

David Spratt's Climate Code Red warns that 1.5°C of warming is likely by 2030. The Australian Climate Council states: "Multiple lines of evidence strongly suggest that ... the global average temperature rise will exceed 1.5°C during the 2030s."

To achieve net zero – emissions shouldn't add to the global temperature rise. There's a serious risk of passing a tipping point (of irreversible change) if our emissions increase global warming over the next 20 years, even if some of the effect is much smaller over longer periods of time.

Burning biomass for energy releases a pulse of CO2, and in many cases also methane and black carbon, all of which immediately start to warm the planet. This leads to higher temperatures and more melting of glaciers, polar ice and methane released from permafrost and sub-sea ice – a positive feedback mechanism that leads to further increases global temperatures, melting ice and so on until. By the time new biomass has grown to replace what was burned, the positive feedback mechanisms will have created higher temperatures and we’ll be closer to the tipping point than if no biomass burning had taken place.

Comparing greenhouse pollutants over 20 years. Although CO2 causes the most warming –1.68 W/m2 (watts per square metre), the diagram (left) from the US EPA report: Methane and Black carbon, impacts on the Arctic shows that methane (0.97 W/m2, including the warming of ground-level ozone formed from CH4) and black carbon (0.88 W/m2) together cause more warming than CO2.

In fact, methane and black carbon are known as super-pollutants or short-lived-climate-pollutants (SLCP), because they cause substantial amounts of global warming, but rapidly disappear from the atmosphere if we stop emitting them.

To maximize our chances of avoiding a disastrous climate tipping point, we must consider all greenhouse pollutants and reduce both CO2 and SLCP emissions (pull both the CO2 and SLCP levers as advised by Xu and Ramanathan, 2017) or take a simpler approach of minimizing their combined warming over the next 20 years, using the IPCC’s 20-year global warming potentials (GWP).

Target SLCP: 0.25°C-0.5°C less warming by 2050, 1.2°C by 2100. Targeting SLCP emissions could reduce warming by around 0.5 °C by 2050, according to analyses by UNEP 2011; Ramanathan and Xu 2010; Shindell et al. 2012; Hu et al. 2013. In 2017, Xu and Ramanathan concluded that pulling the SLCP lever to the maximum could reduce warming by 0.6°C by 2050 and 1.2°C by 2100.

Research published in 2020 modelled the combined effect of reducing emissions of CO2, methane and black and organic carbon (BC and OC) using the best available technology for transportation and phasing-out direct use of biomass and coal in residential and commercial buildings. These measures to reduce CO2 methane, BC and OC were estimated to avoid a further 0.18–0.26 °C in 2040 compared to just reducing CO2.

So by targeting both CO2 and SLCP, e.g. choosing mitigation strategies by calculating climate impacts over the next 20 years - a critical period if we are to avoid tipping points - we'll do a better job of slowing the global temperature rise as quickly as possible, buying time to develop and implement the best possible long-term strategies, as technology changes and improves, e.g. pull the sequestration lever by growing biomass to eventually remove excess CO2 from the atmosphere and return to a safe, stable climate.

Other Insights from calculating 20-year Climate Impacts

'Gas-led' recovery obviously flawed! A 'gas-led recovery' might seem plausible if we mistakenly believe that the climate damage is spread over 100 years. In reality, the impact of methane leaks from fracking and infrastructure happens in the first 20 years, creating potentially dangerous increases in temperature and serious risks of passing tipping points.

Destroying forests for biomass power obviously counter-productive! Methane, black carbon, CO and CO2 from burning biomass pose a similar risk. More than 500 top scientists and economists appealed in February 2021 to stop burning forest biomass for electricity because it's dirtier than burning coal. They argue one of the best ways to curb climate change and sequester carbon is to allow forests to keep growing

More important to eat less red meat. The 2.1 million tonnes of CH4 emitted in 2014 by enteric fermentation of Australian livestock will warm our planet over the next 20 years as much as the 182 million tonnes of CO2-equivalent emitted by Australian electricity and heat production. The problem could be solved using red algae (Asparagopsis taxiformis) as a feed supplement. But until this happens, encouraging a switch to other forms of protein could reduce global warming by as much as switching to renewable energy.

More encouragement to store carbon in trees and biomass. Better accounting procedures would consider the climate damage in the 20 years after emission, count all emissions (including biomass burning) and give climate credits for growing trees, or other biomass. As well as reducing the immediate risk, more informative accounting procedures could lead to better ways of mitigating the climate damage, one possibility being wood harvesting and storage.

Better understanding of the climate impact of methane, black carbon, CO and CO2 from wood stoves. As well as the predicted 0.18–0.26 °C reduction in global warming by 2040 better accounting procedures might also help ordinary folk understand that the methane, black carbon, CO and CO2 emissions from burning two to four tonnes of wood in an enclosed wood heater will, in the 20 years after emission, contribute as much to the global temperature increase as 15 to 31 similar households heating their homes with efficient reverse cycle heat pumps.

Does wood bioenergy help or harm the climate? "the first impact of wood bioenergy is to increase the carbon dioxide in the atmosphere, worsening climate change. Forest regrowth might eventually remove that extra carbon dioxide from the atmosphere, but regrowth is uncertain and takes time – decades to a century or mor e, depending on forest composition and climatic zone – time we do not have to cut emissions enough to avoid the worst harms from climate change." (Sterman et al., Bulletin of the Atomic Scientists, 2022).

Why wood stoves increase the risk of dangerous climate change

Many households in colder areas burn 4 tonnes of wood per year. For the 20 years after emission, this will cause as much global warming as 50-75 tonnes of CO2 - more global warming than heating 50 similar houses with an efficient electric heat pump.

Slow combustion wood heaters limit airflow, creating CH4, CO and BC as well as CO2 emissions. Individuals with wood heating (10% of all Australian households) can dramatically reduce their impact over the next 20 years by replacing the wood heater with an efficient heat pump.

Modern, efficient heat pumps have superseded wood stoves and natural gas as the most cost-effective heating. They can deliver 5 or 6 times as much heat to the home as they use in electric power and are effective at low temperatures. They are affordable (cheaper than buying a wood stove), cause less global warming (zero in households that use green power) and have lower running costs than buying firewood.

Notes: emissions in red & black; emissions avoided in green.

Softwood: Black carbon (BC), carbon monoxide (CO) and methane (CH4) emitted by burning softwood are averages of all tests for generally well-operated AS4103 wood stove in John Gras’ comprehensive study [1].

Burning Hardwood: CH4 emissions of 18.7 g/kg for hardwood are from a peer-reviewed paper published in Atmospheric Pollution Research [2]. Estimated BC emissions for hardwood use the California Air Resources Board methodology that BC represents about 12.5% of PM2.5 emissions [4]. CO emissions from burning hardwood are based on the real-life emissions study showing 15% of carbon emitted as CO [3].

2 kW of solar power (Origin energy figures, 1 kW saves 1,500 kWh, 2 kW 3,000 kWh), i.e.3 tonnes of CO2 at an emissions intensity of 1 (coal-fired power).

Burning 1 litre of petrol emits 2.2 kg CO2.

GWP. IPCC 5th Assessment report: 1 kg of methane (CH4) causes as much warming over 20 years as 86 kg CO2 (including direct and indirect aerosol effects; including CO2 produced when methane is oxidized gives a slightly higher GWP of 88); 1 kg CO causes as much warming over 20 years as 18.6 kg of CO2 (see Tables 8.7 and A.8.4 of Chapter 8, AR5 WG1).

The 20-year GWP of 3203 for BC is from the California Air Resources Board [4].

References
1. Gras, J., Emissions from Domestic Solid Fuel Burning Appliances., 2002, Environment Australia Technical Report No. 5, March 2002. Available at: http://www.environment.gov.au/atmosphere/airquality/publications/report5/index.html.

2. Robinson, D.L., Australian wood heaters currently increase global warming and health costs. Atmospheric Pollution Research, 2011. 2(3): p. 267-274.

3. Meyer, C.P., et al., Measurement of real-world PM10 emission factors and emission profiles from woodheaters by in situ source monitoring and atmospheric verification methods, 2008, CSIRO Marine and Atmospheric Research (CMAR), (available at: http://www.environment.gov.au/atmosphere/airquality/publications/emission-factor.html ).

4. Revised Proposed Short-Lived Climate Pollutant Reduction Strategy, California Air Resources Board, November 2016. Available at: www.arb.ca.gov/cc/shortlived/shortlived.htm