Is wood heating climate change friendly?

Using wood for home heating is often touted as a climate change and environmentally friendly fuel. But is it?

Although it is clear that burning wood emits a notable amount of carbon dioxide, a significant greenhouse gas, some still argue that biomass burning is carbon neutral. The growing of new trees is believed to counterbalance the CO2 released through burning. As the new tree grows, the argument goes, it will absorb the equivalent amount of CO2.

Stored carbon released immediately

However, burning wood releases the carbon that has been stored over decades in the tree, putting out more CO2 per gigajoule of energy than the burning of gas, oil and even coal.

This addition of CO2 is immediate; yet it will take many decades for a new tree to grow to reabsorb the equivalent amount of carbon. And that is assuming that one is actually planted for every tree burned.

If the wood was instead left to grow and then rot slowly in the forest, it would provide nutrients to the soil and new plant life which would also help to absorb CO2. And it would take many years for the carbon stored in the wood to be released into the atmosphere.

European Union wood heat dilemma

The European Union (EU), however, continues to consider the burning of wood as a carbon neutral and renewable source of energy.

According to the Danish and German organization, Clean Heat, “Solid biomass as a renewable source is considered to play a crucial role in the transition towards more climate-friendly heating sources.” [1] As the EU considers wood burning to be carbon neutral, it has seen an increase in popularity.

Yet, at the same time, the EU has set standards for air quality and national emission ceilings for many pollutants, including fine particulate matter which, according to the European Environmental Agency, causes approximately 400,000 premature deaths a year.[2] Residential wood heat is recognized as a major source of fine particulate matter.

So, on the one hand, wood burning is being touted as a climate change friendly fuel based on the misconception that it is carbon neutral and, on the other, it is seen to be a major source of harmful pollution.

Wood smoke negating other reductions in pollution

An article in the Guardian (February 22, 2018), “Is your wood stove choking you? How indoor fires are suffocating cities” highlights how this move to supposed ‘renewable’ and ‘climate friendly’ energy, has meant that gains in other areas to reduce pollution are being negated by the increase in wood smoke.

Scientists in the UK are warning that the increasing popularity of wood fires is threatening to erase any progress big cities might achieve in reducing pollution from traffic. One study[3] from 2014 found that wood smoke was adding more particle pollution to London’s air than the first two phases of the city’s low-emission zone were expected to remove.

A separate 2017 study by the Air Quality Expert Group in the UK concluded that “On an equivalent hourly operational basis, a domestic stove is likely to emit a much higher mass of PM than a diesel vehicle meeting Euro 4/IV standards or above.” [4] One eco-designed stove rated to at 3.1 grams/hour of fine particulate matter puts out more than three times a the Euro IV/V (2004-08) diesel Heavy Goods Vehicle.

In other words, a modern wood stove would not come close to meeting current vehicle emission standards for even large trucks but it is, nonetheless, allowed to idle for hours on end in one spot.

Meanwhile In Canada

We know that wood burning is also major source of harmful fine particulate pollution in Canada. Residential wood heat alone accounted for approximately 10% of the nation’s PM2.5 emissions in 2015.[5] In some areas of the country these numbers are much higher. In the Comox Valley, for example, wood heat accounts for over 35% of annual emissions of PM2.5.[6] In the Lower Fraser Valley, home heating accounted for 32.2% of the annual PM2.5 emissions.[7]

Residential wood burning contributes over 30% of Canada’s black carbon, a component of fine particulates and a known climate change forcing agent.

At the same time, residential wood burning also contributes over 30% of Canada’s black carbon, a component of fine particulates and a known climate change forcing agent.[8]

Black Carbon has recently emerged as a major contributor to global climate change, possibly second only to CO2 as the main driver of change. Black Carbon particles strongly absorb sunlight and give soot its black color. It is produced both naturally and by human activities as a result of the incomplete combustion of fossil fuels, biofuels, and biomass. Primary sources include emissions from diesel engines, cook stoves, wood burning and forest fires.[9]

If home heating contributes 10% of the country’s fine particulate matter, and 30% of its Black Carbon, it is likely that areas with higher proportion of PM2.5 emissions from home heating, like many regions of BC, would also have a corresponding higher contribution to black carbon emissions.

Reductions of wood smoke can have double benefit

Every type of heating fuel has its environmental pros and cons; yet wood heat is often touted as being environmentally friendly. It is time to end that myth. It is a substantial source of harmful fine particulate as well as black carbon.

The governments and organizations that work to reduce pollution from traffic, create anti-idling zones or promote active transportation may want to turn their attention instead to the use of wood heat and other forms of burning.

Reductions in this sector could go a very long way to both improving public health and reaching climate change targets.

[1] http://www.clean-heat.eu/de/aktivitaeten/infomaterial/download/background-paper-residential-wood-burning-2.html

[2] https://www.eea.europa.eu/media/newsreleases/many-europeans-still-exposed-to-air-pollution-2015/premature-deaths-attributable-to-air-pollution

[3] https://www.sciencedirect.com/science/article/pii/S1352231013009825

[4] P. 17, The Potential Air Quality Impacts from Biomass Combustion https://uk-air.defra.gov.uk/assets/documents/reports/cat11/1708081027_170807_AQEG_Biomass_report.pdf

[5] https://www.canada.ca/en/environment-climate-change/services/environmental-indicators/air-pollutant-emissions/fine-particulate-matter.html

[6] http://breathecleanair.ca/wp-content/uploads/2017/12/170317_CV_PM_Emissions_Inventory_Final_Report.pdf

[7] http://www.metrovancouver.org/services/air-quality/AirQualityPublications/2015LowerFraserValleyAirEmissionsInventory-Nov2017.pdf

[8] http://ec.gc.ca/pollution/default.asp?lang=En&n=D521BDDF-1&offset=3&toc=show

[9] https://www.c2es.org/document/what-is-black-carbon/

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