Is it Time to Rethink Burning Wood for Heat?

The perception has been that plant matter is self-renewing, and that carbon released from wood burning can be reabsorbed by forests. Many people use a log burner in their homes for this reason and in the recent past, the government subsidised wood pellet boilers through the Renewable Heat Incentive (RHI). However, the reality is much more complex.

Trees use CO₂ from the atmosphere, water and sunshine to power their growth. When we burn wood, we return that same CO₂ into the atmosphere. When viewed over many decades or centuries, the process is essentially carbon neutral with no net addition of atmospheric CO₂ (as long as the transportation and drying of the wood were also carbon neutral). So why does burning wood lead to increased carbon emissions in the UK?

Think of the amount of CO₂ in the atmosphere like the water level in a bathtub. When setting climate targets, scientists analyse data, politicians negotiate, and we collectively decide to draw a line just above the current water level. We commit to preventing the water level from exceeding this mark, as allowing that to happen could increase the risk of triggering tipping points and lead to the unpredictable and potentially catastrophic effects of climate change. The tap is fully open, and the water level is quickly approaching its maximum limit.

There is a plughole in this bathtub which represents the CO₂ removed from the atmosphere by natural biological, chemical, and physical processes. Our plans to stop the water level from passing our mark involve making the plughole a lot bigger by either enhancing these natural processes or by using technologies that, as I write, do not currently exist or can't be deployed economically at anything like the scale we require.

Burning wood has a short-term effect which can be compared to pouring water into the bathtub using a bucket while only slightly increasing the size of the plughole. Over decades or centuries, the water level (i.e. the amount of CO2 in the atmosphere) will return to its original level. However, with today's emissions, the water level will rise above our mark in just under six years; time is a luxury we don't have. The fact that the water level will eventually drop does not change the fact that the water level will go above the line. Once we are above the line, events may be triggered that we can't reverse.

Acknowledgement that burning wood for heat is not sustainable in the short term is now finally impacting policy. The RHI scheme is now over; no new applications can be made (although taxpayers will continue to subsidise this unsustainable practice until 2029). Only replacing a gas or oil boiler with a heat pump is now subsidised through the Boiler Upgrade Scheme in England. And in terms of fighting climate change, heat pumps are one the best weapons we have.

Heat pumps are a reliable and efficient heating solution that can significantly reduce carbon emissions while saving on heating costs. These technologies are currently available and have proven to be effective, and UK homeowners are increasingly opting for renewable energy solutions. According to data from MCS, the body that certifies low-carbon installations, there has been a 62 per cent rise in installations this year compared to last, with 2023 the first year to see more than 3,000 heat pumps installed in one month.

If we want to avoid breaching the critical 1.5 C warming threshold in the next six years, we need to take every step possible to reduce the amount of carbon we release into the atmosphere. It’s time to move away from using wood as a heat source and instead adopt genuinely low-carbon technologies.