Cleaning up our wood fires

The more we try to slow a fire down the more it is bound to crash into a smoulder.

letters

Cleaning up our wood fires

Much as I appreciate the CVRD’s iniative to help people to swap out old woodstoves for newer high efficiency ones, this does not solve the problem of woodstove pollution. Although the newer stoves with secondary combustion technology can burn cleaner, this only occurs when they are being run hot enough. Whenever there is blue or dark grey smoke exiting a chimney the fire is smouldering, and operating way below the stove’s touted 70 per cent efficiency. In my rural neighbourhood four out of five new high efficiency woodstoves are frequently smouldering in this manner.

The more we try to slow a fire down the more it is bound to crash into a smoulder. Smoke/gas is released from the wood at above 150 C, but ignition into flame only occurs above 300 C. When a woodstove’s reburn process is operating in between these temperatures, too much smoke/gas is passing through too little flame to achieve full combustion, and the wasted fuel is going straight up the chimney to become atmospheric pollution.

The most common contributing factors to this kind of mis-fire are:

• burning wet/green wood;

• not enough kindling and mid size pieces on start up and reload;

• ramping the draft down too soon after start up;

• not ramping the drarft up long enough after reload.

Back in the days of drafty cabins and poorly insulated houses we had reason to run our stoves hotter. But the better insulated our houses become, the slower we try to burn, the more often our fire crashes into smoulder. Burning slow is a flawed paradigm, and there is only so much reburn technology can do to compensate. As long as common operator errors are at play, woodsmoke air pollution is a reality.

The only sure-fire way to acheive clean combustion is to burn as hot as possible. Once the fire is over 600 C all of the volatile woodgases burn completely. The question then is: what to do with all of this rapidly generated heat? Some people have tried water jackets and tanks, but this is dangerous due to water’s explosive expansion pressures at over 100 C. Also, water is the universal solvent, constantly working to get out of whatever container we put it in (and eventually it will).

The safest and simplest way to store post-combustion heat is in earthen mass such as brick, stone, ceramics, or cobb (clay-sand). These are the materials used in the construction of masonry heaters, with high-mass bodies that absorb the thermal energy from a hot fire for gradual delivery into the living space. Such heaters have been around for thousands of years, and are still quite common in Northern Europe and other cooler regions of the world. For more information about this see: mha-net.org.

If you are not feeling ready to let go of your old (or new) metal box stove, or run it hotter, but you would like to improve its combustion efficiency, then you might want to consider burning from the top down. This involves loading larger splits on the bottom, placing smaller pieces above them, kindling above that, and lighting from the top. This way, all the smoke rises upwards into the flame path (rather than above it). It may seem upside down at first, but when you think of how a candle functions, ignition of fuel is more dependent upon radiant heat than flame contact. When we locate the flame above the fuel the base of the flame sends heat downward into the fuel below.

Loading a fire box to burn this way may take some getting used to. The wood must be well seasoned, dry, and a fair amount of kindling is required. But once the kindling catches, the fire will ramp up slowly and surely. And this gradual nested burn is exactly what we want. The video link below offers a clear demonstration of top down burning, as well as info on how best to reload for optimal efficiency: https://woodheat.org/wood-heat-videos.html

One final note. Top down burning requires a steady supply of smaller diameter wood (3 inch, 2 inch, 1 inch). Chopping wood into these smaller pieces may seem a daunting chore, but it can be done simply and efficiently by finding an old car or truck tire and setting it up at a good chopping height. Stack a bunch of bigger splits or rounds into the hole (with grain up and down) til it is fairly tightly packed. Then whack away at it with a maul. You’ll find the wood splits easy and stays in place, which eliminates bending down over and over to pick up stuff that otherwise goes flying. This is a BIG back-saver. And the cushion of the rubber perimeter makes it easy on the wrists too. An internet search for “splitting wood in a tire” will show all kids of examples. Eg: https://www.youtube.com/watch?v=H2d2GTBga6I

OK, hope that helps. Please kindly pass this info along to your wood-burning neighbours.

And happy heating as we clear the air.

Patrick Amos

Duncan

Letters

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

A rockfall closed Finlayson Arm Road and West Shore Parkway on Friday (March 5) afternoon. (Twitter/BC Transportation)
UPDATED: Malahat reopens following rockfall

Section of Trans-Canada Highway was scheduled for intermittent closures today for rock scaling work

In years past in-person ceremonies have been held for International Women’s Day. This year the observance is going online on Monday, March 8, 2021 due to the COVID-19 pandemic. (file photo)
Virtual ceremony for Women’s Day in Cowichan on Monday

Audrey George, manager of the Ts’i’ts’uwatul’ Lelum assisted living facility, will be keynote speaker.

North Cowichan councillor Rob Douglas is advocating for a pilot project that would see the forest industry on Vancouver Island and the coast managed regionally. (File photo)
N. Cowichan councillor continues push for regional management of forestry

North Cowichan councillor wants pilot project established

Cowichan-Malahat-Langford MP Alistair MacGregor. (Photo by Bernard Thibodeau)
NDP tables dental care program

Millions of Canadians don’t visit the dentist every year because they can’t afford to.

The James C Richardson Pipe Band marches in a Remembrance Day parade on Nov. 11, 2019 in Chilliwack. Wednesday, March 10 is International Bagpipe Day. (Jenna Hauck/ Chilliwack Progress file)
Unofficial holidays: Here’s what people are celebrating for the week of March 7 to 13

International Bagpipe Day, Wash Your Nose Day and Kidney Day are all coming up this week

Cannabis bought in British Columbia (Ashley Wadhwani/Black Press Media)
Is it time to start thinking about greener ways to package cannabis?

Packaging suppliers are still figuring eco-friendly and affordable packaging options that fit the mandates of Cannabis Regulations

Malawian police guard AstraZeneca COVID-19 vaccines after the shipment arrived in Lilongwe, Malawi, Friday March 5, 2021. Canada is expecting its first shipments of AstraZeneca vaccine next week. (Associated Press/Thoko Chikondi)
B.C.’s daily COVID-19 cases climb to 634 Friday, four more deaths

Currently 255 people in hospital, 66 in intensive care

A crashed helicopter is seen near Mt. Gardner on Bowen Island on Friday March 5, 2021. Two people were taken to hospital in serious but stable condition after the crash. (Irene Paulus/contributed)
2 people in serious condition after helicopter goes down on Bowen Island

Unclear how many passengers aboard and unclear where the helicopter was going

Surrey Pretrial in Newton. (Photo: Tom Zytaruk)
B.C. transgender inmate to get human rights hearing after being held in mostly male jail

B.C. Human Rights Tribunal member Amber Prince on March 3 dismissed the pretrial’s application to have Makayla Sandve’s complaint dismissed

Supporters rally outside court as Pastor James Coates of GraceLife Church is in court to appeal bail conditions, after he was arrested for holding day services in violation of COVID-19 rules, in Edmonton, Alta., on Thursday March 4, 2021. THE CANADIAN PRESS/Jason Franson
‘Law remains valid:’ Pastor accused of violating health orders to remain in jail

The Justice Centre for Constitutional Freedoms is representing the pastor

The Netflix logo on an iPhone. B.C. delayed imposing sales tax on digital services and sweetened carbonated beverages as part of its response to COVID-19. Those taxes take effect April 1, 2021. THE CANADIAN PRESS/AP, Matt Rourke
B.C. applies 7% sales tax on streaming, vaping, sweet drinks April 1

Measures from 2020 budget were delayed due to COVID-19

Chief Don Tom of the Tsartlip First Nation was outraged after Green MLA Adam Olsen revealed on social media that the community had been experiencing a COVID-19 outbreak – a fact the First Nation had chosen to keep private to avoid racist backlash as experienced by the Cowichan Tribes when an outbreak was declared there in January. (Black Press Media file photo)
B.C. First Nation ‘outraged’ after Green MLA reveals COVID-19 outbreak

Tsartlip First Nation chief shares concerns about racist backlash, MLA apologizes

A lawyer wears a face mask and gloves to curb the spread of COVID-19 while waiting to enter B.C. Supreme Court, in Vancouver, B.C., Friday, Aug. 28, 2020. British Columbia’s highest court has sided with the land owner in a dispute over public access to public land. THE CANADIAN PRESS/Darryl Dyck
B.C. high court finds in favour of large landowner in fight over access to pair of lakes

The Nicola Valley Fish and Game Club launched legal action after the cattle company blocked road and trail access

Most Read