LETTER: A reply to Andrew Bennett's comment on a previous letter regarding wood stoves

LETTER: A reply to Andrew Bennett's comment on a previous letter regarding wood stoves
Hi Andrew,
 
Thanks for your excellent comment to my letter in the Telegraph on wood smoke. I was very interested to read about your experiences with the Rocket Mass Heater.
 
I became interested in more efficient wood burning after staying in a house in Llamac in Peru in 2007 where the lady shown holding her grandchild in the upper photograph cooked us a fantastic typical Peruvian meal on the ‘wood stove’ she is sitting next to. We had hired her husband and his donkeys for a 12 day trek around the Huayhuash mountain range in the Cordillera Blanca and stayed in his house after finishing the trek. When I questioned them about a chimney (or lack of it) they just pointed to a hole in the roof.
 
 
 
In addition to spending a big part of her life next to this smoky “stove” she also spends a chunk of her life looking for scarce firewood. I thought that it was just “nuts” that she and her kids and grandkids should be exposed to so much wood smoke unnecessarily for most of their lives.
 
I thought that I could, and should, design something much more efficient in terms of efficiency...using less wood and improving heat transfer, which would really help people in this situation. After I got home I started thinking about it and “Doodled’ a few design concepts based on my engineering background. But then after “Googling” the topic I found that it had all been done decades before by various people.
 
I found information on the Rocket Stove design developed in 1982 by Dr Larry Winiarski (Aprovecho Research Centre) and read about how this had been developed and used in other countries such as by Dona Justa in Honduras to suit their local cooking methods etc. (Internet picture of her and her Rocket Stove in the lower picture shows a world of difference). The “icing on the cake”was that Aprovecho published a 40 page design manual in Spanish on the “Design Principles for Wood Burning Cook Stoves”. So I bought a copy and mailed it off to my hosts in Llamac, Peru with hopes that they would build one and spread the word in their village and surroundings. It would be interesting to go back there and see if it ever happened. Maybe one day!
 
The situation in Rossland and typically North America is very different to developing countries. You are right in that it is also a different situation in rural areas. The difference is that in rural areas neighbours are often far away from each other and wood smoke can disperse. Urban situations are very different from rural situations since the density of housing is much greater and ‘neighbours’ and neighbourhoods can be affected by wood smoke. Also, in cities and towns, a majority of people buy and operate wood stoves not out of need, but for the ‘aesthetics’ of having a “cozy” wood fire they can see through a glass fronted stove on a cold winter evening. This majority has little interest in spending the time and effort needed to attain efficient combustion conditions.
 
Wood can be burned efficiently but in a majority of domestic situations in North America it is not. The following is copied from a research paper on biomass burning which quotes various EPA documents:
 
Burning a kilogram of wood in a new stove will produce about 130 grams of carbon monoxide, 51 grams of hydrocarbons (including up to 10 grams of carcinogenic benzene), 21 grams of fine particulate, and about 0.3 grams of highly carcinogenic poly cyclic organic hydrocarbons(EPA 1984, Larson 1993). Wood burning also produces from 10 to 167 milligrams of highly carcinogenic dioxin per kilogram of fuel burning (Abelsen). Wood burning is responsible for about 3 percent of the total suspended particulates, 6 percent of the total carbon monoxide and 51 percent of the highly carcinogenic polycyclic organic matter produced by all U.S. sources (EPA 1986). Wood smoke is usually released near ground level in populated areas and thus is especially apt to hurt people. Wood burning pollution is often concentrated in certain areas of the country (USA) such as the Northwest and at specific times, such as winter evenings. Biomass smoke is generally heavier than air and tends to sink to the ground. It causes high concentrations of particulates where ever it is burned, from a food cart in New York City to a neighbour or restaurant near you.
 
When I look out of my windows I can see 6 out of 9 houses with wood stove chimneys all within about a hundred metres from my house. What has prompted me to change from “passive acceptance” and “become active” on this topic is a house below me in a state of re-construction where the City of Rossland has allowed a wood stove chimney that is only about 65 feet from my living room sliding doors and below the level of my bedroom windows. This is too close for comfort and smoke can, and does on occasions, drift directly to my house.
 
Unfortunately I don’t think anything will change as I’m sure many people consider that their right to burn wood supersedes the rights of others to breathe unpolluted air.
 
Ken Holmes
Rossland

Comments

The number of wood burning

The number of wood burning appliances in Rossland is obviously the starting point for any calculations of particulate emissions.

The 2009 and 2011 Rossland Energy Surveys both indicated that 9 - 10% of households used wood as a primary source of heat....say 140 homes.

The 2009 survey indicated that about 50% of households used wood as a secondary source of heat......say 700 homes. The 2011 survey did not ask a question on this so this number was not verified.

It is reasonable to assume that all the primary heating appliances are high efficiency or catalytic types whereas the secondary heating appliances can be anything from fireplaces through conventional airtight or non-airtight stoves to high efficiency and catalytic units.

The only guide I could find on this is a report on residential wood wood burning emissions published in 2005 by the BC Government which gives results of percent by type of appliance for the Kootenay region.

Two methods for calculating particulate emissions are available. One uses EPA "emission factors" in terms of kg of emissions per tonne of fuel burned for different appliances. The other method uses grams/hour of particulates. In both cases assumptions or "guesstimates" have to be made about either the quantity of fuel burned or the hours of operation for both types of wood users...primary and secondary.

The "emission factor" method gives higher results than the "gram/hour" method which may reflect the fact that EPA test results obtained under very carefully controlled and specified conditions are rarely duplicated in day to day operation of stoves.

Grams per hour usually exceed EPA test results due to variables such as types of wood, moisture content, cold starts (versus hot starts in the tests), stove / catalyst deterioration with age and other operational factors. Some reports indicate that particulate emissions from older "conventional" stoves and fireplaces can be 3 to 5 times higher than EPA certified stoves.

Information on operating hours is scarce, however studies from 2004 and 2006 indicate an average of 5.8 hours per operation with 44% exceeding 8 hours.

Information of quantitiy of wood burned is available in the 2005 BC Government report and some idea can also be obtained by asking friends in Rossland what amount they burn.

Punching all these variables into the two calculation methods using a range of optimistic and pessimistic assumptions produced a spread of results from a low of 0.7 tonnes of particulates in a winter month to a high of about 1.5 tonnes, with about 1 tonne as a reasonable average.

Its difficult to share pages of research notes and calculations with people who make their comments or criticisms under an anonymous name however I think my calculations can stand up against a "shot from the hip"!     

Okay, but what's the alternative?

Instead of wood—which we can harvest as a free waste product or pay someone local to collect and stack for us—what are the options?

Brand new homes should obviously take care to consider "passive" heating methods, from solar gain to a tight envelope that reduces heat loss. We should also be trending towards more compact homes: less heat, less maintenance, more time and money.

But what next? Furnaces and fireplaces that burn natural gas? It burns clean, sure, but how do we feel about fracking, pipelines, trucks, wells, and industrial wastelands? How do we feel about sending money out of the community to bloated multinationals, even if they are Canadian?

Coal? Next.

Oil? Next.

Okay, electricity. We've got lots, but if everyone switched to electrical heat, you know we'd be damming (or damning) more precious rivers at some point soon...

And there's something about a baseboard that doesn't strike the ol' spirutual bell like the ringing in my heart when I sit by the hearth. That's got to count for something.

Yes, there are other great ideas we should pursue: take solar hot water pumped through the floor for one, or there's geothermal for the financially fortunate.

But for the rest of us, in our old leaky homes, with our strong belief that we vote with our dollars (and we'd rather not vote for mega-business), what can we expect beyond the good work of the wood stove exchange program, aiming for higher efficiency and cleaner burning?

The 1 tonne per month of

The 1 tonne per month of particulate emissions is just Rossland. My apologies to Phil F and your readers for being unclear on that. The estimate is based on 10% of homes using wood as a primary heating source and 50% having wood stoves as a secondary heating source.

EPA reports seem to indicate that more than 90% of particles from wood stoves are 2.5 microns or less under most burning conditions. These small particulates stay in the air longer and, according to published information, pose the greatest health risk.

What comes out of the chimney is meaningful information as a starting point and is the only measure that can be used in regulations. Where the particulates go once in the air obviously depends on local conditions, wind, meteorological conditions, geography etc. Although there are some published studies of measurements on the ground and in homes, I agree it is meaningless to try and apply results from Quesnel, Williams Lake or Golden to Rossland.

The smoke problems of woodpile burning, I agree, are orders of magnitude greater than wood stoves, however the impact on urban areas depends on their relative location and wind conditions, as outlined by Phil F. Hopefully the "Smoke Management Framework for BC" published last year will lead to improvements. 

Personally, I would like to see fuel from slash piles burned efficiently in power plants, however that depends on the economics of fuel preparation costs, transportation distances and many other economic factors.

Another "stat" to "bandy around" is that the quantity of particulates emitted from the wood-waste burning power plant at Kettle Falls is also just over 1 tonne per month, comparable with Rossland wood stoves on a winter day. However that plant generates enough electrical power for about 46,000 homes from burning 70 tons an hour of woodwaste.    

1 ton?

I'd like to see the math on your calculation that we produce 1 ton of emissions per month.

 

If we had 1000 homes heating with wood 6 hours a day, 30 days a month, generating 7.5 gm/hr (using inefficient old stoves), we'd get 1.35 tonnes.

But I highly doubt there are 1000 homes in Rossland with old wood stoves that are being used for the sole source of heat and that are also so poorly insulated that they actually require 6 hours of burn time each day.

Regulations and Policy

I agree that emission numbers for woodstoves are useful to regulate the sale of woodstoves.  But that is to prevent unnecessary pollution, and in effect to also mandate efficiency, since for woodstoves, efficiency and emissions are closely related.

But, those numbers are not useful to create municipal or provincial policy regarding the use of wood stoves, since they are not an indicator of air quality. 

And from personal experience here in Rossland, because of our geographic location, smoke is usually quickly dissipated except perhaps in localized areas and at certain times.  It's a far cry from the situation in places like Ymir where you can literally see a cloud of smog on some mornings hanging over the area, despite its low housing density.  So once again, this is a clear indicator that chimney emissions does not equal a health or general air quality problem. 

Something else that you might want to bear in mind is that while wood smoke particulate can contribute to health problems if breathed in in large quantities, once it dissipates it either settles right away to the ground or rises high in the atmosphere and comes back down to the ground with rain (the particles help seed clouds to form precipitation).  That in turn fertilizes the ground.  This is what happens during natural forest fire cycles.

So while I'm all for reclaiming wood waste to generate electricity, until the day where we can't find wood waste within close proximity to our town, using it heat our homes (as efficiently and cleanly as possible) is a close approximation of the natural cycle (ashes into the garden) and smoke dispersed into the environment to spread nutrients back to the ground.  So for now, in Rossland, it makes sense to keep allowing wood burning stoves, while continuing to push and educate people to burn more efficiently, and also reducing our energy needs by insulating our houses properly.

We're a long way from cooking over wood fires in houses without chimneys.

A "Residential Wood Burning

A "Residential Wood Burning Emissions" report issued in 2005 by the Provincial Government, showed that more than 50% of wood burning stoves and fireplaces in the Kootenay Region were "conventional" (> 15 year-old) and that less than 50% were of advanced or catalytic design.

Even if all the old stoves were replaced by modern stoves under the Wood Stove Exchange programme, there would still be more than 1 tonne per month of particulates emitted in a typical winter month.

This assumes that all the primary heat wood stoves are used full-time and one-third of the secondary heat or "recreational" wood stoves are used for 4 hours per day

That's still a lot of particulates being emitted into Rossland's "clean" air.

Localized particulate emissions

I'm not sure what you're trying to point out here.  Are you saying 1 tonne of particulate per month for the entire Kootenay Region?  That's a big region and a long stretch of time for all that particulate to dissipate into.  And how does that compare to particulates released by woodpile burning in forestry in the same region?  It's probably peanuts.  I've personally lit single piles that are probably bigger than all the wood used by all Rossland wood stoves in a whole winter - and no the wood wasn't particularly dry or well cured, and it was only one of many piles I lit that day.  But that isn't usually a problem unless there is unusual atmospheric air circulation that traps the smoke in a low-lying region (and good forestry crews will check venting reports to prevent that very thing from happening).  So I'd rather see some of that wood diverted to wood stoves so we can at least benefit from the heat it will give off, and probably reduce net atmospheric pollution at the same time (from cleaner burning).

Secondly, the dangers of particulates isn't from the emitting of them, it's from breathing them in.  So "tailpipe" emissions numbers from woodstoves is of little value.  You need air quality research that shows average ground level exposure to particulates and length and consistency of exposure to indicate a health concern.  Unfortunately, this kind of research is tough to get useful results from, because they are extremely localized.  For example if you measured it outside your front door, it might be very different than outside your back door, or your second story window.  And since you don't usually keep doors or windows open in winter, it's going to be completely different from your indoor air quality where you spend much of your time.  Remember that small particulates will easily rise and disperse upon leaving the chimney stack, and bigger particulate will be more likely to reach the ground near you, but it will also settle onto the ground fairly quickly, so it's only a temporary problem.

I'm not saying wood smoke is never a problem, or isn't a problem for you coming from your neighbours if your house lies in the path that your neighbour's wood smoke  generally drifts to (and I sympathize, believe me).  But for the most part, all the stats you are bandying about don't amount to much useful information.  Specially in Rossland which isn't a low-lying valley and usually has good air circulation.

Rather than spending our

Rather than spending our money on toys and holidays my family and I decided to bite the bullet and invested into a fuel-efficient catalytic wood-burning stove, certified to 1.0 g/hour. All the seasoned wood comes from waste destined to the slash piles around the area.

I would find it ironic if, eventually, a bylaw was proposed to ban efficient and responsible stove wood burning for residential heating in Rossland. First, let's have City Hall starting to enforce the bylaw banning yard waste burning, and the one banning idling. Only then an enforceable bylaw against inefficient and irresponsible residential heating (regardless of the energy source used) should be suggested.

I believe I am as environmentally conscious as they come, and I have made my peace with using wood waste responsibly  for heating my house. I know we are not the only ones.

well I thought I was doing a good thing.

I have used a modern efficient stove for quite a while. a lopi from the states and now since moving to town a pacific energy stove. I get my wood from logging site who cut everything and burn what they dont haul away,(slash and burn). the wood I heat my house with would have been burned in huge piles, wet and smoking,Im sure everyone has seen those big pillars of smoke on the edges of town.its better to burn that waste wood in a hot clean burning stove and avoid burning more natural gas.I learned alot about stoves. my lopi was the most efficient stove on the market when I bought it and it put out a lot of heat with almost no ash.well my new stove is clean burning but aparently therre was no thought to heat transfer as it burns hot and clean but the heat goes up the chimney.I still think it is better to use wood that would be burned in the woods to heat my house. why is noone upset about the huge burns that go on outside of town and still make your eyes water here in town?

Comparing to cigarettes

I have to scratch my head at studies that compare chimney emissions to cigarette smoke.  The big difference is that cigarette smoke is inhaled directly from the cigarette into the mouth.  Unless you're standing on your neighbour's roof inhaling from their chimney, such numbers are essentially worthless. If that chimney is emitting the equivalent particulates to 100 cigarettes at the point of emission, what is that equivalent to at 65 feet from the point of emission?  Obviously that's going to vary considerably depending on atmospheric conditions, but I guarantee you're not breathing in the equivalent of 100 cigarettes' worth of smoke per hour.

 

That being said, I also have neighbours who seem to be polluting the air quite a bit using their wood burning stove.  Innefficient stoves are one thing, but something else that is worth mentioning is the use of inproperly dried and stored wood.  I see many people collecting and chopping their wood in the fall, and storing it against the side of their house.  This doesn't give enough time to properly dry the wood  to achieve a clean burn, no matter what kind of stove you use.  Wood should be dried for at least a summer, if not more, without any exposure to moisture - which means  covered and well ventilated - I simply don't see that many people using that much foresight, with the end result of them polluting their neighbour's air.

Whilst modern, EPA Certified

Whilst modern, EPA Certified wood stoves are far more efficient than older wood stoves, there are still many older non-certified stoves in use.

However, even EPA certified stoves emit particulates and other impurities. The particulate level allowed for a non-catalytic EPA stove is 7.5 gm/hour and 4.1 gm/hr for a catalytic stove. This is equivalent to particulates from about 190 and 100 cigarettes respectively.

Keep in mind also that the EPA tests are carried out under very carefully prescribed conditions during the burning of varied fuel loads and at different burn rates.The fuel is carefully sized, with a specific moisture content and the pieces are even separated with wood spacers to allow good air movement which is carefully controlled. This is far from the reality of how wood stoves are operated in practice.

The situation is analagous to 'gas mileage' tests on cars. How many people achieve the 'gas mileage' given in the brochure for their new car?

It's the same with wood stoves...it all depends on how carefully you operate and maintain it. Often, wood stoves are oversized, firewood is not always dried, catalysts burn out and are not always replaced because they are to expensive and just throwing a couple of logs into the stove when it dies down is a far cry from the carefully controlled EPA test conditions. How often do you see a wood stove with a smouldering fire as opposed to a firebox full of bright flames.

Some of the older emission test numbers are probably more representative of how stoves are operated in practice

Ken   

all stoves created equal?

Well, there are woodstoves and there are woodstoves.  The difference between emisisons from a good one with a catalytic secondary chamber and the emissions from a clunky old box are pretty significant. Ken has my sympathies, of course.  But he's quoting numbers from studies based on decades-old woodstove technologies.

Some more info on

Some more info on fires...

Fanning The Flames of Indifference

While many of our elected officials sit in the council chamber fanning the flames of indifference regarding their lack of concern about banning Recreational Residential Woodsmoke Pollution, millions of Canadians are left suffering during the hottest of seasons-though we suffer all year round- from breathing the toxic emissions from outdoor open air burning within their communities.

Wood burning fire pits, chimeneas, fire rings, wood fuelled BBqs, wood smokers, pellet BBQs, bon fires, beach burns, outdoor cooking ovens and all devices and appliances that use wood as a fuel source continue daily to contaminate the air with a host of deadly toxins.  Many of the same cancer causing compounds are found in tobacco smoke.

Knowing that Tobacco smoke is addictive, deadly and a staggering burden on our already overtaxed health care system, Woodsmoke is leading the way as the other second hand smoke Canadians are being subjected to breathe.

When our municipal Fire Departments receive nuisance complaints about Wood burning fire pits, and other forms of recreational burning, it is due to the fact that city residents are being made ill, suffering and having difficulty breathing the acrid, reeking emissions from Woodsmoke.

When will all our elected leaders, including our Fire Departments and Health Boards take pro-active action to ban/end/prohibit all forms of community wood burning?  When will our Health Board issue community public service announcements to inform/warn the public of the deadly danger of fine particulate matter (PM2.5) that is part of the toxic chemical make up of Woodsmoke?  When will Woodsmoke be addressed as a Public Health Issue that is a threat to all community residents?

Why would people filter their drinking water, avoid tanning beds, take precautions to avoid the flu by means of thorough hand washing and immunization, avoid the deadly chemicals found in Tobacco, be willing to adopt and adapt to new community by-laws that will ban all patio Tobacco smoking and outdoor open air smoking in public areas, only to continue sitting by fire pits, bon fires, back yard wood burning ovens, fire rings or wood fuelled BBqs, exposing themselves and everyone else in the existing area to the deadly chemicals found in Woodsmoke?

It is long overdue that Woodsmoke and all Wood burning receive the same acknowledgment as a health and environmental issue that is in each and every Canadian community.

While Mayors and council members deliberate the ongoing budgets and implementation of new green initiatives, smouldering, reeking, woodsmoke fills the air in urban neighbourhoods threatening the health of the young, fragile elderly, those with pre-existing conditions and those with heart and lung disease.

It is time to stop fanning the flames of indifference regarding Recreational Residential Woodsmoke Pollution and take immediate action to ban wood burning before more people become ill, suffer and die from Woodsmoke polluted air in their community!

Linda Baker Beaudin

Air Is Precious