Hacker News Reader

Comment by pas | Hacker News Reader

Aaaand it's directly bad for our health too. Air quality in winter is absolutely shit around houses that burn wood.

easily more people die - probably in every leg of this biomass face (logging and transportation are both notoriously accident prone industries, and neither of them are kind to the human body, and flying ash at the place of burning) every year than died due to the Chernobyl disaster.

View on HN

It seems like we are damned if we do, damned if we don’t. I was starting to feel smug for having a 2-year-old catalytic wood stove fired by locally grown hardwoods (I am in NH). Then I found this article [1] about a Finnish study showing high dioxin and furan emissions due to the catalyst.

Luckily we just added hyper heat air source heat pumps to the rest of the house. We also have hydronic heat from an oil-fired boiler, which we are planning to only use when it’s too cold for the heat pumps (less than 25 degrees F).

The boiler also supplies hot water, so looking to replace that with a heat pump water heater to avoid burning oil in the summer. However, even with the efficiency of heat pumps, the electricity is mostly generated with gas, which is <40% efficient (factoring in transmission and distribution losses). Our boiler is 82% efficient, so from a carbon/GHG point of view, heat pump water heater may not be any better. Of course electricity is fungible, so more nuclear, solar, and wind would change the equation.

What I want to know is, where is the Department of Energy, etc. guidance on this. I have a fair amount of experience with energy policy and technology and the right path is far from clear to me.

[1] https://www.familiesforcleanair.org/catalytic-wood-stoves-sh...

Even heavy oil for boilers requires some energy to produce from raw oil. Plus there are transportation losses. They are less than transport losses for electricity but not much.

Great post. We're in a parallel situation in Vermont: current EPA woodstove using locally harvested wood, fuel oil backup that we use only when we aren't home. We did install a heat pump hot water heater and have been happy with it, but it was replacing electric so a clearer win.

I'm not sure what to make of the Finnish study. Full version is here: https://sci-hub.se/10.1016/j.chemosphere.2012.02.027. It's hard to know how the elevated levels compare to other sources, since 2x of almost zero might still be negligible. It does mention though that the "PCDD/F level exceeded the emission limit in Europe for MSW incinerators" so maybe it's real.

One other factor that might help us remain "smug" about our modern wood stoves is that the Finnish study was done on sauna stoves without secondary combustion and with high flue gas temps. I suspect the results might be completely different for compliant woodstove with good secondary and much lower flue temps. Of course, different might end up worse.

Thanks for posting the original article. One of these days I’ll look for citations that might elaborate this work.

I keep telling people that and all I ever get in response is denial and „oh but the fireplace makes such a nice warmth“.

People also don’t understand you can’t regulate the output of fireplaces short-term. „Oh it’s getting hot in here, I’m gonna close the air supply” - and boom you’ve turned subpar unclean combustion into oxygen-starved combustion. Good job! But wood is CO2 neutral /s

You may enjoy this old piece by Sam Harris on what he calls The Fireplace Delusion: https://www.samharris.org/blog/the-fireplace-delusion

To be fair, wood-burning fireplaces are fine as long as they're used only for special occasions. (Think Christmas dinner and that sort of thing.) But any urban wood-burning fireplace or stove that's used regularly is a real problem in this day and age.

In that case I don't think anyone would bother to have it properly cleaned - a safety risk - and you just end up with the chimney acting as a source of heat and air loss when it's not being used.

What safety risk? You’re not going to get meaningful creosote buildup on any reasonable timescale using it so infrequently.

It’s trivial to plug the fireplace when it’s not being used, to mitigate heat loss.

I wonder if that could be somehow fixed in some kind of two step combustion. Like if you cut oxygen supply and are now basically pouring coal particulated up the chimney could that the somehow "afterburned" to be turned back into heat and CO2?

Catalytic converters basically do that with CO

This is how modern wood stoves work either with a catalyst or with oxygenating tubes that sit in the ceiling of the firebox to help more completely burn the soot. Big increase in efficiency and reduction in particulates.

FYI the article is talking about industrial power wood burning, not personal consumption.

If your stove has a catalytic converter then the oxygen-starved combustion is also very efficient at producing heat. It's common to put some pieces of wood in at night, turn it all the way down, and still have enough in the morning to keep the fire going.

Modern wood burning stoves have catalytic combusters that significantly reduce the emissions coming out of the chimney. They essentially burn the wood, then re-burn the smoke from that fire at a very high temperature (and then sometimes a third time). This results in much lower emissions and much more efficient burning where more heat is extracted.

They're mandated by law in many places now.

Anecdotally, friends in the Yukon used to burn ~10 cords of wood a winter. After upgrading to a catalytic combusting wood stove they now burn about 5 cords. Same house, same wood.

>Anecdotally, friends in the Yukon used to burn ~10 cords of wood a winter. After upgrading to a catalytic combusting wood stove they now burn about 5 cords. Same house, same wood.

Thank you, I just learned a new word/unit of measure (cord) and went down the rabbit hole:

https://en.wikipedia.org/wiki/Cord_(unit)

has a photo that really helps in visually dimensioning the amount it represents.

Maine has the "loose thrown cord", and then there are:

>Other non-official terms for firewood volume include standing cord, kitchen cord, running cord, face cord, fencing cord, country cord, long cord, and rick, all subject to local variation.

Wood pellet combustion is significantly better than thick wood logs but it does produce particulates so it's not as clean as gas.

Reply on news.ycombinator.com