Fireplace Inserts

For those of you with working fireplaces...

Two people on my street (Milton suburbia) use wood-burning fireplace inserts to heat their entire house all winter.  The inserts convert the fireplace from being net-negative to a highly efficient wood stove without a signficant change in appearance or construction.  A $2000 wood stove can heat 2000 sq.ft. with roughly 2 cords of wood for the winter.  Even paying Boston prices of $200/cord for split and dried wood, that pays back in 3 years, and uses a renewable source of energy.  If you use dead-fall, you are not increasing the CO2 emissions, even in the short term.  Leading manufacturers are Vermont Castings and Yodel.

I know what I want for Christmas.

Comments

[nlseaver]

How is it that by using deadfall, you're not increasing CO2 concentrations? Doesn't burning wood put CO2 into the atmosphere that would otherwise stay in the wood on the ground?

[nlseaver]

One other question on this: by my calculations (per the spreadsheet), 2 cords of wood results in 6100 lbs of CO2 emitted, which is a lot higher than, say, a natural gas-based heating system. Are you sure that a wood-based system is emissions-positive?

[Tom Wideman]

One thing that is very important to realize about the carbon cycle is that when a tree dies, falls to the ground, and is completely broken down by decomposers, ALL of the CO2 in the tree is re-released into the atmosphere. Therefore, the same amount of CO2 is released whether the tree is burned or decomposes. (In our area, decomposition of litter is complete and the cycle is balanced - there is no additional carbon stored in the soil; in northern forests, the extremely short summer does not provide enough time for decomposers to fully break down the litter, and the forests are functioning as carbon sinks - the organic matter in the soil is actually increasing). Therefore, once the tree dies, it's only a relatively short time before its CO2 is released, by whatever means. Provided that you get all of your firewood from "dead fall" (which is what I do) or you let a tree grow in the place of the one you took down, you will not be adding any additional CO2 to the atmosphere, and the cycle is in balance.

Compare this to the burning of fossil fuels. In this case, you are taking carbon out of a carbon sink (oil and gas resevoirs) and converting it to carbon dioxide. There is no way for the carbon dioxide to naturally make it back into the resevoir, so the process is net positive. That is why the burning of fossil fuels has lead to the increase in CO2 in our atmosphere.

[Tom Wideman]

You are absolutely right that wood stoves are less efficient than gas boilers. The difference is that trees are part of a cycle. They absorb CO2 when they grow and release all of it when they die. As long as you let new trees grow in their place, there is no increase in CO2. Hense, they are a renewable resource.

Fossil fuels, on the other hand, are a form of carbon sink that is locked permanently underground. By pumping it out and burning it, we are releasing additional CO2 into the atmosphere that cannot be reabsorbed by the sink.

[nlseaver]

Interesting. I had no idea wood returns CO2 to the atmosphere so quickly. Thx.

I wouldn't say that it returns quickly...my intuition says that it's probably on the order of a decade before a tree completely decomposes, but when it does, it's all CO2 again (in a mature forest).

BTW, that's one of the scarey feedback loops. In addition to the methane trapped in the permafrost, there is a lot of carbon trapped in soil in northern climates where the decomposers don't have enough time in the summer to break down all the dead fall. If it gets warmer for longer periods each year, the decomposers can release the carbon from this sink.