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Old 05-26-17, 08:54 AM
  #61  
cyccommute 
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Originally Posted by willibrord View Post
The carbon comes from fossil fuels and instead of being burned and added to the earth's atmosphere it is turned into carbon fiber and into a bicycle, a solid form of carbon.

The small wood burning camp stove takes wood pellets, wood which would normally be discarded. so it is truly carbon neutral.
The issue is that the carbon is removed from "storage" in the lithosphere and reintroduced into the atmosphere where it hasn't been in millions of years. That's not "sequestration".

Originally Posted by Happy Feet View Post
Well.. not really.

To make carbon fiber you take one form of sequestered carbon (oil product) and turn it into another form of sequestered carbon (fiber). But along the way you need to process that oil to make the fiber via manufacturing and that generates a carbon footprint.
Exactly.

Originally Posted by Happy Feet View Post
Wood pellets are also a form of sequestered carbon (trees) but when you burn them you release that carbon into the atmosphere (CO2). That CO2 will eventually be sequestered again by plants via photosynthesis but you can't say using a wood stove is carbon neutral. Everytime you use it you are creating a (small) carbon footprint.
Well you got the first half right but you fell flat at the end there. If you really split hairs, burning biomass that is only a few months to a few years old has an infinitesimal carbon footprint but that carbon is being rapidly exchanged though (almost) natural processes. There needs to be some carbon exchange between plants and animals as well as natural processes (mostly fire). If there isn't, the carbon would all be sucked up into the lignin of trees which is buried and taken out of the carbon cycle.

If too much carbon is removed from the cycle...either through burying the carbon or through the formation of calcium carbonate...it can be just a detrimental as having too much carbon. The planet cools and plant growth slows which reduces the carbon in the atmosphere which leads to more cooling, etc. The Little Ice Age that occurred from 1300 to about 1600 may actually have been caused by the increase in plant growth caused by the Black death in the early part and the death of native peoples in the Americas in the latter part. No one was clearing fields and plant growth was rampant, sucking up too much carbon and causing cooling on a global scale.

Originally Posted by willibrord View Post
Depends where the energy to do that comes from. If it comes from a renewable source that carbon footprint is negligible.
It's not likely that the energy comes from renewable sources for making the acrylonitrile precursor for making the fiber. The acrylonitrile is made from propylene (which is made catalytically from petroleum) and ammonia passing over catalysts at 400 to 500C (800 to 900F). It's difficult to get that kind of heat from biomass.

The carbon fiber is made by polymerizing the the acrylonitrile at elevated temperatures and then carbonizing the polymer at 1000C (1800F) which is, again, too high a temperature for energy from renewable sources.

Originally Posted by willibrord View Post
There is some carbon exchange between the wood and the atmosphere and then back into plant material again. It is not like you are taking million year old oil and suddenly releasing that stored carbon into the atmosphere.
Just to be fair: Exactly.

Originally Posted by willibrord View Post
Okay I was wondering if Carbon fiber would burn. I found this video



It burns, sort of. Maybe it is just the resin burning off. I would not recommend it for your portable wood stove.
Even if it is carbon neutral.
Carbon fiber and the resins used to hold it together are heavily cross-linked and will burn as long as a heat source is applied. But they are self-extinguishing. It's hard for the flame front to propagate into the matrix so that oxidation of the carbon is slowed significantly. Basically, the material is just too tightly bound to release carbon easily.

And, from personal experience, I can tell you that the smell from burning that part in the video was horrible. I worked on trying to recycle carbon fiber briefly and it was one of the worst jobs I've ever worked on.

Originally Posted by Happy Feet View Post
I agree it's a matter of degrees but that is how the process works and how footprints are measured. It's the release of greenhouse gasses (primarily CO2) during the manufacturing phase, whether it's manufacturing a product (CF) or heat to cook food (wood pellets). Carbon neutral would be to use a solar oven, for example. No release of CO2.

As someone said: bicycle riders are already pretty low on the polluting scale to be worried about CF or wood pellet stoves in that way.
I would say that is how carbon footprints are improperly measured. Carbon has a bad name...and for some good reason...but it is a very necessary element for live on the planet. You can't get rid of all of it. A "carbon footprint" measurement shouldn't include the natural processes or utilizing natural products. Those are "gimmes" in renewable energy calculations that I've seen. It's what utilizing biomass is based on, i.e. biomass is (mostly) carbon neutral.
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