Rev. J see below
On Aug 21, 2013, at 12:08 AM, "[email protected]" <[email protected]> wrote: > > Is the following statement correct? > > ...biomass stoves are carbon neutral. RWL1: Mostly "Yes". I supported Andrew's statement on this - but for the purpose of making a defense of carbon negative stoves. Upon reflection, I think it safe to say there are some biomass stoves (5-10%??) that today should be called carbon neutral - mint be worse than a stove using fossil fuels. This would be the case when the local biomass in a specific region is disappearing - so more CO2 is being emitted from the stove than is being replaced via photosynthesis. My understanding is that globally annual productivity is growing rather nicely - maybe because the market for pulp is down, success in saving forests, etc. > > Would somebody explain, in layman's language, the claim (made elsewhere, > e.g., Terra Preta discussion) re carbon negative impact of biochar-producing > TLUD gasifier stoves.) [RWL2: Start with carbon positive: all fossil fuels are carbon positive - they are adding carbon dioxide to the atmosphere at a rate of about 30 giga (billion) tons of CO2 per year. Divide by 3.67 to put that "30" in terms of carbon, getting 7-8 gigatonnes C per year added annually, about half of which stays, the other half going into the oceans, soils, and plants. That half (>4) shows up as an annual growth in CO2 of about 2.5 ppm, now about 400. The exact ratio between ppm and GtC is 2.12, with about 800 Gt C now in the atmosphere, about 40% due to you and I and our relatives. Carbon neutral refers to any energy source that displaces anything carbon positive (anything fossil OR biomass not being used sustainably). The vast majority (a guess is 90-95%) of biomass stoves do not add CO2 to the atmosphere in a long term sense. Within a year or two (or less) an equivalent amount of the released CO2 is back (through photosynthesis) as plant matter. But quite a few countries, especially in sub-Sahara-Africa (SSA), are losing their forests. Mostly due to conversion to farmland, but maybe 20-25% due to charcoal making. This is why I backed off a little today in #1 in supporting Andrew. Carbon negative technologies are those that take CO2 out of the atmosphere. Some claim to do so for infinite time (conversions of CO2 to carbonates may be close to infinity), while the 4-5 biomass CDR (Carbon Dioxide Removal) approaches have a wide range of claimed lifetime. The technology called BECCS (biomass energy with carbon capture and sequestration) essentially claims an infinite time as it places liquid CO2 deep underground. Conservation farming (no till, etc) can claim hundreds of years, but the stored carbon can be released again if the practice is stopped. Reforestation and Afforestation are similar - with concerns of release following a fire. There are a few other biomass-related options out there, but the main one for the stove community is biochar. Biochar is a char (most chars, not all qualify to be called "biochar") that is placed in the ground. Lifetimes are hard to give accurately since conversion of char back to CO2 is so slow. In the Amazon, biochar (terra preta) is dated back 4000+ years by carbon dating, but we don't/can't know how much was placed and has disappeared. Closing the loop, TLUD stoves (I much prefer the term "pyrolyzer" over your "gasifier" - as we have a sister list called gasification, where they try hard to convert char to gases) are designed mainly to produce char. I think most char produced in TLUd stoves could be said to have a lifetime well over 100 years (I like the number 1000 as an average), and few economic analyses of char benefits even go out to 30 years. There are several other ways to make char while cooking besides the TLUD approach All these char producing stoves have other virtues (and drawbacks), but they should not be called biochar-producers (i.e. replace "biochar" with "char"). If that char is itself combusted, that stove would in most cases be able to be called carbon neutral. The IPCC is not so picky; all biomass use is said to be carbon neutral - same as wind or solar. Note that wind and solar have almost no ways available to be called carbon negative. Biomass (and in my mind biochar) seems to be ahead in the world of CDR (of carbon negativity). The economics of CDR are measured in trillions of dollars - so this is not a minor topic. These fine distinctions on char (especially biochar) lifetime are very important and subject of much discussion, but (mostly) go beyond your question, which I hope I have answered. If not - try again. Yours is a very important question. Ron > > > > ---------- Original Message ---------- > From: "Andrew C. Parker" <[email protected]> > To: "Discussion of biomass cooking stoves" <[email protected]> > Subject: Re: [Stoves] Climate Panel Cites Near Certainty on Warming > Date: Tue, 20 Aug 2013 09:48:21 -0600 > > [Sorry, fumble fingers sent my reply before I was finished] > > Paul, > > In regards to CO2 as a dangerous greenhouse gas, biomass stoves are carbon > neutral. > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://stoves.bioenergylists.org/ >
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