David
Apologies. That was not supposed to imply that you had lied but rather
that those who make claims that biomass is carbon neutral are, in my
experience, either practicing wishful thinking or attempting to
mislead. I wasn't actually meaning to put you in the latter camp but i
understand, given where we stand in other debates, how you assumed
this was an attack. For now.. chill out, no attack intended.
Second I was replying in general terms to a set of general assertions
in an email and not to a peer-reviewed paper so no I didn't provide
footnoted references. Let me read the paper you are referring to and
i'll get back to you.
Third, glad to hear there is some agreement that using purpose grown
biomass for sequestration (whether burned, buried or biocharred)
doesn't make sense. Looking at the figures on "earth overshoot" and
the dire state of ecosystem collapse documented in the millennium
ecosystem assesment I can't help but concluding there's no spare
stock of existing 'waste' biomass sensibly available for energy use
either.... when in balance, nature doesn't really do wastes...
go well
Jim
On Sep 16, 2010, at 2:27 PM, David Keith wrote:
Jim
"Lie" is a pretty strong word. What specifically do you think I lied
about? Can you back this claim up? Is this really the way you want
to engage in public debate on issues where we must make sensible
choices to protect our environment?
Two responses, one general one specific:
First, your claims about the efficiency of cofiring to not match an
extensive body of literature based on widespread industrial
experience. While there's nothing magic, about peer-reviewed
literature, and experts can certainly be wrong, I think that the
standard of evidence here needs to be a little higher than pure
assertion and reference to journalistic accounts. You might start
out by pointing out specific errors in the discussion of biomass
combustion efficiencies in our co-fire paper or one of the many
papers we cite therein. For example, there are a number of fine
papers on the energy requirements for biomass transportation. I
think you need to provide some pointers to why these are wrong.
Second, I agree with you that there's a great deal of over promotion
about the speed and productivity of biomass regrowth and about
offsets. For that reason, I have I have spent a fair amount of time
argued against use of purpose grown biomass because it takes so much
land for nature. I can point you to a nice section in my student
Jamie's thesis that documents the over estimates of biomass
availability by some who promote BECS. Indeed on closely related
point, we just got a paper into ES&T that examines biomass emissions
from fossil fuel production, finding that, for example, clearing of
peat lands for oil sands operations can have a surprisingly large
emissions, and have a very long time horizon because of the slow (or
not) recovery of the peat. If we tried to solve a significant part
of the climate problem using large-scale purpose grown biomass we
would, to put it bluntly, create an environmental disaster. So I
think on this one we may be on the same side. It would be nice if
here and elsewhere you would do a bit more work to check a person's
views before you attack them.
However, when it comes to use of waste fuels (the topic of our
biomass cofiring paper) these arguments aren't relevant. Of course
there are other issues, nutrients, emissions from transportation of
the fuel that have been discussed in this thread and elsewhere.
There are no free lunches here.
Yours,
David
-----Original Message-----
From: jim thomas [mailto:[email protected]]
Sent: Thursday, September 16, 2010 10:51 AM
To: David Keith
Cc: Stuart Strand; [email protected]; [email protected]; [email protected]
; James Rhodes
Subject: Re: [geo] Carbon sequestration workshop Sep 9-10, Heinz
Center, Washington DC
On Sep 16, 2010, at 11:38 AM, David Keith wrote:
while cofiring biomass in coal-fired power plants without capture
does
not rank on your list at all, because there is no capture, it still
avoids emissions of carbon. And because the capital cost of
retrofitting plants large coal plants for biomass co-feed is very low
and their combustion efficiency (for the biomass) is high this can be
a very cost-effective way to reduce carbon emissions with biomass. Of
course, it's not sexy and it's limited.
David this simply isn't right.
Firstly there IS carbon emission. Depending on how wet your
feedstock, is biomass can in some casess emit more co2 per kilowatt
produced than coal - thats real co2 aloft in the atmosphere for the
next century.
Whether that Co2 can subsequently be quickly fixed by theoretical
replacement plants depends on what those plants are and how
assiduosly they are managed. At present most co-firing of coal for
electricity is using woodchips and other forest biomass. Releasing
the carbon from a mature tree takes seconds, refixing it in another
mature tree takes
decades - maybe as long as seventy to a hundred years. All of that
time the initial Co2 released is still aloft and still impacting the
climate. That biomass can't even pretend to be carbon neutral for
several decades and as we all know timeframes are critical in
addressing climate change. Environmental journalist david baumann
puts it starkly: "it would take over 100,000 one-year old trees to
equal the weight of a 50 year old tree of similar species. Five year
old trees take around 30,000. So you see for every tree we cut down
and burn we'd have to plant 100,000 to resequester that much carbon
in one year, 30,000 in five years. We'd also have to find the space
to plant them." .
The orthodoxy used to be that you can just plant fast growing
eucalypts to sequester the CO2 faster than the older trees but that
was based on a single study from the 1960's only applicable to one
particular forest type and in fact its now understod that old
growth forests sequester much more carbon than young plantations and
that for the first 20 years or so a young plantation that replaces
old growth is stil giving more co2 into the atmosphere than its
fixing.
Moreover the carbon footprint of bringing biomass to the power plant
is not insignificant as biomass is heavy stuff with low energy
content (heavier when wet but drying consumes space and energy too).
Heres one quick back of teh envelope calculation on that: a standard
40 ton truck full of recently harvested woodchips will emit close
to a kilogram (0.91kg) of CO2 for every km that it drives when
delivering those woodchips for burning at a biomass electricity
plant. Even a smallish 50MW plant would require 12750 such
truckloads per year. At an average distance for sourcing woodchips
of 68 km, that amounts to almost 790 tons (788,970 kg) of extra CO
2 emissions per year just for transport of wood chips alone. or put
another way an additional 15 tonnes of Co2 per megawatt.
Lets say instead of wood you can use a biomass feedstock that
replenishes quickly such as annual crops, grasses or algae. (This
doesn't address the transport problem in fact it worsens it- you
would likely need more truckloads of crop residue than woodchips to
get teh
same energy output). As Andrew correctly noted, production of
agricultural biomass feedstocks have significant greenhouse
emissions associated with them. The more material you take from the
land for burning, the less you have to replenish soil fertiity and
hence the more nitrogen fertiliser is required to maintain
productivity.
Fertiliser production is responsible for approximately 1.2% of
total GHG emissions - equivalent to the full greenhouse gas
emissions of Indonesia or Brazil. In the US alone thirty percent of
energy use in agriculture is accounted by fertilizer use and
production. Thats before acount for nitrous oxide emission from
fertiizer applications and then again any methane or nitrous
emissions form eutrophication and runoff into dead zones such as the
gulf of mexico. Algae is no better - commercial freshwater algae
systems require higher concentrations of fertiliser than corn
because they have no soil to pull nutrients from and we know what
large scale saltwater algal production looks like - its called ocean
fertilization and it raises its own problems. You can harvest wild
algae from eutrophic systems and deadzones but thats building
dependence on an ecoloically unhealthy feedstock for your energy
needs.
Even before you plant biomass feedstocks there will be significant
soil carbon release from land clearances and land use change
associated with turning so-called 'marginal'/unproductive lands over
to biomass cropping. The Stern report identified a full 18 percent
of climate gas emissions were the result of land use changes, second
only to emissions from the power sector. This is the reason why the
folks who initially argued for biomass to be counted as carbon
neutral within the IPCC last year admitted they had made a 'critical
accounting error' (searchinger et al)
and so on...
The claim that industrially burning biomass for power 'avoids
emissions of carbon' is at best unexamined wishful thinking, at
worst an outright lie.
Jim
Jim Thomas
ETC Group (Montreal)
[email protected]
+1 514 2739994
Jim Thomas
ETC Group (Montreal)
[email protected]
+1 514 2739994
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