[Committee] How much land for Biomass (WAS : Effect of methane leakage on Carbon footprint of gas)

Sun Feb 25 20:23:27 UTC 2007

This is probably a bit off topic but please can you give me your quick
opinions. I'm doing the maths on the CCS yields possible from Biomass with
all the lifecycle process deficiencies included. Target is 1Gt CO2 per year
as per the Virgin Earth Prize!

Question) Given the land available, efficiencies and energy output, would 9%
of the global land surface area needed to yield the 1Gt be a field too far
in your opinions?

Brgds
Robin.

> -----Original Message-----
> From: Steve Stretton [mailto:sjstretton at googlemail.com] 
> Sent: 27 January 2007 01:48
> To: 'David J.C. MacKay'; 'Gunnar M?ller'
> Cc: committee at zerocarbonnow.org; 'Adrian Wrigley'; 'Adam 
> Barnes'; 'Jonathan Kohler'; 'Philip Sargent'; 'Philip 
> Slater'; 'Robin Smith'; 'Ronan Kavanagh'
> Subject: FYI: Effect of methane leakage on Carbon footprint of gas
> 
> As far as gas leakages are concerned...
> 
> The effect of CH4 (Global Warming Potential over 100years by 
> mass = 23) [1] translates to 23x(16/44)= 8.4 times the GHG 
> effect of CO2 per Molecule.
> 
> So we multiply the leakage rate by 8.4 to get the additional 
> greenhouse effect If we assume (cf. [2]) a high (4%) methane 
> leakage rate, then methane leakage has 34% the 100y-effect of 
> the CO2 from burning the same gas.
> 
> Assuming 350g/kWh for gas electricity, there is a boost of 
> ~120gCO2 equiv/kWh so ~470gCO2equiv/kWh total GHG effect. 
> (this is consistent with the *text* which says "around half 
> that of coal (~500gCO2eq/kWh)"; figure 3 is lower).
> 
> Assuming 50g/kwh for CCS (85% effective[3]), we would then 
> also add 120g/kWh from methane leakage to get 170g/kWh for gas + CCS. 
> So it's a significant increase, but still slightly below the 
> 240g/kWh shown on figure 3.
> 
> I haven't included the extra gas needed per kWh for CCS in 
> order to power the compression and storage of the CO2, but 
> I'm assuming this isn't too significant.
> 
> So gas leakages are significant in the case of gas+CCS, but 
> don't seem to explain all the increase.
> 
> All the best,
> Steve
> 
> (Apologies for anyone copied in but not interested).
> 
> 
> NOTES
> 
> I enclose the figures from the POST note. BTW there's lots of 
> these post notes on all sorts of interesting topics (there's 
> one on CCS) and they're quite useful.
> http://www.parliament.uk/parliamentary_offices/post/pubs2005.cfm
> 
> 
> [1] IPCC 2001 quoted in Wikipedia
> http://en.wikipedia.org/wiki/Global_warming_potential
> The effect of Methane per unit mass is 23
> (23 times more potent than CO2 over 100 years).
> 
> [2] James Lovelock 'The Revenge of Gaia' p74-76. Original Sources:
> Lelieveld J. et al., Nature, April 2006
> (Max Plank Institute for Chemistry, Mainz, Germany). Leakage 
> rate of 1.4% from Russian Pipelines, comparable with 1.5% 
> leakage rate reported in the US. Does not include leakage at 
> production and burning sites.
> cf. Society of Chemical Industry (2004). Overall leakage rate 2-4%
> 
> [3]Ecofyn study on CCS, included
> -----Original Message-----
> From: David J.C. MacKay [mailto:mackay at mrao.cam.ac.uk]
> Sent: 26 January 2007 14:33
> To: Stephen Stretton
> Cc: Gunnar M?ller; committee at zerocarbonnow.org; Adrian 
> Wrigley; Adam Barnes; Jonathan Kohler; Philip Sargent; Philip 
> Slater; Robin Smith; Ronan Kavanagh
> Subject: Re: Parliamentary Office of Science and Technology / 
> Electricity Generation Carbon Footprints
> 
> 
> very nice document.
> 
> The only thing I didn't understand is figure 3 gas with CCS.
> 
> Why do they have such an ineffective figure for CCS?
> Anyone understand?
> 
> Is it because of accidental leakage of CH4? (Stephen's suggestion.)
> 
> thanks
> 
> David 
> 
> * Stephen Stretton <sjstretton at googlemail.com> [2007-01-26 13:56]:
> > Hi,
> > I've just noticed the work of the Parliamentary Office of 
> Science and 
> > Technology (POST). "POST is an office of both Houses of Parliament, 
> > charged with providing independent and balanced analysis of public 
> > policy issues that have a basis in science and technology."
> > http://www.parliament.uk/parliamentary_offices/post/new.cfm
> > You can register for email updates online.
> > 
> > Attached is the report of the carbon footprint for electricity 
> > generation. Any comments?
> > 
> > Best regards,
> > Steve
> > 
> > 
> > 
> > POST is grateful to all contributors and reviewers. For further 
> > information on this subject please contact Dr Stephanie 
> Baldwin at PO 
> > ST. P arliamentary Copyright 2006
> > 
> > Parliamentary Office of Science and Technology, 7 Millbank, London 
> > SW1P 3JA
> > 
> > t el: 020 7219 2840 email: post at parliament.uk
> > *
> > 
> > www.parliament.uk/post
> > *
> 
> 
> 
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> David J.C. MacKay                                 
> mackay at mrao.cam.ac.uk
>                              
> http://www.inference.phy.cam.ac.uk/mackay/
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