[USCC] Carbon credits food waste

[Stephan Pollard]

This thread resembles one entitled "Emissions from composting" that 
occurred back in May '05 on this listserv.

It is perhaps worth reviewing again that when accounting for greenhouse 
gases there is still disagreement on methods.  However, the general 
consensus/agreement amongst researchers is that biogenic sources 
(sources that would be part of global biogeochemical cycles without 
human intervention) should represent neither a gain nor loss to the system.

Early modeling of biogeochemical cycles indicated that composting 
generally represented a net good.  However, it has been suggested that 
these models were NOT complex enough!  Compost piles, as it happens, are 
capable of producing methane (CH4) and nitrogen oxides.  How much is 
produced depends on a complex mix of composting practices including 
conditions, feedstocks, processes, moisture content, etc.  The amount of 
carbon sequestration and pesticide offset is not clear either.  At the 
moment, there is no agreement on just what is the "average" compost 
process and other parameters, and the question has been raised as to 
whether or not the average process can even be modeled.

Complicating matters further, and as was pointed out by Tim Evans back 
in April or May of 2005 on this listserv, if carbon (from decaying 
organics) in a compost pile is converted to CH4 or nitrogen (N) is 
converted to NO2, it represents a "new" form or addition to the system.  
Plants take up carbon as CO2 and N as NO3.  They do not take up the 
greenhouse gases CH4 or NO2.  The intake - release ratio is 1 to 21 in 
the case of CH4 and 1 to 270 in the case of NO!


References:

Peigne, J. and P. Girardin (2004). "Environmental impacts of farm-scale 
composting practices." Water, Air, and Soil Pollution 153(1): 45-68.

Zeman, C., D. Depken, et al. (2002). "Research on how the composting 
process impacts greenhouse gas emissions and global warming." Compost 
Science and Utilization 10(1): 72-86.


Best Regards,
Stephan