[USCC] Carbon Sequestration & composting

Tue Feb 12 13:27:21 CST 2008

Check out item #7 on page iv of that report. It says, "For mainstream options for dealing with bulk MSW as pre-treatment for landfill, the
option producing the lowest greenhouse gas flux (a negative flux of some 340 kg CO2 eq/tonne MSW) is MBT (including metals recovery for recycling) with landfilling of the rejects and stabilised compost.

To understand that, you have to look at the definitions on page i, MBT is "Mechanical Biological Treatment" and is defined as "Bulk MSW, or residual wastes enriched in putrescible materials after the removal of dry recyclables, is subjected to a prolonged composting or digestion process which reduces the biodegradable materials to an inert, stabilised compost residue. The compost, which cannot be used in agriculture or
horticulture because of its poor quality, is then landfilled. The treatment results in a significant reduction in methane forming potential of the compost in the landfill compared with untreated waste. Metals are recovered for recycling during the MBT process. Some of the paper and plastics in the incoming waste are diverted from the MBT process. These rejects are sent for either direct landfilling or incineration."

In other words, pull out some recyclables, do dirty composting, then landfill your product.

OMG, what kind of waste management strategy is that?! If the report is right, maybe we're on the wrong track.

The part you reference in your e-mail (below) says, "Carbon sequestration plays a relatively small role in the overall greenhouse gas flux attributed to composting, because of the relatively rapid rate of decomposition of the compost after its application to (aerobic) soils." So they prefer using landfills to sequester carbon? Wow.

Providing some confusing reassurance, page iii, in the conclusions of the Executive Summary, says, "overall, source segregation of MSW followed by recycling (for paper, metals, textiles and plastics) and composting /AD (for putrescible wastes) gives the lowest net flux of greenhouse gases." In that conclusion at least they break away from just looking at carbon emissions. The methane that gets past landfill gas collectors is supposedly over 20x worse than CO2 emissions for climate change.

The report is hard to read because it is tied up in dependent clauses and qualifiers (those Europeans sure don't speak American), but it's interesting.

I'm writing my weekly "Eye on the Environment" column in the Ventura County Star on this topic (simplified to the eighth grade reading level of our average reader and with as much local information put into it as possible), so I'd appreciate it if others on this list have simple stuff they can add regarding the lifecycle benefits of yard-waste derived compost and mulch.

Thanks.

david.goldstein at ventura.org
Ventura County PWA, W&S Dept.,
IWMD
800 S. Victoria Ave. #1650  Ventura, CA 93009-1650
(805) 658-4312    www.wasteless.org

>>> "Allison L H Jack" <alh54 at cornell.edu> 01/23/2008 11:01 AM >>>

>Hi Brenda,

There is a good European study looking at energy use in the whole cycle of 
composting and compares it to other waste management options. The report 
has a section on carbon sequestration and discusses short and long term. I 
this model, in the longer term (100 years) only a very small percentage of 
the carbon in compost applied to soil is sequestered.

1.      Smith, A., K. Brown, S. Ogilvie, K. Rushton, and J. Bates. Waste 
management options and climate change: Report to the European 
Commission.  2001  [cited 2007 October 10]; Available from: 
http://ec.europa.eu/environment/waste/studies/pdf/climate_change.pdf.

Hope this helps,
Allison

**************************************************************************************
Allison L H Jack
Graduate Student
Department of Plant Pathology and Plant-Microbe Biology
Cornell University
335 Plant Science
Ithaca, NY 14850
607.273.5762
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