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					A Green House Gas Balance
       for Compost

          Sally Brown
    University of Washington
          Global Warming Basics

• Everyday the
  sun heats the
• Every night
  much of this
  heat leaves the
  atmosphere and
  we cool down
  While this has been happening since
       we’ve had an atmosphere

• Some gasses are more efficient than
  retaining heat than others
• With global warming the concentration of
  these gases in the atmosphere is
• And as a result, the temperature on the
  surface of the earth and in the oceans
     Different gasses that trap heat
                      CO2      CH4    N2O
Concentration in      ppm      ppb    ppb
   Pre- industrial    280      700    270
   Current            370      1745   314
Lifetime in atmosphere 5-200   12     114
CO2 equivalent         1       23     296
Major culprits
• Fossil fuels
  – Cars
  – Power plants
             Landfill or Lagoon
• What you work with (solid waste) falls under a
  different classification
• Most material that gets landfilled or stored in
  lagoons falls under the short term carbon cycle
• It is expected that this will decompose and
  release CO2
Landfill-Lagoon feedstocks
   Short term carbon cycle
  Short term carbon cycle is too fast
and is not considered in GHG accounting
              Landfill or Lagoon
• If the material is sent to
  a landfill or lagoon where
  it will decompose
  anaerobically, it has the
  potential to release CH4
  into the atmosphere
• As CH4 is 23X worse than
  CO2- all of a sudden these
  short term organic
  residuals start to count
                                            QuickTime™ and a
                                   TIFF (Uncompressed) decompressor
                                      are need ed to see this picture.
• Landfill gas capture
• Anaerobic digestion
• Direct land
• Composting
A Greenhouse Gas Balance
     for Composting
            How it works:
             Basic Rules

• You make a difference by stopping
  gasses from being released
• Or by putting carbon back into

           Federal Reserve Bank
     In Greenhouse Gas Parlance

• Avoidance- stopping gasses from
  being released
• Sequestration- putting carbon
  back into storage

• CA regulations
  – Protocols being developed
  – Well intentioned, political
• Chicago Climate Exchange-
  – Voluntary exchange where
    carbon credits are bought
    and sold
        For accounting purposes:
         Credits are conditional
• In order for something to qualify for credits, it has
  to be a new and innovative practice
• The status quo, even if it is an environmentally
  beneficial practice, doesn’t count
• Projects have to be approved
• If the project is undertaken by a large entity (like
  the City of San Diego) the project has to be
  considered as part of a whole GHG accounting
               Compost Accounting-
          Divide process into three parts
1.       What you compost
     •     Outside of compost, would feedstocks generate
2.       How you compost
     •     Energy use and gas emissions during composting
3.       What you do with your compost
     •     Use of compost qualify for sequestration or
           avoidance credits
    Methane generation potential
• Food waste- 12 Mg CO2equiv per Mg food waste
       Yard Waste-
Methane generation potential

        • Grass clippings
           – 5.5 Mg CO2equiv per Mg
        • Leaves
          – 1.2 Mg CO2equiv per Mg
              Avoidance Credits
• Compost facility that processes 1000 dry metric
  tons of waste per year
• Mix of 33% manure, 33% newsprint and 33% food
   – 333 x 2.6 Mg CO2 for hog manure
   – 333 x 3 Mg CO2 for newsprint
   – 333 x 12 Mg CO2 for food waste
• 5900 Mg CO2- an optimum value for avoidance

• This is an ideal case- a maximum value for methane
• If the landfill does methane capture value will be
• If the manure is already directly land applied- the
  value will be reduce….
• This was done to show potential
         Composting Process

• When you compost organics there is the
  potential for GHGs other than CO2 to be
  released during decomposition
• These releases will count as debits

• When a pile goes
• Odor will be first
  indication of anaerobic
• In addition to
  odoriferous compounds
   – CH4
   – N2O

                             Photo:Cogger, WSU

• Methane is formed as microbes break down
  carbon in environments where O2 is really
  limiting- very inefficient way to compost
• N2O is formed primarily as nitrate is
  transformed into nitrogen gas- will occur in
  N rich environments with mildly anaerobic
Methane and Nitrous Oxide in a Compost Pile

              Hao et al., 2001
     Methane and Nitrous Release

Release can occur from pile surface as well as
        when the pile is being turned
       Potential N2O and CH4 release

• 0.7 g of N2O per kg biosolids (Czepiel et
  al., 1996)
• 1.9 kg CH4 per Mg OM (Hao et al, 2004)
• For your 1000 Mg dry that equals
  – 0.233 Mg N2O
  – 0.95 Mg CH4

            5900 Mg CO2 -

•   0.233 Mg N2O = 296 X 0.233
•   0.95 Mg CH4= 23 x 0.95
•   Total 91 Mg CO2
•   You would end up with 5800

          Release can be controlled

        Mixing high C amendments like
      straw into wetter feedstocks is a
       way to prevent release of GHGs
     Then you have the compost
• Potential for carbon credits for using
                           Back in the bank
            Compost is stable organic matter

• Compost is 50% organic
• Assume that 50% of
  this is stable
• Credit for carbon
  equivalent of 25% of
  dry weight of compost
        Recycled Organics Unit
• Benefits with
  reduced water
  use, fertilizer
  value, and
  herbicide use
• Avoidance
              To Conclude

• Potential to get
  GHG credits
  from compost
  both from
  avoidance and
               To Conclude

• Avoidance credits
  are larger-
  primarily from
  methane avoidance
  from feedstocks
• Sequestration- from
  replenishing soil OM
              To Conclude

• Debits as well
• These primarily
  from GHG emissions
  during composting,
  transport to and
  from site also can
  figure in

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