A Green House Gas Balance for Compost

1. A Green House Gas Balance for Compost Sally Brown University of Washington

2. Global Warming Basics • Everyday the sun heats the earth • Every night much of this heat leaves the earth’s atmosphere and we cool down

3. 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 increasing • And as a result, the temperature on the surface of the earth and in the oceans increases

4. Different gasses that trap heat

6. Major culprits • Fossil fuels • Cars • Power plants

7. 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

8. Landfill-Lagoon feedstocksShort term carbon cycle

9. Short term carbon cycle is too fastand is not considered in GHG accounting except

10. 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

11. Options • Landfill gas capture • Anaerobic digestion • Direct land application • Composting

12. A Greenhouse Gas Balance for Composting

13. How it works:Basic Rules • You make a difference by stopping gasses from being released • Or by putting carbon back into storage Federal Reserve Bank

14. In Greenhouse Gas Parlance • Avoidance- stopping gasses from being released • Sequestration- putting carbon back into storage

15. Two Accounting Firms • CA regulations • Protocols being developed • Well intentioned, political process • Chicago Climate Exchange- • Voluntary exchange where carbon credits are bought and sold

16. 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

17. Compost Accounting-Divide process into three parts • What you compost • Outside of compost, would feedstocks generate CH4? • How you compost • Energy use and gas emissions during composting • What you do with your compost • Use of compost qualify for sequestration or avoidance credits

18. Feedstocks-Methane generation potential • Food waste- 12 Mg CO2equiv per Mg food waste

19. Yard Waste-Methane generation potential • Grass clippings • 5.5 Mg CO2equiv per Mg • Leaves • 1.2 Mg CO2equiv per Mg

20. Avoidance Credits • Compost facility that processes 1000 dry metric tons of waste per year • Mix of 33% manure, 33% newsprint and 33% food waste • 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

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

22. 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

23. Windrow • When a pile goes anaerobic- • Odor will be first indication of anaerobic conditions • In addition to odoriferous compounds • CH4 • N2O Photo:Cogger, WSU

24. Formation • 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 conditions

25. Methane and Nitrous Oxide in a Compost Pile Hao et al., 2001

26. Methane and Nitrous Release Release can occur from pile surface as well as when the pile is being turned

27. 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 http://www.ipic.iastate.edu/

28. 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 http://www.ipic.iastate.edu/

29. Release can be controlled Mixing high C amendments like straw into wetter feedstocks is a way to prevent release of GHGs http://score.rims.k12.ca.us/activity/experimentalfarm/sfarm.htm

30. Then you have the compost • Potential for carbon credits for using compost

31. Back in the bankCompost 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 used

32. Recycled Organics Unit(http://www.recycledorganics.com/publications/reports/) • Benefits with reduced water use, fertilizer value, and reduced herbicide use • Avoidance credits

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

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

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