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## PowerPoint Slideshow about ' Methane from SWDS' - ciara-white

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2004 revision of model from 1999

- Many reasons. For reasons and results see www.sft.no/publikasjoner/luft/2079/2079.pdf
- Two of the reasons were:
- Complicated model, difficult, poor view of calculations (black box).
- Faulty mathematics.

Basic mathematics, first order reaction

Rate of reaction equation, reactant transforming to methane:

dDDOC =DDOC * k * e^-kt *dt

Integrated equation for mass calculations, year t:

DDOCdiss = DDOC * (e^-k(t-1) – e^-kt)

(DDOC = dissimilable organic carbon)

Important theory

- First order reaction
- Amount of product formed (DDOCdiss) always proportional to the amount of reactant (DDOC)
- When we know the full amount of DDOC it is of no concern to the calculations when the DDOC came into the SWDS: Every year can be regarded as the first year.
- First order reaction equation the same as the compound interest equation, with negative interest rate.

Yearly steps in new calculating model

- Calculate reactant deposited (DDOCd)
- Add this to the reactant left as not dis-similated from last year (DDOCd+DDOCly)
- Calculate DDOCdiss from 2.
- Calculate the amount of methane formed from DDOCdiss.
- Calculate DDOC not dissimilated for next year’s calculations (new DDOCly).

The ”motor” of the new model

Two main equations:

DDOCdiss = (DDOCd+DDOCly) * (1-e^-k)

DDOCly = (DDOCd+DDOCly) * e^-k

- (The presented workbook model is a little more complicated because it also handles the option of reaction start in the year of deposition)

The workbook

- Sheet 3
- Parameters

- Sheet 4
- Material input and final result

- Sheets 5-7
- Calculations for the different materials

- Sheet 8
- The accumulation of plastics

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