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# Methane from SWDS - PowerPoint PPT Presentation

Methane from SWDS. New Norwegian calculating model. Per Svardal. 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).

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### Methane from SWDS

New Norwegian calculating model

Per Svardal

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