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Estimation of the ADM1 input parameters for modelling the anaerobic digestion of waste

materials using laboratory scale batch testing of methane production

International Conference on Advances in Energy Research

10-12th December 2013 Indian Institute of Technology Bombay

Davide Poggio, Mark Walker, William Nimmo and Mohamed Pourkashanianm.walker@leeds.ac.uk

Introduction

Anaerobic Digestion Model 1 (ADM1) is the current benchmark in modelling of AD and biogas production

ADM1 is a large, complex model (35 states, 29 conversion processes, 100+ parameters) therefore feedstock characterisation and parameter estimation is important for each application

Previous methods used; Literature data for similar substrate,

direct analysis of the biochemical fractions (Carbohydrate, protein, fat…)

Kinetic based methods

In this paper a methodology for the estimation of the feedstock biomass composition and hydrolysis/fermentation kinetics is presented

Method based on a hybrid biochemical and kinetic approach

Parameters estimated using statistical analysis of batch methane production tests

Mark Walker, ICAER, 10-12th December 2013, IITB

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Methods

Energy Technology & Innovation InitiativeFaculty of Engineering

Outline

Mark Walker, ICAER, 10-12th December 2013, IITB

Kinetic Models

Increasing model complexity

• More parameters estimated

• Better fit

• More uncertainty

1 Particulate

1 Particulate

& 1 Soluble

2 Particulate

2 Particulate

& 1 Soluble

Model Fractionation of COD and Kinetic Equations

Mark Walker, ICAER, 10-12th December 2013, IITB

Biomass Feedstocks

Food Waste

(Source segregated)

TS = 30.1%

VS = 27.3%

Green Waste

(Source segregated)

TS = 39.8%

VS = 25.9%

Mark Walker, ICAER, 10-12th December 2013, IITB

Laboratory equipment

15 x 0.5-litre heated, stirred reactors

Automated gas flow monitoring

Carbon dioxide absorption

Mark Walker, ICAER, 10-12th December 2013, IITB

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Results and Discussion

Energy Technology & Innovation InitiativeFaculty of Engineering

Biochemical Fractionation

FW

GW

COD (gCOD/gVS)

1.73

1.55

Mark Walker, ICAER, 10-12th December 2013, IITB

Results

FW

GW

Cellulose

Mark Walker, ICAER, 10-12th December 2013, IITB

Kinetic Fractionation - GW

 Model  X^2  Parameter Value Std. Error 95% confidence1 particulate 0.058            fd 0.249 0.99 %  0.244 - 0.254

    khyd 0.623 3.38 %  0.581 - 0.664

1 Particulate & 1 Soluble

0.040          fd 0.250 0.66% 0.799 - 0.820

  fS 0.216 3.42% 0.285 - 0.326

  khyd 0.347 3.42% 0.345 - 0.395

2 Particulate 0.0          fd 0.246 NA NA

    fXr 0.216  NA NA

    khyd,r >20  unbounded  unbounded

    khyd,s 0.336 NA  NA

1 Particulate Fraction

1 Particulate & 1 Soluble Fraction

Kinetic Fractionation - GW

1 Particulate & 1 Soluble

χ2 = 0.23

Max. Std. Error = 3.4%

1 Particulate

χ2 = 0.53

Max. Std. Error = 2.5%

2 Particulate

χ2 = 0.17

Max. Std. Error = 6.6%

2 Particulate & 1 Soluble

χ2 = 0.16

Max. Std. Error = 23.2%

Mark Walker, ICAER, 10-12th December 2013, IITB

On-going workModelling Semi-Continuous AD

Food Waste

2 Particulate Fraction Model

Under-prediction of fast kinetics (no soluble fraction)

Green Waste

1 Particulate & 1 Soluble Fraction Model

Over-prediction of fast kinetics (overestimated

soluble fraction)Mark Walker, ICAER, 10-12th December 2013, IITB

Conclusion

A Procedure for the Anaerobic Digestion Model 1 (ADM1) characterization of a biomass feedstock has been described

Two stage process; Biochemical fractionation using elemental analysis Kinetic fraction using experimental data methane production tests

Biochemical fractionation of green waste samples resulted in high predicted level of lipids → modification of the method required in high lignin samples

Statistical analysis permitted the identification of the most appropriate model and the relevant parameters to describe the anaerobic digestion process.

Food wastes is a more complex substrate requiring at least two fractions to describe the kinetics, while only one fraction gives a satisfactory description for green waste degradation.

Future works will include the validation of the procedure in laboratory continuous systems and investigation into the co-digestion behaviour

Mark Walker, ICAER, 10-12th December 2013, IITB

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Thank you!

Any questions?

Energy Technology & Innovation InitiativeFaculty of Engineering