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Hydrothermal

Carbonisation (HTC)

for the Treatment of

AD Digestate

Sarah Farthing, Colin Snape, Jon McKechnie

Centre for

Doctoral Training in

Sustainable Chemistry

What can we do with AD digestate?

Low economic return

Nutrient level policies

Regional and seasonal restrictions

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

Anaerobic

Digestion Digestate

Crop

Growth

Land

Application

?

What can we do with AD digestate?

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

High moisture content =

High drying requirement

Anaerobic

Digestion Digestate

Thermal

Treatment

Hydrothermal Carbonisation

CO2-rich gas

Hydrochar

Process Liquid

Wet Digestate

HTC Reactor

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

Hydrothermal Carbonisation, but:

How?• Operating conditions

• Integration opportunities

Where?• Feedstock selection

• Plant scale

When?• Policy

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

Hydrochar Energy Content (MJ)

=

How? – Modelling

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

+

Pro

cess

Model

Experi

menta

l Work

Hydrochar Energy Content(MJ/kg)

Hyd

roch

ar E

nerg

y C

onte

nt(

MJ/kg)

How? – Integration

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

How? – Integration

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

How? – Integration

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

Where and when? –Techno-economics + LCA

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

• Economic analysis

• CAPEX and OPEX of HTC

• Different configurations

• Life Cycle Assessment

• Fossil energy use

• CO2 emissions

• Water use

Summary

Digestate ››› Hydrothermal Carbonisation (HTC) ››› Scope ››› Modelling ››› Integration ››› Feasibility ››› Summary

Hydrothermal Carbonisation of Digestate

Understanding: operation, opportunities, potential

Acknowledgements

Supervisors: Jon McKechnie and

Colin Snape

Experimental support: Clement Uguna

and Robert Stirling

CDT in Sustainable Chemistry

SPT Research Group

EPSRC