Environment & Resources DTUTechnical University of Denmark

ObjectiveTo assess the energy balance, emission of global warming gasses, and quantify the recycled nutrients by anaerobic digestion of source separated organic household waste compared to incineration.

To compare anaerobic digestion of source separated organic household waste with different technologies for pre-treatment, biogas plants, incineration of residues etc.

Environmental Assessment of Source-separation of Organic Household Waste

Janus Kirkeby, Prague April 15, 2004

Environment & Resources DTUTechnical University of Denmark

Primary energy consumption for different pre-treatment

-5000

-4000

-3000

-2000

-1000

0

1000

Dis

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reen

Scr

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ref.

sc.

Pre

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ure

50 %

rej

ect

32 %

rej

ect w

ithT

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56%

Ref

. inc

iner

atio

n

MJ/

ton

Collection +transportPre-treatment

Incineration

Biogas plant

Fertiliser subs.

Janus Kirkeby, Prague April 15, 2004

Environment & Resources DTUTechnical University of Denmark

Conclusions

Janus Kirkeby, Prague April 15, 2004

For anaerobic digestion, the most important parameters are:An effective pre-treatment that makes a dry reject; the quantity is of minor importance when incinerating the residue with energy recovery.An effective degradation obtaining high gas yields.Utilize the biogas best possible, i.e. for both heat and electricity production.

Other conclusions are:The fuel consumption has only minor influence on the overall energy balance.Very long transport distances to a biogas plant have only limited influence.Reduction of unburned methane and emission from storage have some importance for the overall emission of global warming gasses.Energy efficiencies from biogas as well as incineration are very important for the results of the assessment.

Finally,Not all environmental effects were included in this assessment – these will follow