Sludge Watch ==> STUDY: assessment of sewage sludge handling options - land application is worst

[Maureen Reilly]

Sludgewatch Admin:

This report states that land application of sewage sludge has the worst 
environmental impact of all the 4 management approaches.

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Resources, Conservation and Recycling
Volume 41, Issue 4, July 2004, Pages 255-278
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Environmental and economic assessment of sewage sludge handling options

M. Lundina, M. Olofsson, , b, G. J. Petterssonc and H. Zetterlundd
a Environmental Systems Analysis, Chalmers University of Technology, S-412 
96, Göteborg, Sweden
b Energy Systems Technology Division, Chalmers University of Technology, 
S-412 96, Göteborg, Sweden
c Göteborg Water and Sewage Works, Planning and Design, P.O. Box 123, S-424 
23, Angered, Sweden
d Health and Environment, Volvo Aero Corporation, Dept. 1414HZ, S-461 81, 
Trollhättan, Sweden
Received 8 January 2003;  Revised 30 October 2003;  accepted 31 October 
2003.  Available online 25 January 2004.



Abstract
The environmental and economic consequences of four recycling and disposal 
options for municipal sewage sludge have been assessed. The four options 
were: agricultural application, co-incineration with waste, incineration 
combined with phosphorus recovery (Bio-Con) and fractionation including 
phosphorus recovery (Cambi-KREPRO). Life cycle assessment (LCA) was used to 
assess the environmental consequences, while effects in the district heating 
system were analysed using the energy system model MARTES. Co-incineration 
had the best energy balance, but without recovery of phosphorus.

In the Bio-Con and Cambi-KREPRO processes both phosphorus and energy could 
be recovered. Compared to Cambi-KREPRO, Bio-Con was more effective in most 
respects, but suffered from higher emissions to air.

Spreading sludge on agricultural land was the least preferable option from 
an environmental point of view. Energy was required for transportation, 
spreading and pasteurisation of the sludge, whereas the other three options 
enabled energy recovery. Spreading also caused release of nutrients and 
acidifying substances and transferred the content of heavy metals in the 
sludge to agricultural soil. The economic assessment showed that 
agricultural application had the lowest cost of the options, whereas 
co-incineration had the highest cost.

The difference in cost between Bio-Con and Cambi-KREPRO was small, but since 
the technologies are new and untried in a commercial context, these results 
are uncertain. This study has shown that two sludge handling options, 
incineration and direct application to agricultural soil, have respectively 
economic and environmental restrictions. The development of relatively low 
cost phosphorus recovery technologies has the potential to reconcile the 
environmental and economic aspects of sustainability.