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From waste management to greenhouse trend


Detailed description of the Good Practice

Cities can progress from consuming energy and emitting greenhouse gases (GHG) to actually producing energy while saving on GHG emissions, due to substitution of fossil fuels elsewhere. These findings are based on research in the city of Aalborg in Northern Denmark, published this week in Waste Management & Research, published by SAGE. Cities following similar waste management strategies are already having a far-reaching impact on GHG emissions in some regions of Europe.

Given the global interest in GHG emissions it is perhaps surprising that to date few scientists have produced studies that measure the impact of waste treatment system changes over the longer term. Tjalfe Poulsen and Jens Aage Hansen from Aalborg University in Denmark used historical data from their own municipality of Aalborg to gain a broader, longer term overview of how a 'joined-up' approach to waste impacts GHG emissions. The assessment included sewage sludge, food waste, yard waste and other organic waste (including paper and plastic).

Aalborg's citizens have already implemented a package of measures to take on waste that benefits the environment. In 1970 Aalborg's municipal organic waste management system resulted in net GHG emissions with methane from landfill accounting for almost 100%. But between 1970 and 2005, the city changed its waste treatment strategy to include yard waste composting, with the city's remaining organic waste incinerated for combined heat and power production. Of this, waste incineration contributed 80% to net energy production and GHG turnover, wastewater treatment (including sludge digestion) contributed another 10%, while other waste treatment processes used (composting, transport, and land application of treated waste) had minor impacts.
Poulsen and Hansen calculate that the energy potential tied up in municipal organic waste in Denmark is equivalent to 5% of the country's total energy consumption including transport. The Aalborg municipality represents about four percent of the Danish population.

The researchers also looked forward to 2020, and predict that further improvements are possible by reducing energy consumed by wastewater treatment (for aeration), increasing anaerobic digestion and incineration process efficiency and source separating food waste for anaerobic co-digestion.

Aalborg's progress shows how far reaching waste management can be in reaching energy and GHG goals, and should offer encouragement to other cities embarking on greener waste management strategies for the future.

waste management

Objectives of the Good Practice

to change the cities's waste management strategy in order to create net energy production and GHG turnover.

Participants of the Good Practice

City of Aalborg

Target group of the Good Practice

citizens of Aalborg

Funding of the Good Practice

City of Aalborg

More Details of the Good Practice

Available files

Contact details

Tjalfe G. Poulsen (tgp@bio.aau.dk)

Data sources and references

Back to Erekt alert
(Accessed April 26, 2010)