Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
This Master’s thesis is integrated in a European Union LIFE-project called “Short-Circuit”.The main purposes of the Short-Circuit project are to contribute to the optimization of thecommunity strategies of recovering nutrients and organic carbon from organic waste and tothe minimization of the transportations within the system.
The scope of this paper is to analyse a treatment system at Solum A/S which includes an aerobic and aerobic digestion. A custom-made simulation-model, built in ORWARE,calculates flows, emissions, environmental impacts and recovering of nutrients and organic carbon. This thesis compares three different scenarios. In scenario 1 and 2 the organic waste is sent to the AIKAN facility at Solum. Scenario 1 represents present time andscenario 2 represents a future set-up with less impurity in the organic waste. In scenario 3the organic waste is sent to a conventional incineration plant. The functional unit is one tonorganic household waste. An addition of structural materials is needed in scenario 1 and 2,and these amounts are included within the system boundaries.
A system analysis approach is used in the three scenarios. The methods used in ORWAREare substance flow analysis, SFA, and life cycle assessment, LCA. The interpretation part ofthis rapport contains sensitivity analyses, consistency checks and discussions about the completeness of the study.
The sensitivity analysis shows that an increase of water percentage in the organic waste hasa significant effect on all environmental impact categories. The more water the organic waste contains, the more efficient is the AIKAN treatment alternative compared to anincineration plant.
The sensitivity analysis also shows that if structural materials are not included within the system boundaries the results will be very different. When structural materials are not included the recovering of nutrients and organic carbon diminishes with up to 47 percent.
The electricity turnover for AIKAN is much higher than for the incineration plant. But the energy turnover in general benefits scenario 3. Often the production of electricity is higher ranked than the production of heat. When comparing the environmental impacts fromAIAKN and the incineration plant you see that the contribution to global warming is much lower in scenario 1 and 2 than in scenario 3. On the other hand, the eutrophication, the acidification, the production of photochemical oxidants and the emissions of heavy metals are lower in scenario 3. But no nutrients or organic carbon is recycled in scenario 3.
Comparing scenario 1, the AIKAN facility at present time, to scenario 2, AIKAN in the future, shows that the differences are not that large considering the energy turnover and therecovering of organic carbon and nutrients. But in the environmental impact categories, the differences between the two scenarios are more significant.
2006. , 72 p.