Environmental-Economic Analysis of Integrated Organic Waste and Wastewater Management Systems: A Case Study from Aarhus City (Denmark)
Abstract
:1. Introduction
- What is the best technology for the utilization of energy and other resources in organic waste—a wastewater treatment plant with biogas production or WtE plant?
- What is the most environmentally sustainable and economically viable food waste collection and transportation method from households to biogas plants—via sewage system or a “dry” transport (by trucks)?
- What is an optimal scale for biogas production from food waste?
- Evaluation of economic viability in support of future business models considering the increased content of organic matter in the influent wastewater and increased renewable energy generation and utilization.
2. Materials and Methods
2.1. Systemic Framework
2.2. System Description
- Reference scenario (REF): Mixed household waste is collected by trucks and transported to Aarhus incineration plant, “AffaldVarme”.
- Alternative scenario 1 (AS1): 16% of the organic fraction of the domestic organic waste (D-OF) dry weight is ground in FWDs in private households and transported via the collective sewer system to Egaa and Marselisborg WWTP.
- Alternative scenario 2 (AS2): Two versions of AS2 were modelled diverting, respectively, 16% (AS2a) and 100% (AS2b) of the D-OF away from incineration, by separate collection and transport by trucks to biogas plants at Egaa and Marselisborg WWTP.
2.3. Life Cycle Assessment
- Climate Change, quantified in units of kg CO2 equivalents, [kg CO2e];
- Fossil Depletion, quantified in units of kg oil equivalents, [kg oil eq.];
- Human Toxicity, quantified in units of kg 1,4-dichlorobenzene equivalents, [kg 1,4-DB eq.];
- Terrestrial Ecotoxicity, quantified in units of kg 1,4-dichlorobenzene equivalents, [kg 1,4-DB eq.];
- Marine Eutrophication, quantified in units of kg nitrogen equivalents, [kg N eq.]; and
- Freshwater Eutrophication, quantified in units of kg phosphorous equivalents, [kg P eq.].
- Climate Change, quantified in units of kg CO2 equivalents, [kg CO2e] and Euro2003;
- Human toxicity, carcinogens, quantified in units of kg chloroethylene equivalents, [kg C2H3Cl eq.] and Euro2003;
- Human toxicity, non-carcinogens, quantified in units of kg chloroethylene equivalents, [kg C2H3Cl eq.] and Euro2003; and
- Eutrophication, aquatic, quantified in units of kg nitrates equivalents, [kg NO3 eq.] and Euro2003.
2.4. Cost Benefit Analysis
3. Results
3.1. Energy Efficiency at the System Level
3.2. Life Cycle Impact Assessment
3.2.1. Climate Change
3.2.2. Fossil Depletion
3.2.3. Human Toxicity
3.2.4. Terrestrial Toxicity
3.2.5. Eutrophication
3.2.6. Total Environmental Costs
3.3. Cost-Benefits Analysis
3.3.1. WWTP Owners Return of Investments (RoI)
3.3.2. Farmers’ Benefits
3.3.3. Social Costs and Benefits
3.3.4. System Level Performance
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Plant | REF | AS1 | AS2a | AS2b |
---|---|---|---|---|
WtE—Heat | 603,699 | 590,052 | 590,052 | 516,700 |
WtE—Electricity | 71,652 | 70,032 | 70,032 | 61,326 |
WWTP Egaa—Heat | 3000 | 3733 | 4222 | 10,791 |
WWTP Egaa—Electricity | 3700 | 4592 | 5948 | 18,031 |
WWTP Marselisborg—Heat | 14,547 | 17,267 | 19,080 | 43,447 |
WWTP Marselisborg—Electricity | 5469 | 6454 | 9115 | 28,715 |
Total Heat | 621,246 | 611,052 | 613,355 | 570,939 |
Total Electricity | 80,821 | 81,079 | 85,095 | 108,072 |
Total energy | 702,067 | 692,131 | 698,450 | 679,011 |
Total Heat—Change * | - | −10,194 | −7891 | −50,307 |
Total Electricity—Change * | - | 258 | 4275 | 27,251 |
Total Energy—Change * | - | −9936 | −3617 | −23,056 |
Change in heat production—% ** | - | −2% | −1% | −9% |
Change in Electricity production—% ** | - | 0.3% | 5% | 25% |
Change total energy—% ** | - | −1.4% | −0.5% | −3% |
I1. Plants’ Return on Investment (%) | I2. Plants’ Unit Return (DKK/m3 Wastewater) | I3. Plants’ Return on Investment (%) Internalizing the FWD Costs 1 | I4. Plants’ Unit Return (DKK/m3 Waste water) Internalizing the FWD Costs 1 | I5. Unit Social Net Cost (DKK/m3 Wastewater) | I6. Unit Farmers’ Benefit (DKK/m3 Wastewater) | I7. Households’ Costs (DKK/Household) | I8. Unit System Benefit (DKK/m3 Wastewater) | I9. Unit System Benefit in Total (Weights:Maselisborg = 0.7; Egaa = 0.3) | ||
---|---|---|---|---|---|---|---|---|---|---|
Plants within the three Scenarios | ||||||||||
REF-Marselisborg (2026)’ | 10.69 | 8.55 | 10.69 | 8.55 | 0.35 | 0.09 | n.a. | 8.29 | 9.06 | |
REF-Egaa | 49.39 | 10.91 | 49.39 | 10.91 | 0.11 | 0.06 | n.a. | 10.86 | ||
AS1-Marselisborg | 10.90 | 8.62 | 10.40 1 | 8.22 1 | 0.38 | 0.11 | 167.09 | 7.95 | 8.94 | |
AS1-Egaa | 122.70 | 11.62 | 116.92 1 | 11.07 1 | 0.14 | 0.07 | 167.09 | 11.24 | ||
AS2a-Marselisborg | 10.63 | 8.50 | 10.63 | 8.50 | 0.38 | 0.12 | n.a. | 8.32 | 9.29 | |
AS2a-Egaa | 121.75 | 11.63 | 121.75 | 11.63 | 0.14 | 0.08 | n.a. | 11.57 | ||
AS2b-Marselisborg | 10.30 | 8.23 | 10.30 | 8.23 | 0.6 | 0.31 | n.a. | 7.94 | 9.08 | |
AS2b-Egaa | 123.75 | 11.81 | 123.75 | 11.81 | 0.27 | 0.19 | n.a. | 11.73 |
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Thomsen, M.; Romeo, D.; Caro, D.; Seghetta, M.; Cong, R.-G. Environmental-Economic Analysis of Integrated Organic Waste and Wastewater Management Systems: A Case Study from Aarhus City (Denmark). Sustainability 2018, 10, 3742. https://doi.org/10.3390/su10103742
Thomsen M, Romeo D, Caro D, Seghetta M, Cong R-G. Environmental-Economic Analysis of Integrated Organic Waste and Wastewater Management Systems: A Case Study from Aarhus City (Denmark). Sustainability. 2018; 10(10):3742. https://doi.org/10.3390/su10103742
Chicago/Turabian StyleThomsen, Marianne, Daina Romeo, Dario Caro, Michele Seghetta, and Rong-Gang Cong. 2018. "Environmental-Economic Analysis of Integrated Organic Waste and Wastewater Management Systems: A Case Study from Aarhus City (Denmark)" Sustainability 10, no. 10: 3742. https://doi.org/10.3390/su10103742