Iranian Journal of Soil and Water Research

Iranian Journal of Soil and Water Research

Economic and Environmental Assessment and Prioritization of Wood‑Farming Options Using Treated Wastewater (Case Study: Mahdasht, Karaj)

Document Type : Research Paper

Authors
Mahdi Malekpour 1
Bizan Nazari 1
Abdolmajid Liaghat 1
Hamze Ali Alizadeh 2
Mojtaba Mohammadi zadeh 3
1 Department of Irrigation and Reclamation Engineering, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
2 Department of Water Engineering, College of Agriculture and Natural Resources, University of Ilam, Ilam, Iran.
3 Department of Engineering and Studies, General Department of Natural Resources and Watershed Management, Alborz Province, Iran
10.22059/ijswr.2026.412832.670137
Abstract
The restrictive policies regarding timber harvesting from natural forests, compounded by critical water scarcity, have necessitated the exploration of sustainable alternatives for industrial wood production. This study investigates the feasibility of using treated wastewater for irrigation in commercial-scale plantations (2 ha) in Mahdasht, Karaj, Iran. The economic and environmental performance of three fast-growing species—Populus spp., Eucalyptus spp., and Paulownia spp.—was evaluated. Economic viability was determined using Net Present Value (NPV), Internal Rate of Return (IRR), and Benefit–Cost Ratio (BCR), alongside sensitivity analyses. Our findings indicate significant inter-species variations in financial performance. Paulownia demonstrated the highest economic potential (NPV: 2.48 billion Tomans; IRR: 28.8%; BCR: 1.56), followed by Eucalyptus and Populus. Sensitivity analysis identified timber market price as the primary driver of long-term profitability; notably, Populus showed higher vulnerability to land-cost fluctuations, while Eucalyptus was sensitive to irrigation expenditures. Crucially, this study demonstrates that reliance solely on financial metrics is insufficient for species selection. While Paulownia offered superior returns, it entails higher ecological and management risks. Populus, despite lower economic gains, exhibited the highest environmental sustainability and ecological compatibility, aligning better with national conservation objectives. We conclude that a multi criteria decision-making (MCDM) framework—balancing economic profitability, environmental sustainability, and implementation feasibility—is essential for the development of resilient plantation forestry in water-limited arid and semi-arid regions.
Keywords
Net Present Value (NPV)
Internal Rate of Return (IRR)
Benefit Cost Ratio (BCR)
Subjects

Introduction

Following the implementation of Iran’s forest harvesting restrictions and the decline in industrial timber imports, a considerable gap has emerged between domestic timber demand and supply. Fast-growing plantations irrigated with treated municipal wastewater offer a promising solution by providing sustainable raw materials while reducing pressure on natural forests. However, wastewater irrigation may also pose environmental risks such as soil salinity and degradation, requiring integrated evaluation of economic and environmental performance. Therefore, this study compared Paulownia spp., Eucalyptus spp., and Populus spp. cultivated under treated wastewater irrigation in Mahdasht, Karaj, using Net Present Value (NPV), Internal Rate of Return (IRR), Benefit–Cost Ratio (BCR), and an Environmental Sustainability Index (ESI) to identify the most suitable species.

Materials and Methods

The study was conducted in the Mahdasht Plain (Karaj, Iran). Economic feasibility was assessed using a discounted cash flow approach with a 15% discount rate by calculating NPV, IRR, and BCR based on establishment, irrigation, maintenance, harvesting, transportation costs, and timber revenues. Wastewater quality was evaluated according to FAO and WHO guidelines. One-way sensitivity analysis was performed by varying land, wastewater, seedling costs, and timber prices by ±10–30%. Additional scenarios examined plantation distances of 3, 7, and 10 km from the wastewater treatment plant. Environmental sustainability was evaluated using a composite ESI based on water requirement, wastewater compatibility, soil impacts, ecological risk, and legal compliance.

Results and Discussion

Paulownia showed the highest economic performance, with the greatest NPV (2.48 billion tomans), IRR (28.8%), and BCR (1.56), followed by Eucalyptus and Populus. Sensitivity analysis identified timber selling price as the most influential factor affecting profitability, whereas Eucalyptus was particularly sensitive to irrigation costs and Populus to land costs. Increasing transportation distance reduced profitability for all species, although Paulownia remained economically viable even at 10 km.

Environmental assessment produced a different ranking. Populus achieved the highest ESI (8.4/10) because of its lower ecological risk, moderate water demand, and compliance with conservation policies. Eucalyptus showed moderate environmental performance (6.4/10), whereas Paulownia obtained the lowest score (4.4/10) despite its superior economic returns. These findings demonstrate that economic profitability does not necessarily correspond to environmental sustainability.

Discussion and Conclusion

Paulownia was identified as the most profitable species for wastewater-irrigated plantations, while Populus provided the highest environmental sustainability and the lowest ecological risk. Eucalyptus represented a balanced alternative with acceptable economic and environmental performance. Overall, species selection should be based on an integrated assessment of economic, environmental, operational, and regulatory criteria rather than financial indicators alone. Such a multi-criteria approach can support sustainable plantation development and efficient wastewater utilization in water-scarce regions.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Authorship contribution

All authors contributed equally to this work. All authors participated in the conception and design of the study, data acquisition, analysis and interpretation of the results, manuscript writing, and critical revision. All authors approved the final manuscript and agree to be accountable for all aspects of the work.

Declaration of Generative AI and AI-assisted technologies in the writing process

The authors confirm that no generative artificial intelligence (AI) or AI-assisted technologies were used in the preparation, writing, editing, or revision of this manuscript. The entire content of the manuscript was created exclusively by the authors, who assume full responsibility for its scientific accuracy, originality, and integrity.

Data availability statement

The datasets generated and/or analyzed during this study are available from the corresponding author upon reasonable request. Access to the data will be provided in accordance with applicable research ethics, data management policies, and institutional regulations.

Acknowledgements

The authors sincerely thank the anonymous reviewers for their thorough evaluation, constructive comments, and valuable recommendations. Their insightful feedback has made a significant contribution to improving the scientific quality, clarity, coherence, and overall presentation of this manuscript.

Ethical considerations

This study was based solely on data analysis and economic evaluation and did not involve human participants, animals, biological specimens, or any experimental intervention. Therefore, ethical approval from an institutional review board or ethics committee was not required.

Conflict of interest

The authors declare that they have no known competing financial, professional, personal, or institutional interests that could have influenced the design, conduct, analysis, interpretation, or publication of this study.

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Iranian Journal of Soil and Water Research
Volume 57, Issue 7
September 2026
Pages 1683-1706