農地污染場址再利用評估工具-以桃園市為例

Assessment tool for contaminated farmlands regeneration: A case study in Taoyuan City, Taiwan.

葛凡宇(Fan-Yu Ko)

指導教授 ： 闕蓓德

國立臺灣大學/工學院/環境工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202104324

摘要

政府機關近年積極投入整治農地污染場址，不僅採納傳統整治工法，亦推廣轉作非食用作物、植生復育，以及作為生質能原料方法，然而土壤污染濃度達到整治標準而解除列管的農地，由於未善加管理或無法阻斷污染源，出現再次污染或農產品重金屬超標情形；農民考量投入成本和改善時程，不願轉作或採用植生復育改善方法；作為生質能原料則因農地狹小分散，不適合於國內發展。上述情形突顯政府機關耗資經費的整治作為，並未達到農地恢復種植功能的預期成效。因此本研究旨於建立一個兼顧環境面和經濟社會面的農地污染場址再利用評估工具，透過探討住宅、商業、工業、太陽光電和農業五種方案的再利用適宜性和效益，作為決策者優化農地污染場址管理效用以及國土規劃策略之參考。
本評估工具分為兩階段，首先為再利用方案適宜性分析，採納18個環境面和社會經濟面因子，設定住宅、商業、工業、太陽光電和農業共五種再利用方案，透過土地利用適宜性分析 (land use suitability analysis, LUSA) 評選適宜性分數最高方案為未來的再利用方案。第二階段運用成本效益分析 (cost-benefit analysis, CBA) 計算場址以適宜方案再利用的耗費成本和產出效益，成本效益項目劃分為外部成本效益與內部成本效益；外部成本效益包括透過生命週期評估 (life cycle assessment, LCA) 計算的碳排成本與碳減緩效益，以及藉由生態系統服務評估方法 (ecosystem services valuation, ESV) 量化的農地生態系統服務價值；內部成本效益定義場址以適宜方案再利用的商品生產或服務提供所涵蓋的直接成本和直接效益。最後採用淨現值方法 (net present value, NPV) 整合場址生命週期所有的外部成本效益和內部成本效益，評定適宜方案中淨效益最高方案為最佳再利用方案；若再利用成本高於再利用效益則恢復農業使用。
本研究以桃園市農地污染控制場址為研究案例，方案適宜性分析結果指出三個農地污染場址密集區適合採用太陽光電方案，剩下二個農地污染場址密集區適合採用農業方案。內部效益評估結果說明五個密集區的場址，25年生命週期共能產出97,246,975~776,238,657元的內部效益，顯示污染農地整治後恢復耕作或是開發作為太陽能發電設施皆能帶來直接的經濟價值，具有內部效益；然而因為蒸發散量和期作天數的不確定性，太陽能發電量約為926.77~1162.01 kWh/kWp/yr，售電效益可能低於整治改善成本，而造成五個密集區內採太陽光電方案之場址產生約為0~-1,662,839元的內部成本。外部效益評估結果包含溫室氣體排放衝擊評估結果和農地生態系統服務價值評估結果，溫室氣體排放衝擊評估結果指出由於三個密集區以太陽光電方案再利用，因此五個密集區可產出約324,396,311~409,605,211元的溫室氣體減緩效益；不過也因為三個密集區開發作為太陽能發電設施，因此造成五個密集區約-218,943,042~-276,225,400元的農地生態系統價值損失。整合以上兩項外部效益評估結果，五個農地污染場址密集區整治改善後再利用能產出約48,170,913~190,662,182元的外部效益，突顯將污染農地開發作為其他用途，會損失高額的農地生態系統服務效益，因此相較採用太陽光電方案，污染農地整治後回復耕作能創造更高的外部效益。
本評估工具最後一個步驟係整合外部效益評估結果和內部效益評估結果，透過以NPV方法計算農地污染場址再利用的生命週期淨效益。由於應用太陽光電方案的場址再利用所產生的外部成本衝擊高於再生能源販售的效益，造成淨效益為負值，說明本研究區域內之污染農地不宜作為太陽能發電設施，應回復農業耕作以創造更高的淨效益。因此本研究建議五個密集區內的場址最佳再利用方案為農業方案，約能帶來1,602,586,602~1,966,861,607元的淨效益，證明整治改善污染農地場址能帶來換環境價值和實際經濟效益，提供兼顧環境面和社會經濟面的土地利用效益。

關鍵字

農地污染場址 ； 再利用 ； 土地利用適宜性分析 ； 生命週期評估 ； 生態系統服務價值評估 ； 成本效益分析

並列摘要

Since contaminated farmlands formed severe issues in Taiwan, the government has implementd with remediation plans, from common remediation method to innovative technologies, including growing inedible plants, bioremediation and re-powering with renewable energy. However, improper management, stakeholders’ ignorance, or farmlands’ restrictions made expectation achievement in difficulty. Therefore, this study establishes an assessment tool on the basis of environmental and economical-social aspects for contamintated farmlands regeneration planning. Contaminated control farmlands in Taoyuan is the case study and this study will focus on five densly contaminated districts. The tool is supportive of contaminated farmlands management and land use planning by deciding the most suitable regeneration plan from five kinds of plans, which are residential, commercial, industrial, solar power and agricultural.
This assessment tool consists of land use suitability analysis (LUSA), life cycle assessment (LCA), ecosystem services valuation (ESV), and cost-benefit analysis (CBA). First, LUSA is performed by 18 factors which are separated into environmental aspect and economical-social aspect to decide the most suitable plan for each contaminated farmland. After determing the most suitable plan, CBA is conducted to calculate the net benefits which includes the internal benefits of products or services from contaminated farmlands revitalization, and external benefits consist of greenhouse gas reduction benefits and agricultural ecosystem benefits. The result of CBA is presented by net present value (NPV). The net benefits indicate the only suitable regeneration plan can be performed, while the net costs mean the plan is not suggested and the original agricultural plan should be used. If LUSA suggested the contaminated farmland with more than one plan, the best regeneration plan for the site is determined by the plan with the highest net benefits.
The result of LUSA indicates that solar power regeneration plans are suitable for three of the five densly contaminated distircts and agricultural regeneration plans are suitable for the other two densly contaminated distircts. The result of internal value assessment indicates that the five densly contamainated districts can create 97 million~ 776 million dollars. It proves regeneration plans suggested by LUSA for contaminated farmlands in this study area can bring direct economic incomes. However, the uncertainty of power generation produced from solar power could cause up to 1.66 million dollars internal costs. As for external value assessment, it consistd of Greenhouse Gas LCA and ESV. The resulut of GHG-LCA proves solar power plan could bring GHG reduction benefits, it creates 324 million~410 million dollars in the five densly contaminated districts. Although implementing solar power also causes 219 million~276 million dollars agricultural ecosystem costs in the five densly contaminated districts. In total, regenerating the five densly contaminated districts by LUSA suggestion creates 48 million~191 million dollars external benefits.
The final step of this assessment tool is calculating the NPV by conluding internal value assessment result and external value assessment result. In this study area, agricultural plan is the best regeneration plan for the five densly contaminated districts, and it can bring 1.60 billion~1.97 billion dollars. This assessment tool proves that remediating contaminated farmlands and regenerating with agricultural plan create both environmental and economical-social benefits.

並列關鍵字

contaminated farmlands ； regeneration ； land use suitability analysis ； life cycle assessment ； ecosystem services valuation ； cost-benefit analysis

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