八里衛生掩埋場沼氣發電系統之效益評估

Abstract

垃圾掩埋場溢散的沼氣組成成分甲烷，屬國際公約「京都議定書」規範管制溫室氣體之一，國內掩埋場沼氣為溫室氣體甲烷最大之排放源，沼氣若未經處理直接排放至大氣中，不僅造成當地環境污染，亦造成溫室效應與全球暖化。沼氣屬於生質能源，具有達到資源永續利用、提供替代能源、能源利用效率提升及減少溫室效應氣體產出之優點，目前新北市已有許多生質能再利用的計畫，以垃圾掩埋場沼氣作為生質能再利用的僅有三峽及八里兩座掩埋場。本研究以八里掩埋場沼氣處理及回收發電之案例，以發展潛力、環境效應及經濟效益評估三方面加以探討。評估結果顯示，沼氣存於掩埋層內，因與大氣壓力差而快速溢散至大氣中，於掩埋場覆土層不足或產生裂縫時，污染量大增，除應定期檢視掩埋場覆土狀況外，應依垃圾掩埋場使用年限及掩埋量體訂定不同的沼氣處理準則，如為小規模掩埋場開發沼氣發電不符經濟規模者，建議於封場後直接收集沼氣燃燒，大規模掩埋場則應優先以沼氣發電為考量，電力可提供場內作為替代能源或躉售臺電，減輕甲烷及二氧化碳對大氣的影響。

Methane is one of the major greenhouse gases. And it is also a main component of landfill gas. Emission of methane from landfill is considered to be the major source of fugitive methane emission in Taiwan. Without proper control, methane emission could adversely affect local air quality and cause problems of global warning. Landfill gas is a form of bioenergy. Recovery and use of landfill gas as an energy source can enhance economic growth, strengthen energy security, improve air quality, and reduce emission of greenhouse gases. The New Taipei City has established quite a few projects on bioenergy. However, there are only two that use landfill gas for recovery and use of bioenergy. (Three Gorges and Bali landfills) This research evaluated the recovery and use of landfill gas at the Bali landfill with emphases on potential for landfill gas recovery, environmental impacts and economic benefits. It was found that the inappropriate top cover (insufficient thickness) and cracks are the major source of massive methane emissions. The surface covers landfills should be routinely inspected. Different management approaches may need to be employed for different landfills depend on factors such as age and capacity of the landfill. For small landfills that recovery of landfill gas for energy generation may not be economically efficient, recovery and flaring should be considered. On the other hand, energy generation should be considered as one of the top alternatives for larger landfills which can be a source of sustainable energy and reduce the emission of greenhouses gases.