The energy used to separate oxygen from air before burning is almost as great as that needed to filter out nitrogen afterwards, leading to a similar loss of efficiency.
【核心詞彙】
separate v.使分離，使分開
filter v.過濾，滲透
efficiency n.效率，效能
lead to 導致
【結構分析】
本句是主系表結構，主幹是The energy used to separate oxygen from air before burning is almost as great as that needed to filter out nitrogen afterwards，使用了...結構，其中被比較的對象that needed to filter out nitrogen afterwards中，that指代上文的energy，過去分詞結構needed to...作後置定語體現被動。其中主語energy由過去分詞結構used to separate oxygen from air before burning作後置定語體現被動;句末的`現在分詞結構leading to a similar loss of efficiency做全句的結果狀語。
【參考譯文】
燃燒前將氧氣從空氣中分離所需要的能源幾乎與隨後將氮氣過濾所需的耗費一樣多，這就使得兩者在效率損失上不相上下。