1 EXHIBIT 12 LAIDLAW ENVIRONMENTAL SERVICES, INC. COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES Six Months Ended Year Ended August 31, February 28, 1998 1993(1) 1994 1995 1996 1997 1997 1998 ------- ---- ---- ---- ---- ---- ---- (dollars in thousands) Income (loss) from continuing operations before income tax - 25,731 21,684 11,860 (306,122) 7,351 23,361 Add: Portion of rents representative of the interest factor - 8,577 11,800 11,967 12,033 6,016 5,135 Interest on indebtedness - 34,000 41,142 46,850 43,642 18,629 28,230 Amortization of deferred financing charges - - - - 631 - 1,259 ----------------------------------------- - ------------------------------ Income as adjusted - 63,308 74,626 70,677 (249,816) 31,996 57,985 ========================================= ============================== Fixed charges: Portion of rents representative of the interest factor - 8,577 11,800 11,967 12,033 6,016 5,135 Interest on indebtedness - 34,000 41,142 46,850 43,642 18,629 28,230 Amortization of deferred financing charges - - - - 631 - 1,259 ----------------------------------------- - ------------------------------ Total Fixed Charges - 42,577 52,942 58,817 56,306 24,645 34,624 ========================================= ============================== Ratio of earnings to fixed charges - 1.60 1.41 1.20 (4.44) 1.30 1.67 ========================================= ============================== (1) Prior to May 15, 1997, the date of the Rollins Acquisition, the Company was operated as a division of Laidlaw and, accordingly, the Company's results of operations were included in the financial statements of Laidlaw. Certain of the selected financial data for fiscal 1993 were combined with that of Laidlaw and were not available on a separate basis. 2 SAFETY-KLEEN CORP. COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES Fiscal Year Twelve Weeks Ended March 22, March 28, 1993 1994 1995 1996 1997 1997 1998 ---- ---- ---- ---- ---- ---- ---- (dollars in thousands) Income (loss) from continuing operations before income tax (168,609) 84,826 92,468 101,648 100,500 19,437 16,243 Add: Portion of rents representative of the interest factor 6,933 7,067 8,267 10,500 13,467 2,936 3,256 Interest on indebtedness 11,111 15,209 20,230 19,240 18,108 4,361 3,612 --------------------------------------- - ----------------------------- Income as adjusted (150,565) 107,102 -120,965 131,388 132,075 26,734 23,111 ======================================= ============================= Fixed charges: Portion of rents representative of the interest factor 6,933 7,067 8,267 10,500 13,467 2,936 3,256 Interest on indebtedness 11,111 15,209 20,230 19,240 18,108 4,361 3,612 --------------------------------------- - ----------------------------- Total Fixed Charges 18,044 22,276 28,497 29,740 31,575 7,297 6,868 ======================================= ============================= Ratio of earnings to fixed charges (8.34) 4.81 4.24 4.42 4.18 3.66 3.37 ======================================= ============================= 3 LAIDLAW ENVIRONMENTAL SERVICES, INC. PRO FORMA COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES The following computations for fiscal 1997 and the six and twelve months ended February 28, 1998 reflect, on a pro forma basis, earnings available for fixed charges, and resultant ratios. Six Months Twelve Fiscal Year Ended Months Ended Ended February 28, February 28, August 31, 1997 1998 1998 (dollars in thousands) Income (loss) from continuing operations before income tax (393,503) 10,818 (352,388) Add: Portion of rents representative of the interest factor 24,466 10,892 24,939 Interest on indebtedness, including amortization of deferred financing charges 180,456 89,840 180,525 ------------------------------------- Income as adjusted (188,581) 111,550 (146,924) ===================================== Fixed charges: Portion of rents representative of the interest factor 24,466 10,892 24,939 Interest on indebtedness, including amortization of deferred financing charges 180,456 89,840 180,525 ------------------------------------- Total Fixed Charges 204,922 100,732 205,464 ===================================== Ratio of earnings to fixed charges (0.92) 1.11 (0.72) =====================================