Inventory - Carrying Value of Inventory (Details) - USD ($)	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018
Inventory Disclosure [Abstract]
Solvents and solutions	$ 8,694,000	$ 8,216,000
Used oil and processed oil	8,349,000	12,124,000
Machines	5,440,000	5,334,000
Drums and supplies	4,697,000	5,231,000
Other	2,632,000	2,378,000
Total inventory	29,812,000	33,283,000
Less: machine refurbishing reserve	439,000	224,000
Total inventory - net	29,373,000	33,059,000
Inventory impairment charge	$ 0	$ 0