The decision ends six years of composting household waste at sites in Farington and Thornton with the loss of about 250 out of 330 jobs.
The Labour-run council said it will no longer process food and green waste but store it for treatment elsewhere.
Tory councillor Michael Green said it was "a failure of catastrophic proportions costing millions".
Mr Green said, who represents Leyland South West, added: "We are being asked to believe it was the 'wrong kind of waste', which is what I have been told for the last six years.
"Surely someone should have done due diligence on the kind of waste it would process."
Lancashire County Council said the sites were no longer economical blaming  changes in households attitudes and a drop in the amount of organic material to compost in the last 10 years.
Cabinet member responsible for environmental services, councillor Marcus Johnstone, said: "What we are left with is a high cost, high liability and highly complicated plant."
The two sites were built following a £2bn Private Finance Initiative (PFI) over 25 years with Global Renewables, an Australian-based company.
Composting began in 2010 but annual costs of £12m a year forced the council to scrap the contract in 2014.
On Friday 19 February, the council's executive decided that composting will stop immediately at Thornton with composting ending at Farington on 31 March.
Council leader Jennifer Mein said: "Lancashire is in a much better position than a number of other local authorities which also invested in PFI-funded mechanical and biological treatment facilities because we successfully restructured the financing for the sites in 2014 to make an annual saving on the contract of £12m."
A visitor and education centre at Farington will also close.

The 40-year-old has succeeded compatriot Jose Riga, who helped the Addicks avoid relegation from the Championship.
Peeters was most recently in charge of Belgian outfit Waasland-Beveren and has also managed Cercle Brugge and Gent.
The former striker, who was capped 13 times by Belgium, also had a two-year spell as a player at Millwall between 2003 and 2005.
Peeters will work alongside Charlton first-team coach Damien Matthew.
Former Charlton assistant manager Alex Dyer will not be part of the new setup and has left the club after after three-and-a-half years at The Valley.
Riga, 56, took over as  Charlton manager in March following Chris Powell's sacking and had hoped to remain in charge after seven wins from 16 games.
But Charlton owner Roland Duchatelet, who also owns Standard Liege, decided against that in favour of Peeters.
A £2bn waste treatment scheme has been shut down by a county council to save £8.5m per year.
[NEXT_CONCEPT]
Charlton have appointed former Belgium international Bob Peeters as manager.