This includes both domestic and trade waste, and materials collected through the council's recycling scheme.
The contract is an extension of SITA's existing five-year deal, due to end in April. The company will process around 100,000 tonnes of rubbish a year.
North Lincolnshire has achieved an 18% recycling and composting rate, but hopes to hit the statutory 24% level under the new contract.
John Briggs (Con), cabinet member for housing and neighbourhood services, said the contract was designed to ensure the council would not be fined under regulations penalising excess use of landfill disposal.