Scottish rubbish may have to be sent to England in order to meet a planned ban on household waste going to landfill by 2021.
The Scottish government wants to stop traditional black bag waste and a range of recyclable materials being buried in the ground.
But a new study has found the cost of the ban could be more than £1bn.
Less than half of Scotland's 32 councils have plans in place to meet the 2021 target.
The study of waste markets predicts there will be insufficient capacity to meet the expected level of need, with a gap predicted of one million tonnes of waste per year in 2021.
That could fall to 90,000 tonnes by 2035 if councils take action to reduce waste and build more energy-from-waste processing facilities.
But if this does not happen quickly enough then the waste would need to be exported out of Scotland.
The report, commissioned by Scottish ministers, states: "Excluding consideration of waste minimisation and recycling, the ban will result in significant economic costs to Scotland due to the need to export an increased amount of residual waste - whether as an interim solution until new thermal treatment capacity comes online, or as a long-term solution."
If this involved payment in tax or to private processing facilities, then at least the penalty would be circulated within the Scottish economy but instead, the report points out, that the payments would go elsewhere: "This has the effect of exporting revenue to English or continental landfill or treatment providers."
Researchers modelled the likely costs of the landfill ban, which ranged from £414m to £1.156bn.
The independent study also found that, as of 2017, only 14 out of 32 councils had plans in place to process all their expected biodegradable waste and avoid sending it to landfill.
'Unlikely to be fully achievable'
This is despite the "significant notice" given of the planned ban, announced in 2012.
Local authority body Cosla has already warned that "as it stands it seems unlikely that the 2021 ban will be fully achievable".
The Scottish Environment Protection Agency last year warned landfill operators that they will have the statutory duty to check what is being placed in their dumps, to ensure that none of it is biodegradable.
Opposition politicians criticised the Scottish government's handling of the ban.
Scottish Liberal Democrat leader Willie Rennie said: "It would make a mockery of the law if the SNP's solution to meeting their own landfill ban is to ship it to England or abroad."
Scottish Conservative environment spokesman Maurice Golden said the target was an "SNP gimmick".
He said: "This damning report shows that their target is wildly off-schedule."
'A more sustainable way'
A Scottish government spokeswoman said: "The Scottish government is committed to ending the practice of sending biodegradable municipal waste to landfill.
"This will contribute to progress on climate change targets and increase incentives to deal with waste in a more sustainable way. We have been working closely with local authorities and commercial bodies to assess and support progress towards implementing the ban.
"Our focus now is on working with authorities who do not yet have a solution in place to identify ways, such as collaborative procurement and improved recycling, in which they can comply with the ban."