Other companies that produce more than 50,000 tonnes of greenhouse gases a year, will pay the carbon price on anything over 80 per cent.
In "a small number of sectors", the limit will be even higher and allow emissions up to 90 per cent of the industry average.
The government in Ontario has eliminated the province's cap-and-trade system and is joining Saskatchewan in challenging the federal government's jurisdiction to impose a carbon price on provinces.
Cement producers were named among those industries that would will be entitled to a 90 per cent subsidy rate on their carbon tax burden, compared with a previously published subsidy rate of 70 per cent.
The Liberal government said the changed guidelines were aimed at addressing concerns among industries that are at a high risk of suffering from foreign competition.
The government says the plan all along was to set an initial target and then amend it after more specific review, and that the changes made will not have a material impact on the amount of greenhouse gases that will be cut from Canada's total annual emissions.
The Trudeau government has said it would use these powers as part of a national strategy to fight climate change and honour Canada's worldwide commitments, supported by all political parties, under the 2015 Paris Agreement to reduce greenhouse gas pollution and prevent unsafe levels of atmospheric warming.
British holidaymakers swelter in record-breaking European heatwave
Homes in Finland are created to handle the extreme cold and damp typical of the Nordic region, not the recent high temperatures. Tourists were urged to avoid the sun during the hottest part of the day and to remember that children are particularly at risk.
Premier Doug Ford has vowed to scrap Ontario's cap-and-trade system and has taken steps to end the program since taking office last month.
A spokeswoman for Environment Minister Catherine McKenna confirmed the move to CTV News following a report in the Globe and Mail. We want to have the most energy efficient, smart industries here that create good jobs, at the same time do what we need to do to tackle emissions.
The Ford government greeted Ottawa's move to scale back a federally mandated carbon tax as a victory for the Premier.
He reiterated that Ottawa's carbon tax policy is flawed and won't work in Canada if it hasn't worked around the world.
Taxing above 10 to 20 per cent would hurt a company's ability to innovate and find a viable solution, Elgie said.
With the case possibly headed from there to the Supreme Court, Moe said it was unlikely there would be a decision ahead of the January implementation date for the carbon tax. "We are committed to providing draft regulations in Fall 2018".
"It seems to be politics driving the policy rather than economics or the environmental outcome", Mr. McMillan said.