The protesters staged a creative demonstration outside Scotland's only crude oil refinery in Grangemouth, spitting out a vegetable liquid from cans worn over their heads.
"We don't want to hear more pledges for 2030, for 2035, for 2050. We need action immediately, right now," said Rob Higgs, one of the Ocean Rebellion activists.
The refinery's owner INEOS said in September it will convert its vast Scottish petrochemicals plant and oil refinery to run on hydrogen at a cost of more than $1.4 billion to make it 'net zero' for carbon emissions by 2045.
Britain has a target to reach net zero by 2050 and has significantly reduced emissions from power generation, but has found it harder to cut industry's carbon footprint.