Could synthetic limestone in concrete and massive kelp farms sequester 1 TRILLION tons CO2 by 2050, taking us back to 300ppm?

[Eclipse Now]

Could synthetic limestone in the world's concrete market and massive kelp farms to stimulate fisheries REALLY sequester 50 GT CO2 per year, sequestering a TRILLION TONS of CO2 by 2050 and putting us back to 300ppm? That's the claim of the Foundation For Climate Restoration - PDF at link below.
https://eclipsenow.wordpress.com/2021/09/29/climate-back-to-normal-by-2050/