Massive CO2 biofixation process and seaweed biomass production with the use of gravels from oil well drilling

A method for producing seaweed biomass, comprising:

• adding ground drilling gravel in a concentration ranging from 0.01% to 95% based on mass/mass (kg/kg) or mass/volume (kg/L) units to a culture medium to form a gravel-containing culture medium, wherein the ground drilling gravel comprises Al, Fe, Ca, Mg, Cu, Mn, Zn, Ni, Cr, P, K, and Na;
• inoculating a first sample of macroalgae and microalgae in the gravel-containing culture medium at a concentration ranging from 1 mg/L to 1 g/L in a first transparent container subjected to natural or artificial sunlight with luminous intensity greater than 60 klux for 8 to 14 hours;
• inoculating a second sample of the macroalgae and microalgae in a control medium comprising the culture medium without the ground drilling gravel at a concentration of 1 mg/L to 1 g/L in a second transparent container subjected to natural or artificial sunlight with luminous intensity greater than 60 klux for 8 to 14 hours;
• supplying CO2 to each sample through a solenoid valve triggered by a pH controller with an electrochemical sensor comprising a glass electrode, wherein a pH of each sample is maintained between 6 and 7, over 3 to 12 days of growth;
• a salinity of each sample, measured with reference to a mass of sodium chloride, is maintained between 0.001 and 150 g/L;
• and a temperature of each sample is maintained between 24 and 48° C.;
• and
• performing daily observations under an optical microscope and macroscopic observations to attest a presence of healthy microalgae growing in the gravel-containing culture medium and in the control medium.