Process for improved seaweed biomass conversion for fuel intermediates, agricultural nutrients and fresh water

An integrated process for the production of fuel intermediates, agri-nutrients and potable water from Kappaphycus alvarezii seaweed comprising the steps of:

• i. of mechanically shearing Kappaphycus alvarezii seaweed to obtain a slurry, and filtering the slurry to separate a first solid residual biomass from a first aqueous phase;
• ii. mixing the first solid residual with seawater and incubating at 105° C.-120° C. at a pressure of 25 to 35 kPa for 50 to 70 minutes, then centrifuging to obtain an a second solid insoluble residue and a second aqueous phase, mixing the second aqueous phase with isopropyl alcohol and centrifuging to obtain κ-carrageenan as a solid;
• iii. suspending the κ-carrageenan solid at 5-10% (w/v) in an aqueous solution containing an acid catalyst and incubating at 100-110° C. for 1-3 hours at 25-30 kPa to obtain a third aqueous phase comprising 5-hydroxymethyl furfural (HMF), galactose and potassium bisulphate;
• iv. mixing the third aqueous phase with an organic solvent to obtain an organic phase containing HMF and a fourth aqueous phase, separating said organic phase from the fourth aqueous phase and extracting HMF from the organic phase to obtain recycled organic solvent;
• v. optionally suspending additional κ-carrageenan solid into the fourth aqueous phase and repeating the process of step (iii), and repeating step (iv) with the recycled organic solvent;
• vi. adding magnesium hydroxide to the fourth aqueous phase in an amount sufficient to achieve pH-neutral fourth aqueous phase;
• vii. adding the first aqueous phase to the pH-neutral fourth aqueous phase to produce a fifth aqueous phase, and subjecting the fifth aqueous phase to evaporative concentration to obtain crystals of potassium sulphate and a sixth aqueous phase containing galactose;
• viii. subjecting the sixth aqueous phase to further processing selected from (a) concentrating through evaporation to obtain crystals of galactose and a seventh aqueous phase (b) fermenting to obtain ethanol and a seventh aqueous phase or (c) adding dilute aqueous acid and incubating at 100-110° C. for 1-3hours at 25-30 kPa to obtain a levulinic acid and formic acid and a seventh aqueous phase;
• ix. neutralizing the seventh aqueous phase and recovering magnesium hydroxide.