Co-products: what leaves the reactor besides fuel, and where it goes

Three streams, one process

The conversion process yields distinct fractions: liquid fuel precursors, an aqueous phase, and solid residues. The liquid fractions are the main product; they are refined toward diesel-like, marine and, in time, aviation routes. The other two streams are where the circular model is decided.

The aqueous phase

Because the process converts the seaweed with its water present, the largest stream by mass is a water-rich phase that carries dissolved organic compounds and nutrients. It is a resource of its own. Part of it is recycled within the process, which reduces fresh-water needs; the rest can be reused by other industries, for instance where a nutrient-bearing water has value. The aim is that no water leaves as waste.

The solids

The solid stream holds what the fuel must not contain: the mineral fraction of the seaweed, the salts of seawater, the sand that came with collection, and the heavy metals such as arsenic that sargassum takes up from seawater. The first conversion step separates these elements from the fuel path while the valuable molecules are transformed. That separation is deliberate: it keeps the fuel clean and concentrates the unwanted elements in one stream that can be characterised and handled. Where the composition allows, mineral solids have reuse routes in construction materials or soil improvement; where it does not, they are treated as regulated residues. Which route applies is decided by analysis and by the rules of each territory, not assumed in advance.

What "circular" means here

• Marine collection: macroalgae and coastal biomass that would otherwise be landfilled.
• Pre-processing: preparation and conditioning, where sand and debris are removed.
• Conversion: the Salacia process, which sorts the streams at the first step.
• Fuel outputs: renewable drop-in fuels for existing engines.
• Circular valorisation: the aqueous phase and solids put to use rather than discarded.
• Resilience loop: local industrial reuse, so that value and materials stay in the territory that supplied the biomass.

Selling co-products improves the economics of the fuel, but the model is built for a second reason: a coastal plant that leaves residues behind would recreate the problem it set out to solve. Every stage of the value chain is designed to minimise waste and reuse resources systematically, closing the loop at industrial scale.