Ocean Acidification Reversal by Self-Replicating Biomass Cultivation and Processing Systems: Prospects and Questions

Accumulated anthropogenic insults to climate and biosphere have initiated further feedbacks presently threatening to intensify climate change, with attendant ill effects to ecosystems and human populations. At present, the scope of the problem is such that concerted efforts by the vast majority of nation-states would be required to avert global atmospheric temperature rise of over 1.5°C or ocean pH decline below 8.0 through conventional means, and restoration of these parameters to preindustrial levels is not anticipated in the foreseeable future. While some mitigation proposals themselves exploit feedback effects, those which are not uncontrolled involve significant effort and resource inputs. We outline a strategy to restore preindustrial ocean photic zone pH and atmospheric p_CO2 within a few decades utilizing self replicating systems (SRSs) that cultivate macro- and micro-algae to yield biomass at high areal productivity (35-110g/d.m², 100-fold or more above open-ocean background) which is then processed into useful materials including most material inputs for system replication. These SRSs eploit light management to separate insolated thermal and photosynthetically active radiation and utilize solar-thermal energy for operation. Biomass produced by the full scale system (occupying 1-2% ocean surface) is a source of raw materials (effecting carbon sequestration through use), food and agricultural feed including for mariculture, potentially reducing overfishing and demand on terrestrial resources and agriculture, thus enabling rewilding. Ocean deacidification occurs by utilizing HCO₃^- or CO₃^-2 as carbon sources (consuming protons) or through avoided CO₂ hydration. While such an endeavor would have clear benefits and avoid substantial risks, the scale entails that close attention be paid to local carbon and proton fluxes and minimizing any consequent ecological effects; we pose questions concerning best modes by which to conduct ocean acidification reversal.