The US Navy is developing a technology that it expects will allow it to produce jet fuel out of seawater.
Carbon is abundant in seawater, with the concentration in the ocean being about 140 times greater than in air. Most of the carbon is in the form of bicarbonates with about 1% being carbonates.
The US Naval Research Laboratory has made significant advances in developing an electrochemical acidification cell which uses small quantities of electricity to exchange hydrogen ions produced at the anode with sodium ions in the seawater stream. This turns the carbonates and bicarbonates into carbon dioxde and sodium hydroxide and releases hydrogen as a byproduct. Currently, up to 92% of the carbon in the seawater is captured.
The carbon dioxide and hydrogen are then combined, using iron catalysts in fixed-bed reactors, to form liquid hydrocarbons. Chemical processes, using a nickel catalyst, are then used to convert these hydrocarbons into jet fuel.
The Navy predicts that it will eventually be able to make jet fuel from seawater for between $3 and $6 a gallon ($0.80 and $1.60 a litre) – comparable with current costs.