A solar-thermal aerosol flow reactor process is being developed to dissociate natural gas (NG) to hydrogen (H-2) and carbon black at high rates. Concentrated sunlight approaching 10 kW heats a 9.4 cm long x 2.4 cm diameter graphite reaction tube to temperatures similar to2000 K using a 74% theoretically efficient secondary concentrator. Pure methane feed has been dissociated to 70% for residence times less than 0.1 s. The resulting carbon black is 20-40 nm in size, amorphous, and pure. A 5 million (M) kg/yr carbon black/1.67 M kg/yr H-2 plant is considered for process scale-up. The total permanent investment (TPI) of this plant is $12.7 M. A 15% IRR after tax is achieved when the carbon black is sold for $0.66/ kg and the H-2 for $13.80/GJ. This plant could supply 0.06% of the world carbon black market. For this scenario, the solar-thermal process avoids 277 MJ fossil fuel and 13.9 kg-equivalent CO2/kg H-2 produced as compared to conventional steam-methane reforming and furnace black processing. (C) 2003 Elsevier Ltd. All rights reserved.