Life cycle assessment of the conventional and solar thermal production of zinc and synthesis gas

The current industrial productions of zinc and synthesis gas are characteri zed by their high energy consumption and their concomitant environmental po llution. Emissions of greenhouse gases (GHG) could be reduced substantially by combining both productions and by replacing fossil fuels with concentra ted solar energy as the source of high-temperature process heat. The extent of such a GHG mitigation has been quantified by conducting a Life Cycle As sessment on the solar- and fossil-fuel-based processes. Total GHG emissions for the conventional zinc production are 3.14 CO2-eq per kg primary zinc ( 99.995% purity), of which 64% are derived from the electricity consumption in the electrolytic step. Total GHG emissions for the conventional syngas p roduction are 1.04 CO2-eq per kg syngas (molar ratio H-2/CO=2), of which 84 % are derived from the combustion of fossil fuels in the endothermic steam- reforming step. Total emissions for the solar combined process are 1.51 CO2 -eq per 1 kg zinc and 0.527 kg syngas, of which 78% are derived from the pr e-/post-processing of reactants and products of the solar reactor, and 16% are derived from their transportation to/from the solar site. However, CO2- eq emissions derived from the solar processing step and its infrastructure are negligible. (C) 2000 Elsevier Science Ltd. All rights reserved.