Long-term market reactions to changes in demand for NaOH
Wesnæs M, Weidema B P (2006)
Study for Novozymes. Copenhagen: 2.-0 LCA consultants.
NaOH (sodium hydroxide or caustic soda) is a by-product of the chlorine-alkali process. As this process is determined by the long-term demand for chlorine, changes in demand for NaOH does not affect the output of NaOH from this process.
An analysis of the NaOH market reveals that long-term changes in demand for NaOH will affect the least essential uses of NaOH, i.e. those uses where NaOH can readily displace sodium carbonate (soda ash). A long-term increase in demand for NaOH will thus be met by an increased use of sodium carbonate for those uses where NaOH is not essential, e.g. in pulp and paper, water treatment, and certain chemical sectors where it is used as a neutralising agent. Likewise, a long-term decrease in demand for NaOH will lead to increased displacement of sodium carbonate.
In the current market situation, where there is a global increase in demand for chlorine, the continuously increasing output of NaOH is adequate to cover the applications where NaOH is essential, and a marginal increase in NaOH demand will therefore not lead to a need to produce NaOH from the alternative process route (the caustification process, where NaOH is produced from lime and soda). If there is a further increase in demand for NaOH for essential applications, without a simultaneous increase in demand for chlorine, the caustification process will again be able to play a role as a marginal production route for NaOH, as has been the case previously.
To model the current long-term market reaction to a decreased demand for NaOH in a life cycle assessment, we thus recommend using the derived decrease in sodium carbonate supply. Sodium carbonate is currently produced from NaCl and CaCO3 in the Solvay process (in Europe), and in addition directly from naturally occurring ores (trona) or brines (USA). The displaced sodium carbonate supply may therefore depend on the location and transport costs. The Solvay process is still the dominating process globally, implying that the output from the naturally occurring sources are not globally competitive, and that a decrease in NaOH demand will primarily affect the Solvay process. Sources for environmental data for the Solvay and the trona mining processes are identified.