Alkaline injection technology: Field demonstration

In December 2001, 2225 tonnes of fluidized bed combustion (FBC) ash were injected into an abandoned coal mine in eastern Oklahoma. Post-injection monitoring continued for 24 months, during which the mine system appeared to be reestablishing equilibrium with CO₂ in the mine headspace. Alkalinity and pH gradually increased, and as of December 2003 were roughly 65 ppm and 7.3, respectively. Metal concentrations were still significantly lower than pre-injection levels, but iron and manganese concentrations had increased from non-detect levels shortly after injection to roughly 30 ppm and 1.25 ppm, respectively. Aluminum, nickel, and zinc were less than pre-injection concentrations and did not appear to be increasing (roughly