Volatile organic acid adsorption, cation dissociation by porphyritic andesite, and their effects on the hydrolysis and acidogenesis of solid food wastes were evaluated through batch experiments. The acetic acid adsorption experiments show that pH was mainly regulated by H(+) adsorption. The mono-layer and multi-layer adsorption were found under the low (8.3-83.2 mmol/L) and high (133.22-532.89 mmol/L) initial acetic acid concentration, respectively. The dissociated cations concentration in acidic solution showed the predominance of Ca(2+). Porphyritic andesite addition elevated the pH levels and accelerated hydrolysis and acidogenesis in the batch fermentation experiment. Leachate of porphyritic andesite addition achieved the highest hydrolysis constant of 22.1 x 10(-3) kg m(-2) d(-1) and VS degradation rates of 3.9 g L(-1) d(-1). The highest activity of microorganisms represented by specific growth rate of ATP, 0.16 d(-1), and specific consumption rate of Ca(2+), 0.18 d(-1), was obtained by adding leachate of porphyritic andesite. (C) 2010 Elsevier Ltd. All rights reserved.