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3014702 
Journal Article 
Determining the pH Buffering Capacity of Compost Via Titration with Dilute Sulfuric Acid 
Costello, RC; Sullivan, DanM 
2014 
Waste and Biomass Valorization
ISSN: 1877-2641
EISSN: 1877-265X 
505-513 
Development of high-value horticultural markets for compost requires improved characterization of compost properties. Most composts have pH of 7-8 and act as a partial substitute for lime in potting media. The objective of this research was to develop and validate a reproducible method for determining the pH buffering capacity of compost. To estimate compost buffering capacity (CBC), the quantity of acidity needed to reduce pH by one unit, dilute sulfuric acid (H2SO4; 0.1-1.0 mol H+/kg compost) was allowed to equilibrate with compost at 22 degrees C for 72 h. The CBC was calculated as the negative reciprocal of the slope of the linear regression: compost pH (y-axis) versus acid addition rate (x-axis). The CBC for eight composts ranged from 0.21 to 0.45 mol H+ per kg compost per pH unit (avg = 0.31). The CBC determined from dilute acid addition for 72 h was validated via incubation of compost plus S degrees dust at 22 degrees C for 28 days. For the eight composts evaluated, S degrees addition to acidify compost by 1 pH unit (as predicted by CBC) resulted in an actual pH decline of 1.1 units (SE = 0.2), and predicted S degrees addition to acidify it by 2 pH units resulted in an actual decline of 1.7 units (SE = 0.2). The CBC test method is recommended for evaluation by commercial compost testing laboratories. 
Compost analysis; Acidification; Elemental S; Lime; Titration; Potting media; Acid loving plants; Calcifuge; Compost acidification requirement; Dairy manure solids; Deciduous tree leaves; EC; Electrical conductivity; H+ buffering capacity; H+ consumption capacity; Horse manure; Lime requirement; Manure; Organic matter; Peat; Peppermint; Saturation extract method; Soluble salt; Straw; Yard debris