Statistical Verification of a Biochemical Methane Potential Test

Abstract

The Biochemical Methane Potential (BMP) assay is commonly used for determining the viability of feedstocks for anaerobic digestion (AD). The results from these tests have been adopted for a variety of applications; including preliminary screening, toxicity testing, as well as the design and prediction of biogas production from full-scale operational digesters. The use of the BMP as the foundation for making the aforementioned decisions is problematic because of the variation in BMP protocols available and a lack of statistical analysis to verify accuracy of the results. This paper will detail selected results from a series of BMP assays conducted on several dairy manure and milking center wastewater samples, collected over a period of six weeks from three New Mexico dairy farms. The manure and wastewater samples were characterized individually and also as an array of blends. Each blend was set up in triplicate in serum bottles with the contents of each bottle being tested individually for a series of parameters both pre and post-digestion (pH, alkalinity, chemical oxygen demand (COD), total solids (TS), total volatile solids(VS) and ammonia). At the end of the BMP, a biogas potential ratio was calculated based on the initial VS and COD (mL per mg VS Fed and mL per mg COD Fed derived from pre-digestion analysis. A statistical analysis was completed to compare this method for calculating the biogas potential ratio with a more traditional method.