Anaerobic co-digestion of dairy manure and sugar beets

Abstract

Batch and continuously fed experiments were conducted with laboratory-scale digesters to evaluate the performance of anaerobic co-digestion of dairy manure and sugar beets under thermophilic temperatures. The sugar beets were divided into two portions of tops and roots. Four types of influent feedstocks were utilized: 100% dairy manure, a mixture of beet tops, a mixture of whole beets (tops and roots) and a mixture of roots and dairy manure. From the results of the batch fed experiments, co-digestion of dairy manure with sugar beets increased the methane production per unit of digester volume. However, when an excess amount of beets was added digestion was inhibited as evidenced by the lack of gas production. From the results of the continuously fed experiments at 20 days of hydraulic retention time, the average yield of methane was greatest for the dairy manure and 40% beet top mixture which produced 1.49 times more methane compared with the 100% dairy manure mixture.