Anaerobic digestion: A promising technology of utilizing radioactively contaminated plant biomass

Abstract

Anaerobic digestion (AD) is a widely used technology that allows for the reprocessing and reduction of waste biomass. A study was conducted to see if the AD technology might be used to process radioactively polluted agricultural biomass. For this purpose, laboratory tests were carried out with a 20-liter model biogas plant (BGP) with the radionuclide 134Cs and operational tests with the South Bohemian commercial biogas plant monitoring the radionuclide 137Cs. The activities of 134Cs in inputs, contaminated grass or maize silage and in emerging fractions were investigated in the model fermenter. The activity of 134Cs in the dry matter during the fermentation process increased by 46% on average, which corresponds to a reduction of dry matter by 43% due to the production of biogas. 137Cs activities were measured in commercial BGP maize, grass, and whole plant silage, wheat, digestate, biogas, and aerosol samples. The commercial BGP fermentation process was more efficient, with an 80% reduction in dry mass weight. Dry biomass (1.37 Bq/kg) had a 137Cs massic activity that was 4.4 times lower than the activity of dry digestate mass (6.01 Bq/kg). The activity of the 137Cs in biogas aerosol was 1.1 × 10−7 Bq/m3 or less, and the decontamination factor was 6.9 × 106 or greater. Most Cs remain in the digestate. No other ways of radioactivity leakage have been identified.