CPI Project Develops Novel Animal Bedding

CPI’s scientists carried out a six week laboratory scale study that including a series of bench scale anaerobic digestion assays on a range of bedding products. EnviroSystems has developed a novel, paper-based animal bedding called ​‘Envirobed’. It was hypothesised that this product would provide fewer inhibitory effects for farm-based AD plants and provide a healthier environment for the cattle shed. CPI was tasked with designing and executing an independent lab scale appraisal to assess these potential benefits. 

CPI’s scientists designed a rigorous scientific protocol, comparing lime ash, gypsum, straw/​sawdust and Envirobed. These bedding materials were blended with dairy manure, to provide ample nutrients, and seed inoculum, to establish a microbial culture. Characterisation of the different raw samples was made prior to assay start-up, with the analysis of pH, chemical oxygen demand (COD), total solids (TS) and volatile solids (VS). Results of the study suggest that the use of Envirobed and/​or straw/​sawdust would seem to be the less inhibitory options for AD in comparison to gypsum or lime ash. The data suggests that the overall gas production from the mono-digestion of manure would not be exceeded but the least antagonistic relationships would be observed from the addition of Envirobed or Straw/​Sawdust.

The use of gypsum as a co-substrate in an AD system would not only cause a negative impact on the production of biogas but also emit much higher levels of potentially harmful Hydrogen Sulphide gas. The addition of lime ash has a significant impact on the pH of an anaerobic digester and must be carefully utilised in order to not upset system stability. Lime ash also seemed to have an adverse impact on gas production but this was subsequently overcome after acclimatisation of the microbial population. 

CPI recommended that further work on the addition of the bedding materials to manure should be carried out in order to optimise the process and investigate the impact of co-digestion over a longer period of time and at a larger scale. Given the promising data and an exceptionally strong market demand, EnviroSystems is already planning a follow on project with CPI to test more permutations and build an even stronger business case for Envirobed.