Performance evaluation of cellulose fiber's effectiveness as a thermal insulation material for productive biogas systems

Cellulose fiber (CF) is a cost-effective and eco-friendly thermal insulation material which has largely found its application in the construction industry to provide wall insulation in residential and commercial buildings. Biogas digesters too are constructed with walls which should be insulated to limit digester temperature fluctuations which are unfavorable for methane formation. The objective of this study therefore was to evaluate the effectiveness of CF as a thermal insulation material for biogas digesters. Design, development and testing strategies were thus adopted to determine the percentage heat loss reduction on a cylindrical biogas digester insulated with locally made cellulose fiber material. Pilot study results indicate that over 82% of heat loss reduction was achieved with cellulose fiber density of 44.4 kg/m(3) on horizontal application, and 62.7 kg/m(3) on vertical application with external digester heating from a solar thermal siphon-heat exchanger configuration. This was only 2% less that the analytical frame of 84% with an optimum insulation thickness of 9 cm. CF is thus an effective insulation material for bio-digesters, but must be protected from hazard as might be caused by vermin and moisture penetration. This can be made possible by enclosing the insulation with a rigid protective envelop, which also supports its loose-fill installation. (C) 2020 The Authors. Published by Elsevier Ltd.