The growing demand for energy because of population growth, lack of clean energy and inadequate availability of natural resources has led to the growing demand of anaerobic digestion technologies in rural areas of many developing countries.
Biogas, a renewable, clean and efficient source of alternative energy which can be used as a substitute for fuels such as firewood, charcoal and cattle dung, usually used by rural dwellers.
The domestic digester is an example of an anaerobic digester usually applied in a single decentralized system mostly in rural areas of developing countries and can serve as energy solution to meet their cooking needs. Among all household digesters, the Chinese dome digester (CDD) is the most popular and most implemented reactor because of its reliability, requirement of low maintenance and long lifespan.
Mixing in the Chinese dome digester (CDD) depends on the change of slurry level in the digester and extension chamber during gas use and could be regarded as intermittent natural mixing. Mixing is an important process in anaerobic digestion for establishing contact between micro-organisms and feed, for homogenization of temperature throughout the digester, and preventing settling and floating layers. However, mixing is limited the CDD and are therefore operated at long hydraulic retention times (more 40 days) and low influent total solid concentrations (i.e lot of water is added to feedstock) when compared to forced mixed reactors, leading to a large reactor volume and higher cost.
In this study conducted at Wageningen University, in the Netherlands and Obafemi Awolowo University, mixing was optimized in the Chinese dome digester without the inclusion of moveable parts with lower water dilution at reduced hydraulic retention times, 40 and 30 days to achieve a smaller reactor volume.