1. The product (biogas) value is rather low; this makes it an unattractive commercial activity.
2. The biogas yields are lower due to the dilute nature of substrates.
3. The process is not very attractive economically (as compared to other biofuels) on a large industrial scale.
4. Recombinant DNA technology and even strain improvement techniques can not be used to enhance the efficiency of the process.
5. The only improvement in the process, can be brought about by optimising the environmental conditions of the anaerobic digestion.
6. Biogas contains some gases as impurities, which are corrosive to the metal paris of internal combustion engines.