what is the disadvantages of biogas plant ?

DISADVANTAGES OF BIO GAS PLANT

 1) The process of digestion reduces the total solids content in the sludge and thus there is a volume loss of the organic waste compared to composting, however both can produce a fertiliser

2) Biogas contains contaminant gases which can be corrosive to gas engines and boilers;
3) Digestate must meet high standards in order to be used on land without detrimental effects on agricultural uses especially food crops;
4) Biogas plants and gas upgrading plants both have a relatively high heat and energy demand which demand some of the biogas produced to be used on-site; 
5) Will only produce a limited quantity of energy demand and is dependant upon location in proximity to feedstock and energy users; 
6) There is little or no control on the rate of gas production, although the gas can, to some extent be stored and used as required.