I could use a microbial fuel cell ( MFC ) to convert chemical energy , available in a bio-convertible substrate, directly into electricity. To achieve this, bacteria are used as a catalyst to convert substrate into electrons. Bacteria are very small ( size approximately 1µm ) organisms which can convert a huge variety of organic compounds into carbondioxide , water , and energy. The micro-organisms use the produced energy to grow and to maintain their metabolism. However, by using a MFC I could harvest a part of this microbial energy in the form of electricity to charge my mobile phone.