© 2017 Elsevier B.V. Living architectures and green energy are hot topics of the applied sciences. They aim to develop buildings that co-live with their environment and co-habit with people they house. An ultimate goal would be to make every block in a building capable of producing energy. We present results of scoping, and somewhat illustrative, experiments on generating electrical energy in modified aerated concrete blocks. These blocks are commonly used in modern building industry and therefore make an ideal candidate for ‘inbuilt’ microbial bio-reactors. We fill the blocks with milk to evaluate electro-generation potential of a pasteurised milk and to study power generating potential of the medium nutrient rich for micro-organisms. We assess the practicality of using bio-reactors which become colonised by local micro-flora.