"Cradle To Cradle Design" is a set of design principles for sustainable living. The principles are based on organic systems. * All materials used should have a 'life cycle'. That is, there should be a planned route for their re-use. A life cycle that ends in landfill or sea-fill is not valid. Currently in our society even our sewerage system has a toxic cradle-to-grave design, in that it ends in sea-fill. Cradle-to-cradle design would have it producing bio-gas and fertiliser. * Environmental cost of energy used should be of high consideration in the design. In designing aircraft wings, reduction in noise has two fold value as reducing it simultaneously reduces energy requirements. High grade energy (electricity) should be used only where appropriate, e.g. electronics and small motors