Thermochemical processing of meat and bone meal: A review

Since the Bovine Spongiform Encephalopathy crisis, meat and bone meal (MBM) have been considered animal wastes. Nowadays, these animal residues are generally burnt in cement kilns and disposed of in landfills. However, several technologies are being developed in order to achieve energy valorisation of MBM by means of combustion, pyrolysis and gasification. These thermal treatments of MBM will reduce the environmental impact of landfill and, at the same time, take advantage of the MBM heating value (13-30 MJ/kg). The main results of research into combustion, pyrolysis and gasification of MBM show that the products could be used as fertilizer (solid product) and as fuel (gas and liquid products). The present work aims at reviewing the most significant studies about energy valorisation of MBM and the potential application of the products obtained in these thermochemical processes.     

Friction and solid-solid adhesion on complex metallic alloys

The discovery in 1987 of stable quasicrystals in the Al–Cu–Fe system was soon exploited to patent specific coatings that showed reduced friction in ambient air against hard antagonists. Henceforth, it was possible to develop a number of applications, potential or commercially exploited to date, that will be alluded to in this topical review. A deeper understanding of the characteristics of complex metallic alloys (CMAs) may explain why material made of metals like Al, Cu and Fe offers reduced friction; low solid–solid adhesion came later. It is linked to the surface energy being significantly lower on those materials, in which translational symmetry has become a weak property, that is determined by the depth of the pseudo-gap at the Fermi energy. As a result, friction is anisotropic in CMAs that builds up according to the translation symmetry along one direction, but is aperiodic along the other two directions. A review is given in this article of the most salient data found along these lines during the past two decades or so.