The objective of the ACUA (Autonomous Composting Units for Urban Areas) is to develop, within the urban fabric and focusing on the block of flats or a small number of blocks of flats or on any area of urban interest, a system for the collection and processing of the bio-waste produced (partial and/or total) in the same area, without of course creating any nuisance. The European legislation (Directive 98/2008, Waste Directive) necessarily leads to strengthening the source-separation of municipal solid waste. Moreover, the focus of the separation is transferred from recyclable materials, where it was focused during the last decade, to bio-waste, i.e. food and plant decay residues, etc. According to the Directive, the requirement is that, until 2020, all member states should have a separate collection system of at least 10% of the bio-waste produced. At the heart of these actions are Autonomous Composting Units which are systems that are the spearhead of composting technology.