The degree of purity of materials recovered from municipal solid waste (MSW) depends mainly on the objective: the intended use of the recovered material and the cost to recover this material in its pure form, determined by the intensity of the effort and the technology involved. The Bio-waste to Bio-plastic (B2B) Project aims to develop an integrated separation process at the bio-waste source, focusing on Hospitality Units. The quality of the collected bio-waste will be upgraded by removing foreign bodies or even specific categories of food waste, or by adding bio-waste from other, more specialized, sources (e.g. bakery residues) to produce compostable bio-plastics through an optimal synthesis process. Compostable bio-plastics are high added value products, which justify an increase in the cost of the preceding processes. After examining the possibility of further source separation and its results, B2B will study the optimal collection and transport system which decisively affects many qualitative elements, testing and evaluating a relatively high-cost but highly effective solution, that of hand-sorting in order to optimize materials recovery. B2B will identify all the parameters of the production process of PLA monomers and (poly) lactic acid in relation to the quality characteristics of the raw material (bio-waste) collected from Hospitality Units. Quantitative and qualitative analysis of food waste (bio-waste) produced in Hospitality Units will then take place. All the above will be tested on a bench-scale unit that will allow their further study and their substantial improvement, as well as the extraction of realistic results. Finally, the effect of the end-product bio-plastic on the composting and anaerobic digestion of bio-waste will be examined. The expected results from the B2B implementation are an optimized source separation scheme for Hospitality Units, the identification of the appropriate method of upgrading the quality of residues collected for the purpose of bio-plastic production, and eventually an integrated process of converting bio-waste into a high added value product.

A significant issue is reducing the amount of biological waste that is disposed of in landfills, particularly in high-density residential areas. The Wastes Framework Directive (98/2008), in particular, sets forward the legal requirements for source separation in the European Union’s (EU) environmental legislation. The directive sets a target for separate collection of 10% of the organic waste produced in each municipality by 2030, especially with regard to organic waste. The pilot experience of an integrated biowaste management system that supports source separation and urban composting in an Autonomous Composting Unit (ACU) was presented in this study. The Municipality of Rhodes installed five ACUs in various locations. Used food and green waste are the two types of waste that are deposited in the ACUs. The development of a system for the collection of produced biowaste and its treatment at the source, without producing a nuisance, within an urban area, is the goal of this innovation. Since landfilling of mixed municipal solid waste has long been a common practice on the island of Rhodes, as well as in many other locations of insular and mainland Greece, this technique was introduced as a novel implementation and innovation for the region. The results showed that biowaste source separation was successfully carried out by citizens, resulting in high-purity feed. All ACUs produce compost that is of a standard quality. In accordance with the principles of the circular economy, this study showed that ACUs are a sustainable solution for taking a closed unit approach to the biowaste management problem in urban areas.

Biodegradable plastics have been introduced to the market to substitute petro-based plastics to alleviate plastic pollution. Biochemical methane potential tests were carried out on food wastes (FW), with or without pre-treatment, compostable bag and a mixture of food waste and compostable bag (CB) to examine the anaerobic biodegradability of those materials. Anaerobic tests were carried out in mesophilic (35oC) conditions. The aim of this work is to study the residuality of compostable bags in anaerobic digestion. At the end of the process, a dry mass of 26 % and 28 % was recorded for compostable bag and co-digestion of compostable bag and food waste respectively. The CB added to the feed did not have a negative effect on reactor performance, but seemed to have higher biogas production. Moreover, co-digestion with CB improved biogas production by 0.8-1 times. The best VS removal efficiency of approximately 68% was achieved for FW & CB substrate. Therefore, when the compostable bag was used as a combination of substrate with food residues it produced larger amounts of biogas than samples containing only food residues. This result highlights the fact that the compostable bag does not adversely affect the process.