Ricerc@Sapienza

Although the organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) originate from the same urban area and contain similar organic matter, they are collected separately and handled with different technologies. In this work, a combined treatment of OFMSW-SS mixture was investigated at pilot scale, by using a three-step mixed microbial culture (MMC) process in order to produce polyhydroxyalkanoate (PHA) as final high value biobased product.

In recent years, the attention to organic wastes as a new feedstock for the production of PHA is increased based on the idea that this is the only way to reduce their high cost and to increase their sustainability. For this reason, a pilot platform has been designed to produce PHA from the source-sorted organic fraction of municipal solid waste (OFMSW). The cost-effective system consists in the three-steps anaerobic-aerobic process: the fermentation step was performed in a 200 L CSTR (OLR 20.0 kgVS/m3.d, HRT 3.3 d) in thermophilic conditions (55°C).

In line with the Circular Economy approach, the production of polyhydroxyalkanoate (PHA) with organic waste as the feedstock may a biotechnological application to reduce waste and recover high-value materials. The potential contaminants that could transfer from bio-waste to a PHA include inorganic elements, such as heavy metals. Hence, the total content and migratability of certain elements were evaluated in several PHA samples produced from different origins and following different methods. The total content of certain elements in PHA ranged between 0.0001 (Be) and 49500 mg kg-1 (Na).

The microbial synthesis of polyhydroxyalkanoates (PHA) from organic wastes is a valuable
process to valorize available renewable resources, such as food wastes and biological sludge.
Bioplastics find many applications in various sectors, from medical field to food industry. However,
persistent organic pollutants could be transferred from wastes to the final product. The present
paper demonstrates that the use of municipal wastes in PHA production is safe for the environment

Among the organic contaminants that could pass from waste to polyhydroxyalkanoates (PHAs), there are the polycyclic aromatic hydrocarbons (PAHs). For this reason, we have developed a rapid analytical method for the determination of sixteen PAHs in PHAs. PAHs were extracted by n-hexane, after matrix dispersion and crumbling into sand; the extract was purified by solid phase extraction using florisil as adsorbent. Recoveries in the range of 89–101% were obtained for the deuterated analytes, except for the two with the lowest molecular weight.

Polyhydroxyalkanoates (PHA) are biodegradable polyesters that can be produced in bioprocesses from renewable resources in contrast to fossil-based bio-recalcitrant polymers. Research efforts have been directed towards establishing technical feasibility in the use of mixed microbial cultures (MMC) for PHA production using residuals as feedstock, mainly consisting of industrial process effluent waters and wastewaters. In this context, PHA production can be integrated with waste and wastewater biological treatment, with concurrent benefits of resource recovery and sludge minimization.