Biodegradabilidade de embalagens biodegradáveis e sua compostabilidade com resíduos orgânicos domiciliares

Abstract

Biopolymers are polymeric substances produced from raw materials that comes from renewable resources, such as corn, sugarcane and cellulose. The advantages of these materials in relation to conventional polymers is the biodegradability, and even compostability that most of them present. Since the Brazilian Policy of Solid Waste establishes that only refuse must be disposed at sanitary landfills, alternative treatments must be researched for organic waste, for instance composting. The utilisation of compostable bags to dispose residential organic waste stands out as an interesting strategy to improve compost quality and to facilitate the process at composting plants, since there is technical difficulty to separate materials. Studies that assess not only the biodegradability, but also the compostability of biopolymers must be realised in order to establish the most appropriate materials for the production of compostable bags. Similarly, the expanded polystyrene trays: due to the difficulty at sanitising and recycling, they end up being disposed along with organic waste. Accordingly, the aim of this study was to assess the biodegradability of biodegradable packaging with different applications – starch trays and PBAT/starch films - and their compostability in the treatment of residential solid organic waste. Packaging aerobic biodegradation was then monitored by means of carbon dioxide evolution, by the respirometric method, calculating their Biodegradation Efficiencies. Composting windrows were then set with residential organic waste and twigs from tree pruning, on the presence of the packaging for assessing their compostability. The monitoring of the process was held for the parameters: temperature, pH, electrical conductivity, solids, total nitrogen, C/N ratio and mass and volume reductions, besides qualitative analysis of mischaracterisation for the residues and the packaging. At the first experiment, with duration of 47 days, the starch and PBAT/starch packaging presented Biodegradation Efficiencies very close to each other (34 and 38%, respectively) and to the reference material (35%). During composting, the thermophilic phase was observed during the first 20 days. The compost pH was neutralised and electrical conductivity has increased for the concentration of salts. There were reductions of volatile solids, C/N ratio, volume and mass of the compost, indicating the volatilisation of the organic matter. Either the residues or the packaging presented good mischaracterisation and it was verified that the presence of the latter did not prejudiced the composting process. It was concluded that the utilisation of biodegradable packaging to assist the urban solid waste management at municipalities must be encouraged, in order to improve the final quality of the compost and to facilitate the processing of residues at composting plants.