RESUMO
Organic waste management is challenging in low-middle income countries. Environmental impacts and high management costs affect the sustainable development of cities, an issue that is exacerbated by the lack of social involvement. The research conducted in Iran aims to assess the benefits of organic waste home composting in Shiraz to improve solid waste management (SWM) sustainability. The introduction of a pilot project to assess home composting systems was described, together with an economic, social and environmental analysis. The current SWM system (S0) has been compared with the new strategy proposed (S1), where home composting is considered to be introduced to collect about 10% of the municipal solid waste generated in a 10-year horizon. An economic balance related to the capital costs and operational costs of both systems was introduced, in parallel with a life cycle assessment (LCA) of the SWM system, and a questionnaire survey of the local population. Results showed that S1 leads to around 5% economic savings for the municipality due to the avoidance of organic waste transportation and disposal. Environmental benefits include a lowering of CO2-Eq emissions of about 19,076 tonnes year-1. In addition, about 28% of the interviewed (n = 319) agreed to employ the home composting system at home (CI 5.5%, 95% of confidence level) supporting the theory that about 10% of the organic waste can be segregated and home-composted. The research underlines that home composting can contribute to improve the sustainability of SWM systems in developing countries.
RESUMO
The study focuses on an Italian composting plant and aims to investigate the impact of the presence of plastic impurities in the collected biowaste on the environmental and economic performance of the plant. The study is divided into two main steps: firstly, a material flow analysis was conducted to quantify the number of impurities (e.g., conventional plastics and compostable plastics) before and after the composting process. Secondly, a life cycle assessment (LCA) and a complementary life cycle costing (LCC) of the composting process were conducted. The results of the material flow analysis confirmed the initial assumption that conventional plastic remains almost constant before and after the composting treatment, while compostable plastic almost disappears. As far as the life cycle analyses are concerned, the most environmentally damaging phases of the process were the shredding and mixing phases, while the operating costs (OPEX) contributed the most to the total annual costs of the company. Finally, a further scenario analysis was performed, assuming that the plastic contaminants in the treated biowaste consisted exclusively of compostable plastics. The comparison with this ideal scenario can support decision-makers to understand the potential improvements achievable by addressing the presence of plastic impurities in the biowaste. The results show that the treatment of plastic impurities causes relevant environmental and economic impacts, being responsible for 46% of the total waste to treat at the end of the process, almost 7% of the total annual costs covered by the plant owners, and about 30% of all negative externalities.
