ABSTRACT
Biological and mechanical biological treatment plants combine mechanical and biological treatments to recover the greatest possible amount of materials from municipal solid waste (MSW) and biostabilize the organic fraction to be landfilled or applied in land. These plants handle a high percentage of the MSW generated in Europe. This work presents an exhaustive analysis of the existing plants in Spain which evaluates their typology as well as their performance. In Spain, 137 plants, which receive 13 Mt/year of waste, provide the country with total coverage. Twenty-two types of plants have been identified and grouped into six categories. There are four categories that receive mixed MSW: 1) sorting plants; 2) recovery and composting plants; 3) biodrying and recovery plants; and 4) recovery, biomethanation and composting plants and two that receive separately collected biowaste: 5) composting plants, and 6) biomethanation and composting plants. In plants that receive mixed waste, around 5% of the total input is recovered as recyclable materials (662,182 t/year), of which 29% corresponds to plastics, 27% to metals, and 27% to paper and cardboard. In addition, biostabilized material and/or biogas, and rejects (45-77% of the input) are obtained. In the biowaste plants, high-quality compost (more than 105,000 t/year), a higher biogas yield (43.60 Nm3/t·year) and a lower proportion of rejects (around 29%) are obtained.
ABSTRACT
Biodrying consists of reducing moisture by using the heat from aerobic bio-degradation. The parameters that control the process are: aeration, temperature during the process, initial moisture of biowaste, and temperature and relative humidity of the input air. Lawn mowing and garden waste from the gardens of the University Jaume I, Castellón (Spain) were used as a substrate. Biodrying was performed in 10 reactors with known air volumes from 0.88 to 6.42 L/(min x kg dry weight). To promote aeration, 5 of the reactors had 15% of a bulking agent added. The experiment lasted 20 days. After the experiments it was found that the bulking agent led to greater weight loss. However, the increased airflow rate was not linearly proportional to the weight loss.
Subject(s)
Acacia , Air Movements , Bioreactors , Poaceae , Gardening , Temperature , Waste Products , Water/chemistryABSTRACT
The aim of this study is to compare, from an environmental point of view, different alternatives for the management of municipal solid waste generated in the town of Castellón de la Plana (Spain). This town currently produces 207 ton of waste per day and the waste management system employed today involves the collection of paper/cardboard, glass and light packaging from materials banks and of rest waste at street-side containers. The proposed alternative scenarios were based on a combination of the following elements: selective collection targets to be accomplished by the year 2015 as specified in the Spanish National Waste Plan (assuming they are reached to an extent of 50% and 100%), different collection models implemented nationally, and diverse treatments of both the separated biodegradable fraction and the rest waste to be disposed of on landfills. This resulted in 24 scenarios, whose environmental behaviour was studied by applying the life cycle assessment methodology. In accordance with the ISO 14040-44 (2006) standard, an inventory model was developed for the following stages of the waste management life cycle: pre-collection (bags and containers), collection, transport, pre-treatment (waste separation) and treatment/disposal (recycling, composting, biogasification+composting, landfill with/without energy recovery). Environmental indicators were obtained for different impact categories, which made it possible to identify the key variables in the waste management system and the scenario that offers the best environmental behaviour. Finally, a sensitivity analysis was used to test some of the assumptions made in the initial life cycle inventory model.
