Biostabilization of mechanically separated municipal solid waste fraction

Abstract

Municipal solid waste was processed by a mechanicalbiological end composting process both in pilot and full-scale plants. The organic fraction obtained by mechanical treatment (fraction &rarr; < 50 mm) was processed at a high composting rate for 37 days followed by a curing phase of 79 days. Process parameters were registered and kept in an optimal range (oxygen > 140 ml 1 -1 , temperature < 65&deg;C, moisture > 500 g kg -1 w.w.). After the high-rate phase, the products obtained showed a high degradation coefficient and good biological stability (&Delta;VS = -54.75% and -35.35%, DRI = 300 and 500 mg O 2 kg -1 VS h -1 , respectively, for pilot and full-scale plants) especially for the pilot plant, indicating that it is not possible to obtain the same performance for a full-scale plant as obtained under laboratory conditions. Nevertheless, the successive curing phase showed less of a discrepancy between the two processes (&Delta;VS = -66.33% and -56.87%, DRI = 280 and 360 mg O 2 kg -1 VS h -1 , respectively, for pilot and full scale plants).The quality of the stabilized product was tested by biogas production tests. As expected, a sample processed in the pilot plant produced less biogas (26 1 kg TS -1 ) than that obtained at full scale (40 1 kg TS -1 ). An unprocessed sample produced less biogas owing to the production of organic acids, which, by lowering the pH, inhibit the generation of gas.

Biostabilization of municipal solid waste

“…It should be borne in mind that the samples considered in this experiment did not represent homogeneous fractions due to the sifting of the final product at £ < 20 mm. Adani et al (2000), in studying 25 organic matrices of different types and provenance, obtained very low DRI regressions vs fermentable volatile solids (R 2 ¼ 0:20; p > 0:05). To conclude, the fermentable volatile solids were not able, in this case, to describe biological stability.…”

“…Numerous studies (Stegmann, 1997;Stegmann, 1997;Andreottola, 1999;Adani et al, 2000) have pointed out that production of organic acids and CO 2 (Stage II) by lowering the pH caused inhibition of methane genesis (Binner and Zach, 1998). Nevertheless, although this could explain the behavior of the ''fresh'' sample (0), it could not explain the others, since the pH values were measured in the optimum range for methane genesis (Table 6).…”

“…For untreated samples (t ¼ 0 days), Adani et al (2000) found that biogas production was approximately 20 L kg TS À1 , while that for the treated samples (t ¼ 116 days) was double (40 L kg TS À1 ). In order to understand the results better, it should be borne in mind that the production of biogas takes place in four phases (Fig.…”

“…This indicated a more advanced state of decomposition than initial samples. In fact, in well stabilized waste (t ¼ 116 days), Adani et al (2000) showed CH 4 production starting from the fourth day of the test and in quantities equal to 500 mL L À1 of total biogas. This indicated that the sample was at the (Fig.…”

Municipal solid waste compost amendment in agricultural soil: changes in soil microbial biomass

“…Consequently, the management of the MSW needs to be revamped to accommodate the changes in the quantity and quality to ensure the longevity of the environment. Due to several legislative, environmental, economic and social constraints, the identification of most sustainable disposal route for MSW management remains an important issue in almost all industrialized countries (Adani et al 2000). Agricultural application of MSW, as nutrient source for plants and as soil conditioner, is the most cost-effective MSW disposal option because of its advantages over traditional means such as landfilling or incineration.…”