title: Assessment of methane production from shredder waste in landfills: The influence of temperature, moisture and metals.
abstract: In this study, methane (CH4) production rates from shredder waste (SW) were determined by incubation of waste samples over a period of 230days under different operating conditions, and first-order decay kinetic constants (k-values) were calculated. SW and sterilized SW were incubated under different temperatures (20-25°C, 37°C, and 55°C), moisture contents (35% and 75% w/w) and amounts of inoculum (5% and 30% of the samples wet weight). The biochemical methane potential (BMP) from different types of SW (fresh, old and sieved) was determined and compared. The ability of metals (iron, aluminum, zinc, and copper) contained in SW to provide electrons for methanogens resulting in gas compositions with high CH4contents and very low CO2contents was investigated. The BMP of SW was 1.5-6.2kg CH4/ton waste. The highest BMP was observed in fresh SW samples, while the lowest was observed in sieved samples (fine fraction of SW). Abiotic production of CH4was not observed in laboratory incubations. The biotic experiments showed that when the moisture content was 35% w/w and the temperature was 20-25°C, CH4production was extremely low. Increasing the temperature from 20-25°C to 37°C resulted in significantly higher CH4production while increasing the temperature from 37°C to 55°C resulted in higher CH4production, but to a lower extent. Increasing the moisture and inoculum content also increased CH4production. The k-values were 0.033-0.075yr-1at room temperature, 0.220-0.429yr-1at 37°C and 0.235-0.488yr-1at 55°C, indicating that higher temperatures resulted in higher k-values. It was observed that H2can be produced by biocorrosion of iron, aluminum, and zinc and it was shown that produced H2can be utilized by hydrogenotrophic methanogens to convert CO2to CH4. Addition of iron and copper to SW resulted in inhibition of CH4production, while addition of aluminum and zinc resulted in higher CH4production. This suggested that aluminum and zinc contribute to high CH4production from SW by providing H2for hydrogenotrophic methanogens. Gas compositions with higher CH4and lower CO2observed in landfilled SW are thus most likely due to the consumption of existing CO2in the produced biogas and the produced H2by biocorrosion of aluminum and zinc by methanogens.
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark. Electronic address: ehag@env.dtu.dk.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Fathi Aghdam
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Scheutz
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Kjeldsen
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002245:Carbon Dioxide; D008670:Metals / Q000737:chemistry; D008697:Methane / Q000032:analysis*; D012037:Refuse Disposal / Q000379:methods*; D013696:Temperature; D064091:Waste Disposal Facilities
chemical_list: D000393:Air Pollutants; D008670:Metals; D002245:Carbon Dioxide; D008697:Methane
keywords: Anaerobic digestion; Biochemical methane potential (BMP); Biocorrosion; Biogenic carbon; End-of-life vehicles; First-order decay kinetic constant