Bacterial community and decomposition rate in long term fed-batch composting using woodchip and Polyethylene terephthalate (PET) as bulking agents

Abstract

Long term fed-batch composting experiments were conducted for 200 days using two types of bulking agents; woodchip and PET flake, with periodic compost withdrawal through a washing process. The bacterial communities of composting materials in the two different bulking agents were also investigated by 16S rRNA gene clone analysis. The decomposition rate in both composting reactors was 86.1% and 88.2% of the total organic load, respectively. The control experiment of dead-end operation without compost withdrawal by washing process could not be maintained for more than 102 days because of its low performance. The reactor with compost withdrawal, however, improved the decomposition rate in the composting process, and could be applied in the long run. There was a significant difference in the bacterial community between the FBC reactor with woodchip and another with PET flake as the bulking agent though the decomposition rates were similar. The reactor with woodchip as the bulking agent consisted of 95% Bacillales while the PET flake reactor contained 54% of total bacteria count. In addition, Lactobacillales was dominant at 38% in the PET flake reactor and the bacterial community in general significantly differed from the woodchip reactor. Furthermore, there was a difference in the species composition in the Bacillales and the bacterial community showed a significant difference at the species level between the two reactors. Although bacterial community differed, the decomposition rates between the two reactors were similar and PET flake showed greater viability than woodchip as a bulking agent due to its high abrasion resistance and non-biodegradability.

The dominant bacteria shifted from the order “Lactobacillales” to Bacillales and Actinomycetales during a start-up period of large-scale, completely-mixed composting reactor using plastic bottle flakes as bulking agent

“…These results showed a dominance of the order Bacillales (54%) and ''Lactobacillales'' (38%) in the reactor using plastic bottle flakes. On the other hand, the order Bacillales dominant (95%) and ''Lactobacillales'' was not detected from the reactor using woodchips (Nagao et al 2008). The dominance of the order ''Lactobacillales'' might be correlated with the oxygen concentration and temperature in the reactor.…”

“…In general, the genus Bacillus is often detected from the composting reactors as the major species (Dees and Ghiorse 2001;Strom 1985a, b;Pedro et al 2001). And there are only a few reports in which the order ''Lactobacillales'' in the composting process is dominant (Ishii et al 2000;Hemmi et al 2004;Nagao et al 2008). Nagao et al (2008) revealed the bacterial communities in the small-scale reactor using woodchips and plastic bottle flakes as bulking agents.…”

“…And there are only a few reports in which the order ''Lactobacillales'' in the composting process is dominant (Ishii et al 2000;Hemmi et al 2004;Nagao et al 2008). Nagao et al (2008) revealed the bacterial communities in the small-scale reactor using woodchips and plastic bottle flakes as bulking agents. These results showed a dominance of the order Bacillales (54%) and ''Lactobacillales'' (38%) in the reactor using plastic bottle flakes.…”

“…The reuse of plastic bottle flakes as bulking agent has some merits. For example, it is cheap, easily available in Japan, resistance to abrasion and there is no need to add the bulking agents again throughout the operating period (Nagao et al 2008). Six hundred kilogram wet weight food waste derived from a school cafeteria with 72.8% moisture content, was loaded into the reactor at the start of experiment.…”

Insights of the degradation of plastics PET and PE type under composting conditions using coffee pulp as substrate

“…The serious problem of plastic pollution has generated a wake-up call for searching effective and friendly alternatives for the treatment of plastics with the aim to reduce their impact on the environment, alleviate disposal problems and achieve their sustainability [4], [9]. In recent years, a promising alternative for the solid waste management by composting processes has emerged as an attractive option to the conventional recycling process (such as incineration) which generate toxic compounds released in the air and low heat e ciency due to its high moisture content [10]. The composting strategy can reduce the impact of the plastic at the end of its useful life, mainly when it comes to plastic products which are most likely mismanaged or whose recycling is not feasible, as those used for packaging (PET and PE).…”