Thermophilic methane production and oxidation in compost

Abstract

Methane cycling within compost heaps has not yet been investigated in detail. We show that thermophilic methane oxidation occurred after a lag phase of up to one day in 4-week old, 8-week old and mature (>10-week old) compost material. The potential rate of methane oxidation was between 2.6 and 4.1 micromol CH4(gdw)(-1)h(-1). Profiles of methane concentrations within heaps of different ages indicated that 46-98% of the methane produced was oxidised by methanotrophic bacteria. The population size of thermophilic methanotrophs was estimated at 10(9) cells (gdw)(-1), based on methane oxidation rates. A methanotroph (strain KTM-1) was isolated from the highest positive step of a serial dilution series. This strain belonged to the genus Methylocaldum, which contains thermotolerant and thermophilic methanotrophs. The closest relative organism on the basis of 16S rRNA gene sequence identity was M. szegediense (>99%), a species originally isolated from hot springs. The temperature optimum (45-55 degrees C) for methane oxidation within the compost material was identical to that of strain KTM-1, suggesting that this strain was well adapted to the conditions in the compost material. The temperatures measured in the upper layer (0-40 cm) of the compost heaps were also in this range, so we assume that these organisms are capable of effectively reducing the potential methane emissions from compost.

Rapid start-up of thermophilic anaerobic digestion with the turf fraction of MSW as inoculum

“…Moreover, composting of MSW has been reported to produce methane (Beck-Friis et al, 2000;Jäckel et al, 2005). This implies that methanogens may already be present in MSW.…”

Life Cycle Assessment (LCA) of Light-Weight Eco-composites

“…Limited data have been reported on trace gas emissions from composting of BFMSW (Jackel et al, 2005). As summarized in Table C.3, mainly the data concerning organic household waste were included, except two studies (Paillat et al, 2005, Szanto et al, 2007 which explored animal waste; however their C/N ratio was close with other studies thus they gave good indication of C/N dynamics of organic household waste.…”

“…According to previous research (Hellmann et al, 1997), high temperatures lead to lower nitrification processes, reducing N 2 O emission. This could explain why N 2 O is mainly emitted during the mesophilic phase (Paillat et al, 2005) although NH 4 + can be oxidized under thermophilic condition by methanotrophs (Jackel et al, 2005, Szanto et al, 2007. In addition, it was reported that O 2 plays a key role in N 2 O emission, the absence of O 2 results in anaerobic zones developing a main cause of higher production of N 2 O (Szanto et al, 2007).…”

“…As for other potential N gaseous losses, as discussed before, only few publications are available (Szanto et al, 2007, Fukumoto andInubushi, 2009) (Jackel et al, 2005)) and over 90% of CH 4 produced is usually assumed to be oxidized to CO 2 in the compost before it reaches the atmosphere (Jackel et al, 2005, Halet et al, 2006, Thummes et al, 2007.…”

“…In addition, mesophilic temperatures more favour nitrification which is inhibited at temperatures above 54ºC (Willers et al, 1998). However, even under unfavourable conditions, other pathways could take place to oxidize NH 4 + such as anaerobic process anommox with NO 3 -and N 2 produced, thermophilic oxidation pathway by methanotrophs (Jackel et al, 2005, Szanto et al, 2007. The NO 3 -could be further reduced by denitrifiers under either anaerobic or anoxic environments.…”