Marion Humer's research while affiliated with Fachhochschule des bfi Wien and other places

Landfill methane (CH4) emissions have been cited as one of the anthropogenic gas releases that can and should be controlled to reduce global climate change. This article reviews recent research that identifies ways to enhance microbial consumption of the gas in the aerobic portion of a landfill cover. Use of these methods can augment CH4 emission reductions achieved by gas collection or provide a sole means to consume CH4 at small landfills that do not have active gas collection systems. Field studies indicate that high levels of CH4 removal can be achieved by optimizing natural soil microbial processes. Further, during biotic conversion, not all of the CH4 carbon is converted to carbon dioxide (CO2) gas and released to the atmosphere; some of it will be sequestered in microbial biomass. Because biotic covers can employ residuals from other municipal processes, financial benefits can also accrue from avoided costs for residuals disposal.

Landfills are considered to be an important global source of the greenhouse gas methane. These emissions are especially caused by inadequate gas collection systems, uncontrolled emissions from old dumps and unauthorized open dumping. The subsequent capturing and disposal of landfill gas from old landfills is technically difficult and very costly. A low-cost alternative to the conventional methods is the microbial oxidation of methane. For this purpose it is necessary to spread cover layers much in the same way as is done for large biofilters. This calls for sufficient knowledge about the biology of the methane oxidising microorganisms and the resulting requirements to be met by the substrate. Laboratory studies have proved municipal solid waste compost and sewage sludge compost to be suitable carrier substrates.

: By creating optimal ambient conditions for methanotrophic bacteria in cover layers, it is possible to foster the natural potential of methane oxidation and to attain very high oxidation rates. Laboratory tests have proven that ripe waste compost, such as sewage sludge compost and municipal solid waste compost, make suitable substrates for methane oxidation. The oxidation rates in these composts were clearly higher than in natural soils. Apart from a proper compost quality, the design of the cover layer is also very important. In summer 1999 a field experiment was started on an Austrian landfill in order to investigate the effect of seasonal conditions on methane oxidation in differently built up compost covers. This paper contains the results of this two year field experiment and pays particular attention to the technical design of the cover layers, which are capable for oxidising methane emission.