This material has been shown (3, 4) to be permeable but with some
capacity to retain water; to be adequately traffic bearing, to be non combustible, heavy and
abbrasive enough to prevent litter problems and to behave as a highly effective biofilter with
respect to odour (50-70% reduction). This material is also readily available at landfill sites
and 300mm thick layers adds to the gas generation potential and energy recovery value of
the site long term. Some low permeability interim cover does need to be used to make gas
harvesting close to the active face more efficient, but this material can be recovered from
above the MWM/earth mixture for reuse quite readily.