A well-known feature of traditional landfills containing potentially biodegradable
matter has been major spatial variations in biodegradative activity as a result of a lack
of system design, but in more recent times, with the advent of engineered landfills, the
requirement for optimisation to maintain anaerobic biodegradation and possibly enhance
biogas production rates was recognised. Some of the operating conditions that were
identified as impacting on process rates were the need for elevated moisture contents and
elevated moisture throughputs by leachate recirculation, pH control/buffer addition,
nutrient addition, anaerobic sewage sludge inoculation and elevation of the operating
temperature (Kinman et al., 1987). However, the practicability of some of these proposals
is questionable and, clearly, others could introduce deleterious side effects with respect to
overall system operation. Both the potential environmental impact of massive engineered
landfills for the degradation of biodegradable organic wastes and their extended, but
declining rate of residual biogas production, seems to suggest that landfills provide only an
interim solution for biodegradable solid waste management. In the future, landfills would
seem to be only appropriate for essentially stable wastes such as that derived from
construction and demolition or from incineration, but even here, avoidance of dust,
particularly in situations where asbestos or sorbed carcinogens are present, is paramount. If
landfill is not to be used for biodegradable solid waste and slurry disposal, the critical
question that arises is: What economically viable and safe alternative large scale processes
exist that will satisfy legislation and will be acceptable to the general public? The two most
widely discussed options are biotreatment and incineration, but it must be noted that both
require waste segregation either at source or immediately before processing.