32    ACCELERATED METHANE PRODUCTION IN
LANDFILLS BY PRETREATMENT OF MUNICIPAL
SOLID WASTE
G.M. Davidson, Research Assistant
G.K. Anderson, Senior Lecturer
D.M. Anderson, Research Manager
Solid & Hazardous Waste Research Unit (SHWRU)
Department of Civil Engineering
University of Newcastle upon Tyne
Newcastle upon Tyne, England
INTRODUCTION
Landfilling has been the traditional method of waste disposal for many years, accounting for
the disposal of about 90% of municipal solid waste (MSW) generated in the U.K., but operation
of sites to poor standards has often resulted in environmental problems. One particular concern is
that of biogas production by the anaerobic degradation of the biodegradable matter present in
MSW. The main constituents of biogas from a landfill are methane and carbon dioxide, although
gases such as hydrogen, hydrogen sulfide, and other gaseous hydrocarbons may also be present.
The factors that require consideration in the management of landfill gas are: the way in which
gas is generated; the biochemical and microbiological processes which give rise to the production of gas; and perhaps most importantly, the migration, monitoring, and control of the gas produced. The migration and uncontrolled release of biogas from a landfill can cause major problems in terms of unpleasant odors, vegetation die-off, and potential danger of fire or explosion in
nearby buildings.
PRODUCTION OF BIOGAS
The processes of decomposition occurring in landfill sites are complex and not fully understood. The biodegradable organic matter in wastes can undergo two forms of decomposition involving aerobic (acetogenic) and anaerobic (methanogenic) microorganisms.
There are several important factors controlling the rates and amounts of gas likely to be produced by the aerobic and anaerobic processes which occur. These include physical dimensions of
the site, waste characteristics, waste input rates, site operations, waste density, waste moisture
content, and waste temperature.
LANDFILL DESIGN
The design of landfills in order to reduce the potential for environmental pollution caused by
deposited waste has to date mainly been concerned with the aspect of site selection and subsequent site preparation. Designing landfill sites to allow for the accelerated stabilization of the
waste and the controlled abstraction of the biogas produced is a recent development. The guidelines for this method of operation are primarily concerned with isolating the waste from the environment by use of a containment system which creates an effective anaerobic bioreactor.
Within this method of operation there are a number of criteria that can be controlled in order to
attain the optimum biochemical conditions within the waste mass necessary for accelerated land-
51st Purdue Industrial Waste Conference Proceedings, 1996, Ann Arbor Press, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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