524132
research-article2014
WMR0010.1177/0734242X14524132Waste Management & ResearchEditorial
Editorial
Landfilling, past, present and future
Landfilling, which is probably the oldest organized waste management technology, has been in use for about as long as human civilization has existed. Some of the oldest known landfill sites date back 5000 to 10 000 years (with several examples in Europe, and Asia) and although these have long gone out of use, they are still of major interest for archeologists as they contain a lot of valuable information about the way people lived in those times. Waste landfilling has until recently (about the 1970s) simply been carried out as the unceremonious dumping of waste in any convenient location without any particular concern for health, safety, environmental protection, or cost efficiency. In addition to providing a central location for indefinite waste deposit away from population centers, landfilling of waste was also often used as a means for filling unwanted depressions in the ground, or ‘reclaiming’ land from the sea, land which subsequently could be used for urban development. In fact many coastal cities are built partially on areas claimed from the sea by deposition of waste material. In more recent times, landfilling has often been carried out using old gravel pits or quarries, which were filled in with waste, covered with soil and turned into recreational or urbanized areas, again without any particular environmental protection. For instance, about 30% of the land abutting the San Francisco Bay is ‘fill’, much of it comprised of waste materials and dredge spoils. This practice has resulted in numerous problems such as drinking water contamination, explosions due to landfill gas intrusion into nearby buildings, and land subsidence due to decomposition of waste deposited below them. Landfills have also been recognized as major contributors to global warming via the emissions of uncollected landfill gas (about 50% methane) into the atmosphere. Despite these and numerous other negative impacts of landfilling, the technology remains the most widely used option for waste disposal globally. More than 50% of the world’s waste materials are still deposited in landfills, many of which are without any form of environmental protection, particularly in developing countries. Recognition of the negative environmental impacts associated with landfilling has, however, prompted an improvement in landfill construction and operation and landfills, especially in developed countries, are now being constructed with liners, leachate collection, and gas collection systems, to reduce negative environmental impacts. In many locations landfills also contribute to the energy supply via capture of extracted landfill gas that is used as fuel to generate heat and electricity. The gas production (but not necessarily the economic) efficiency of this process, however, is usually inferior in comparison with the use of a typical high technology anaerobic digestion plant.
Waste Management & Research 2014, Vol. 32(3) 177–178 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X14524132 wmr.sagepub.com
This is primarily because the methane content of landfill gas is generally lower than gas produced in a digester (on average 50% versus 65%) due to partial oxidation in the landfill, and because part of the gas produced in landfills is lost to the atmosphere even with an effective gas collection system. The negative environmental impacts of landfilling, in comparison with other waste management technologies, together with increasing difficulties in finding suitable landfill sites (due to expanding urbanization and the NIMBY effect) has also resulted in an increasing political pressure to divert waste away from landfills toward energy production and recycling in several regions. This has resulted in the reduction of the quantities of waste materials being deposited in landfills in these regions. In some countries less than 10% of the waste (by weight) entering the waste management system ends up in landfills. The current trend in countries with advanced waste management system is therefore that the quantities of waste being deposited in landfills are continuously decreasing although at very different rates depending on country. So what is the future of the landfill? Will we be able to completely abandon this long used technology in favour of more sustainable methods? Let us look at some current trends in waste management that affect landfilling directly. It is evident that the current trends of increasing waste-toenergy and materials recycling will further reduce the quantities of waste going to landfills in the future, especially in those regions where these technologies are not yet fully implemented. It may also be expected that improved and more sustainable product design which is currently gaining increased attention, will further reduce waste production and landfilling requirements in the future. The rapidly increasing demand for certain materials such as precious metals and rare earth elements is thought to prompt mining of old landfill sites for such materials, a process sometimes called ‘urban mining’. In fact this is already taking place to a limited degree in many locations. In Aalborg, Denmark, a municipal landfill is being ‘mined’ for combustible waste which is then used in the city’s energy supply. An industrial landfill site containing gypsum (a waste from flue gas cleaning) in the same city is being mined as raw material for production of new building materials. Although these examples involve relatively simple waste materials it is an indication that urban mining may become a reality and could increase in importance in response to increasing prices of virgin materials. We are continuously developing new materials and new products without necessarily having the required technology for their
Downloaded from wmr.sagepub.com at IOWA TESTING PROGRAMS on May 31, 2015
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Waste Management & Research 32(3)
recycling in place. For economic reasons development of appropriate recycling technology is usually initiated when the materials start to appear in the waste stream in sufficient quantities for recycling to be economically viable. This means that although we may expect future recycling systems to be increasingly efficient, at least for the foreseeable future there probably will be waste materials that cannot be recycled directly but must be deposited somewhere until an appropriate recycling or reclamation technology becomes available. Again this approach is already being used to a small degree. In Aalborg, wooden railroad sleepers treated with creosote are stored at the municipal landfill in special landfill cells until an incinerator with adequate flue gas cleaning to be able to safely consume this waste is available. Furthermore, soil contaminated with heavy metals is deposited in special cells from
where it may be excavated once appropriate cleaning or metals recovery technology becomes available. Thus it appears that landfilling as a means of waste management will not be abandoned entirely in the foreseeable future. However, landfills will gradually change function from being used for deposition and indefinite storage of mixed waste materials without aiming at any further treatment or use of these materials, to become temporary storage for specific waste materials until they can be recycled. It is also likely that many old landfills will be re-opened for urban mining resulting in the removal or reduction of the waste volumes contained in these landfills. Thus, we will probably see future landfills becoming mere recycling and temporary storage stations and that the requirements for new landfill space will be reduced in the long term.
Tjalfe G. Poulsen Xi’an Jiaotong – Liverpool University, Suzhou, 215123, Jiangsu, China Email: [email protected]
Downloaded from wmr.sagepub.com at IOWA TESTING PROGRAMS on May 31, 2015
research-article2014
WMR0010.1177/0734242X14524132Waste Management & ResearchEditorial
Editorial
Landfilling, past, present and future
Landfilling, which is probably the oldest organized waste management technology, has been in use for about as long as human civilization has existed. Some of the oldest known landfill sites date back 5000 to 10 000 years (with several examples in Europe, and Asia) and although these have long gone out of use, they are still of major interest for archeologists as they contain a lot of valuable information about the way people lived in those times. Waste landfilling has until recently (about the 1970s) simply been carried out as the unceremonious dumping of waste in any convenient location without any particular concern for health, safety, environmental protection, or cost efficiency. In addition to providing a central location for indefinite waste deposit away from population centers, landfilling of waste was also often used as a means for filling unwanted depressions in the ground, or ‘reclaiming’ land from the sea, land which subsequently could be used for urban development. In fact many coastal cities are built partially on areas claimed from the sea by deposition of waste material. In more recent times, landfilling has often been carried out using old gravel pits or quarries, which were filled in with waste, covered with soil and turned into recreational or urbanized areas, again without any particular environmental protection. For instance, about 30% of the land abutting the San Francisco Bay is ‘fill’, much of it comprised of waste materials and dredge spoils. This practice has resulted in numerous problems such as drinking water contamination, explosions due to landfill gas intrusion into nearby buildings, and land subsidence due to decomposition of waste deposited below them. Landfills have also been recognized as major contributors to global warming via the emissions of uncollected landfill gas (about 50% methane) into the atmosphere. Despite these and numerous other negative impacts of landfilling, the technology remains the most widely used option for waste disposal globally. More than 50% of the world’s waste materials are still deposited in landfills, many of which are without any form of environmental protection, particularly in developing countries. Recognition of the negative environmental impacts associated with landfilling has, however, prompted an improvement in landfill construction and operation and landfills, especially in developed countries, are now being constructed with liners, leachate collection, and gas collection systems, to reduce negative environmental impacts. In many locations landfills also contribute to the energy supply via capture of extracted landfill gas that is used as fuel to generate heat and electricity. The gas production (but not necessarily the economic) efficiency of this process, however, is usually inferior in comparison with the use of a typical high technology anaerobic digestion plant.
Waste Management & Research 2014, Vol. 32(3) 177–178 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X14524132 wmr.sagepub.com
This is primarily because the methane content of landfill gas is generally lower than gas produced in a digester (on average 50% versus 65%) due to partial oxidation in the landfill, and because part of the gas produced in landfills is lost to the atmosphere even with an effective gas collection system. The negative environmental impacts of landfilling, in comparison with other waste management technologies, together with increasing difficulties in finding suitable landfill sites (due to expanding urbanization and the NIMBY effect) has also resulted in an increasing political pressure to divert waste away from landfills toward energy production and recycling in several regions. This has resulted in the reduction of the quantities of waste materials being deposited in landfills in these regions. In some countries less than 10% of the waste (by weight) entering the waste management system ends up in landfills. The current trend in countries with advanced waste management system is therefore that the quantities of waste being deposited in landfills are continuously decreasing although at very different rates depending on country. So what is the future of the landfill? Will we be able to completely abandon this long used technology in favour of more sustainable methods? Let us look at some current trends in waste management that affect landfilling directly. It is evident that the current trends of increasing waste-toenergy and materials recycling will further reduce the quantities of waste going to landfills in the future, especially in those regions where these technologies are not yet fully implemented. It may also be expected that improved and more sustainable product design which is currently gaining increased attention, will further reduce waste production and landfilling requirements in the future. The rapidly increasing demand for certain materials such as precious metals and rare earth elements is thought to prompt mining of old landfill sites for such materials, a process sometimes called ‘urban mining’. In fact this is already taking place to a limited degree in many locations. In Aalborg, Denmark, a municipal landfill is being ‘mined’ for combustible waste which is then used in the city’s energy supply. An industrial landfill site containing gypsum (a waste from flue gas cleaning) in the same city is being mined as raw material for production of new building materials. Although these examples involve relatively simple waste materials it is an indication that urban mining may become a reality and could increase in importance in response to increasing prices of virgin materials. We are continuously developing new materials and new products without necessarily having the required technology for their
Downloaded from wmr.sagepub.com at IOWA TESTING PROGRAMS on May 31, 2015
178
Waste Management & Research 32(3)
recycling in place. For economic reasons development of appropriate recycling technology is usually initiated when the materials start to appear in the waste stream in sufficient quantities for recycling to be economically viable. This means that although we may expect future recycling systems to be increasingly efficient, at least for the foreseeable future there probably will be waste materials that cannot be recycled directly but must be deposited somewhere until an appropriate recycling or reclamation technology becomes available. Again this approach is already being used to a small degree. In Aalborg, wooden railroad sleepers treated with creosote are stored at the municipal landfill in special landfill cells until an incinerator with adequate flue gas cleaning to be able to safely consume this waste is available. Furthermore, soil contaminated with heavy metals is deposited in special cells from
where it may be excavated once appropriate cleaning or metals recovery technology becomes available. Thus it appears that landfilling as a means of waste management will not be abandoned entirely in the foreseeable future. However, landfills will gradually change function from being used for deposition and indefinite storage of mixed waste materials without aiming at any further treatment or use of these materials, to become temporary storage for specific waste materials until they can be recycled. It is also likely that many old landfills will be re-opened for urban mining resulting in the removal or reduction of the waste volumes contained in these landfills. Thus, we will probably see future landfills becoming mere recycling and temporary storage stations and that the requirements for new landfill space will be reduced in the long term.
Tjalfe G. Poulsen Xi’an Jiaotong – Liverpool University, Suzhou, 215123, Jiangsu, China Email: [email protected]
Downloaded from wmr.sagepub.com at IOWA TESTING PROGRAMS on May 31, 2015
