There’s life in the old dog yetby Martin Steiner
For decades mechanical-biological waste treatment (MBT) has competed with incineration in the more industrialized countries of the world. Although incineration has generally been favoured by the politicians, uptake of MBT in these developed countries nevertheless continues. For example, in the UK and Italy at present, more MBT than conventional thermal treatment capacity is being installed. And in less developed environments, cost comparisons alone make the MBT option attractive.
This article overviews the status of MBT in Europe and appraises key issues currently facing this sector.General situation of MBT in Europe
Generally speaking, the share of MBT systems across Europe is determined by two factors:from a retrospective point of view, by the historical development of MSW composting by European legislation, which, through the Landfill Directive (Directive 1999/31/EC of 26 April 1999) restricts the proportion of the biodegradable fraction of MSW intended to go to landfill.
In Switzerland, the construction of the MSW compost plant at Schaffhausen (which has been recognized internationally but not in Switzerland) set the trend in the material-flow-specific treatment of residual waste back in the early 1990s. This technique consisted of shredding the waste and sieving off the fraction with a high calorific value for intermediate storage; in winter, this fraction was used as a fuel in some of the adjacent waste-to-energy (WtE) plants for the production of heat in the district. The fraction with a low calorific value was mixed with sewage sludge and composted; after separating insignificant quantities for use in landscape design, it was eventually landfilled. Except for this one-off achievement, Switzerland has remained a ‘blank space’ on the European MBT map (as shown in Figure 1). On account of a 2000 national ban on the landfilling of MSW (as well as other combustible wastes that cannot be recovered), all residual waste in Switzerland is thermally processed.
Austria remains far in advance of the upper time limits established by European legislation regarding the reduction of biodegradable waste fractions. Since 2004, the country’s Landfill Ordinance has included a ban on the landfilling of untreated wastes. Currently 15 MBT facilities are in operation. Exclusively aerobic systems are in use - which is what distinguishes Austria from the German position and is a consequence of Austria’s considerable experience with MSW composting between the mid 1970s and 1990. Six of these MBT facilities are converted MSW compost plants using certain components of the previous structure.
FIGURE 1. Estimated percentage of MBT system users in Europe. Source: TBU Environmental Engineering Consultants Click here to enlarge image
Newly erected plants are chiefly equipped with composting tunnels for the primary biological treatment stage. National standards concerning both the material quality of MBT before being landfilled and the emissions of the MBT process itself were and still are very restrictive (as in Germany). On the one hand, this makes MBT a very ‘clean’ treatment technology in Austria but, on the other - as a result of the related costs - it closes the economic ‘gap’ between MBT and incineration costs. Figure 2 reveals that treatment costs for the two options are comparable; larger differences are due to plant sizes and other factors not related to the technology. A map of Germany would, in substance, show the same information.
Vienna operates two high-standard WTE plants; the more ‘famous’ one is depicted in this photograph; a third facility is under construction. About 20% of the city’s residual waste is pre-treated in a large mechanical processing plant; this diverts metals and a bulk fraction (which is channelled to conventional incineration) while the remaining 90% is thermally recovered in a fluidized bed furnace. Such ‘MT + fluidized bed incineration’ concepts are gaining interest throughout Central Europe. source: erich vogel Click here to enlarge image
In Germany there has been a similar landfill ban on untreated MSW since mid 2005. Currently the country boasts about 45 MBT plants with an overall capacity of 5 million tonnes/year. Emission standards are very strict; however, recent studies revealed that most of the MBT in Germany complies with these severe standards.
Italy has, contrary to most expectations, a long tradition of MBT and is currently the country with the largest MBT capacities worldwide. In the past three decades, some 20 MSW composting plants (mostly with integrated RDF production) have been constructed throughout the country; two thirds of these, however, were only in operation for a very short period (closing soon after their opening). The causes for this are to be found partly in the bold technical concepts that have been pursued, often associated with a lack of public acceptance (citing reasons such as odour).
Expected development of MBT in Europe. Source: TBU Environmental Engineering Consultants Click here to enlarge image
A key concept for the second generation of plants in Italy was not recovery but volume reduction, accompanied by an improvement of the landfill features of waste (such as the quantity of leachate produced). Much attention was given to a scheme in Milan (‘Ex-Maserati’), depicted in the photo, which served to bridge a ‘waste treatment bottleneck’ However, this plant - always intended as an intermediate solution - was shut down after five years of operation as extended incineration capacities had meanwhile become available.
Recently reported difficulties in Germany refer mainly to anaerobic systems - one internationally well registered technology supplier left the market earlier this year, and certain faults in the start-up phase of new plants have been reported widely. In fact, a similar development was observed with the WTE option over recent years without ‘derailing’ progress in the uptake of this technology. This photograph depicts Germany’s largest MBT facility in Hanover (200,000 tonnes per year), operated by AHA Hanover. Source: AHA Hanover Click here to enlarge image
RDF today in Italy is an established term with specific quality standards and ample market opportunities. In 1999, a special type of MBT for the production of a ‘dry stabilate’ (HerHof system) started operation near Venice. An Italian supplier (EcoDeco) with a similar concept erected several facilities in the country’s north, and is now also seeking to gain a share internationally. Italy is one of less than a dozen European countries exporting MBT technology; recent examples (Sorain Cecchini SCT) can be found in Australia (Sydney) and the Arabian Gulf (Abu Dhabi).
Ex-Maserati Milan MBT plant in 1997. The facility consists of four plants with a combined capacity of 2000 tonnes per year. Successful operation of this plant at a highly sensitive site eventually spurred developments in flue gas management and emission monitoring. It also resulted in increased acceptance of MBT in Italy as a whole. Source: SCT Sorain Cecchini Technologies Click here to enlarge image
At present, more than 100 plants with a throughput of about 10 million tonnes per year are in operation in Italy. Venice, Florence, Rome and Naples are the most prominent cities using MBT systems. In the last two cities, new large-scale facilities have been constructed. In all, some 25% of MSW is handled via MBT in Italy.
On the Iberian Peninsula, where MBT is firmly established, an exclusively product-based concept still exists. In Spain, about one million tonnes of household waste are processed in composting plants annually. Including the facilities for the recovery of separately collected organic waste (which so far is popular only in Catalonia), 75-80 composting plants are currently in operation, most of them financed by funds from Brussels (this also goes for Portugal). About 20 fermentation plants for MSW are either in operation or under construction. The waste stream that is mechanically sorted prior to biological treatment is usually split into recyclable fractions (this also applies in aerobic digestion systems), while thermal recovery is of relatively little importance. A shift in thinking has meanwhile been set in motion in terms of the contaminant load of waste compost. A definition of the quality of compost produced from separately collected waste material is currently being drafted. Criteria for the landfilling of mechanical-biological pre-treated waste materials do not exist.
Madrid and Barcelona have modern tunnel composting systems with an annual throughput capacity of >100,000 tonnes, partly combined with anaerobic technologies. Source: TBU Environmental Engineering Consultants Click here to enlarge image
Portugal has several state-of-the-art MSW compost plants. Compost quality plays a more prominent role in Portugal than in Spain. A forthcoming law envisages three quality classes, with the low-end category ‘waste compost’ being permitted for use in agriculture only until 2008. After 2009, MSW compost may only be used for recultivation purposes. This marks the transition from a recovery-based concept (composting) to MBT as a treatment method.From France to Scandinavia
In France, composting is still a widely used MSW treatment method. The technical design of the first generation of plants (still in use today) may in many cases be described as landfills with organic decomposition of the biodegradable waste fraction and optional composting. Yet the majority of the 70 plants have only limited capacity (<30,000 tonnes/year) and, after problems with acceptance among winegrowers in the late 1990s, this type of compost is no longer in great demand and is now mainly used in landfill recultivation projects. Currently, many of these plants are being redefined and ‘converted’ into MBT facilities. There are no landfill criteria for MB processed material and no legal standards for a facultative use of the high calorific fractions. A handful of MBT projects are under way; yet even after construction is completed, not more than 5% of the population will be served by MBT systems.
In Belgium MBT systems are under consideration as an alternative treatment method to incineration and landfilling. An MBT (HerHof dry stabilate system) recently started operation. The Netherlands is among the leading countries in material-flow-specific waste treatment, having triggered some vital developments in terms of both energy recovery of the high calorific fraction and biological treatment. Untreated household waste has been practically banned from landfill since 2000. Existing MBT facilities mainly comprise ‘upstream’ systems prior to thermal treatment.
Strict national environmental standards may give strong support to certaineconomic sectors. Switzerland, Germany, Austria and Denmark are known for both low emission threshold values in waste incineration and having major shares in the international WTE technology market. Komptech, founded in 1992 in Austria, is probably the world’s leading supplier of MBT equipment (such as the shredder pictured). Source: Komptech Click here to enlarge image
The British Isles hold a special place among Western European countries in that a ‘tradition’ of MSW composting is practically non-existent. In particular over the last couple of years, however, MBT has moved into the limelight as a treatment method for residual waste. Much of this was triggered by the EU Landfill Directive requiring the reduction of organic materials in residual waste, which has resulted in a plethora of waste management activities and programmes in both Great Britain and Ireland. These activities are taking shape in all areas and at all institutional levels. In Great Britain, responsibility for waste disposal is vested primarily at county level. Local authorities decide which residual waste treatment method shall be adopted, and they are also in charge of accomplishing the mandatory targets of the EU Landfill Directive - in this Great Britain drastically differs from the other 24 EU Member States, where national legislation is paramount. As a result, in Great Britain the Landfill Allowance Trading Scheme (LATS), similar to the concept of ‘carbon trading’, has been implemented. The outcomes are awaited with great interest on the continent. A dozen high-grade MBT systems are under construction and in the pipeline in England, most of them using aerobic decomposition technology. Much importance is attached to the aspect of hygiene, a circumstance that was mainly triggered by the country’s problems with BSE (with regulations concerning the handling of solid waste streams but not of waste air, as provided, for example, in the German laws).
In Denmark, similar to Switzerland, the landfilling of combustible wastes has been prohibited since 2003. MBT systems will not have an impact, at least in the near future, as nearly 100% of the country’s residual waste stream is processed thermally.
In Sweden, several small MSW composting plants for the production of RDF were built in the 1980s. A MSW composting facility located near Stockholm (core technology: rotary drum) dates back to 2000. There is also evidence of some minor research and development projects (Helsingborg, Stockholm).
Norway has two facilities that may be classified as MBT systems: one is used for the production of RDF, while the second produces material for landfill cultivation only.
Finland possesses several smaller waste composting facilities, all of which are equipped with rotary drums of domestic origin.
In the three Baltic States, there is no past or current evidence of any mechanical-biological waste treatment, or of any other type of treatment.
Poland has traditionally been the country among the former Eastern Bloc nations where MBT - in the form of classical MSW composting - has been most widely used and, by comparison with Western European standards, would equate with Italy in terms of MBT popularity. At present, roughly 10% of all MSW is processed in about 20 facilities using a variety of different technologies and equipment (fermentation plants for the treatment of MSW fractions are also documented). These plants were partly built in the 1980s. Tendering procedures are currently under way for several larger plants (all of them financially supported with EU funds).
In the Czech Republic, MBT also has a certain tradition (with MSW compost plants built in the 1970s and 1980s). Although reference to MBT systems is made in the National Waste Management Plan, currently no concrete activities are taking shape. In short, waste in the Czech Republic (and Slovakia can be characterized similarly) is mainly regarded as a replacement fuel for brown coal, the country’s traditional source of energy. This explains why decision-makers generally opt for the conventional type of thermal treatment capacities. In Hungary, the first MBT facility started operation in 2004. Other plants are yet to follow.
Slovenia, where all existing landfill capacities have been fully exploited, is under great pressure to take immediate action and create waste-conditioning capacities for the future; high-grade MBT systems are taken into consideration in the decision-making process.
In Croatia, the first MBT project is being launched in the coastal town of Zadar. Further plans exist for several medium-sized towns, such as Split and Rijeka.
Waste authorities in the other Yugoslavian successor states are using the scarce resources that exist to (re)establish nationwide collection systems and take the first organizational steps towards the construction of sanitary landfills.
MBT facility in Istanbul: the ‘Wendelin’ windrow turning scheme, a technology developed in the mid 1980s in Austria. Source: TBU Environmental Engineering Consultants Click here to enlarge image
Waste treatment in South-eastern Europe is generally a task for the future, with simple MBT systems having a real prospect in the long term. This goes for Albania, the new EU members Romania and Bulgaria, as well as Greece, which joined the EU in 1981. A large MT plant near Athens was temporarily in operation (from 2000); however, the European Commission, after urging the Greek authorities to speed up the implementation of a sound landfill programme (in Greece more than 40% of MSW is reported to be disposed of in illegal dumps), also imposed sanctions on the country. Attention has recently been drawn to Cyprus where in Larnaka a BOT (build-operate-transfer) contract for a 160,000 tonnes/year MBT plant has been awarded to a bidder with dry stabilate technology (the same as in Venice). Start-up of the operation is expected in 2009.
Tariffs for the disposal of residual waste in Austria, depending on treatment option. Note that other treatments as well as landfill are subject to a national levy (landfill after MBT: e26/tonne; WTE: e7/tonne). The tariffs shown are from 2005 and include this levy. Source: TBU Environmental Engineering Consultants Click here to enlarge image
Turkey has a sorting and composting facility located in Istanbul, which started operation in 1999. The plant is part of a comprehensive environmental programme, which was initiated by the city’s former mayor, Recep Tayyip Erdogan (the current Prime Minister of Turkey). The plant has a daily treatment capacity of 1000 tonnes, which equates to about one sixth of all MSW generated on the European side of the Bosporus.
In the central and northern European countries with their highly developed waste management structure, MBT is either widely established as a reliable MSW conditioning method prior to landfilling (this goes for Germany, Austria and, to a lesser extent, the Benelux nations) or does not play any role on account of national legislation and/or because priority is given to a well-established thermal treatment/WTE incineration option (Switzerland, Scandinavia).
In all other western European countries, MBT will become increasingly important, partly by transforming existing capacities of product-oriented MBT systems (waste composting and fermentation) to treatment-oriented systems. The future role of MBT in the remaining EU Member States (Figure 4) will, notwithstanding their individual waste management situation and system cost development, depend on the outcome of an ongoing discussion about the mandatory thresholds for waste material deemed suitable for landfilling.
In the eastern and south-eastern European states with a backlog of demand for environmentally sound MSW management, less-sophisticated MBT systems may become a vital contribution to accomplishing the medium- and long-term standards and targets set out by a future Europe-wide Framework Directive.
Martin Steiner is CEO of TBU Environmental Engineering Consultants.
The term MBT stands for a variety of techniques and combinations thereof. In essence, it involves several mechanical (pre-)processing steps coupled with the reduction of organic matter by biological action. This approach goes hand in hand with the separation of plastics and other biologically inert fractions; in advanced systems such separation can result in the production of secondary fuels.
In this article, the term MBT relates to the treatment of municipal solid waste (MSW) alone. As such, a treatment facility for any type of separately collected organic waste is not an MBT facility. Mechanical treatment (MT) plants are included under MBT if the waste materials are subsequently processed by a material-flow-specific treatment method, such as thermal treatment of fractions with a high calorific value, here generally referred to as refuse-derived fuel (RDF).
The steps in the biological degradation of organics, which normally take place in a landfill over a period of >50 years, occur via MBT in a controlled environment within a matter of months, thereby reducing the potential to produce landfill gas by more than 95%.
In more highly developed waste management schemes, MT and MBT concepts are generally followed by a thermal step (predominantly fluidized bed rather than grate incineration). With this in mind, future debates concerning waste treatment systems could perhaps be labelled ‘conventional waste-to-energy plants versus combined treatment systems’ rather than ‘thermal versus mechanical-biological waste treatment’.