Page 12

Demolition and dismantling costs [€]

65,000

Disposal costs high Personnel costs high

60,000

Disposal costs low Personnel costs high

55,000

50,000 Disposal costs high Personnel costs low

45,000

Disposal costs low Personnel costs low

40,000 Conventional demolition

Selective demolition

Dismantling / Disassembly A 2.13

Here, cost-effectiveness depends on: • Dismantling  /disassembly costs - Workers required (their number and qualifi­ cations) - Use of equipment /machines (type and quantity, operating materials) -  Material (safety measures and equipment) •  Disposal costs When the costs of dismantling in proportion to disposal costs are examined and divided into conventional demolition and selective ­dismantling, it becomes clear that personnel costs are more relevant to the overall costs than the costs of disposal (Fig. A 2.13) [18]. This explains why selective dismantling, which enables recycling but requires an ex­­ tensive deployment of workers, is not used ­universally. The costs of dismantling and demolition are usually calculated based on the contractor’s experience. In contrast to cost estimates for building construction there is no general, pub­ licly available data (e.g. such as the German Construction Price Index). Estimating costs is subject to fairly great uncertainty because many parameters cannot be identified or can only be identified with great difficulty in advance (e.g. structural components covered with cladding). A lack of information on the materials involved often results in very rough estimates of dismantling and disposal costs based on the structure’s gross volume and /or on the average calculated time required for the floor area involved. The chapter on “Cost Comparisons of Conven­ tional and Urban Mining Design Constructions” (p. 120ff.) shows the end-of-life costs for selected structures. The Development of the Anthropogenic ­Deposit Building stocks in Germany have grown con­ tinuously since the Second World War and now form an enormous, man-made, anthropogenic repository of raw materials with an estimated volume of 15 billion tonnes (Fig. A 2.14). To cal­ culate the recycling potential available in the 22

total building stock, scientists have made ­forecasts and carried out sensitivity studies for mass flows in 2030 and 2050 based on ­construction and demolition activities in 2010. According to the mass flow model, the input streams for new building and renovations in 2010, at 121 million tonnes, were three times as large as the output streams from disman­ tling. Based on forecast population growth, this trend will probably reverse from 2030 and by 2050 materials volumes from ­dismantling could exceed those from new building and ­renovations 1.5-fold, if the increase in vacant buildings is to remain m ­ oderate (Fig. A 2.15). One of the study’s main messages was that the use of recyclates, in products in building construction, based on optimistic assumptions of improved conditions for a circular economy and taking theoretical technical upper limits into account, could grow from an average of approximately 7 % currently to 21 % in 2050 [19].

A 2.13 Impact of disposal costs and personnel costs on demolition and dismantling costs based on four model calculations for a solid residential building (built in 1856) with 4,200 m3 of gross volume A 2.14 Material deposited in building stocks in Germany in 2010 in million tonnes by material group A 2.15  Forecast of materials streams in construction A 2.16 Reliability of disposal based on landfill capacity in Germany

As long as the real recycling of concrete and other mineral construction materials remains impracticable, the only the way of conserving these materials, which use up lots of resources and result in large quantities of emissions, is to work with the sustainability principles of effi­ ciency and sufficiency. The examples of build­ ings in the “Detailed Catalogue” (p. 135ff.) therefore focus on construction methods that already ensure recyclability at a high-quality standard. For economic reasons, current demolition tech­ niques are primarily designed to ensure speed and to require as few workers as possible. The stricter rules governing materials separation in the amended German Commercial Waste Ordinance (GewAbfV) and the tendency of dis­ posal costs to rise will mean that selective ­dismantling will become more established. For current new building projects, this means that easy separation of materials by means of detachable connection techniques is the best way forward (see “Detachable Connections and Constructions”, p. 42ff.).

Conclusion and Prospects Currently, the construction sector can only meet the recycling quotas called for in legisla­ tion at a low-quality standard and is far from a real circular economy with closed materials cycles. Since resources are increasingly in short supply, demolition activity is increasing, landfill capacity is shrinking (see “Limited ­landfill capacity”, p. 124 and Fig. A 2.16) and demands on secondary raw materials in build­ ing construction are growing, there is an urgent need to generate closed materials cycles in building construction. This will be a major chal­ lenge for mineral construction materials pro­ ducers. Researchers are, however, already ­providing some solutions. Concrete, for ex­ample, may soon be able to be fragmented into aggregate and hardened cement by means of electrodynamic fragmentation. Ultrashort high-voltage impulses (flashes) under water create a pressure wave in the concrete that reduces it to all its individual components [20]. The question of how reactive cement can be extracted from hardened cement is, how­ ever, currently unresolved.

Notes: [1] Recommended resolution and report of the Commit­ tee for the Environment, Nature Conservation Building and ­Nuclear Safety (Ausschuss für Umwelt, Natur­ schutz, Bau und Reaktorsicherheit - 16. Ausschuss), Drucksache 18/9094, 06.07.2016 [2] Regulation (EU) No. 305/2011 of the European Parlia­ ment and of the Council of 9 March 2011 ­laying down harmonised conditions for the marketing of ­construction products and repealing Council Dir­ ective 89/106/EEC [3] Directive 2008/98/EC of the European Parliament and of the Council of 19.11.2008 on waste and ­repealing certain directives [4] Verordnung zur Einführung einer Ersatzbaustoff­ verordnung, zur Neufassung der Bundes-Boden-

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Manual of Recycling  

Buildings as sources of materials - More information: https://bit.ly/2MPg6wu

Manual of Recycling  

Buildings as sources of materials - More information: https://bit.ly/2MPg6wu