Construction materials recycling

Summary: Europe has set itself an ambitious goal for recycling construction and demolition waste, aiming at 70 % by the year 2020. At present, only a level of 50 % has been managed, and no great improvements have been observed in recent years. Can the goals set still be reached? This article provides a number of answers.

1 Introduction

In Europe, at the last count, construction and demolition waste made up 34.7 % of all waste produced. This group of mate­rials includes concrete, stones, plaster board, wood, glass, metals, ­plastics, excavated soils, but also hazardous substances like asbestos and solvents. In the EU Waste Framework Directive (2008/98/EC), the goal of a 70 % recovery rate for these ­materials by the year 2020 was set. At present, the recovery rates range between 10 % to almost 95 % in the individual countries. The worldwide leading countries in waste recovery, however, are not found in Europe, but in Asia. Japan takes the leading role. There construction waste makes up 20 % of all waste types. In 2016, 99.4 % of 54.0 million t (Mt) construction waste were recovered. In Singapore, recovery rates of 99 % have been achieved since back in 2010. In 2016, 1.586 Mt of 1.595 Mt construction waste were recovered here.

2 Situation for construction waste in Europe

In 2014, according to Eurostat, a total of 2.502 bill. t waste was produced in Europe (EU28). Fig. 1 shows a breakdown of this total by the most important types of waste. According to this, the largest part of this total is made up by construction and demolition waste with 34.7 %, followed by mining/non-metallic minerals (28.2 %) and the manufacturing sector (10.2 %). Household waste accounts for just 8.3 %. In 2012, the total waste produced in EU28 amounted to 2.512 bill. t, in 2010 to 2.460 bill. t, and in 2008 to 2.427 bill. t. The average per capita waste in Europe last amounted to 4.93 t. There are wide differences from country to country. Bulgaria marks up the highest waste level at 24.87 t, while Croatia reaches the lowest level at 0.88 t. This may be attributed partly to different definitions in the waste statistics of the countries, Waste statistics of the EU and the countries return significantly different data in some cases.

The statistics for construction and demolition waste covers four segments. The excavated soils/stonessegment includes, in addition to excavated soil (sand, earth, rocks), dredged spoil and track ballast. The three other segments include building rubble, reclaimed road construction materials and construction site waste (incl. gypsum waste). In 2014, the waste in EU28 amounted to a total of 868.5 Mt. Fig. 2 shows the ten biggest countries in terms of construction and demolition waste. France alone accounted for 227.8 Mt, Germany 206.5 Mt and Great Britain 120.5 Mt. The highest per capita waste level in the TOP 10 in the EU is reported for the Netherlands with 5.4 t, followed by Austria with 4.7 t and France with 3.4 t. Germany reaches 2.7 t, Italy 0.9 t. Spain and Poland show the lowest levels in the TOP 10, each with 0.4 t (data published in the year 2017).

Unfortunately, no precise details are available as yet on the ­recycling or recovery rates for construction and demolition waste in the EU, although this waste makes up the largest part of the waste produced. It is estimated that currently (as of 2014) around 50 % of this waste is recovered in the EU28 countries [1]. Within the scope of the “Waste Framework Directive” (2008/98/EC), a recycling quota of 70 % is targeted by 2020 to close product lifecycles with more recycling and reuse, so as to obtain both ecological and economic benefits. For the purpose of simplifi­cation, in the European Commission (EC), the term recycling is equated with reuse. There are, however, ­differences in the definition. Another important point is whether excavated soil/stones should be included in construction and demolition waste.

Leading countries in Europe are already reaching recycling rates over 90 % for construction and demolition waste. However, excavated soil/stones are not included in these data, because the predominant part of this waste is not recycled but backfilled. Backfilling is by definition the reuse (filling) of non-mining soil material in surface excavations. Fig. 3 shows the recycling rates achieved in the period from 2008 to 2014 in the five most important construction waste countries in the EU. It can be seen that Germany, France and the Netherlands reached recycling rates of approaching 95 % back in 2008. Great Britain now reaches almost 90 %, Italy reached around 75 % at the last count (2012): The image also shows that there are still big gaps in the publication of relevant data.

3 Aggregates recycling

Along with binders and water, aggregates are the main constituents of concrete. For years, recycled aggregates have formed an important and economically and environmentally sound cycle (Fig. 4). With the processing of building rubble and other demolition material, recycled building materials, that is concrete granulate and mixed rubble granulate, are produced. Processed waste that, according to its material analysis, does not meet the specifications for recycled concrete (RC concretes) is reused as secondary granulate. Such usage types mainly concern the road construction and landfill engineering. In the leading countries, only a very small part of these materials ends up at landfills. In the countries of Southern and Eastern Europe, this percentage is sometimes still considerable.

Fig. 5 shows the quantities of aggregates for 2015 in the ten largest production countries of the EU. Germany is clearly the No. 1 in terms of production quantities with 545 Mt, followed by France with 323 Mt and Poland with 256 Mt. In terms of recycling quotas, the Netherlands is in front with 22.5 %, ­followed by Great Britain with 21.0 % and Belgium with 18.5 %. Germany reaches 12.5 % in this respect. The lowest recycling percentages are found in Spain (1.0 %) and Poland (2.0 %). In Great Britain, a levy of 2.5 €/t is currently charged on the production of aggregates. This is to be used to increase the recycling rate. In other countries, the issue is regulated based on landfill costs or statutory requirements for landfills. On the other hand, barriers exist in recycling especially on account of stringent quality requirements, e.g. for concrete or asphalt, and long, uneconomic transport routes.

Fig. 6 shows how the recycled quantities for the produced ­aggregates have developed in EU28. From the trend, in recent years a slight increase can be identified with an average annual growth rate (CAGR) of 1.7 % from 2010 to 2015. An increase can also be seen in the recycling rates from 6.5 % in 2010 to 7.8 % in 2015. At the same time, it can be seen that the increase is not steady and the value for 2015 has gone down again compared to 2014. The reasons for this are complex and include the above-mentioned aspects. At the same time, it should be noted that not all recycling material in aggregates comes from construction waste, but that, for example, slag from the steel industry also plays a part in recycling.

4 Construction materials recycling in Germany

In Germany, the relevant data on construction and demolition waste are published every two years by the Bundesverband Baustoffe – Steine und Erden e.V. (German Building Materials Association) [2]. The last monitoring report comes from this year with figures up to and including 2014. Fig. 7 shows the development of the four segments excavated soil/stones, building rubble, road construction and construction site waste from 2000 to 2014. In the year 2010, the quantities still totalled 252.2 Mt, by 2014 the quantities had fallen to 201.9 Mt. ­Excavated soil/stones had an average share of 60.6 %. Over the years, the percentage fell from 64.9 % to 58.7 % while the share of the other three segments rose to 41.3 %, which has a positive effect on recycling quantities.

The total quantities of building rubble, reclaimed road ­construction materials and construction site waste have changed only little from 88.6 Mt in the year 2000 to 83.4 Mt in 2014 (Fig. 8), the quantities from 2006 to 2014 being largely constant with annual fluctuations of just +1.2 to -2.3 %. This shows at the same time that in Germany, relatively constant quantities of construction and demolition waste can be expected in the near future. The quantity of the waste is so low that reuse, for example, as aggregates for concrete asphalt and road construction, landfill engineering and landscaping is certainly possible. Only the quality of the waste is a factor, and especially how high the percentage of mixed waste is, as this requires special processing technology. Naturally, the question arises whether it is expedient to increase the recycled percentage of the waste?

Fig. 9 shows the recycling quantities and rates for building ­rubble, reclaimed road construction materials and construction site waste for the year 2014. The highest recycling rates were achieved for road construction materials with 93.7 %. The lowest rates of just 1.4 % were obtained for construction site waste. Building rubble achieved recycling rates of 77.8 % and at the same time the largest recycling quantities amounted to 42.5 Mt. The construction site waste amounting to 15.2 Mt includes construction waste on gypsum basis with 0.5 Mt. Around 50 % of construction site waste is made up by steel and iron and 20 % used timber. Mineral constituents are contained particularly in the mixed construction site waste. If we look at complete recovery, for construction site waste, but also for building rubble and reclaimed road construction materials, much higher recovery and reuse rates are achieved than for pure recycling (Fig. 10).

According to the figures of the Germany’s Statistics Office (Destatis), the number of plants processing building rubble has grown enormously (Fig. 11). From a total of 2172 plants in 2012, their number rose to 2579 by 2014. Mobile plants ­account for the largest part, the number of these having climbed from 1393 at a growth rate of 12.7 % to 1770. ­Stationary plants increased by only 1.9 % from 779 to 809. On the other hand, the ­capacity of the stationary building rubble processing plants rose by 6.5 % from 73.2 Mt to 83.0 Mt. ­Interesting is also the distribution of the plants in the German states. According to figures for 2010, Bavaria reached 30 % of the plants, Baden-Württemberg 10.3 % and North Rhine-Westphalia just 8.5 %. In terms of capacity, North Rhine-Westphalia leads with 21 %.

5 Recycling technologies for ­construction waste

Building rubble processing plants often receive as input mixed building rubble and demolition material. Reclaimed road ­construction materials are generally processed in special plants. Despite this, the number and the differences in the input ­materials are great. Accordingly, a wide range of processes are used in building rubble processing (Fig. 12). The most important processes concern ­sorting, classifying (screening), crushing and comminution. Besides these, processes such as air classifying, magnetic separation and wet processing are used. In stationary plants, ­practically all these processes are deployed, in the case of mobile plants, the focus is on crushing and classifying. Interesting is that more and more mobile systems are also used in stationary plants to improve the flexibility of the plants (semi-mobile).

5.1 Stationary and semi-mobile plants

Stationary plants reach capacities of around 0.05 to 0.8 mill. tonnes per year (Mt/a). ­Modern plants today are designed for ­capa­cities from 100 t/h to 400 t/h. Here, it is increasingly important to produce high-quality aggregates for ­recycled concrete, to increase ­processing rates and reduce landfill costs. All these requirements were met in the new processing plant (Fig. 13) at Feess Erdbau in ­Kirchheim Teck in Baden-­Württemberg. The project, which was ­realized in cooperation with the Northern Irish wet ­processing ­design and equipment company CDE, was presented with the ­German Environmental Award in 2016. The plant produces washed, screened and sorted high-quality ­recycled construction ­materials, around of 80 % can be recycled direct in concrete production.

In another CDE plant that was supplied to Velde Pukk in ­Stavanger/Norway, 0.6 Mt/a different input materials are processed (Fig. 14). In the wet processing plant for 300 t/h, building rubble and demolition material as well as overburden from quarries are processed. Basically, with this type of plant, aggregates can be produced with a quality comparable to those processed from primary resources. However, the input materials have to meet certain preconditions. If too many by-products and hazardous materials are fed to the plant, operation can ­easily become uneconomical. Removal of paper/cardboard, scrap wood, plastics, iron and metals as well as clay bricks, ­aerated concrete, glass, plaster board and the like is essential, but also a very complex and cost-intensive process.

5.2 Mobile plants

Mobile plants (Fig. 15) are used increasingly worldwide and are now very efficient as proven technologies from ­quarrying and the mining sector are applied [3]. Such plants have the ­advantage over stationary plants that in many countries no ­operating ­permits are required for them. In Germany, for ­example, this applies only as long as the plants are operated less than 12 months in the same place. Otherwise approval is ­necessary in compliance with Germany’s Federal Immission Control Act (BImSchG). In mobile plants, the individual ­process steps are linked with each other. Basically essential is that mobile plants can be transported on roads as otherwise they are not classed as being mobile.

Efficient mobile processing for recycled material comprises a machine combination of crushing, screening and metal separation. As primary crushers, almost only robust jaw crushers are used. With the Mobicat MC 100 R EVO (Fig. 16) from ­Kleemann with drive powers of 165 kW, maximum feed rates of 220 t/h can be achieved. The QJ241 jaw crusher (Fig. 17) from Sandvik is also a compact and efficient machine. The crushers are equipped with an anti-blocking system, require only short set-up times, are easy to transport and therefore flexible in use. The crushers have a direct drive and, thanks to their track mobility, can be used flexibly. Most leading suppliers, which besides those mentioned also include Terex, Metso, etc., supply various machine options such as a magnetic separator, which is especially useful in the recycling sector.

Depending on the feed particle size and hardness of the ­materials, for recrushing (secondary and tertiary crusher), cone or impact crushers are used, however, cone crushers are more widely found for processing natural rock than for re­cycling. Metso LT 1213 impact crushers (Fig. 18) can be used for feed sizes to 700 mm. With the crushers, crushing rates up to 400 t/h are possible. Equipping the machines with a water spray ­system to avoid dust emission is optional. The ­Sandvik Q1441 ­impact crusher can be used as primary or ­secondary ­crusher and comes with an overbelt magnet. The track-mounted Mobirex MR 110 Z EVO2 and MR 130 Z EVO2 impact crushers from Kleemann are equipped with a double-deck prescreener. ­Generally, it is a trend in impact crushers that additional functions are incorporated in the machine concept.

Versatile classifying screens are an important part of mobile building rubble processing plants. Warrier 2100 heavy-duty screens (Fig. 19) from Powerscreen have three shafts adjustable in stroke and speed, to optimally screen the feed in the oversize, medium and fine particle ranges. The 7 m3 feed ­hopper with overbelt magnet permits feeding of the screen with a wheel loader or excavator or direct feed from an upstream crusher. For stockpiling of the fractions obtained, two generously sized belts with belt widths up to 1.4 m are available. At Kleemann, the ­tripledeck Mobiscreen MS 953 EVO classifying screens (Fig. 20) round off mobile plants. Besides the abovementioned suppliers, numerous other suppliers offer state-of-the-art ­machine technology in all segments.

5.3 Reclaimed road construction materials

A speciality are the machines for recycling reclaimed road ­construction materials. At least in Europe, many more existing roads are simply resurfaced rather than built new. The challenge for almost 100 % recycling of old asphalt is to adjust the grading curve of the comminuted asphalt closely to the grading curve of the new asphalt without destroying the original grain structure. Several machine suppliers have set themselves this challenge. The wheel-mounded MBRG 2000 granulator (Fig. 21) from Benninghoven breaks down reclaimed asphalt up to a lump size of 1.8 m edge length into the required grading curve with a limited content of fines. In the Rockster R900 impact crusher, two impact rocker system, a screen box and a return belt are integrated. With this crusher, setting of the final particle size and easy adjustment of the grading curve can be achieved.

6 Outlook

The data available so far for Europe show that wide differences exist in the recycling rates achieved for construction and demolition waste from country to country. The leading countries have reached a percentage of 95 %, but have been stagnating for some years with regard to recycling rates and tend to show lower waste rates compared to previous years. In the year 2014 the TOP 5 countries Germany, France, Great Britain, Netherlands and Italy took a share of 80 % in the total construction and demolition waste including excavated soil/stones.

For the next five years, this percentage could decline to 75 % while the countries with low recycling rates would increase their percentage to 25 %. These include, however, some countries that have so far made only limited effort in recycling building materials and have so far reached relatively low ­recycling rates. Insofar, without enormous efforts, the 70 % recycling goal by 2020 will unfortunately remain only wishful thinking.