On the use of recycled materials in open spaces
Problem and situation
The debate on sustainable planning and building in architecture and urban development has also reached landscape architecture. Against the background of the increasing scarcity of resources, the keywords reuse, reduce and recycle are becoming increasingly important. In addition to the scarcity of resources in the sense of raw materials, the aspect of the accumulation of construction waste and its landfilling also represents an increasing nationwide land use problem.
Two statistics are cited here to illustrate the problem:
- Construction and demolition waste constituted the bulk of the total waste generated, accounting for 55.4 % (230.9 million tons). [Source: Destatis, Bundesamt für Statistik, Pressemitteilung Nr. 261 vom 4. Juni 2021].
- In 2016, there were still 1108 landfills in operation in Germany, almost 900 fewer than ten years earlier. In the period from 2015 to 2025, another 500 landfills will reach the end of their planned operating life. Even though a hundred landfills are being structurally upgraded, the number of landfills is continuously declining. [Source: Handelsblatt, Zu wenig Deponien – Deutschland weiß nicht mehr wohin mit dem Abfall, vom 01.07.2018]
Responsible consumer behaviour, as expected by consumers, must also be reflected in the building sector in the planning and production of building components and building materials as well as in the consideration of life cycle costs. The building materials industry already shows numerous good approaches in its product range on how to reuse and recycle building materials. As landscape architects, we also play a part in informing and sensitising clients to use appropriate materials in open spaces in the name of sustainability.
Reuse of building materials (Reuse)
The reuse of building materials in landscape architecture or in garden and landscape construction is essentially dependent on the place of planning: what is the initial situation on the area to be planned? Which building materials can be dismantled, secured and reinstalled? Can we perhaps implement the principle of “reuse to reduce” in the future?
Conceivable situations are, for example:
- Taking up and reinstalling unbound paving made of natural stone
- Taking up and reinstalling natural stone ballast
In building construction, there are initial approaches to salvaging components such as windows, doors, railings, steel parts, etc. from demolished buildings and offering them for further use in a component exchange. For open space, this is currently still largely limited to paving.
Reduction of resources (Reduce)
The reduced use and reuse of raw materials inevitably leads to a reduction in the use of tropical woods (even if they come from sustainable forests in accordance with Forest Stewardship Council (FSC) certification).
- Reduction of the use of tropical woods (even if they originate from stocks of sustainable cultivation according to the Forest Stewardship Council – FSC – certifications) for e.g. wooden decks, garden furniture, etc.
- Reduction of sand as a component of concrete and concrete products and thus reduction of land consumption for gravel pits.
- Reduction of waste generation and thus further land consumption for landfills
Reuse of building materials (Recycle)
Of the three aspects mentioned here, the use of recycled building materials is certainly the most advanced and practised process. The basic prerequisite for the high-quality use of recycled building materials is the sorted collection of the waste fractions at the construction site in accordance with the requirements of the Commercial Waste Ordinance (GewAbfV), the use of state-of-the-art processing methods and guaranteed compliance with defined limit values for water management and construction parameters. Finally, when introducing recycled building materials into the soil (e.g. substructure for path construction, creation of vegetation layers), the regulations according to § 12 Bundes-Bodenschutzverordnung (BBodSchV) must be observed. Ultimately, the aim is to produce a product that consists of as much as possible 100 % recycled basic materials and is qualitatively – in terms of construction technology and environmental compatibility – equivalent to a product made from primary raw materials.
There are already numerous areas of application for recycled building materials in outdoor facilities (selection):
|Area of application||Recycled building material|
|Road surface:||unbound base and frost protection layers, asphalt base, binder and surface courses|
|Earthworks, road substructure:||backfill, bedding for power and telecommunications cables and conduits through stone-free fill soil, noise barriers|
|Traffic route construction, sports field construction and landscaping:||RC concretes for path, garden and landscaping construction, exposed concrete elements), concrete paving stones made from recycled concrete, bedding materials, joint fillers, unbound base courses, sports field base courses|
|Sonstiges:||RC expanded granulate, RC tiles for green roofs, tree substrates according to FLL guideline, roof garden substrates, gravel|
In addition to recycled materials that can be installed over a wide area, there are many applications for the recycling of plastics and the manufacture of new products, some of which involve the direct conservation of resources when it comes to “wood substitute products”. Depending on the area of application, these are high-quality, glass fibre-reinforced or natural fibre-reinforced plastic products that represent an absolutely reliable alternative in terms of durability, user-friendliness and environmental compatibility.
|Area of application||recycled building material|
|landscaping:||trafficable grid elements (in conjunction with turf/chippings), fencing, slope protection (palisades), WPC planks for footpaths, terraces and seating decks, raised beds, bulk boxes, benches, playground equipment for public and private playgrounds, drainage channels, wave protection along rivers|
|Bridge construction:||bridge decking, railings, stairs, access paths|
This summary and further information can be found at: Bundesministerum für Inneres, für Bau und Heimat (Federal Ministry of the Interior, for Construction and Home Affairs).
EPD – A contribution to sustainable building
In addition to the aspects of reducing and/or reusing building materials, it is also important in the future to consider products in terms of their environmental impact in the context of sustainable planning and building.
EPD is the abbreviation for Environmental Product Declaration. The EPD of products, be they building materials, building components or manufactured goods such as concrete blocks, plastic elements, steel scaffolding, etc., describes the entire life cycle aspects of a product in addition to its technical properties. This means that in addition to determining the types and quantities of raw materials, their processing (e.g. energy input for production), their expected durability (service life) and their reusability (e.g. energy input for recycling) are presented on the basis of life cycle assessments. In this way, life cycle costs can also be determined for components and products of all kinds.
In future, products declared in this way will form an essential basis for the sustainable planning, construction and operation of buildings and open spaces. In the construction of residential and office buildings, certifications according to various assessment models (e.g. according to DGNB, BNB for buildings and BNB-AA for open spaces, LEED, etc.) have proven themselves and are now widespread (for buildings). The use of products with EPDs leads to comprehensible information on the ecological quality of buildings and open spaces. For open space planning, there are not yet so many product declarations available that a consistent evaluation of an open space can be carried out from the point of view of life cycle aspects.
The above information as well as further aspects on EPD can be found at: Institut für Bauen und Umwelt (IBU) e.V.