As mentioned earlier, the general environmental benefits of recycling are saving of energy, saving of natural resources, reduction of emissions and decreased use of land for extraction of resources and for landfill. (An overview of the recycling possibilities for some common building mate-rials as well as the energy saving through recycling is given in Thormark, 1997.)
The benefits vary considerably with the form of recycling and with dif-ferent materials. The environmental impact can actually even increase through recycling. Transport is mostly the major reason for the increase in environmental impact through recycling.
Transport can for specific materials account for a considerable pro-portion of the environmental impact. Transport must therefore be taken into consideration in order not to overestimate the benefit of recycling.
The significance of transport depends on the gross energy saving, the weight of the material, the distance to recycling plant, the distance to raw material resource site and the transport logistics. The environmental im-pact of transport may be as much as the gross savings and may even turn the gross savings into increased environmental impact. But reduced need for transport because of recycling can also be the main cause of a consid-erable decrease in environmental impact. An example of this is recycling of concrete on site for use as coarse aggregate in roads as a substitute for gravel. (Torring, 2000).
Parameters beyond energy use
It is here suggested that when the general recycling potential is assessed, energy is used as an indicator of the environmental impact (see Chapter 3).
When the effects of recycling are limited to energy, there are several important parameters that will be disregarded such as emissions to air, water and soil, noise, dust, working environment, use of resources, use of land area for extraction of raw materials and for landfill. Much research is in progress worldwide to develop methods for assessments of noise, dust, working environment, use of resources. For the moment, however, there is no obvious way in which these parameters are to be assessed.
Deconstruction, i.e. dismantling for recycling, is the best way of demo-lition in order to recycle. Noise and dust can then be considerably duced compared with conventional demolition. On the other hand, re-cycling on site can result in an increase in noise and dust. An increase in noise and dust will e.g. occur when concrete is crushed on site.
As regards the working environment connected with deconstruction, few studies have so far been performed. In (Sternudd & Swensson, 1997, Miljo…, 1996) it was concluded that training and education of the work-ers are important in order to reduce the risk of accidents, to increase the motivation for the work and in this way also increase the efficiency of dismantling.
The effect on the use of land area for extraction of raw materials is a complex and difficult thing to assess. Besides, for the time being, avail-able data give little information on this issue.
Recycling and environmental effects There is so far very little or no information on the specific effects on landfill from building waste. The assessment must be mainly limited to the amount put to landfill.
Emissions
When the effects of a specific recycling event of today are assessed, the emissions to air, water and soil have to be included. The emissions from processes can vary considerably. An obvious example is the energy source used in a process. A theoretical example limited to the energy use can be given to illustrate this. It is assumed that production of a product re-quires 100 MJ electricity, Swedish mix. To reuse this product, lorry trans-port, requiring 20 MJ, is needed. If the product were not recycled, a new product would have to be produced. The net result is then made up of the gain due to avoidance of production less the use of transport, i.e. a saving of 80 MJ. Regarding energy use, recycling can be concluded to be obviously beneficial. See Figure 4.1.
However, if emissions caused by the energy use were included, the result of this reuse would look quite different. The emissions contribut-ing to four impact categories; global warmcontribut-ing, acidification, eutrophication and photochemical oxidants, can be seen in Figure 4.2. Regarding these four impact categories, reuse is obviously not desirable.
Another example is reuse of wood. Assumed that the wood, unless reused, would be burnt with energy recovery. If the wood as a fuel source is replaced by oil, the emission of CO2 would increase radically despite a fairly equal energy use.
-100 -80 -60 -40 -20 0 20 40 60 80 100 120
No recycling Recycling
No recycling Recycling (MJ)
Figure 4.1 The result limited to energy use in the case with no recycling and the case with recycling. Negative value is an avoided energy use.
0,00E+00 2,00E-05 4,00E-05 6,00E-05 8,00E-05 1,00E-04 1,20E-04 1,40E-04 1,60E-04 1,80E-04
AP GWP NP POCP
(indices)
No recycling Recycling
Figure 4.2 The result regarding the contribution to global warming (GWP), acidification (AP), eutrophication (NP) and photochemical oxi-dants (POCP) in the case with no recycling and the case with recy-cling. In the case with no recycling, the contribution is caused by energy use for producing a new product that is a substitute for the old one. In the case with recycling, the contribution is caused by energy use for transporting the product that will be reused.
Recycling and environmental effects