22 P.J. Fraanje / Resources, Conservation and Recycling 19 (1997) 21-28leads to resource depletion, loss of biodiversity and pollution (Reijnders, 1995).This is not in line with sustainable development as defined by the UN-Commissionon Sustainable Development (World Commission on Environment and Develop-ment, 1987). Based on the concept of sustainability in the Netherlands there is a case for areduced use of virgin natural resources and a relative shift from virtually n o nrenewables to renewable resources (Ministerie van VROM, 1989, 1990). An ex-panded use of renewables following from the replacement of non renewableresources however ceteris paribus leads to an unacceptable pressure on landresources. To reduce or rather avoid this pressure, the efficiency of resource-utiliza-tion should be increased. Similar considerations hold for other industrializedcountries. Resource-cascading, which can be defined as the sequential exploitation of thefull potential of a resource during its use, is one of the ways to improve efficiencyof the raw materials use. The word cascading originates from the analogy of thecascade of a (mountain)river, where the water is descending from one level to thenext, towards the sea or a lake (Sirkin and ten Houten, 1993). The concept ofresource-cascading can help designers and policy makers to find ways to a moreefficient use of raw materials. In this contribution the potential of cascading the renewable resource wood isdiscussed. It focusses on the cascading of wood of the pine tree (Pinus Sylvestris).2. Cascading of renewable resources In Sirkin and ten Houten (1993) and Sirkin and ten Houten (1994) the theory ofcascading is described extensively. Based on experience with the practical applica-tion of cascading (Sienknecht and Fraanje, 1992, Fraanje and Lafleur, 1994) asimplified approach is presented here. Whereas Sirken and ten Houten employ fourdimensions (quality, time, consumption rate and salvageability) I here use twodimensions, quality and time. A similar simplification has also been suggested bySirkin and ten Houten (1994). This simplified approach appears to be suitable todesign a resource conservation policy strategy. Following this approach cascading is about starting at a high Q (Q -- resource-quality), increasing AT ( = life time per application) and ZAT (overall life time) andminimizing AQ (quality loss per application) (see Fig. 1). The quality of a resource depends on the energy embodied in the resource, itschemical composition and its organization. For renewable resources a definition ofquality could be the measure in which the original functional properties are present.In general the dispersion of matter and/or energy and loss of organisation can beseen as a loss of quality. In case of a renewable resource like wood from a tree,solar energy, nutrients and water made it possible for the tree to develop a woodystructure with certain properties like strength, durability etc. Some of these proper-ties can be useful to man. At the moment a tree is cut into pieces its propertieschange and certain uses or applications are not possible anymore without invest-
P.J. Fraalz/e .; Resources, Consert:ation amt Recycling 19 (I 997) 21- 28 23meat of (non renewable) energy and materials. The joist which is made out of apiece of roundwood has not the original strength of the trunk anymore. Only withthe input of additional energy and materials it is possible to restore the loss offunctional properties. The actual use of resources is often in contrast with the ideas of cascading: woodwith good (construction)qualities is made to pulp (in Fig. 1 this can be shown as alower Q as the potential). Crops are often used partly (e.g. only the seeds) and oftenonly used for low quality applications, with a short life span. Therefore currentlythe area (A) under the curve is usually relatively small (see Fig. 1), this in oppositeto the area under the curve when cascading. The nodes shown in the graph represent the moments where concious choicesshould be made. The utilization time of the resource in a certain application can beextended at cost of investing (non renewable) energy and other resources. Anotherpossibility is to find a next application and thereby minimize the loss of quality. Tooptimize the environmental choice, at every node the decisionmaker should studywhich is the best solution. In doing so one should think ahead. Some choices blockother applications in the future. In practice the differences between the options willoften be clear and if not, determination of the parameters energy and (other)resource-use can be helpful. Q Convert- ~, t t "J U / / / / U / L / L J //,//////T *, • , ,, , Z~T ~l TFig. 1. A resource cascade and conventional resource use in industrial countries (Fraanje and Lafleur,1994). Q = resource-quality; T = utilization time; AT= life time per application: EAT = overall lifetime; AQ = quality loss per application.
24 P.J. Fraanje / Resources, Conservation and Recycling 19 (1997) 21-28 The principles of (renewable) resource cascading are:(1) appropriate application (high Q). Appropriate application means that the resource is applied on the basis of its (typical) properties, at the highest quality level that is possible. In this view one should not make pulp out of tree directly, but first profit by specific qualities of massive wood (like strength). When making paper directly from vegetable resources, one should rather use flax or hemp, instead of wood. Appropriate application has reference to the whole resource. A tree consists of more than a trunk. In case of for instance a cork-oak the wood and the cork find both their useful applications; for both the wood and the cork seperate cascades can be made. In case of vegetable renewables whole crop use should be the starting point for cascading.(2) life time extension (increase AT and ]EAT). The AT (life time per application) can be extended through: - optimal design of the product: in case of production of a window frame for instance, it should be designed in such a way that water cannot easily stay on it, thereby preventing rot; - optimal application of the product: this aspect is less strongly related to the product, but can be influenced by giving prescriptions or conditions for application. For instance in case of the window frame it means that the building in which it is placed should preferably be designed in such a way that the frames are protected against weathering; - good maintainance of the applicated product, aimed at postponing the replacement of the product by using small quantities of energy and raw materials (cleaning, painting and so on). Increasing ZAT (accumulated life time of all applications) may be helped by increasing the number of steps in the cascade. If maintainance cannot meet the technical requirements anymore, if too much energy and materials are required, or if such a measure brings about too much pollution, then one may look for an application lower in the cascade, for example using pieces of massive wood in board.(3) quality-conservation (minimise AQ) For a next step in the cascade, a next application should minimize quality- loss. An example of this principle is that a discarded large dimensioned window frame can be processed into a window frame with smaller dimensions, instead of being pulped or burnt, which would result in a greater quality loss.3. Pine-wood Commissioned by WWF Holland a study (Fraanje and Lafleur, 1994) has beenexecuted how to use wood in a more sustainable way. Except for reduction of thewoodconsumption, the total amount of primary wood used in the Netherlands canbe further decreased by cascading wood. In this report with the (translated) title"Sustainable use of wood in the Netherlands", four examples are given of cascadingthe renewable resource wood (Fraanje and Lafleur, 1994).
P.J. Fraan/e / Resources, Conservation and Re~3,clmg 19 (1997) 21 28 25 Some possible uses o f the pine tree as a whole pine tree (alive) pine tree (when cat) needles insulation material needle-wool flowers pine bee-honey pine apples energy gum-resin turpentine kolphonium bark energy footpaths top-wood fertilizer (in the forest) energy pulpwood branch-wood fertilizer energy pulpwood trunk column floor-joist floor-plank window- frame Fig, 2. Some possible uses of the pine tree as a whole. In this contribution the pine tree (Pinus Silvestris) is subject of research. The treeis quite abundant (at about a quarter of the whole Dutch forest area) in theNetherlands. In Fig. 2 the possible uses of the whole pine tree are shown. For everyapplication of a part of the tree a cascading strategy can be formulated. If, as in this case, the resource is defined as wood of the pine tree, it is importantto find an application which is in accordance with the typical properties of pinewood. For a high quality application it is necessary to know what size (length,diameter) and qualities of pine wood are available. Here attention is focussed onthe wood derived from the trunk of the pine tree, pine wood. In Fig. 3 one of thepossible cascades for such pine wood is shown. When exploiting the full potential of cascading, the total using-time of pine wood(EAT) can be expanded from about 75 years to more than 350 years. In theNetherlands, a country where labour is relatively expensive, parts of this cascadeare realised in practice. Step 1 could be normal practice in the Netherlands, but as the Dutch pine forestis relatively young there is not much pine wood available with large diameters. Thesecond step in the cascade (see Fig. 3, step 2) is put into practice by a specializeddemolition firm located near Utrecht. Floorboard is made out of old floorjoists (deWeert, 1992), (Fraanje and Lafleur, 1994). The floorjoists measure 0.75 × 0.20-0.25m average and are at about 4.5 m long. After the removal of the 75-100 year oldbeams with special equipment, the joists are made nail-free by hand and controlledwith a metal-detector. Nothing is thrown away, as the nails go to a companyrecycling old metal. After that, the joists are planed and often it is necessary to cutof the ends that were in contact with the wall. Then the beam is sawn in floorboardsof 2.5 cm thickness, with tongue and groove joints. In case of average quality some
26 P.J. Fraanje / Resources, Conservation and Recycling 19 (1997) 21 288 planks, 0.7 m wide and at least 4 meters long, can be produced out of one beam.About 75% of the old beam is used for floorboard. The rest is used in otherapplications such as wood with smaller dimensions, pile caps (pieces of wood of badquality, often the unusable ends of the old beams) and for fibreboard. For everyseperate application, a new cascade can be made. For pile caps for instance it willbe a very short cascade, as they are used once or twice and than burned, but for woodof certain measures the cascade can be much longer. The manager told that thedemand for old floorboards appears much bigger than that the company can produce.The Dutch consumer appreciates such planks, because they are worked out, they arewider than the new planks and the quality of the old wood is better (probably dueto slower rotation in production-forests) (Fraanje and Lafleur, 1994). As a floorcovering the floorboards produced by the company involved can starta second life (step 3) and easily a third by planing them once more. Other companiesin Holland sell second hand floor planks too (step 3). The only processing thesecompanies are doing is making the old floor board nail free and plane them. Sincewooden floors are more popular, second hand floorboard is almost a common productin the Netherlands. When a floorplank is worn out it could be used in a jointed wooden frame (step4 in Fig. 3). For such a frame pieces of at least a length of 0.20 m are required;technically it is possible to build up such a frame out of very thin layers, but the thinnerthe layer (in this case it would be at about 20 cm, a normal thickness is 3-4 cm), themore glue is needed. Q resource qu~lity 1 3 floorjoist floor board floor f l ~ 4 5 board ( jointed) I window- flake ! i,~ fibreboard frame board I ~" i 7 I jinc!nera- I I t~on 1 I 75 75 75 75 75 30 • time T (years) Fig. 3. A possible cascade for wood of the pine tree.
P.J. Fraan/e / Resources, Conservation amt Rec:veling 19 (1997) 21 28 27 Step 4 (see Fig. 3) is put into practice by a Dutch firm that makes, depending onthe size of the wood, floorjoists or window frames out of second hand pine wood.The company sells window frames of this pine wood as an alternative for tropicalhardwood. After use of the jointed window frame the wood can be used as a resource forboard production (step 6). In the end this board can be burned in combination withenergy-recovery (step 7 in Fig. 3). These steps are quite common, though oftenimmediate incineration also occurs. In theory before the application of wood infibre board there could be another step (step 5): application in flake-board. Flakesmeasure at about 6.5 × 2.5 cm. Now European flake board is made of fresh sawnpine-wood pieces, but probably such a process can be adapted for secondary wood.4. Discussion Though parts of the wood cascade are a proven possibility, until now, in theNetherlands only a small percentage of the total amount of wood follows (parts of)the cascade as shown in Fig. 3. This leads to the unnecessary waste of valuablenatural resources. Thus measures to increase cascading are well advised. For suchmeasures several options may be considered: eco taxation which means a shift of the tax burden from labour to resources, which is expected to make resources relatively more expensive, probably stimu- lating the efficient use of raw materials; deposit money on newly built houses, to make a more sophisticated demolition economically possible; regulations which allot more responsibility to producers for post-consumer waste (Reijnders, 1993); prohibition to dump waste-wood (Lafleur and Fraanje, 1995); a digital wood-bank showing which kind of wood with certain properties is available at a certain moment, to prevent unnecessary low quality application of wood as a result of inadequate communication (Fraanje and Lafleur, 1994). The last two options will be probably introduced in the Netherlands on a shortterm and are expected to have a positive influence on the efficient use (includingcascading) of the raw material wood. Recently deposit money on new cars issuccesfully introduced in the Netherlands to make disassembly of old cars econom-ically possible. It may be an effective measure for houses too, with a positive effecton the labourmarket. The third option may not be easily applicable for buildingmaterials which have a long life time. It can be complicated to make arrangementsor give garantees for an action which takes place in the far future, e.g. after 50years. The first option can be effective, but only if the eco-taxation on raw materialsis substantial. One remark should be made on differences in quality of pine wood. In theNetherlands in the past most of the pine wood was imported from the Baltic, wherepine trees where growing relatively slow and regularly in a continental climate, incontrast with pines growing in the Netherlands. Pine wood which was harvested
28 P.J. Fraanje / Resources, Conservation and Recycling 19 (1997) 21-28and applied a hundred years ago and now appears as second hand wood on themarket is different, often better, in quality than that of new pine wood.5. Conclusion In this article it is shown that cascading of the renewable resource wood can leadto large savings in primary resource use. Applicated on a large scale, cascading ofrenewable resources can make a greater share of renewable resources in the totalresource use a distinct possibility. Cascading can increase the overall life time of the resource wood strongly. Forpine wood a cascade of five or six steps can be set up, which extends the using timefrom about 75 to over 350 years. By cascading resources the efficiency of resourceuse increases significantly. Cascading of wood on a large scale can also be interesting as a means of limitingthe amount of carbondioxide emitted. The carbon which is locked up in the woodstays there for a longer time and CO2 emissions are postponed. In a cascading-strat-egy, incineration is often the last step, but before that second hand wood can havemany other applications.Acknowledgements The author thanks Professor Dr. U Reijnders of the Interfaculty Department ofEnvironmental Sciences (IDES) of the University of Amsterdam for his commentsand contributions and the companies Bevers in Harmelen, TASB in Beverwijk andNorbord Industries in Zaandam for their cooperation and information.ReferencesFraanje, P.J. and Lafleur, M.C.C., 1994. Verantwoord gebruik van hout in Nederland. IVAM Environ- mental Research, nr.94/08; University of Amsterdam, Amsterdam.Lafleur, M.C.C. and Fraanje, P.J., 1995. Bos- en houtbeleid in Nederland. IVAM Environmental Research, nr. 95/05; University of Amsterdam, Amsterdam.Meadows, D., 1972. Grenzen aan de groei. Het Spektrum, Utrecht.Ministerie van VROM, 1989. Nationaal Milieubeleidsplan. TK 1988-1989, 21137, nrs. 1-2, Den Haag.Ministerie van VROM, 1990. Nationaal Milieubeleidsplan Plus; bijlage 2 Duurzaam Bouwen,.TK 1989-1990, 21137, nrs. 23, Den Haag.Reijnders, L., 1993. Expanding producer responsibility for reducing environmental impact. TMA, 3: 69-72.Reijnders, L., 1995. Environmentally improved products and production. Kluwer, Dordrecht, 1995.Sienknecht, K. and Fraanje, P.J., 1992. Bouwen met riet. WIE; Gouda.Sirkin, T. and ten Houten, M., 1993. Resource cascading and the cascade chain. IVAM no. 71; University of Amsterdam, Amsterdam.Sirkin, T. and ten Houten, M., 1994. The cascade chain. Res. Cons. Recycling, 11: 215-277.Weert, P. de, 1992. Hour op herhaling - hergebruik loont de moeite. In: het Houtblad, 16-17.World Commission on Environment and Development, 1987. Our common future. Oxford University Press, Geneva.