This study was supported by funds from the German Ministry of Agriculture through the Fachagentur für Nachwachsenden Rohstoffen (FNR). It examined the prospects for thermal and acoustic insulation materials based on renewable materials, particularly plant fibres. It was initiated in 1998 in response to increasing industral and consumer interest in ‘alternative’ building materials, particularly novel materials from agricultural crops such as hemp and flax.
The work was based on a combination of review of literature and other information sources; the team’s own experimental work on the thermal conductivity of plant-based fibre materials, direct observations made in visits to production sites across Germany, and on systematic engagement with a wide range of stakeholders in the building sector.
The information base built up includes scientific literature, industry data relating to products, laboratory data from the team's own experiments, information from expert interviews, the results a postal survey of seven expert groups, and information gathered at a specially organised workshop (FAL, Braunschweig, 16. - 17.03.1998).
The study was conducted under the assumption that a sustainable acceptance of the use of industrial crop material in insulation depends on the interaction between technical advantages for the consumer, environmental advantages for society, and the product price.
The survey of manufacturers showed that products based on agricultural crop materials, wood and wool accounted for 3 % of the insulation material market in Germany in 1998. Wood and recycled paper cellulose account for a large proportion of this 3 %. The market had grown over the previous years and was assumed to have a maximum potential of 10 %. All the expert groups considered that the greatest barrier to market expansion, and thus expansion of the market for the relevant raw materials, is the high price of biogenic products compared with conventional materials (200 – 400 % more expensive). Even though the raw material represents a small proportion (10 – 25 %) of production costs, the market for these raw materials is very competitive and cost-conscience. The industry indicated clearly that the market for suitable agricultural raw materials is strongly linked to, and influenced by, the market for low-value materials (recycling materials, agricultural by-products and low grade wood). Recycling materials and agricultural by-products are not only low cost materials, they also have a good environmental profile. The future for primary agricultural materials (e.g. bast fibres, ryegrain and miscanthus) in this market is considered limited. This is not only because of economic factors (the cost of primary materials) but is also because of low raw material availability. It is unlikely that agriculture will be in a position to supply the quantities of bast fibre as a primary product required to make a significant impact on the insulation materials market. In contrast to this, there already exists large quantities of low grade wood, agricultural by-products (e.g. flax tow fibre and cereal straw) and recycling materials (e.g. cellulose and jute).
The study paid special attention to the use of bast fibre produced using modern fibre extraction technologies. Laboratory examinations of the thermal conductivity of mats made from these materials show that flax fibre is one of the few biogenic materials that compares directly with glass fibre in terms of thermal insulation. However, these investigations also show the potential of much lower cost materials such as cereal straw and recycled jute. If products with a 10 – 12 % higher thermal conductivity (in comparison with mineral wool) were acceptable to the market, a wide range of low cost agricultural and wood materials can be considered. The economic analysis shows that the production of insulation material from flax involves greater costs compared with products based on recycling paper, jute, or wood.
Despite the expected growth in the market for wood based products, a significant increase in raw wood consumption by this industry was not expected. This is due to the development of lower density wood fibre products. These products are not only cheaper and have a better environmental profile compared with older dense wood-fibre products, but also have better thermal insulation qualities.
The biogenic insulation materials industry was characterised by over-capacity in 1998, especially in the manufacture of bast fibre-based products. Assuming that fixed costs account for 45 % of manufacturing costs (manufacturing costs in turn account for 75 – 90 % of production costs), there is considerable scope for reducing costs by better utilisation of the existing capacity. Provided that these cost savings are passed on to the consumer, public policy should aim to obtain better use of existing manufacturing capacity.
In the expert interviews and surveys, advantages for room climate and consumers health were cited as the main reason for the decision to purchase these biogenic insulation materials. The scientific literature does not support the view that these materials bring such advantages. In contrast to these unsupported claims, the industry has paid little attention to some advantages that are supported in the scientific literature. In general, biogenic materials are denser than conventional materials and have a high specific thermal capacity. The advantages for summer heat protection and sound insulation are rarely mentioned and seldom clearly explained in the marketing of the products. A clarification of these technical advantages would have a greater influence on the purchase decision than questionable statements relating to effects on building biology and indoor environment.
Environmental advantages were the second most cited reason for a purchase decision. These advantages are claimed by all manufacturers. In this study, the environmental impact of the use of flax for insulation materials was studied in detail. This shows that, in many cases, the claims made by manufacturers are exaggerated. The environmental advantage of biogenic insulation materials is closely linked to the energy consumption in production. In general, the production of biogenic insulation materials consumes less energy compared with the conventional materials. However, particularly for non-woven textile products, this advantage is not as great as statements from the industry suggest. In addition, the energy advantage (over conventional products) is greatly reduced where primary energy inputs into the production of conventional materials are reduced to the minimum through the use of the most efficient energy carriers (e.g. natural gas) and modern processes.
The environmental profile of biogenic materials is strongly influenced by the disposal or recycling phase of the life-cycle. Because of the long consumption phase, there is practically no experience with the disposal of biogenic insulation materials. The discussion concerning the composting of these products is largely irrelevant. Under present circumstances, the recycling of conventional materials is easier and more practical than the recycling of biogenic materials. This is due to the large quantities needed to support a recycling infrastructure. Because of the small quantities, the direct recycling of biogenic materials is difficult. The study shows that the incineration (with energy recovery) is likely to the most acceptable disposal method.
The trend towards the use of biogenic insulation materials is to be greeted in general, especially from an environmental viewpoint. These products could, especially when combined with other ecological building practices, contribute to a more natural building environment. The study uncovers a range of barriers to market development. Development, product labelling, product registration and marketing activities in the industry are not co-ordinated. In contrast, the much larger companies in the conventional industry work together to reduce their costs in these areas. Architects play a dominating role in the consumer’s decision to purchase, conservative attitudes to new products and building practices are seen as a barrier here. Apart from marketing, investigations into construction and building physics are regarded as urgently required. Even though the registration procedure functions efficiently in Germany, it is regarded by many manufacturers as a barrier to product development. Discussions with the industry and the registration authorities revealed that a large proportion of the negative experiences could be greatly reduced by manufacturers co-ordinating their activities.
The identification of policies that could support the use of agricultural and forest materials for the production of insulation materials was an aim of this study. The results show that there is no simple recipe for a market breakthrough for home-grown raw materials. In particular it is emphasised that these materials compete with conventional materials on one side and with biogenic recycling materials and very low cost imported by-products which have similar technical ecological characteristics on the other. Against this background, priorities for policy making and support are proposed. Efforts should concentrate on raw materials that are already available in quantities sufficient to support an expansion in the industry. Policy should also give priority to identifying the technical advantages of these products. Scientifically-founded data relating to the technical effects for consumers are an urgent prerequisite for a middle and long term successful market development. Effective co-operation between producers is essential to the future of these products, especially with regard to marketing. Similar close co-operation in dealing with standards authorities and product registration is necessary if the biogenic insulation materials industry is to expand markets share. An effective producers association could also function as a vehicle for other supporting measures, and should be seen as a perquisite of such support. Priority should also be given to reviewing the registration procedures, norms etc. so that, while maintaining safety standards, new products can be easily introduced to the market.
Postscript in 2013
This study remains one of the most comprehensive compendia of information on insulation materials from plant and animal fibres. At the time the study was conducted, public policy was focused on the potential ‘new’ insulation products based on flax and hemp (particularly flax) grown specifically for this purpose. The immediate impact of the findings was the revision of investment plans. The study draw attention to the competitiveness of well-established products based on recycling materials, such as products from cellulose (recycling paper), compared with new non-woven textile products. It also drew attention to over-capacity in the non-woven materials industry, which had consequences for the competiveness of non-woven textile-based products and the propects of successful investment in new capacity. This refocused public policy towards marketing measures and towards investigations of the technical characteristics of these products in buildings.
It was with great sadness that authors of this report learnt of the untimely death in July 2013 of Prof. Dr. Franz-Josef Bockisch. As Head of the Institute for Agricultural Engineering and Farm Building Research, Herr Bockisch initiated the research work on biogenic building materials in Braunschweig in 1995. He enabled the development of a diverse research team, kindly supported them in their work, and worked to ensure the full publication of this study.