|Composites Design and Manufacture (BEng) - MATS 324|
Natural Fibres - environmental, technical and economic issues.
CAUTION: For the purpose of the Sustainable Composites pages, the materials described are those from natural sources, without prejudice to the results of any future Quantitative Life Cycle Analysis (QLCA) which may (or may not) make the case for these materials being more environmentally-friendly than equivalent systems manufactured from man-made fibres and synthetic resins. The inclusion of any specific system here is not an endorsement of that product: potential users will need to fully consider each system in the context of their specific technical requirements.
The value of Eco-System Services
Glossary of fibre/textile terms
Suppliers of natural fibres
The Environment Agency has issued a consultation document on aquatic eutrophication in England and Wales . Around 70% of the nitrogen input to inland surface waters is estimated to come primarily from agriculture, then precipitation and urban run-off respectively. The remaining 30% was from sewage effluent and industrial discharges. Agricultural activities (livestock and fertilisers) release 44% of the phosphorus present in surface waters, putting the UK third amongst 16 EU/EFTA nations. Most UK farms operate on the basis of an annual phosphorus surplus, as this is normal agricultural practice across Europe.
The environmental impact of natural fibres in industrial applications has been reviewed by van Dam and Bos . They include quantitative data [Table 1] and suggest that:
In the ADAS review and analysis of the breeding and regulations of hemp and flax varieties available for growing in the United Kingdom  they note "that if changes are to be made to hemp & flax varieties that affect the agronomic requirements of the crops (e.g. higher N inputs to hemp in particular), then careful consideration is needed of how this might affect the perception of an environmentally benign, or even beneficial, status that hemp and flax currently enjoy. Stakeholders promote the perceived environmental advantages (of hemp in particular) as a key selling point".
Embodied energy is the energy consumed during the production of a material at all stages from acquisition (growing or mining), conversion processes (manufacturing) through to product delivery (including transport) and hence is a significant component of the lifecycle impact of that material.
|Material|| Embodied energy
|Air dried sawn hardwood||0.5||4, 6|
|Kiln dried sawn hardwood||2.0||4, 6|
|Kiln-dried sawn softwood||1.6 -3.4 ||4, 6|
|Glue-laminated timber||4.6 -11.0 ||4, 6|
|Natural fibre (china reed)||yields 8.3 MJ/kg||2|
|Jute fibre cultivation (excluding field labour, retting and decortication)||3.75-8.02||-2.4 [Note 1]||2|
|Wet decortication (sisal and henequen)||2.0||100||100 m3 water and biomass||2|
|Flax fibre non-woven mat||9.6||2, 7|
|Woollen and worsted: spinning and winding frames||10.8-12.8||5|
|Woollen and worsted: spinning (ring frame)||18.7-28.6||5|
|Fibreglass insulation||27.9 -30.3 ||6, 8|
|Fibreglass reinforcement mats||54.7||demands 1.7 MJ/kg||2, 7|
|Polypropylene||64  - 84.3 ||3.7-7.5||5.5 ton/tonne||2, 6|
|Polypropylene fibres||90||yields 21.5 MJ/kg||2|
|Plastics - general||90||4|
|Aluminium (virgin) sheet||170 -199 ||4, 6|
|Aluminium (recycled) sheet||14.8||6|
Note 1: Use of non-fibre material as fuel and of leaves to improve soil
fertility are not accounted.
Note 2: A more comprehensive table of embodied energies can be found at reference .
Note 3: There is a Table of CO2 emissions for a broader range of materials at http://www.tech.plym.ac.uk/sme/mst324/MST324-05 Azapagic.htm#CO2.
Cunliffe, Jones and Williams  have published data for the calorific value of pyrolysis gas derived from various composite materials (Table 2).
|Material||Pyrolysis temperature (ºC)||Gross Calorific Value (MJ m-3)|
|Epoxy resin with glass and carbon fibre reinforcement||350||51.1|
|Epoxy resin with glass and carbon fibre reinforcement||400||39.8|
|Epoxy resin with glass and carbon fibre reinforcement||500||42.0|
|Epoxy resin with glass and carbon fibre reinforcement||600||28.9|
|Epoxy resin with glass and carbon fibre reinforcement||800||23.9|
|Poly(ethylene terephthalate) with 50 weight % glass fibre and silane binder||550||7.8|
|Poly(propylene) with 40% glass fibre and silane binder||550||44.7|
|Unsaturated polyester resin with 20-30 weight % glass fibre and silane binder||550||13.0|
|Vinylester resin with 70% woven glass fibre fabric||550||18.7|
The Stern Review  on the economics of climate change notes that raising the cost of fossil fuel energy will significantly impact on costs and prices in the most carbon-intensive industries. There are 123 industries assessed. For profits to remain unchanged with a carbon price of £70/tonne-of-carbon, prices for the top six industries would have to rise by the following percentages:
|Industry||Price change to maintain profit
|Energy as a percentage
of total costs
|gas supply and distribution||+25%||42.9%|
|electricity production and distribution||+16%||26.7%|
|cement, lime and plaster||+9%||5.0%|
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