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Novel Processing of Cereal Straws for Fibre Packaging Materials - LK0818

Description of the proposed research

Overview of the project background
Over 67 million tonnes of packaging waste is generated annually in the EU[1], comprising about one third of all municipal solid waste. This has caused increasing environmental concerns, as most of the waste in UK the has ended up in landfill sites. In recent years, development of biodegradable packaging materials from renewable natural resources has received significant government support in EU countries and many national/international organisations have been established to facilitate research in this area. These include European Renewable Resource Materials Association (ERRMA), the Alternative Crops Technology Interaction Network (ACTIN) in the UK, International Biodegradable Polymers Association and Work Group (IBAW) based in Germany and Interactive European Network for Industrial Crops Application (IENICA). The UK Government-Industry Forum has recommended greater use of non-food crops, particularly for biodegradable packaging applications[2]. Many bio-based packaging materials have been developed in order to replace oil-based synthetic polymers and to facilitate the treatment of waste by local composting instead of incorporating it as landfill. Starch and natural fibres are the front runners of renewable raw materials for producing a wide range of packaging materials in the forms of moulded objects (e.g. Mater-biTM and SolanylTM ) films/sheets (e.g. Eco Bio-SacTMand BioskaTM ) and foams (e.g. Eco–FoamsTM). To date, significant technical advances have been achieved in materials processing to provide comparable functionality to synthetic polymers. However, relatively high costs remain a constraint to the widespread exploitation of these materials, being at present 2-4 times the price of oil-based plastics [3].

The use of natural fibres in packaging applications is currently dominated by wood fibres [4]. Such packaging is commonly based on paper and cardboard. These materials are compostable and can also be recycled. However, pulping effluents and finite forestland areas are still major concerns in the future development of wood fibre-based products.

Cereal straws, on the other hand, are annually renewable, low cost and abundant sources of natural fibre. The national production of wheat straw in the UK, for instance, is estimated as 5 to 6 million tonne/annum [5] and this is produced as a residue from the primary food production activity. The tonnage of wheat straw trading is only 50,000-80,000 at about £25-30/tonne for baled straw [6], compared with starch at about £300-1500/tonne and synthetic polymers typically £600-1000/tonne. Most straw is used for animal feedstock, bedding or incorporated back into agricultural fields.

The strength of cereal straw fibres is relatively low compared to other natural fibres, such as flax and hemp. This restricts their use as effective reinforcements in high performance polymeric composites. However, for packaging applications, straw fibres have adequate strength for fibre composites, or potentially as a reinforcing phase in a wide range of starch based bio-plastics. Previously many attempts have been made to extract cellulose from cereal straws for paper making, or for partial substitution of wood fibre in fibreboard[7-9]. These techniques are based on extraction of cellulose by combined thermal, mechanical and chemical treatments, followed by washing and bleaching operations to remove the non-cellulose species, during which large quantities of complex and toxic effluents are generated. In addition to the adverse environmental impact, this creates enhanced cost, through the need for further treatment of effluents produced and drying of the fibre.

The proposed work seeks to address the two key issues that restrict the industrial utilisation and significant potential of straw fibre in moulded packaging items:

a) the lack of low-environmental impact processing technology for mass production of low cost quality straw fibre;
b) the lack of processing technology to fabricate useful fibre packaging materials from straw feedstock.

The proposed work will focus principally on wheat straw, the most abundant source of annually renewable cereal straw from UK home grown wheat. The technologies, though, should be applicable to other types of cereal fibres, which will also be evaluated in the programme.

The aim of this proposal is to address the key scientific and technical issues in the development of processing technologies for industrial production of straw fibre and its utilisation as a packaging material. It comprises three inter-related packages, each with specific objectives:

· To develop a novel extrusion steam explosion (ESE) technology to establish a cost effective and low environmental impact process for mass production of finely separated and purified straw fibre, suitable for packaging applications.
· To develop a new gel-moulding process for fabrication of straw fibre packaging composites and to modify existing bio-plastics with straw fibre for the purpose of property enhancement and cost reduction.
· To carry out a life cycle analysis (LCA) to validate that the ‘eco-profile’ of the new straw based packaging is genuinely a better environmental option than current approaches.
Time-Scale and Cost
From: 2003

To: 2007

Cost: £435,704
Contractor / Funded Organisations
John Ebbage Seeds, Dassett Process Engineering Ltd, University - Brunel, Biopac UK Ltd, Biopac UK, The Imperial College of Science Technology and Medicine, Green Light Products Ltd
Arable Farming              
Cereal Production              
Materials Science              
Process Technology              
Fields of Study
Non-Food Crops