Each year in North America over 200 million tons of straw remains as a by-product of the agricultural crops of wheat, rice, rye, corn and grass seed. This straw is generally left to compost in the fields or is burned. The burning of agricultural straw is a significant cause of air pollution and contributes to global warming.
Because of the large quantity of straw available, and their tensile qualities, many types of agricultural straw are ideal for a wide array of products including paper, building materials, textiles and other fiber-based products.
Where storage of agricultural straw was once a limiting factor in its supply, modern harvest methods support year-round storage thus facilitating a ready and available supply of the fibre.
Although the process of pulping agri-fibres is currently more expensive than for wood-based fibres, the overall cost is lower as the price of the raw materials are significantly cheaper. The chemical processes involved with the pulping of agricultural straw are generally much more benign than with the pulping of wood fibre.
One particulat application is for "agri-pulp" paper that is made from the residue straw of agricultural crops. The residue is combined with post-consumer recycled paper to make high quality papers.
The advantages of using straw for making paper include:
- A large volume of fibre is available on an annual basis.
- Straw is easy to pre-process and has greater uniformity than wood.
- Chemical pulps can be produced from straw by relatively mild treatments.
- Straw fibres are easily accessible to bleaching chemicals.
- Straw requires only low energy mechanical treatment to produce fibres.
- Straws' thin-walled, low coarseness fibres are well suited for papermaking.
- Straw fibres have good printability and ink receptivity. The high hemicellulose and low lignin content should make straw pulps suitable for specific applications such as tissue- making or papermaking with enhanced fibre bonding.
- Paper – newsprint and office papers
- Medium density and particle boards
- Other building materials, including insulation and countertops