|CERES No. 135 (FAO Ceres, 1992, 50 p.)|
A new guar gum substitute derived from ipil-ipil (Leucaena leucocephala) seeds could cut paper-manufacturing costs by as much as 30 per cent in some developing countries, according to researchers in the Philippines.
The guar substitute, formulated by researchers at the Forest Products Research and Development Institute in Los Banos, has aroused the interest of paper manufacturers, who normally import the gums used in production. Use of Leucaena leucocephala, a well-known agroforestly tree species grown widely in the tropics, would provide a locally-grown, economical replacement for the expensive chemical imports. According to an institute spokesman, Philippine imports of gumbased additives for the paper industry, food products and cosmetics averaged 5 500 tons per year between 1985 and 1987, representing US$2.8 million.
Gum additives are mixed with paper pulp at various stages of the paper-making process, and are used as sizing agents, fillers, strengthening agents, pigments, defoamers, slimicides, surfactants, dispersants and pitch control agents.
Three varieties analysed
Workers at the institute have analysed the chemical composition of three varieties of ipil-ipil seed, including the K-28 variety of the El Salvador group and the K-6 and K-8 varieties from Peru and Mexico, respectively. The K-28 is one of the so-called "Hawaii giants", said to have been introduced in the Philippines some 12 years ago to provide shade for coffee plants.
The finely-ground seeds of the three varieties produced two forms of gum additive - extract and powder - for paper. Experiments showed that additive levels of 0.2 to 0.4 per cent of powder imparted considerable strength to unbleached kraft pulp, kraft cuttings and sugar cane bagasse hand-sheets (cellulose-rich sugar cane residues after crushing).
Based on the absolute dry weight of the pulp, the addition of 0.5 per cent aqueous crude gum extract obtained from giant K-28 seeds greatly increased the dry-tensile strength of the pure bagasse and lauan pulp hand-sheets. Ipil-ipil gum costs roughly US$1.00 per unit, compared to approximately US$1.50 for imported guar gum. It also saves on fibres and fillers and results in clearer waste water.
Researchers believe a paper mill that produces 100 tons per day of dry strengthened paper using 400 kilograms of ipil-ipil gum could save approximately 600 000 pesos (US$30 000) when operating on a 300-day working year.
L. Ieucocephala is known to agroforesters as an MPT (multi-purpose tree) species (Ceres No. 133). Its wood is used for construction, fuelwood and charcoal, its leaves as an animal fodder and its cooked fruit as a food for humans. Being a leguminous, or nitrogen-fixing species, the ipil-ipil also has a beneficial effect on soils.