Non-wood plants as raw material for pulp and paper

Abstract

This study was begun in 1990 when there was a marked shortage of short fibre raw material for the pulp industry. During the last ten years the situation has changed little, and the shortage is still apparent. It was estimated that 0.5 to 1 million hectares of arable land would be set aside from cultivation in Finland during this period. An alternative to using hardwoods in printing papers is non-wood fibres from herbaceous field crops. The study aimed at determining the feasibility of using non-wood plants as raw material for the pulp and paper industry, and developing crop management methods for the selected species. The properties considered important for a fibre crop were high yielding ability, high pulping quality and good adaptation to the prevailing climatic conditions and possibilities for low cost production. A strategy and a process to identify, select and introduce a crop for domestic short fibre production is described in this thesis. The experimental part of the study consisted of screening plant species by analysing fibre and mineral content, evaluating crop management methods and varieties, resulting in description of an appropriate cropping system for large-scale fibre plant production. Of the 17 herbaceous plant species studied, monocotyledons were most suitable for pulping. They were productive and well adapted to Finnish climatic conditions. Of the monocots, reed canary grass (Phalaris arundinacea L.) and tall fescue (Festuca arundinacea Schreb.) were the most promising. These were chosen for further studies and were included in field experiments to determine the most suitable harvesting system and fertilizer application procedures for biomass production. Reed canary grass was favoured by delayed harvesting in spring when the moisture content of the crop stand was 10-15% of DM before production of new tillers. When sown in early spring, reed canary grass typically yielded 7-8 t ha-1 within three years on clay soil. The yield exceeded 10 t ha-1 on organic soil after the second harvest year. Spring harvesting was not suitable for tall fescue and resulted in only 37-54% of dry matter yields and in far fewer stems and panicles than harvested during the growing season. The economic optimum for fertilizer application rate for reed canary grass ranged from 50 to 100 kg N ha-1 when grown on clay soil and harvested in spring. On organic soil the fertilizer rates needed were lower. If tall fescue is used for raw material for paper, fertilizer application rates higher than 100 kg N ha-1 were not of any additional benefit. It was possible to decrease the mineral content of raw material by harvesting in spring, using moderate fertilizer application rates, removing leaf blades from the raw material and growing the crop on organic soil. The fibre content of the raw material increased the later the crop was harvested, being highest in spring. Removing leaf blades and using minimum fertilizer application rates in-creased the fibre content of biomass.;