Fiber- och energigrödor som råvara till produktion av dissolvingcellulosa och biprodukter

This pilot study had the aim of indentifying a number of crops that can be interesting as raw material for production of special cellulose and bioenergy i northern Sweden. Based on a literature study it aimed at presenting which aspects of these crops relevant for this purpose where investigated earlier. Based on potential yield levels for both fibre and biomass, five crops have been chosen for a more detailed literature study. These crops are reed canary grass, tall fescue, meadow fescue, timothy and hemp. For each crop it was investigated which harvest dates can be relevant and how these affect biomass quality. A number of pre-treatment processes have been listed that potentially can improve economics of transport and fibre yield and can reduce problems related to the pulping process. Co-cultivation of the grasses tall fescue, meadow fescue and timothy as sole crops or in a ley crop mix with nitrogen-fixing legume crops can decrease fertilization costs and therefore improve economics. Co-cultivation can potentially lead to more stable biomass yields, men should be proved in field trials. The five crops studied in more detail display yields of fibre, pulp and biomass, respectively, which are equal or higher compared to birch, which is the source of fibres these agricultural crops can potentially replace. There is no obvious logistic chain for harvest, transport and storage of these five crops. However, this study shows options for these logistics that are relevant, but need testing in reality. The potential pulp respectively fibre quality has been investigated to a very limited extent with help of some indicators such as ash respectively silicon content and fibre length. The results show a need for a recycling process for pulping chemicals that is adjusted to higher mineral contents than in birch. Alternatively, one or several pre-treatment steps could improve the raw material´s chemical composition. A number of pre-treatment processes are presented in this report. Furthermore, the fraction of fines in pulps made of these five crops will be higher than usual, i.e. for birch. This indicates a need to adjust the process respectively a need to pre-treat the fibre raw materials. Since some pre-treatment methods tend to decrease problems in connection with high fines fractions and high mineral content both, the proportion of the effect needs to be investigated further. Production of bioenergy from by-products of the fibre production process has been investigated and a number of different potential sources of by-products are presented. The most promising by-products for e.g. ethanol production originate from fractionation processes and from the pulping process. Since experiences of agricultural crops in a sulphite pulping process are limited, it is unclear how large ethanol yields may be. It is therefore advised to investigate the composition of monomeric sugars in the different biomass fractions.