Dimensionering av industrilager för biobränsle

Sammanfattning: The aim of this study was to develop a simple model for calculating stock costs for bio fuel at Billerud Karlsborg and subsequently recommending a suitable stock level of bio fuel. The stock components considered in the model are GROT (branches and tops), bark, dry wood chips, raw wood chips from barking and sawdust. The calculations are based on a probability distribution of historical deviations between ordered and delivered volumes. The model presents two different ways to manage the supply in case of irregular deliveries. The first way is to stock enough volume to cover the deviations and the second way is to compensate with a quick purchase from the spot market (at extra high purchase prices). In some situations the best solution might be a combination of these two alternatives. The stock model is used to support such decisions concerning dimensioning of stock levels. The model has a number of limitations. Firstly it only deals with delivery deficits and assumes that all delivery surpluses are stopped. Secondly it does not deal with variations in the consumption of the bio fuel burner. Key variables used in the calculations are delivery precision, purchase prices and stock costs (where stock costs include handling costs, capital costs and loss due to decomposition). The results of this study recommend a reduction from today's level of bio fuel stocks. The model suggests a stock level that avoids any extra purchases from the spot market. At present there is insufficient stock space for large stocks near the bio fuel burner, which brings up the need for an intermediate stock and therefore extra handling. When extra handling is required the model shows considerably increased costs and therefore the model proposes avoiding high stock levels. The stock levels proposed by the model are between 2450 and 8000MWh.