Dynamic simulation of straw harvesting systems: Influence of climatic, geographical and biological factors on performance and costs

In this study, a dynamic simulation model, called Straw Handling Model (SHAM), was used to analyse the influence of various climatic, geographical and biological factors on performance and costs for delivering the fuel straw to district heating plants in Sweden. The simulations showed that the following factors were important and should be considered when designing more cost-effective handling systems and when locating new heating plants: frequency and duration of precipitation, potential evapotranspiration and equilibrium moisture content which, in turn, are dependent on temperature, relative humidity, radiation and wind speed; held size, fraction of land area with harvestable straw and transport distances between stores and heating plant; ability of straw to release external moisture (i.e, rain), straw yield per hectare, and starting time and duration of the combining season. Harvest of straw at three locations, i.e. Svalov, Vara and Enkoping, was also simulated in order to find the reasons for the more unfavourable performance and costs at the two later locations. The simulations showed, for example, that longer transport distances and lower straw yields per hectare were the main causes for higher costs at Vara and Enkoping. (C) 2000 Silsoe Research Institute.