Epsilon Archive for Student Projects

Abstract

Svensk Växtkraft is the owner of the biogas plant in Västerås. The company is planning to increase
their treatment capacity at their biogas plant. In connection to this work it is also possible to make
some energy saving changes to the biogas plant. The objective of this study was therefore to make
an electricity and heat survey of the biogas plant, a detailed study of the heat consumption in the
sanitation step and also a comparison of energy consumption with the present sanitation method
and an alternative strategy where the waste is treated in 55 °C during 10 hours (the current method
is heating to 70 °C during 1 hour).
The energy survey was conducted in close collaboration with staff at the biogas plant. The current
during normal operation was measured, power was calculated and multiplied by the time of usage to
obtain the energy consumed. This was performed for each of the larger energy consuming
components on the plant. To make the energy comparison of sanitation methods a model of the
sanitation step was built. The model describes the largest sources of heat loss in the current
sanitation step and estimates how they would change if the sanitation method changes.
During one day of normal operation conditions the biogas plant in Västerås consume 64 kWh
electricity per ton feedstock received and 97 kWh heat per ton feedstock received. The largest
energy consuming components are estimated to use about 80 % of the total electricity at the plant.
The sanitation step is the only large heat consuming step in the production.
Modeling of the sanitation step and comparison of sanitation methods showed that it was possible to
reduce heat consumption by 44 % when changing sanitation method to 55 °C during 10 hours. This
result is based on a 90 % heat recovery.