Independent thesis Advanced level (professional degree), 20 credits / 30 HE credits
Each year, the coffee machines at Ericsson in Kista produce around 100 tons of ground coffee waste.
The companies Coor Service Management, Löfbergs Lila and Selecta are all responsible for different
stages in the logistical chain in delivering coffee and, together with Ericsson, they want to increase
their environmental benefit. The plan is to produce biogas through anaerobic digestion instead of
incinerating the coffee waste in a heating plant. The results are to be presented as different business
cases in which different biogas plants are compared with the reference case (heating plant),
comparing costs and environmental impacts.
There are two major environmental benefits from producing biogas; reduced carbon dioxide
emissions from when fossile fule is replaced by carbon neutral biogas, and reduced emissions from
returning digestate from the bio reactor to farmland instead of using industrial fertelizer.
In order to determine the biogas potential in coffee waste, a couple of properties had to be
determined in a laboratory. Properties such as the dry substance content, heating value, moisture
content and ash content. The results show that 100 tons coffee waste could produce around 16 500
Nm3 biogas which would contain 163 MWh.
The biogas reactor and upgrade plant both need energy gas to function and uses around 14 MWh of
the produced gas. In the end, the resulting upgraded biogas contains 149 MWh energy. Such an
amount of gas can replace 15,1 m3 of diesel and thus reduce carbon dioxide emissions by 39,4 ton.
The emissions from running the reactor and upgrade plant, combined with methane leakage
amounts to 4,8 ton carbon dioxide.
All of the biogas plants that were examined returns digestate and nutrients to farmlands which
reduces the need for industrial fertelizer. The production of fertelizer uses alot of energy, and by
returning digestate a reduction of 58 GJ energy and 3 ton CO2 can be achieved. This is not the case
with the heat plant which instead has to place some of its produced ashes in landfills.
If the exergy content in the biogas is compared to that of the heat it shows that there is a point to
making gas instead of incinerating the waste. The biogas has about 50 % higher exergy content than
the heat has and therefore it is possible to utilize the substrate more efficiently.
Transporting coffee waste from Ericsson to different biogas plants will result in increased carbon
dioxide emissions. The three plants investigated in this thesis are Henriksdals sewage treatment
plant, the Himmerfjärd plant and Uppsala biogas plant. For each plant, drivning distance, pre
treatment requirements of the coffee waste, and related costs were determined. Using methods
from the Network for transportation and enviroment, the emissions for each case were calculated.
The results show that the Henriksdal case will increase carbon dioxide emissions by two tons per
year, and the other cases will increase emissions by four tons.
The result from combining laboratory work, simulations and calculations show that the case where
Henriksdal recives the coffee waste will reduce carbon dioxide emissions by 15,1 ton at a cost of
72 000 kr per year. The case with the Himmerfjärd plant will reduce emissions by 13,8 ton at a cost of
74 000 kr per year. The final case with Uppsala biogas plant will reduce emissions by 13,7 ton at the
cost of 107 000 kr per year. And thus there are environmental benefits from producing biogas from
the coffee waste, but they do come at a cost.
2013. , 44 p.
Kaffesump, biogas, förbränning, transporter, koldioxidutsläpp, ekonomiska kostnader