Biochar and the district heating system: An investigation of how a district heating system may benefit from the implementation of a biochar production plant
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Typ
Examensarbete för masterexamen
Program
Sustainable energy systems (MPSES), MSc
Publicerad
2021
Författare
Nilsson, Fanny
Rosén, Sofia
Modellbyggare
Tidskriftstitel
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Sammanfattning
In 2017, Sweden established a long-term climate goal of being CO2
-neutral by 2045 [1]. In
order to reach this goal, 15% reduction of the CO2
can be constituted of complementing
measures, such as bioenergy carbon capture and storage (BECCS) and biochar. In line
with the climate goal of Sweden, Göteborg Energi has set a goal of having a 100% renew able and recycled district heating system (DHS) by 2025. Biochar is one of the possible
technologies that could contribute in reaching this goal.
The DHS in Gothenburg was modelled through a Linear Programming (LP) model in
the software General Algebraic Modeling System (GAMS). A yearly biochar demand of
35,750 MWh, approximately 5500 tonne, was implemented. The model invested in the
most suitable capacity for the biochar plant to fulfill the demand while keeping the yearly
cost of the system as low as possible. Apart from producing biochar, the plant produce
excess heat. In the model, the plant could choose to sacrifice biochar to only produce heat,
providing some extra flexibility to the DHS. To investigate the robustness of the results
the following parameters were evaluated in different scenarios: biochar demand, discount
rate, variable cost, feedstock price, biochar price and reduction in investment cost.
The primary results showed no utilisation of flexibility and the capacity of the plant
was instead decided by the biochar demand. The excess heat acted as a base load in
the DHS during winter and the load of the plant was used to cover fluctuations in heat
demand during summer. Flexibility was, however, initiated in four out of six scenarios.
At low feedstock prices around 50-110 SEK/MWh, the production of extra heat amounted
to approximately 9400 and 1000 MWh respectively. Further, a price of biochar have a
significant impact on the investment of the biochar plant as increased prices shift the
driving parameter from demand to generating an income to the DHS.
With suitable economic parameters, a biochar plant could offer both carbon negative DH
as well as an energy buffer to the DHS. As flexibility is initiated between biochar and heat,
the biochar plant becomes more of a intermediate load than a base load. There is still a
scarcity in research regarding the technical possibilities of shifting from biochar to heat
production, thus, more research is needed within this area.
Beskrivning
Ämne/nyckelord
biochar , carbon sequestration , district heating , energy system modelling , linear programming , pyrolysis , biomass