Life cycle assessment of biosyngas from a multifunctional biomass gasification plant in Sweden
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Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Programme
Model builders
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Abstract
The need to increase the use of renewable energy to meet the growing energy demand and
minimize the reliance on fossil fuels is evident. One renewable technology option is bioenergy
due to its availability and resemblance to fossil energy carriers. This study aimed to investigate
the environmental impacts of a biomass gasification plant by conducting a life cycle assessment
(LCA) from cradle to grave, including multiple impact categories and comparing the results to
fossil alternatives.
An LCA of Meva Energy´s gasification technology that produces biosyngas was conducted
with three allocation scenarios. The scenarios consider mass allocation, energy allocation, as
well as one scenario where all environmental impact was allocated to the biosyngas production
and the carbon sequestration effect of the produced biochar was included.
The gasification system was divided into five sections: (i) the production of the plant
components phase, (ii) the construction phase, (iii) the gasification phase, (iv) the use phase
and (v) the end-of-life phase. The results showed that the gasification phase and use phase are
the primary contributors to all impact categories, while the production of plant components
phase, construction phase and end-of-life phase were shown to have negligible impacts. In
terms of climate change, the biomass feedstock (wood pellets) in the gasification phase had the
largest impact. The total results regarding climate change of the life cycle varied notably
depending on the allocation approach applied, with a range from about 23 g CO2-eq/kWh for
the mass allocation scenario to -6 g CO2-eq/kWh for the carbon sequestration scenario.
Furthermore, the results varied also based on secondary material allocation and the
classification of products as either waste or by-products. For example, when the sawdust used
to produce wood pellets was treated as a waste stream and the emissions started upon the
collection of the sawdust, the environmental impact was reduced. Moreover, considering the
produced tar as a by-product rather than a waste stream had a lower but notable influence on
the results, especially in the energy allocation scenario.
The findings of this study highlight that energy produced by Meva Energy’s gasification
technology can contribute to a climate positive impact, assuming that the application of the
biochar equates a negative emission. The study also shows that the thermal energy produced by
this gasification of biomass has lower climate-change impacts than the fossil alternative (liquid
petroleum gas).
Description
Keywords
Biochar, Biosyngas, Gasification, Life cycle assessment (LCA), Climate change