Life cycle assessment of different uses of circulating fluidized bed gasification’s end products

Life cycle assessment (LCA) is a methodology and tool which is continuously gaining attention as it can help evaluate products and services, and identify possible improvements.  LCA has become very popular the last decade because its results can be presented and understood from decision-makers people with a moderate technical background.

On the other hand, gasification of biomass is a thermochemical method which converts biomass into a gas, which can be either combusted in a CHP unit, upgraded to biofuels or processed regarding production of chemicals. The reactors used for gasification of biomass vary depending on the process parameters and the feedstock. However, two of the most frequently used reactors are fixed beds and fluidized beds. Circulating fluidized bed gasification is an established technology already, which is most promising concerning middle-scale applications.  

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The main practice is to pretreat biomass in order to transport it and/or process it afterwards. That said, the main pretreatment method so far is pelletisation. Pelletisation is a technology where biomass is densified in order to improve the calorific value of the biofuel, and to improve logistics and handling. However, novel technologies, such as torrefaction combined with pelletisation, are developing and gain interest. Torrefaction is a promising pretreatment technology of biomass that has gained attention nowadays. Torrefaction has the potential of attaining a major impact on the commodification of biomass. Its considered added value is the production of a more coal-alike solid biofuel with higher energy density and better physical and combustion properties and which consumes substantially less energy when pelletized than fresh biomass. Additionally, when torrefaction and pelletisation are combined, the logistics costs are reduced and the entire supply becomes safer. In The Netherlands there are already a couple of torrefaction plants operating on a commercial market level.

TU Delft is collaborating in two projects; a European project called “Brisk”, in which other universities and research centers are involved, and a national TKI project called “Invent”, in which ECN, Twente University and Dutch torrefaction industries are involved. The “Brisk” project is investigating the improvement of gasification practices and biomass characterization. Whereas, the “Invent” project is focused on investigation and improvement of torrefaction technologies. Therefore, the selected gasification’s feedstock for this MSc graduation project will be straw, miscanthus, wood pellets and torrefied wood pellets.  

In this MSc. graduation project the aim is to investigate which end use of the gasification’s product gas offers more environmental benefits. Main research questions are:

  • Which end-use offers more benefits from an environmental point of view?
  • Which are the stages of the supply chain that can be improved and influence the LCA results significantly?
  • Are there any bottlenecks in the supply chains?

The MSc. Graduation topic will include modelling via an LCA software. The LCA boundaries will be cradle-to-grave; i.e. from the production of the fresh biomass, until the utilisation of the product gas and its waste.