Evaluation of Torrefied Bamboo for Sustainable Bioenergy Production

Bamboo is a potential sustainable biomass source for renewable heat and power production. Bamboo presents common fuel characteristics with other biomass feedstocks regarding heating value and chemical composition. Up to date, there are no studies on fuel properties of the bamboo specie Guadua angustifolia. Bamboo is a difficult fuel and most thermal conversion processes have stringent fuel specifications, which are challenging to fulfil with biomass streams. Bamboo is tenacious and fibrous which makes it difficult and expensive to grind. Furthermore, the characteristics with regard to handling, storage and degradability are not favourable for biomass in general. The thermal pre-treatment torrefaction is a promising upgrading technology that can enhance the fuel quality by addressing these issues. During torrefaction, biomass is heated to 250-320°C in the absence of oxygen. At the end of the process the material is milled and compressed into pellets. In this way, the biomass becomes easy to grind, more hydrophobic and has a high energy density. Alternatively, wet torrefaction (Torwash) allows for combined torrefaction and washing of the feedstock. Wet torrefaction, a form of hydro-thermal treatment, in addition to dry torrefaction removes salts and minerals from biomass, improving even more the quality of the product. This is in particular interesting for feedstock containing significant amounts of undesirable alkali components for combustion or gasification, as is the case of bamboo. This paper presents an evaluation of the use of Guadua angustifolia as a fuel for heat and power applications. The results of biomass fuel properties and characteristics and quality improvement via dry and wet torrefaction are assessed. Torrefaction clearly shows the improvement of fuel properties and grindability of biomass. Wet-torrefied Guadua angustifolia is chemically an attractive fuel, with favourable fuel properties, e.g. the results showed a 98% of alkali removal, and the production of a grindable solid fuel.