The use of steam pretreatment to enhance pellet durability and the enzyme-mediated hydrolysis of pellets to fermentable sugars.

Although densified wood pellets are an attractive biomass feedstock for bioenergy and biofuels production, partly due to their ease of transport, their friability and hygroscopic nature (attraction of moisture) have proven problematic in terms of storage and handling. Pre-steaming the biomass was shown to reduce the need for size reduction, significantly increasing pellet durability by relocating the plant cell wall lignin to the fibre surface and consequently enhancing binding between particles. Although steam pretreatment has been shown to facilitate enzyme-mediated hydrolysis of biomass, by increasing cellulose accessibility, drying and pelletization partially impeded enzymatic hydrolysis. However, the incorporation of alkaline deacetylation or neutral sulfonation step prior to pre-steaming was shown to mitigate many of the negative effects of drying. Although drying and pelletization did not significantly impact the redistribution of lignin, a mild mechanical refining step was shown to further enhance the hydrolysis of the cellulose component of the pelletized biomass.

Impact of forest harvest intensity and transportation distance on biomass delivered costs within sustainable forest management - A case study in southeastern Canada.

This study compares the delivered cost of forest biomass and its associated GHG emissions for three sizes of biorefinery including 50,000 m3 (small scale), 250,000 m3 (medium scale), and 700,000 m3 (large scale). The proposed methodology in this study includes harvest intensity which is often overlooked. The Pontiac region located in the Province of Quebec (Southeastern Canada) is used as a case study due to the availability of data in this forestry biomass rich region. Furthermore, there are significant similarities with other forestry regions to enable generalisation of the proposed case study. Harvest intensities of 423 harvest zones (cutblocks) are considered in cost and GHG emissions analysis of delivered biomass from each cutblock to the biorefinery. The results show that harvest intensities of cutblocks must be prioritized over conventional parameters such as transportation distance. The selection and prioritisation of cutblocks according to transportation distance without considering harvest intensities would result in an increase of about 12.5% in delivered costs of biomass for small and medium scale biorefineries. Results also reveal that the transportation distance would be a more significant parameter when using the same harvest intensity for all the selected cutblocks. Required logistics and harvesting equipment for three biorefinery sizes were also quantified. Sensitivity analysis shows that reduced productivity of harvest equipment by 20% could increase the delivered costs of biomass and GHG emissions by 10% for medium and large scale biorefineries and by 13% for a small scale biorefinery.

Potential yields and emission reductions of biojet fuels produced via hydrotreatment of biocrudes produced through direct thermochemical liquefaction.

BACKGROUND: The hydrotreatment of oleochemical/lipid feedstocks is currently the only technology that provides significant volumes (millions of litres per year) of "conventional" biojet/sustainable aviation fuels (SAF). However, if biojet fuels are to be produced in sustainably sourced volumes (billions of litres per year) at a price comparable with fossil jet fuel, biomass-derived "advanced" biojet fuels will be needed. Three direct thermochemical liquefaction technologies, fast pyrolysis, catalytic fast pyrolysis and hydrothermal liquefaction were assessed for their potential to produce "biocrudes" which were subsequently upgraded to drop-in biofuels by either dedicated hydrotreatment or co-processed hydrotreatment. RESULTS: A significant biojet fraction (between 20.8 and 36.6% of total upgraded fuel volume) was produced by all of the processes. When the fractions were assessed against general ASTM D7566 specifications they showed significant compliance, despite a lack of optimization in any of the process steps. When the life cycle analysis GHGenius model was used to assess the carbon intensity of the various products, significant emission reductions (up to 74%) could be achieved. CONCLUSIONS: It was apparent that the production of biojet fuels based on direct thermochemical liquefaction of biocrudes, followed by hydrotreating, has considerable potential.