(424b) Hydrothermal Upgrading of Algae Paste in a Continuous Plug Flow Reactor

Increasing global demand for energy, food and chemicals is causing unprecedented damage to the ecosystem and changing global climate. The long term repercussion of these is undesirable and a sustainable approach towards their production is necessary [1]. A potential solution comes in the form of biomass. Biomass is considered the oldest source of energy, food and chemicals that has the potential to be carbon neutral if processed appropriately.

Biomass, such as algae is particularly interesting as a processing feedstock due to its high productivity, environmental resilience and lack of lignin. The potential of an integrated algal biorefinery for multiple product manufacturing is a huge driver behind investigating environmentally appealing processing option. Hydrothermal processing technology provides a green route for conversion of macromolecules to fuel like biocrude using wet algae, thus negating drying costs [2].

From our previous algal Hydrothermal Liquefaction investigation [3] using batch reactors, we found that conversion of biomass to oil and functional group transformation of ³¹P-NMR observed OH bound moieties takes place at low residence times. Thus, longer reaction times do not necessarily improve oil quality and the majority of molecular conversion takes place within few minutes[4].

Therefore to investigate further, in this work we present the utilisation of a quartz lined continuous plug flow reactor to convert wet algae suspension to biocrude under hydrothermal conditions with cyclohexane as co-solvent. Neat algae paste and reactive extraction using cyclohexane is investigated at various temperatures (300-380°C) and short residence times (<5 minutes). The produced biocrude is analysed using SIMDIS, FT-IR, elemental  CHN(O), GC-MS and SEC to characterise the oil and gain further insight into sufficient processing conditions. Based on reaction ordinate, we observe that significant proportion of gas is produced under severe conditions and the aqueous phase contains over 50% mass at short residence time. The catalytic upgrading of produced biocrude will also be touched upon.

[1] Mitigation, C. C. (2011)., IPCC special report on renewable energy sources and climate change mitigation.

[2]  Patel, B., Tamburic, B., Zemichael, F. W., Dechatiwongse, P., Hellgardt, K. (2012). Algal Biofuels: A Credible Prospective?. ISRN Renewable Energy, Vol. 2012, Article ID 631574.

[3] Patel B., Richard C., Hellgardt K., Supercritical Upgrading of Algae Paste[abstract]. In: AIChE 2012 Annual Meetings; 2012  Oct 28 – Nov 2; Pittsburgh. Pennsylvania.

[4] Patel, B., & Hellgardt, K. (2013). Hydrothermal upgrading of algae paste: Application of 31P‐NMR. Environmental Progress & Sustainable Energy, 32(4), 1002-1012.