The graphs show the contents of oxygen, hydrogen and carbon in HTL-oil before and after upgrading, compared to other fuel types. Credit: Mørup et al., Energy & Fuels, 2012, 26 (9), 5944-5953

Hydrothermal liquefaction—most promising path to sustainable bio-oil production

February 6, 2013

A new generation of the HTL process can convert all kinds of biomasses to crude bio-oil, which is sufficiently similar to fossil crude oil that a simple thermal upgrade and existing refinery technology can be employed to subsequently obtain all the liquid fuels we know today. What is more, the HTL process only consumes approximately 10-15 percent of the energy in the feedstock biomass, yielding an energy efficiency of 85-90 percent.

To emphasize, the HTL process accepts all biomasses from modern society – sewage sludge, manure, wood, compost and plant material along with waste from households, meat factories, dairy production and similar industries.

It is by far the most feedstock flexible of any liquid fuel producing process, including pyrolysis, bio-ethanol, gasification with Fischer-Tropsch or catalytic upgrading of different vegetable or agro-industrial residual oils, and does not carry higher costs than these.

Hydrothermal liquefaction is basically pressure cooking, but instead of cooking the biomass in batches, one pot-full at a time, this new generation of HTL is based on flow production, where the biomass is injected into a 400 °C pre-heated reactor, “cooked” under high pressure for ~15 minutes and then quickly cooled down to 70°C.

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