In order for hydrothermal liquefaction to work, which of the following are necessary?

A. High pressure and no oxygen

B. High temperatures and high oxygen

C. High temperatures and low oxygen

D. High temperatures and high pressure

Answer: The correct answer is D.

Explanation:

The hydrothermal liquefaction is a process where almost any kind of biomass can be converted into biooil for biocombustible purposes. During this process, the biomass in the presence of hot compressed water is converted into a liquid biocrude, this means that conditions like high temperatures (200 - 350°C) and high pressure (15 - 20 MPa) are needed for the reaction.

Therefore, the correct answer is D.