• The growth of human population increases both the overall energy demand and the environmental footprint in the form of a massive production of waste. 

• Currently energy production and waste treatment are viewed as two separate issues. To change this perspective, the synergy of organic waste conversion and energy production should be developed.
• Various treatments (chemical, thermo-chemical, physical, and biological) can be applied to organic waste and other types of biomass. However, there is still a gap between their working principles and the required performance, robustness and scalability.  
• Hydro-thermal liquefaction (HTL) of organic matter has the potential to provide high conversion efficiency, a range of energy products, such as biocrude and biochar, the flexibility to adjust for different feedstocks and a versatile waste streams process, with simple control (through manipulation of temperature and residence time). . 
• Biomass conversion via Hydrothermal liquefaction pathway occurs generally between about 200 and 370 ℃, with pressures between about 4 and 20 MPa, which keeps the water in a liquid state, while changing the water properties to more reactive medium that functions as catalyst.
• This process produces several products, namely: biochar, biocrude, aqueous phase, and gas phase.

Fig. 1. Schematic of the process steps (yellow squares) and materials (green squares).

Highlights and Advantages
• Applicable for many types of biomass wastes.
• Can be integrated into existing processes or industries to utilize their waste streams.
• Eliminate the need to dry the biomass thus save highly energetic penalties.
• Improving energy security.
• The main energy products and their energetic contents are biocrude (up to 40 MJ/kg) and biochar (up to 35 MJ/kg), which are similar to petroleum and coal, respectively
Possible applications
• Converting agricultural bio-wastes from different industries (i.ie, beer industry, meat industry, sewage sludge, etc.) into biofuels for energy recovery.
• To incorporate the hydrothermal process with industries that have high emissions of residual heat to the environment. 
• Combining the Hydrothermal liquefaction technology with the wastewater treatment sector as a robust method to treat the primary sludge. Furthermore, this technology can cope with stable pollutants that can not be treated by the conventional biological treatment.
• This technology can be implemented in remote places, which require local system for treating the sewage and supplying energy.