Dear Mohammad

The benefit is the purpose of the process itself.

Gasification converts biomass into useful gases but into chemicals. It converts a potential biofuel (just talking about Biomass) into another. This process increases the heating value separating the fuel components from the non-fuel ones, removes sulfur and nitrogen, but oxygen increasing the energy density of the fuel. Compared to direct combustion, gasification drastically decreases the CO2, SO2, NOx and solid emissions in kg/MWh for electricity production, and it is more efficient.

Even for a low moisture biomass, HTL is extremely valuable since through it, a liquefaction of Biomass can be done, obtaining several liquid fuels for different applications, with higher energy density, heating value and easier to transport and storage than the feed biomass.

Therefore the selection of one thermochemical conversion process instead of another is a multifactorial subject related to: costs, energy efficiency, biomass characteristics, but in this case also the production of valuable fuels and chemicals which are not possible by direct combustion. HTL is a de-polymerization process used to convert biomass into a bio-oil, with several energy potential applications. This is impossible by direct combustion.

Do CV Test at different % of moisture content. you will understand its physical nature. and you will get your result with experimental proof.

For test procedure please flow grade test of coal.

Having been on the project side more than research side, I always have the question of a full energy balance and economic analysis for gasification and other fuel conversion technologies. That economic analysis needs to include operating and maintenance costs. Coal gasification never went mainstream in the US due to the sophistication of the process and attendant operating requirements. Similarly CCUS in the US (Petranova as example) has success only when subsidized. I continue to consider mass burn for municipal waste to energy an optimum technology application in many cases. This is when total cost is considered. I acknowledge this is somewhat off topic.

Unfortunately, we need more than heat and electricity for our daily life. Transport fuels and chemicals can be produced from biomass by other fuel conversion technologies than combustion, such as pyrolysis, gasification and hydrothermal liquefaction. Since the fossil fuels don't carry their full costs there is a need for subsidies. The other option is put the full cost on the fossil fuels through taxation but then all countries have to do it to not skew the competitive situation of companies. We see how likely that is, countries are not even able to sign and ratify CO2-reduction agreements such as the Paris Agreement. Therefore we have to live with subsidies of renewable energy for a while longer, wether you like it or not.

The correct answer to the question is far more complex than whatever has been set out by earlier respondents. Biomass with lower moisture content can be very varied in terms of shape, size, density and ash fraction. Solid like wood is one class, leafy like grass, another class, shell like (coconut, groundnut or wall nut shell) is a third class, fibrous with thin shell like - rice husk, rice straw, wheat straw, a fourth class. Each society across regions of the World has its own use for these or is treated as waste. The technical processes have also a variety. One can use air - gasification to get electricity via reciprocating engines or oxy-steam gasification to get synthesis gas (rich in hydrogen and carbon monoxide) to get liquid hydrocarbons. Of course, one can always subject the fuels (after some processing) to combustion. Of these, the least expensive process would be combustion and most expensive would be the process to get liquid fuels.The choice of the process depends on the demand of the local or global market and the ability of the "owner" or "company" to manage the whole range of issues in a non-so-stable political environment. Only a serious techno-economic evaluation in a specific situation in a country will reveal what would be the best. To illustrate this with a clear example from India - Over 30 years back, air-gasification of agro-bio-residues with distributed electricity generation (up to a MWe) was the most appropriate and economical. Once solar photovoltaic energy got its Governmental support, the gasification route was no longer sustainable. Liquid fuels via oxy-steam gasification was the next choice that could possibly become economical. However, the fluctuation oil prices with a free fall in the recent past (due to COVID 19) has long term effects and it is unlikely other approaches can be sustained on a commercial basis. This leaves only combustion route as being economical at this stage. This field has also its own issues of public perception and economic viability and has to struggle to make its presence felt.

This is the "short" answer to the question!

Hanasoge's response is concise and excellent. Thank you so much. I often consider balance points between different technologies. I can understand the optimum techno-economic solution. The issue in execution, and sustainable execution, is management. Preparation and training of staff is essential. One issue in the U.S. is the weakened market for recyclable materials, especially plastics. Reconstitution and reuse has sorting, transportation, and other cost hurdles.

Direct combustion is associated with fouling problems in the combustion chamber and boiler. The idea of HTL is to produce high heating value biooil with low ash content (with most of the minerals ash transferred to solid residue). Moreover, the solid also has significantly high HHV value in comparison to biomass.

Thanks Mukunda Sir for giving valuable information.