**6. Conclusions**

Biomass is a sustainable source of energy. Natural biomass is bulky and usually has a high moisture content which complicates the direct use of biomass as a fuel. Biomass is a complex mixture of polymers consisting of three key elements carbon, oxygen and hydrogen. In addition, there are macronutrients, micronutrients, trace elements and other heavy metals. The three major components of LCB are cellulose, hemicellulose and lignin. Other compounds present in LCB include inorganic compounds and organic extractives. The components of biomass behave differently during thermochemical conversion.

The proximate and ultimate analysis is vital for describing biomass and thus product distribution. Thermochemical conversion is an increasingly feasible route to use biomass sources to fulfill energy needs. Designing effective thermochemical conversion systems that result in proper combinations of biomass feedstocks and conversion technologies is vital. It involves the design of efficient supply chains and conversion technologies suitable to manage variations in biomass properties. It needs to be cost-effective while minimizing harmful emissions and maintaining product quality.

Different thermochemical conversions of biomass are employed to yield varying amounts of gaseous, liquid and solid products of interest. Torrefaction aims to maximize the yield of solid product, torrefied biomass. It is performed at longer residence time, slow heating rates and low temperatures (<300°C). The improved properties of torrefied biomass include increased energy density, hydrophobicity, grindability and reduced biodegradability compared to the initial biomass feed, thus, allowing cheaper transport, handling and processing of the torrefied biomass. Torrefied biomass has a higher O/C ratio than biochar. Biochar is the desired product in slow pyrolysis, and yield is maximized by conversion at longer residence time, slow heating rates, and moderate temperatures. Biochar applications include use as a soil amendment, as an adsorbent or as fuel in power generation. In fast pyrolysis, bio-oil is the desired product and yield is maximized by conversion at short vapor residence times, high heating rates and around 500°C. The gap between biomass feedstock and a usable product can be bridged by incorporating additional processes such as drying and grinding of biomass feed, palletization or briquetting of biomass feed and/or product and mineral leaching of products to treat high ash content. These additional processes have cost implications.

High moisture content is a major barrier in biomass handling and processing. Moisture content has a significant impact on the biomass conversion process. The main problem with the pyrolysis of high moisture biomass is that it requires a large amount of energy to evaporate moisture. Hydrothermal processing is a useful processing technique for biomass feedstocks with high moisture as it does not require the drying and/or dewatering processes, thereby reducing the operating costs.
