Biomass is a significant non-conventional energy reserve, which has been considered as a promising alternative over other renewable sources such as solar, wind or hydroelectric storage due to its comparatively ample availability. A variety of biomass types can be converted into useful products via bioenergy technologies. The deep understanding and knowledge of these processes are necessary for optimization and advancement in a cost-effective way. A comprehensive comparison and discussion is conducted with respect to biochemical and thermochemical conversion technology such as microbic digestion and fermentation, pyrolysis, liquefaction and gasification. Pyrolysis is the process of converting biomass into bio oil, charcoal and gaseous factions by heating anaerobically to above 500°C. Liquefaction is a low temperature (LT) and high-pressure thermochemical process to produce marketable liquid over suitable catalysts under hydrogen or reductive environment. Gasification is the conversion of biomass into preferred combustible gas mixture (syngas) via the partial oxidation at high temperature, typically in the range of 800–900°C. The product gas is more versatile and can be burned in gas turbine for electricity production or synthesis of high-value chemicals. The parametric impact, mechanism, development status and future direction have been summarized for each of these technologies with the aim to pave the way for optimization of future investigation.
Part of the book: Biomass Volume Estimation and Valorization for Energy
The upgrading of unconventional oil using methane, the principal component of natural gas, is a promising alternative method to the conventional hydrotreating process, which consumes naturally unavailable H2 at high pressures. Methanotreating is an economically attractive process with abundant and readily available raw materials to accomplish the upgrading of bio-oil and to attain improved oil quality. The application of methane as the H donor avoids the energy consumption and CO2 rejection during the reforming of methane to produce H2. More product oil is also obtained through the incorporation of methane into the product oil. Ag/ZSM-5, Zn/ZSM-5 and Ag-Zn/ZSM-5 have been employed to upgrade bio-oil under methane environment to achieve increased oil yield and H/C molar ratio, suppressed total acid number and unsaturation degree of the product oil. Ag-Zn/ZSM-5 is used to catalyze the methanotreating of heavy oil to attain lower viscosity accompanied with good stability and compatibility, which are critical for the pipeline transportation of heavy oil to downstream refineries. Higher gasoline and diesel fractions, increased H/C molar ratio, lower total acid number are witnessed upon the upgrading in the presence of Ag-Zn/ZSM-5 under methane environment. The mechanism studies practiced in the literature using methods including solid-state NMR and FTIR have revealed at least two reaction pathways, i.e., carbenium pathway and alkyl pathway, to accomplish the activation of methane, which is crucial for the involvement of methane in the following upgrading reaction steps. The reaction thermodynamics and reaction intermediates have also been explored by computational approaches by researchers. These observations and achievements will encourage more researchers to develop more catalyst systems and attain improved catalytic performance in the unconventional oil upgrading using natural gas.
Part of the book: Advances in Natural Gas Emerging Technologies