Bioenergy will be one component of a suite of alternatives to fossil fuels. Effective conversion of biomass to energy will require the careful pairing of advanced conversion technologies with biomass feedstocks optimized for the purpose. Lignocellulosic biomass can be converted to useful energy products via two distinct pathways: enzymatic or thermochemical conversion. The thermochemical pathways are reviewed and potential biotechnology or breeding targets to improve feedstocks for pyrolysis, gasification, and combustion are identified. Biomass traits influencing the effectiveness of the thermochemical process (cell wall composition, mineral and moisture content) differ from those important for enzymatic conversion and so properties are discussed in the language of biologists (biochemical analysis) as well as that of engineers (proximate and ultimate analysis). We discuss the genetic control, potential environmental influence, and consequences of modification of these traits. Improving feedstocks for thermochemical conversion can be accomplished by the optimization of lignin levels, and the reduction of ash and moisture content. We suggest that ultimate analysis and associated properties such as H:C, O:C, and heating value might be more amenable than traditional biochemical analysis to the high-throughput necessary for the phenotyping of large plant populations. Expanding our knowledge of these biomass traits will play a critical role in the utilization of biomass for energy production globally, and add to our understanding of how plants tailor their composition with their environment.

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Biomass for thermochemical conversion: targets and challenges.

The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might be anticipated that neoteric solvent systems (e.g., ionic liquids) will remain niche, while renewable routes to historically established solvents will continue to grow in importance. This review discusses bio-based solvents from the perspective of their production, identifying suitable feedstocks, platform molecules, and relevant product streams for the sustainable manufacturing of conventional solvents.

Opportunities for Bio-Based Solvents Created as Petrochemical and Fuel Products Transition towards Renewable Resources

Non-woody biomass, having a lower lignin content than woody materials, is a common waste material found in agricultural processing plants and fields. Non-woody biomass is often bulky and has a comparatively low energy content. However, non-woody materials sourced from agricultural waste are abundant and cheap. Experimental studies into gasification of non-woody biomass have been conducted by various researchers. This paper reviews feedstock characteristics, pre-treatments, gasification methods, and future directions of this technology. Due to the heterogeneous nature of non-woody biomass, it is critical to apply suitable pre-treatments prior to gasification. Combining non-woody biomass with a small percentage of high grade carbon sourced from biochar or coal into fuel pellets for co-gasification has the potential to improve fuel quality. Synergistic effects of non-woody biomass-coal/charcoal co-gasification can also reduce tar formation and increase the occurrence of mineral based catalytic reactions. Factors influencing these effects are often complex and require further investigation. 15–20% of the energy content of fuel pellets may be needed to power the biomass pre-treatment process. The gasification of pelletised non-woody waste provides an attractive alternative fuel source to achieve agricultural energy self-sufficiency and off-grid operation.

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Gasification of non-woody biomass: A literature review

Advances in the thermo-chemical production of hydrogen from biomass and residual wastes: Summary of recent techno-economic analyses.

Co-gasification of coal and biomass is emerging as potential clean fuel technology to achieve high thermodynamic efficiency with relatively low CO 2 emission. The coal and biomass have been exclusively gasified more than a century to obtain gas–liquid fuels and the production of chemicals. Co-gasification has higher efficiency than the solitary coal gasification because the cellulose, hemicellulose and lignin content of biomass help to ignite and enhance the rate of gasification. It is suggested that the extensive research on carbon reactivity pattern, heat release, reaction kinetics, etc. may support to reduce the uncertainties in the co-gasification performance of coal and biomass blends, particularly in India. The prospects of co-gasification technology in Indian context have been discussed considering the abundance of varieties of coal and biomass. The suitability of existing gasifier procedures and their limitations with operating parameters like temperature, residence time, density optimisation, feed rate, agglomeration intensity, the tar formation and techno-economics involved are described. Also, this paper reviews the research highlights of the history of co-gasification and the advancement in upcoming challenges like a design of gasifier, access and preparation of biomass, disposal of residue, environmental concerns and reassurance to the operators for execution of large and small-scale projects.

Co-gasification of coal and biomass an emerging clean energy technology: Status and prospects of development in Indian context

Recently, there has been significant research interest in cogasification of coal and various types of biomass blends to improve biomass gasification by reducing the tar content in the product gas. In addition, ash present in biomass catalyzes the gasification of coal. However, due to the fibrous nature of biomass and the large difference in gasification temperature of coal and biomass, cogasification in existing systems presents technical challenges. This paper documents research studies conducted on the cogasification of various types of coal and biomass using different types of gasifiers under various sets of operating conditions. In addition, the influence of cogasification on upstream and downstream processing is presented.

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S. Kumar

Papers

Cogasification of Coal and Biomass: A Review