The U.S. Department of Energy and the National Renewable Energy Laboratory are developing technologies to produce hydrogen from renewable, sustainable sources. A cost goal of $2.00–$3.00 kg−1 of hydrogen has been identified as the range at which delivered hydrogen becomes cost competitive with gasoline for passenger vehicles. Electrolysis of water is a standard commercial technology for producing hydrogen. Using wind and solar resources to produce the electricity for the process creates a renewable system. Biomass-to-hydrogen processes, including gasification, pyrolysis, and fermentation, are less well-developed technologies. These processes offer the possibility of producing hydrogen from energy crops and from biomass materials such as forest residue and municipal sewage. Solar energy can be used to produce hydrogen from water and biomass by several conversion pathways. Concentrated solar energy can generate high temperatures at which thermochemical reactions can be used to split water. Photoelectrochemical water splitting and photobiology are long-term options for producing hydrogen from water using solar energy. All these technologies are in the development stage. Copyright © 2007 John Wiley & Sons, Ltd.

Renewable hydrogen production

Biomass gasification is a widely used thermochemical process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technology. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technology into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technological advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technology.

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An overview of advances in biomass gasification

A review was conducted on the use of thermochemical biomass gasification for producing biofuels, biopower and chemicals. The upstream processes for gasification are similar to other biomass processing methods. However, challenges remain in the gasification and downstream processing for viable commercial applications. The challenges with gasification are to understand the effects of operating conditions on gasification reactions for reliably predicting and optimizing the product compositions, and for obtaining maximal efficiencies. Product gases can be converted to biofuels and chemicals such as Fischer-Tropsch fuels, green gasoline, hydrogen, dimethyl ether, ethanol, methanol, and higher alcohols. Processes and challenges for these conversions are also summarized.

https://www.mdpi.com/1996-1073/2/3/556/pdf

Thermochemical biomass gasification—a review of the current status of the technology

Biomass gasification presents highly interesting possibilities for expanding the utilization of biomass as power generation using internal combustion engines or turbines. However, the need to reduce the tar in the producer gas is very important. The successful application of producer gas depends not only on the quantity of tar, but also on its properties and compositions, which is associated with the dew-point of tar components. Class 5, 4, and 2 tar become a major cause of condensation which can foul the engines and turbines. Hence, the selectivity of tar treatment method to remove or convert class 5, 4, and 2 tar is a challenge in producer gas utilization. This review was conducted to present the recent studies in tar treatment from biomass gasification. The new technologies with their strengths and the weaknesses in term of tar reduction are discussed.

Tar reduction in biomass producer gas via mechanical, catalytic and thermal methods: A review

Hydrogen production from steam gasification of biomass: Influence of process parameters on hydrogen yield – A review

Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier

Gas-solid flow in high-density circulating fluidized-bed risers differs significantly from that in conventional flow regimes, including fast fluidization and pneumatic conveying. It is shown that where there is no downward flux at the wall at high suspension densities, and hence no core/annulus structure, the flow corresponds to a dense suspension upflow regime. This flow regime is explained, and its key properties given. A lower boundary is also proposed for this new flow regime based on available data.

Situating the high‐density circulating fluidized bed

Compared with conventional fluidized beds, circulating fluidized beds have many advantages including better interfacial contacting and reduced backmixing (Lim et al, 1995) While there are many reports on the gas—solid circulating fluidized systems, liquid—solid and gas—liquid—solid circulating fluidized bed systems have been scantily studied However, extending current knowledge obtained in gas—solid systems to liquid—solids and gas—liquid—solid three-phase systems is shown to open new horizons for applications of circulating fluidized bed technology and expected to lead to the development of highly efficient liquid—solid and gas—liquid—solid reactors, especially for the ever growing field of biotechnology In order to fully appreciate the potential of those two types of liquid phase circulating fluidized beds, recent progress is reviewed in this article Their potential applications to biochemical processes are also discussed



Comparativement aux lits fluidises classiques, les lits fluidises circulants offrent de nombreux avantages, dont un meilleur contact interfacial et un retromelange reduit (Lim et al, 1995) Bien qu'un nombre important d'articles paraissent sur les systemes fluidises circulants gaz—solide, les systemes a lits fluidises circulants liquide—solide et gaz—liquide—solide ont fait l'objet de peu d'etudes On montre cependant que l'utilisation des connaissances actuelles sur les systemes gaz—solide pour les etendre aux systemes liquide—solides et aux systemes triphasiques gaz—liquide—solide ouvre de nouveaux horizons a l'application de la technologie du lit fluidise circulant et devrait permettre le developpement de reacteurs liquide—solide et gaz—liquide—solide hautement efficaces, en particulier pour le secteur de la biotechnologie toujours en croissance Afin d'apprecier pleinement le potentiel de ces deux types de lits fluidises circulants en phase liquide, les derniers progres en la matiere sont passes en revue dans cet article Leurs applications potentielles aux procedes biochimiques sont egalement examinees

(Gas-)liquid-solid circulating fluidized beds and their potential applications to bioreactor engineering

A modified langmuir model for the prediction of the effects of ionic strength on the equilibrium characteristics of protein adsorption onto ion exchange/affinity adsorbents

Jingxu Zhu

Papers

Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier

Situating the high‐density circulating fluidized bed

(Gas-)liquid-solid circulating fluidized beds and their potential applications to bioreactor engineering

A modified langmuir model for the prediction of the effects of ionic strength on the equilibrium characteristics of protein adsorption onto ion exchange/affinity adsorbents

Flow characteristics of the liquid–solid circulating fluidized bed