Gasification technology has been investigated to effectively and economically convert low-value and highly distributed solid biomass to a uniform gaseous mixture mainly including hydrogen (H 2 ), carbon monoxide (CO), methane (CH 4 ) and carbon dioxide (CO 2 ). This gaseous mixture can be further used as an industrial feedstock for heat and power generation, H 2 production and synthesis of liquid fuels. Significant advances have been made in the technology of biomass gasification and syngas utilization. This review was conducted to introduce the recent advances in biomass gasification and syngas utilization. The critical technical issues and perspectives of biomass gasification were discussed.

https://ncesr.unl.edu/wordpress/wp-content/uploads/2010/08/Wang-Contemporary-issues-in-thermal-gasifiction.pdf

Contemporary issues in thermal gasification of biomass and its application to electricity and fuel production.

For well over one hundred years, researchers around the world have pursued ways to make ethanol from biomass such as wood, grasses, and waste materials. To distinguish it from ethanol made from starch and sugars in traditional agricultural crops, we refer to ethanol made from biomass as "bioethanol." The effort to develop bioethanol technology gained significant momentum in the late 1970s as a result of the energy crises that occurred in that decade. This article briefly reviews the broader history of bioethanol technology development. With this as a background, we focus our attention on the strategic thinking behind the U.S. Department of Energy's Bioethanol Program, which envisions remarkable advances in cellulase enzyme research and as the basis for significant future process cost reductions.

Enzymes, Energy, and the Environment: A Strategic Perspective on the U.S. Department of Energy's Research and Development Activities for Bioethanol

The use of gas fermentation for the production of low carbon biofuels such as ethanol or butanol from lignocellulosic biomass is an area currently undergoing intensive research and development, with the first commercial units expected to commence operation in the near future. In this process, biomass is first converted into carbon monoxide (CO) and hydrogen (H2)-rich synthesis gas (syngas) via gasification, and subsequently fermented to hydrocarbons by acetogenic bacteria. Several studies have been performed over the last few years to optimise both biomass gasification and syngas fermentation with significant progress being reported in both areas. While challenges associated with the scale-up and operation of this novel process remain, this strategy offers numerous advantages compared with established fermentation and purely thermochemical approaches to biofuel production in terms of feedstock flexibility and production cost. In recent times, metabolic engineering and synthetic biology techniques have been applied to gas fermenting organisms, paving the way for gases to be used as the feedstock for the commercial production of increasingly energy dense fuels and more valuable chemicals.

Commercial Biomass Syngas Fermentation

A strictly anaerobic, gram-positive, sporeforming, rod-like, motile bacterium was enriched from rabbit feces, and isolated using carbon monoxide as sole source of energy and carbon. The isolate metabolizes CO with ethanol, acetate and CO2 as end-products. Other substrates used as carbon and energy sources include CO2 plus H2, pyruvate, xylose, arabinose, fructose, rhamnose, and l-glutamate. The optimum temperature for growth is 37°C. The optimum pH for chemolithotrophic growth lies around 5.8 to 6.0 Sulfate is not reduced. Growth is inhibited either by penicillin, chloramphenicol, tetracyclin or ampicillin, each at 100 μg per ml. The isolate has a DNA-base composition of 25.9±0.6% guanine plus cytosine. The isolate represents a new species of Clostridium for which the name Clostridium autoethanogenum is proposed. The type strain is strain JA1-1

Clostridium autoethanogenum, sp. nov., an anaerobic bacterium that produces ethanol from carbon monoxide

A process is provided for converting waste biomass to useful products by gasifying the biomass to produce synthesis gas and converting the synthesis gas substrate to one or more useful products. The present invention is directed to the conversion of biomass wastes including municipal solid waste, sewage sludge, plastic, tires, agricultural residues and the like, as well as coal, to useful products such as hydrogen, ethanol and acetic acid. The overall process includes the steps of gasifying the waste biomass to produce raw synthesis gas, cooling the synthesis gas, converting the synthesis gas to the desired product or products using anaerobic bioconversion, and then recovering the product or products. In accordance with a particular embodiment of the present invention, waste biomass is converted to synthesis gas containing carbon monoxide and, then, the carbon monoxide is converted to hydrogen by an anaerobic microorganism ERIH2, bacillus smithii ATCC No. 55404.

Bioconversion of waste biomass to useful products

There has been considerable interest recently in the production of liquid fuels from coal through direct or indirect liquefaction. A culture has been isolated from animal waste that is capable of producing ethanol and acetate from carbon monoxide and from hydrogen and carbon dioxide, the major components of synthesis gas. This paper presents results of batch and continuous laboratory studies with this culture. Special efforts are directed toward maximizing the ratio of ethanol to acetate.

The Biological production of ethanol from synthesis gas

Liquid and gaseous fuels may be produced biologically from coal by the indirect conversion of coal synthesis gas. Methane has been produced from synthesis gas using acetate and CO2/H2 as intermediates, utilizing a number of CO-utilizing and methanogenic bacteria. Also, a bacterium that is capable of producing ethanol from synthesis gas through indirect liquefaction has been isolated fron natural inocula. This paper summarizes research to optimize the performance of some of these cultures. These conversions, involving H2 and CO, which are only slightly soluble in the liquid media, may be mass transfer limited, and methods to enhance mass transport are examined. Experimental results and models for several reactor designs, including CSTR and packed columns, are presented and discussed.

B. B. Elmore

Papers

The Biological production of ethanol from synthesis gas

Biological production of liquid and gaseous fuels from synthesis gas