As early as the 19th century, it has been recognized that bacteria and baths have the characteristics of producing molecular hydrogen. Under the action of microorganisms, the fermentation of calcium formate can produce hydrogen from water ; in 1942, scientists observed the growth of some algae and found that by reducing the supply of CO2, green algae stopped releasing oxygen under photosynthesis and turned to produce hydrogen gas. In 1958, scientists found that algae can produce hydrogen directly through the photolysis process without the help of CO2 fixation. In 1966, Lewis first proposed the topic of biological hydrogen production. His research mainly focused on the photolysis and fermentation of hydrogen production by green algae, cyanobacteria and photosynthetic bacteria. The occurrence of the energy crisis in the 1970 s caused widespread concern about biomass hydrogen production and began research. The initial research on hydrogen production from biomass by Pacific Northwest Laboratory ( PNL ) mainly focused on the high temperature vaporization of biomass, the extraction of liquid fuel and syngas from biomass, and the preliminary study of its kinetic characteristics and catalysts. Subsequently, the biomass vaporization system in critical water was studied. The chemical characteristics of biomass reaction in high temperature compressed fluid and supercritical fluid were mainly analyzed, including the selection of catalyst, continuous flow reactor test and carbon gasification process. In the early 1990 s, the University of Hawaii began to use supercritical technology for biomass gasification to produce hydrogen. Using activated carbon as a catalyst, the effects of various biomass vaporization in supercritical water were studied, and high-pressure water was used as a CO2 absorbent. At present, we are working on how to prolong the activity of the catalyst, and complete the design, installation and manufacture of the biomass reforming flow reactor, so as to prepare for the further completion of the pilot test of the new reactor system.
Scientists have developed a device that uses chloroplasts to produce hydrogen, and 1g of chlorophyll can produce 1L of hydrogen in 1h. Usually, the hydrogen prepared by biological method needs to be further purified. The hydrogen content obtained by biological method is usually 60 % -90 % ( volume fraction ). The gas may be mixed with CO2, CO good water vapor and so on. Traditional chemical methods can be used to remove the impurities mixed in it, such as using 50 % ( mass fraction ) KOH solution, phloroglucinol alkali solution, or dryer or cooling.
Biomass hydrogen is produced by photosynthetic bacteria or anaerobic bacteria using carbohydrates as hydrogen donors, and bacteria are immobilized by microbial carriers, embedding agents and other bacterial immobilization methods to achieve hydrogen production. According to whether the biomass needs sunlight in the process of hydrogen production, the methods of biomass hydrogen production are divided into two categories : photosynthetic biological hydrogen production and biological fermentation hydrogen production.