HOME  >   Topics Archives  >  Production of High Purity Hydrogen from Sewage Sludge

Production of High Purity Hydrogen from Sewage Sludge

Production of High Purity Hydrogen from Sewage Sludge

The sewage emitted from Japanese homes and factories is purified in sewage treatment plants, with the sewage sludge that is the treated residue from this coming to the enormous volume of 2.23 million tons (on a dried basis) in FY2008. At present this sewage sludge is treated by having its weight reduced by means of dehydration (160,000 tons), incineration (1.56 million tons), melting (210,000 tons), composting (240,000 tons), and drying (60,000 tons). But for the sake of making the switch over to a recycling-oriented society in the future, there is a need to convert over to a system that will utilize and reuse this as resources and energy by digesting, carbonizing, and composting this sewage sludge, as well as recovering phosphorous from it.

Tohoku University (Professor Fumiyoshi Saito) developed a technique for producing highly pure (89.4%) hydrogen gas from sewage sludge at a low cost. Professor Saito’s group had previously studied hydrogen production from woody biomass (cellulose), and had succeeded at producing highly pure (98%) hydrogen. This time around they took this technique even further by applying it to sewage sludge.

An inorganic powder of calcium hydroxide Ca(OH)2 and nickel hydroxide Ni(OH)2 is mixed with raw materials for biomass like rice straw, printing paper, coffee grounds, and woody biomass from cedar wood and then dry pulverized. Afterwards, it is heated to 400°C in a nonoxidative environment, at which time the cellulose in the woody biomass reacts with the inorganic powder, which produces hydrogen and leaves behind calcium carbonate CaCO3.

With the hydrogen obtained from the sewage sludge with this process, after sewage sludge with a moisture content of 80% is mixed with the inorganic powder, high purity hydrogen can be obtained just by heating it to about 600°C. Compared to hydrogen production from woody biomass, this does not require a drying and pulverizing process, thereby making it possible to lower the hydrogen gas production costs substantially. There are great expectations for this groundbreaking technology from the two dimensions that it both cuts the cost of treating the sewage sludge and makes it possible to produce hydrogen inexpensively.

 

Fig. Switch from reducing the weight of sewage sludge to utilizing and recycling it as resources and energy
Fig.  Switch from reducing the weight of sewage sludge to utilizing and recycling it as resources and energy
Source: Homepage of the Sewage and Wastewater Management Department, Ministry of Land, Infrastructure, Transport and Tourism
(http://www.mlit.go.jp/mizukokudo/sewerage/crd_sewerage_tk_000124.html)

 

Fig.  Producing hydrogen from woody biomass
Fig.  Producing hydrogen from woody biomass
Source: “Gasification of Woody Biomass and the Production of Highly Pure Hydrogen,” Bulletin of the Institute for Advanced Materials Processing Building, Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University (Volume 66, Issue 1,2, Page 44, 2011)

 

Fig. Producing hydrogen from sewage sludge
Fig.  Producing hydrogen from sewage sludge

 

Source:
• Homepage of the Japan Sewage Works Association
  (http://www.jswa.jp/data-room/data.html)
• Homepage of the Sewage and Wastewater Management Department, Ministry of Land, Infrastructure, Transport and Tourism
  (http://www.mlit.go.jp/mizukokudo/sewerage/crd_sewerage_tk_000124.html)
• Tohoku University press release
  http://www.tohoku.ac.jp/english/2011/11/press20111124-1.html

Other Topics

Page Top   
Return to HOME