Fuelization of Italian Ryegrass and Napier Grass through a Biological Treatment and Photocatalytic Reforming

Bio-ethanol production has been receiving a great amount of interest from the viewpoint of being a renewable energy alternative to petroleum-based fuel. And the bioethanol production from lignocellulosic biomass has been recognized as one of the promising approaches to avoid direct competition with food sources. However, the yield is still low compared with the first generation bioethanol from starch, which is commercially produced by SSF (simultaneous saccharification and fermentation) using Saccharomyces cerevisiae and hydrolytic enzymes.

In this paper, fuelization of Italian ryegrass and Napier grass was examined by the combination of biological treatments and photocatalytic reforming (photo-Reform). The alkali-pretreated Italian ryegrass and Napier grass were subjected to the enzymatic saccharification using cellulase and xylanase. Xylose and glucose were produced in 56.6% and 71.1% from Italian ryegrass and in 49.5% and 67.3% from Napier grass, respectively. Xylose and glucose were converted to hydrogen by the photo-Reform using a Pt-loaded titanium oxide (Pt/TiO₂) under UV irradiation.

Moreover, a low-moisture anhydrous ammonia (LMAA) pretreatment was performed for Italian ryegrass and Napier grass by keeping moist powdered biomass under NH3 gas atmosphere at room temperature for four weeks. The Italian ryegrass and Napier grass which were pretreated by LMAA method were subjected to simultaneous saccharification and fermentation (SSF) using a mixture of cellulase and xylanase as well as Saccharomyces cerevisiae in acetate buffer (pH 5.0). Ethanol and xylose were produced in 91.6% and 51.6% from LMAA-pretreated Italian ryegrass and 78.6% and 68.8% from Napier grass, respectively. After the evaporation of ethanol, xylose was converted to hydrogen by the photo-Reform.

In the case of saccharification→photo-Reform, energy was recovered as hydrogen from the alkali-pretreated Italian ryegrass and Napier grass in 71.9% and 77.0% of energy recovery efficiency, respectively. In the case of SSF→photo-Reform, the energy was recovered in 82.7% and 77.2% as ethanol and hydrogen from the LMAA-pretreated Italian ryegrass and Napier grass, respectively.

In conclusion, the saccharides derived from biological treatment of Italian ryegrass and Napier grass were efficiently converted to hydrogen by photo-Reform.

Article by Masahide Yasuda, et al, from Japan and Indonesia.

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Image by BJ Stacey, from Flickr-cc.