Bioethanol plant with sweet sorghum integrating first and second generation ethanol production lines (4 posts)

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  • Alessia Vecchiet said 3 years ago:

    One of the main hypotheses for the future ethanol plants foresees the integration of the second generation ethanol production line in the biorefinery, which can be adapted to different cellulosic raw materials.
    In the case of sweet sorghum, the juice is fermented but also the bagasse can be treated with hydrolysis and then fermented. In this case the facilities of the plant must have the pre-treatment line for cellulosic materials. The problem is the thermal and power supply for the plant that requires the bagasse. Using the bagasse for second generation ethanol, other lignocellulosic residues from other crops have to be burnt in the CHP plant of the biorefinery. Which is the more suitable solution? Which residues can be burnt? What do you think about high-lingin content materials? and organic wastes?

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  • Bernd Rohowsky said 3 years ago:

    Dear Alessia,

    I agree with you that the burning of agricultural residues has one important key role for the sustainability of the process and for sure it would be the best if one could apply any by-product from the process like bagasse or lignin in the case of sweet sorghum.
    The amount of bagasse surplus available from the first generation is influenced by quite a lot of variables like the composition of the feed stock (e.g. dry matter, sugar content), the climate region (e.g. juice thickening in temperate climate zones) and the process itself (e.g. heat integration). In dependence of the heat integration applied, it is for example known from the distilleries in Brazil that bagasse surplus from sugar cane could vary between almost zero and more than 50 %.
    For the combined first and second generation ethanol plants also the residual lignin after fermentation could be applied for process heat. For second generation ethanol processes already some papers are available, which are discussing the burning of lignin for heat or power generation for different kinds of feedstock. Some studies are showing that there could be even one surplus of lignin, which could be sold then as a solid fuel on the market in the form of pellets. In the case of sweet sorghum the fuel source for process energy (bagasse vs. lignin) is more flexible and would be dependent on the market conditions for ethanol and lignin. At the XIX Symposium on Alcohol Fuels in Verona we presented a novel process concept combining first and second generation ethanol production from sweet sorghum. The paper about this topic is currently under way. In our concept, biogas from anaerobic digestion of hemicellulosic sugars is considered as an alternative third option to provide heat and power to the process.
    As a conclusion, I think, one general statement about the question, which fuel source should be applied for the process could not be given and is dependent on the concept applied and the current market conditions. Looking forward to an interesting discussion about this topic!

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  • Luís Filipe Quilhó said 2 years, 11 months ago:

    Dear all,

    This is a subject that I would like to research in the future. Do you know if there are any research institutions, or corporations, with a focus on production of 1st and 2nd generation bioethanol from Sweet Sorghum?

    Thank you,

    Luis

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  • Oscar Leòn said 2 years, 10 months ago:

    Dear Colleagues,

    concerning the first and second generation of bioethanol, the main problem, as Alessia said, is the energy requirement that needs the process . At this moment, these energetic requirements are cover by the bagasse, but if we use this bagasse for bioethanol, only we are going to have aprox 20% of the total mass to be burned. And of course, the second generation process are going to need a lot of energy, including the drying of the lignin after the hydrolysis. Thus, at this moment, we can´t consider that the lignin is going to be enough to cover the energy demand of the process. On the other hand, if we have more bagasse than we need in the ethanol process, like occur with the sugar cane (that usually demand less energy than the potential production with the bagasse), then, we can evaluate several options with second generation process: for example, bioethanol from hemicellulose and cellulose, biogas, bioplastics (lactic and polilactic acids), and so on. But first, we need to ensure that the energetic demand of the first generation process is cover without fossil fuels. If we don´t ensure this, probably, the sustainability of the total process is going to be questioned.

    Best regards.

    Oscar

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