Sweet Sorghum - Biomass ensilage to avoid sugar losses (16 posts)

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  • Denis Picco said 4 years ago:

    One of the main problems of the bioethanol production from the sweet sorghum stalks is the sugar preservation. In order to avoid the construction of big plants (e.g. crusher machine, fermentation unit, etc.) that are able to process all the large amount of necessarily biomass in few days (no more than 20-40 days per year in Europe), it is necessary to study a system for the sugar preservation into the biomass, in order to allow the possibilty to process all the biomass during the entire year.
    One of this systems could be the ensilage of the chopped biomass with additives (e.g. formic acid), in order to stop the natural fermentation process inside the bulk and preserve the sugar (it is possible to control the loss of sugars below 5% of the total amount). Several studies prove the sustainabilty of this storage method.
    This could be one bioethanol production model from sweet sorghum in the European Countries, in case of small decentralised plants.
    Several problems are connected to this type of tecnique, starting from the cost of formic acid, the cost of the final feedstock, the energetic sustainability, etc.

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  • Eugenio Macchia said 4 years ago:

    Perhaps it could be worth thinking of a dedicated ensilage system, in which formic acid is used in small amounts and the ensilage environment is filled with nitrogen in slight overpressure. It’s something different from what usually done, and of course it’s just an idea to be verified…

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  • Roger Ford said 4 years ago:

    Have there been any tests conducted wherein the sorghum is pressed and the juice heated to kill bacteria to increase the shelf-life of the sorghum juice. This is something we are considering a test on, but would welcome your thoughts.

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  • Alessia Vecchiet said 4 years ago:

    Dear Roger,
    we never considered before this option, but we are intersted to know more details about it. We considered the ensiling process to preserve the sugars and after the travel in India we considered also the option that they use there, the concetration of the juice to 60-80 Brix to storage it. Also your option could be evaluated for the model we are studiying. If you can, please give us more details, and if you need more info too, let us know..

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  • Oscar Leòn said 4 years ago:

    As you said, the juice could be heated after the extraction by press or diffusion in order to eliminate bacterial or yeast in it. This could be an option to preserve it.

    The problem is not the existence of bacteria prior to heat treatment, but subsequent contamination during storage.

    Of course, when you have a sugar juice, the yeast or bacterial could affect it if the sugar concentration is less than 45 - 50º Brix, so storage a juice with a concentration of 14-17º Brix with only a thermal treatmen is not going to be enough, you are goint to need other treatments, like SO2, bactericides, inert atmosphere, etc., but only for storing during a short period of time (one or two weeks).

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  • Roger Ford said 4 years ago:

    We are working with the University of Kentucky Center for Applied Energy Research as part of our project to determine preservation of sugars from sweet sorghum juice.

    We are developing a grant proposal to compare acidic ensillage versus heat preservation after juicing.

    Our business model not only produces ethanol from the juicing of sweet sorghum, but also the use of other materials with sugars. In regard to sweet sorghum, we are working with an company for a cellulosic component system to add to the existing technology for the conversion of the cellulosic material for further ethanol production. We are also planning a use of the cellulosic material to produce a co-generation biomass and natural gas power plant to produce heat and electricity for the plant, as well as for sale to the electrical grid. Possible options for us include briquetting of biomass with coal.

    Any collaborative opportunities/join venture opportunities would be welcome in order to aid in the commercialization of the use of sorghum.

    One question our research team has is the effect of the acid on the fermentation process. Does it affect yield? Obvious questions regard the length of time the acid would preserve the sugars.

    Please contact me at [email protected] in order to communicate more frequently. We can exchange agreements to aid our respective companies, etc.

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  • Eugenio Macchia said 3 years, 11 months ago:

    I know that CETA is performing some trials of ensilage with the use of acid to preserve the sugar. For what concern the effects of acids on fermentation , our experience , based on sugar cane molasses, is that it’s often necessary to control the ph adding some acid, to keep the acidity to values suitable to fermentation.
    So i suppose that if acid is used for preservation of sugar in the stalks, we don’t need to add acid in fermentation and otherwise we shall control the ph by adding small amounts of caustic . Finally my idea is that the ph control will be opposite to what happens today (caustic instead of acid) but will be not so much different.
    I’m only afraid of the global cost of the acid to be used for sugar preservation… this is an issue that is very important for the general sustainability of the production. With ensilage we will spend money to buy acids, but we will save money from the syrup evaporation system and from a very large juice extraction line (both these facilities shall be necessary if we don’t use the ensilage).
    A good ensilage system in my opinion is the most innovative way to design the production model, but we have to find a system that allows us to use less acids as possible .

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  • Denis Picco said 3 years, 11 months ago:

    Dear Roger,
    we had some good experience in the use of formic acid for the preservation of ensiled sweet sorghum in the past. The loss of sugar was really low. Really the use of acids is quite high, more or less 0.4-0.5% of biomass, so you have to use about 240 kg of formic acid per hectar (problems with costs!), but this kind of sugar preservation system allow the simplest biomass processing chain, with small crushing plants, no problems with the storage of bagasse, better use of the thermal energy production, etc.
    Really I hope to collaborate between our Research centers for future projects and on the diffusion of the bioethanol production from sweet sorghum.

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  • Denis Picco said 3 years, 9 months ago:

    Dear Roger, after some weeks I could add some information about the ensilage of sweet sorghum. In our Italian Project, called MULTISORGO, we had some sweet sorghum ensilage trials (control, formic acid and L. plantarum) and now we start to have some results; in the next months I could show you some data, or better I could add our scientific rewievs of our work abot the preservation of dry matter and sugars during the ensilage period (3 months and six months) and the experiences of the use of the extracted juice for the bioethanol production in our fermentation units. For sure in the nexts days I insert a specific link to our Multisorgo webpage (now is under construction).
    At this time I can confirm the good results of the acid formic use (0,4% w/w on w.b.) for the preservation of the dry matter and sugars in the ensiled biomass.
    Have you some news about your experiences in the preservation of sugars?

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  • Roger Ford said 3 years, 9 months ago:

    Denis, that’s great progress! We would definitely be interested in working with you all. I’ve spoken with our university research partner and they are interested in working too.

    We have met with molasses producers who are simply cutting the entire stalk at the base just at the ground. The stalks are allowed to lie in the field for several days/weeks. They see an increase in sugar yields by doing this. I wonder if there may be application for sorghum ethanol production.

    We have also pelletized the bagasse/silage. We arechaving lab analysis done to see the Btu value of that material. We will share that result.

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  • Denis Picco said 3 years, 9 months ago:

    I think you could observe a concentration on sugar in the stalks caused by the small loose on water, but the usually the sorghum stalks don’t dry so easy, cause the plant configuration.
    This kind of harvest could be really interesting if it is able to preserve the sugars in the stalks, even if stalks in the ground for week could determine problems with the weather and the final collect of the biomass.
    If you have more news about it , please share with us the information.
    May be next cultivation period we could plan a small experimental field with sweet sorghum, in order to study different ways to preserve sugar in the field, so not only ensilage.

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  • Roger Ford said 3 years, 9 months ago:

    At present, farmers who produce molasses do this process method and see an increase in sugar yield and more molasses. We are planting this spring to test this method and acid ensilage.

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  • Denis Picco said 3 years, 5 months ago:

    Berlin, May 8, 2025
    Dear all,
    during the XIX European Biomass Conference and Exhibition interesting results about the sweet sorghum biomass ensilage was presented. One of our great esse-community members, Ing. Rohowsky, from the Technische Universitat of Munchen, showed the main results of his work about the “Preservation of Sweet Sorghum under Anaerobic Conditions by Using Formic Acid as an Additive”.
    I would like to invite him to add on our forum, or as an brieaf article, a small abstract about its experimental experiences. It could be a relevant moment in order to improve the discussions and the EU model.
    Experiences like the cited one, are going to be done also in a National Italian Project (MULTISORGO), coordinated by CETA, and in the next time some data could be share.
    Compliments again for your work Ing. Rohowsky, and see you soon.
    Denis

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  • Bernd Rohowsky said 3 years, 5 months ago:

    Dear Denis, thank you very much for your kind statement about our work, which is part of the current research project “Ethanol from sweet sorghum – overall concept for sustainable utilisation of sweet sorghum as a raw material for ethanol production” accomplished by the Technology and Support Centre (TFZ) and the Institute of Resource and Energy Technology (TU München). Enclosed please find the abstract from our paper which will be available soon on the conference proceedings (www.conference-biomass.com).
    Abstract: In field trials sweet sorghum variety “Keller” was cultivated to investigate how the chopped biomass can be stored to provide an efficient and quality-conserving low-loss supply of mass and sugar yield for ethanol purposes. For this reason sweet sorghum was harvested with a common self-propelled-forage-chopper and transported by a farm trailer. In pilot plant scale two different particle sizes (length 10 mm and 20 mm) and two different loadings of 0.5 % (FM) and 1.0 % (FM) formic acid were tested to conserve the chopped material under anaerobic conditions in plastic barrels, which is common practice for ensilage studies. After 90, 120 and 150 days the barrels were opened and samples were taken to analyse the remaining soluble sugar content. It was shown that the addition of 1.0 % (FM) formic acid fully preserved the sugars for more than 150 days. With 0.5 % (FM) formic acid the formation of lactic acid could be prevented but not the activity of all microorganisms, which resulted in a slow increase of ethanol with time.
    Bernd

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  • Denis Picco said 3 years, 5 months ago:

    Dear Bernd,
    thanks a lot for your contribution. Your results confirm the positive potential use of additive like formic acid for a good ensilge of biomass and of course the sugar preservation.
    Next steps is of course the economic sustainability evaluation of these application and the impact on the environmental sustainability. I know that, as in our project Multisorgo, you are working on it and so, we are wainting for your future contribution in this forum about these topics.

    Thanks a lot
    Denis

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