• Feedstocks Analysed at Celignis
    Sugarcane Bagasse

Background on Sugarcane Bagasse

Sugarcane bagasse is the solid residue that remains after sugarcane, a C4 plant, has been crushed and the juice removed. In an ideal sugar mill the maximum amount of sucrose would be extracted during the milling process with little left in the sugarcane bagasse. Hence, the bagasse will represent a predominately lignocellulosic feedstock. Taking the example of Brazilian sugarcane, one wet tonne of cane that is processed at the mill will yield approximately 280 kg (wet) of sugarcane bagasse. Typically, sugarcane bagasse has a moisture content of between 45 and 55% on a wet basis. Bagasse is therefore a significant output of the sugar mill. It was estimated that 160 million tonnes of sugarcane bagasse were produced in Brazil 2008.

The first use for this resource is as a heat and steam provider to satisfy the energy needs of the sugar production or fermentation processes. It has been estimated that a minimum of 50% of the bagasse is required for this. In many cases the surplus bagasse represents a problematic waste that could lead to safety issues (e.g. spontaneous combustion) if stored for a long period of time. For that reason some mills deliberately burn the bagasse at a low efficiency so that more of it is consumed for energy production.

It has been estimated that the use of sugarcane bagasse in boilers could be decreased by up to 36% if more efficient combustion schemes are employed, potentially offering an increased supply of biomass for biorefining purposes. Indeed, there has been a significant amount of research into utilising sugarcane bagasse in biorefining technologies that may produce saleable chemicals from the polysaccharides or produce bio-oils via the pyrolysis of this residue.

The sugarcane harvest residue that is left on the field, often referred to as sugarcane trash, is also a potential biomass resource. This feedstock comprises the leaves and the tops of the plant; fractions with insufficient sucrose content to warrant their transportation to the mill. It has been estimated that, for each tonne of harvested cane, 140 kg of trash will exist. This is the case only where the cane is mechanically harvested (which involves the trash being blown back onto the field by the harvester). Manual practices require the crop to be burnt prior to the chopping of the stems by workers. This will burn the leaves of the crop but not damage the stems and roots. Manual harvesting occurs only in developing nations and is being gradually phased out. For example, the Brazilian government has targeted 2020 as a date when all harvesting will be mechanical.

Celignis founder Daniel Hayes has extensive experience in the chemical/infrared analysis of sugarcane bagasse and sugarcane trash. As part of the DIBANET project, he spent approximately 2 years working in Brazil where he was responsible for the analysis of Latin American biomass feedstocks and in the development of near infrared models for these. This work included the installation of an online near-infrared device at a sugar-mill. Daniel Hayes also spent time working in Australia where he undertook chemical and near-infrared analysis of sugarcane bagasse samples.

Analysis of Sugarcane Bagasse at Celignis



Celignis Analytical can determine the following properties of Sugarcane Bagasse samples:



Lignocellulosic Properties of Sugarcane Bagasse

Cellulose Content of Sugarcane Bagasse

Cellulose is the main mass constituent of sugarcane bagasse. The cellulose content will depend on the sugarcane variety and on the harvesting method used. In recent years there has been interest in a variety of sugarcane termed Energy Cane. This has a much lower sucrose content than traditional sugarcane varieties but can be more efficient in producing fibre.

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Hemicellulose Content of Sugarcane Bagasse

As with Miscanthus, switchgrass, and reed canary grass, the main hemicellulose in sugarcane bagasse is arabinoxylan. This hemicellulose is predominately composed of xylose, with a lower proportion of arabinose.

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Lignin Content of Sugarcane Bagasse

The lignin content of sugarcane bagasse will vary according to the sugacane clonal variety and the havesting mechanism used.

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Starch Content of Sugarcane Bagasse

The starch content of sugarcane bagasse is typically quite low but it can vary according to the maturity of the plant.

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Uronic Acid Content of Sugarcane Bagasse

The uronic acids glucuronic acid and galacturonic acid are present in the hemicelluloses of sugarcane bagasse.

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Enzymatic Hydrolysis of Sugarcane Bagasse

We can undertake tests involving the enzymatic hydrolysis of Sugarcane Bagasse. In these experiments we can either use a commercial enzyme mix or you can supply your own enzymes. We also offer analysis packages that compare the enzymatic hydrolysis of a pre-treated sample with that of the native original material.

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Bioenergy Properties of Sugarcane Bagasse

Ash Content of Sugarcane Bagasse

There can be a high variability in the ash content of sugarcane bagasse. This is in large part due to variations in the practices used for harvesting the sugarcane. In some cases the harvested crop can contain a significant proportion of soil, a trend that will lead to increased ash in the bagasse.

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Heating (Calorific) Value of Sugarcane Bagasse

The heating value of sugarcane bagasse will be mostly dependent on the moisture and ash content of the residue.

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Ash Melting Behaviour of Sugarcane Bagasse

Ash melting, also known as ash fusion and ash softening, can lead to slagging, fouling and corrosion in boilers which may reduce conversion efficiency. We can determine the ash melting behaviour of Sugarcane Bagasse using our Carbolite CAF G5 BIO ash melting furnace. It can record the following temperatures:

Ash Shrinkage Starting Temperature (SST) - This occurs when the area of the test piece of Sugarcane Bagasse ash falls below 95% of the original test piece area.

Ash Deformation Temperature (DT) - The temperature at which the first signs of rounding of the edges of the test piece occurs due to melting.

Ash Hemisphere Temperature (HT) - When the test piece of Sugarcane Bagasse ash forms a hemisphere (i.e. the height becomes equal to half the base diameter).

Ash Flow Temperature (FT) - The temperature at which the Sugarcane Bagasse ash is spread out over the supporting tile in a layer, the height of which is half of the test piece at the hemisphere temperature.



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Major and Minor Elements in Sugarcane Bagasse

Examples of major elements that may be present in Sugarcane Bagasse include potassium and sodium which are present in biomass ash in the forms of oxides. These can lead to fouling, ash deposition in the convective section of the boiler. Alkali chlorides can also lead to slagging, the fusion and sintering of ash particles which can lead to deposits on boiler tubes and walls.

We can also determine the levels of 13 different minor elements (such as arsenic, copper, and zinc) that may be present in Sugarcane Bagasse.

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Analysis of Sugarcane Bagasse for Anaerobic Digestion



Biomethane potential (BMP) of Sugarcane Bagasse

At Celignis we can provide you with crucial data on feedstock suitability for AD as well as on the composition of process residues. For example, we can determine the biomethane potential (BMP) of Sugarcane Bagasse. The BMP can be considered to be the experimental theoretical maximum amount of methane produced from a feedstock. We moniotor the volume of biogas produced allowing for a cumulative plot over time, accessed via the Celignis Database. Our BMP packages also involve routine analysis of biogas composition (biomethane, carbon dioxide, hydrogen sulphide, ammonia, oxygen). We also provide detailed analysis of the digestate, the residue that remains after a sample has been digested. Our expertise in lignocellulosic analysis can allow for detailed insight regarding the fate of the different biogenic polymers during digestion.



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Physical Properties of Sugarcane Bagasse



Bulk Density of Sugarcane Bagasse

At Celignis we can determine the bulk density of biomass samples, including Sugarcane Bagasse, according to ISO standard 17828 (2015). This method requires the biomass to be in an appropriate form (chips or powder) for density determination.



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Particle Size of Sugarcane Bagasse

Our lab is equipped with a Retsch AS 400 sieve shaker. It can accommodate sieves of up to 40 cm diameter, corresponding to a surface area of 1256 square centimetres. This allows us to determine the particle size distribution of a range of samples, including Sugarcane Bagasse, by following European Standard methods EN 15149- 1:2010 and EN 15149-2:2010.



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Publications on Sugarcane Bagasse By The Celignis Team

Hayes, D. J. M. (2013) Report on Optimal Use of DIBANET Feedstocks and Technologies, DIBANET WP5 Report84 pages

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The DIBANET process chain, as a result of its patented pre-treatment stage, has significantly increased the yields of levulinic acid, formic acid, and furfural beyond what was considered to be the state of the art. By fractionating lignocellulosic biomass into its three main polymers (cellulose, hemicellulose, lignin) it has also allowed for lignin to be recovered and sold as a higher-value product. These developments have meant that the amount of acid hydrolysis residues (AHRs) that have been produced are significantly (up to 88%) less than in the Biofine process. These AHRs are required to provide process heat for DIBANET. Direct combustion is the most efficient means for doing this. If such combustion does not occur and the AHRs are instead used in other processes, e.g. pyrolysis and gasification, then more biomass will need to be purchased to fuel the core DIBANET process. The AHRs have not been proven to be superior to virgin biomass when put through these thermochemical processes. Indeed, many of the results from DIBANET Work Package 4 indicate the opposite. Hence, given that DIBANET, and the modelling of its optimal configuration, is designed on the basis of an integrated process, centred on the core element of the acid hydrolysis of biomass, then combustion is the only viable end use for the AHRs. Given that realisation, the focus of this modelling Deliverable is on what the optimal configuration of the process chain would be regarding the three core stages (pretreatment, hydrolysis, and the esterification of levulinic acid with ethanol). It has been demonstrated that a scenario incorporating only the first stage can be profitable in its own right and allow for commercial development at much lower capital costs. In this instance bagasse is a much more attractive feedstock, compared with Miscanthus, due to its higher pentose content.

Integrating the second stage increases capital costs but improves the net present value. The esterification step is somewhat capital intensive but an integrated DIBANET biorefinery that incorporates all three stages can still be highly profitable providing the furfural is sold at its current market price and the lignin is sold rather than used as a fuel for process needs. Indeed, the DIBANET process should not be considered only in the context of biofuels but as a true biorefinery that produces lower value fuels (e.g. ethyl-levulinate) in addition to high value chemicals and bio-products (e.g. furfural and lignin).

The energy and carbon balances of the various DIBANET scenarios have been investigated and are highly positive with values significantly superior to those for the energy-intensive Biofine process. A socioeconomic survey has also been carried out and has shown that there can be a positive effect on employment, both direct and indirect, particularly when Miscanthus is used as the feedstock. The DIBANET integrated process also holds up well when its environmental and social performances are ranked for a range of important parameters.

The development of the core DIBANET IP towards commercial deployment appears to be warranted, based on data provided from the models developed. Indeed, these models present possible scenarios whereby even demonstration-scale DIBANET facilities could operate at significant profits and provide healthy returns on the capital invested.

Hayes, D. J. M. (2012) Review of Biomass Feedstocks and Guidelines of Best Practice, DIBANET WP2 Report150 pages

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Shorter Version

This document is the result of the evaluation of biomass feedstocks, from Europe and Latin America, that took place as part of the DIBANET project. That project is co-financed from the 7 th Framework Programme for Research and Technological Demonstration of the European Union. (Title: Enhancing international cooperation between the EU and Latin America in the field of biofuels; Grant Agreement No: 227248-2).

The work in Task 2.1 of Work Package 2 (WP2) at DIBANET partners UL, CTC, and UNICAMP involved evaluating, on a number of levels, potential feedstocks for utilisation in the DIBANET acid-hydrolysis process (WP3). In the early stage of the project a wide number of feedstocks were examined and relevant secondary compositional data were sought from the literature. Selected feedstocks were analysed at the laboratories of UL, CTC, and UNICAMP and, from these, a limited number of feedstocks were subjected to more in-depth analysis/evaluation.

Work at UL focused on Miscanthus, cereal straws, and waste papers. The wet-chemical and spectroscopic analysis that was carried out on a wide number of Miscanthus samples have allowed for in-depth understandings to be reached regarding the changes in lignocellulosic composition, and potential biomass/biofuel yields that could be realised over the harvest window. Straws present much less chemical variation but have enough structural carbohydrates to warrant their processing in the DIBANET technology. Waste papers can have amongst the highest total carbohydrate contents of any of the feedstocks studied.

Work at CTC focused on the residues of the sugarcane industry - sugarcane bagasse and sugarcane trash (field residues from harvesting). A large number of samples were collected from a variety of sugar mills and plantations. It has been seen that there can be a significant variation in the composition of different bagasse samples, particularly with regards to the ash content. Sugarcane trash has lower total carbohydrates contents than bagasse but is still a suitable feedstock for DIBANET.

Work at UNICAMP focused on the evaluation of residues from the banana, coffee, and coconut industries. It was found that these also have potential for utilisation in the DIBANET process, however the value of the residues for this end-use is dependent on which part of the plant is utilised. For instance, coffee husks have sufficient structural carbohydrates to allow for decent yields of levulinic acid, formic acid, and furfural in DIBANET, however the leaves of the coffee plant do not. Leaves from the banana plant are also of less value for DIBANET than the other parts of the plant (e.g. stem).

A major output of this Deliverable is the downloadable electronic database that contains all of the WP2 analytical data obtained during the course of the project. It contains analytical data and predicted biorefining yields for a total of 1,281 samples. It can be obtained, free of charge, from the DIBANET website and will be a valuable tool for stakeholders in biorefining projects.

This document presents the data and evaluations that were made regarding biomass feedstocks, and also puts forward guidelines of best practice in terms of making the best use of these resources. A shortened version of this document can also be downloaded from the DIBANET website.

Hayes, D. J. M. (2011) Analysis of Lignocellulosic Feedstocks for Biorefineries with a Focus on The Development of Near Infrared Spectroscopy as a Primary Analytical Tool, PhD Thesis832 pages (over 2 volumes)

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The processing of lignocellulosic materials in modern biorefineries will allow for the production of transport fuels and platform chemicals that could replace petroleum-derived products. However, there is a critical lack of relevant detailed compositional information regarding feedstocks relevant to Ireland and Irish conditions. This research has involved the collection, preparation, and the analysis, with a high level of precision and accuracy, of a large number of biomass samples from the waste and agricultural sectors. Not all of the waste materials analysed are considered suitable for biorefining; for example the total sugar contents of spent mushroom composts are too low. However, the waste paper/cardboard that is currently exported from Ireland has a chemical composition that could result in high biorefinery yields and so could make a significant contribution to Irelandís biofuel demands.

Miscanthus was focussed on as a major agricultural feedstock. A large number of plants have been sampled over the course of the harvest window (October to April) from several sites. These have been separated into their anatomical fractions and analysed. This has allowed observations to be made regarding the compositional trends observed within plants, between plants, and between harvest dates. Projections are made regarding the extents to which potential chemical yields may vary. For the DIBANET hydrolysis process that is being developed at the University of Limerick, per hectare yields of levulinic acid from Miscanthus could be 20% greater when harvested early compared with a late harvest.

The wet-chemical analysis of biomass is time-consuming. Near infrared spectroscopy (NIRS) has been developed as a rapid primary analytical tool with separate quantitative models developed for the important constituents of Miscanthus, peat, and (Australian) sugarcane bagasse. The work has demonstrated that accurate models are possible, not only for dry homogenous samples, but also for wet heterogeneous samples. For glucose (cellulose) the root mean square error of prediction (RMSEP) for wet samples is 1.24% and the R2 for the validation set ( ) is 0.931. High accuracies are even possible for minor analytes; e.g. for the rhamnose content of wet Miscanthus samples the RMSEP is 0.03% and the is 0.845. Accurate models have also been developed for pre-treated Miscanthus samples and are discussed. In addition, qualitative models have been developed. These allow for samples to be discriminated for on the basis of plant fraction, plant variety (giganteus/non-giganteus), harvest-period (early/late), and stand-age (one-year/older).

Quantitative NIRS models have also been developed for peat, although the heterogeneity of this feedstock means that the accuracies tend to be lower than for Miscanthus. The development of models for sugarcane bagasse has been hindered, in some cases, by the limited chemical variability between the samples in the calibration set. Good models are possible for the glucose and total sugars content, but the accuracy of other models is poorer. NIRS spectra of Brazilian bagasse samples have been projected onto these models, and onto those developed for Miscanthus, and the Miscanthus models appear to provide a better fit than the Australian bagasse models.





Examples of Other Feedstocks Analysed at Celignis



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