• Feedstocks Analysed at Celignis
    Compost

Background on Compost

Compost can be defined as decomposed organic matter. It can be produced from a wide variety of organic feedstocks. Many composts are produced from municipal green (garden) wastes. The composting process can involve reducing the particle size of the biomass and then placing it in mounds where the composting is allowed to take place over an extended period of time. Fully composted material can, in some cases, be suitable for addition to soil.

As part of a research project funded by the Irish Environmental Protection Agency, Celignis founder Daniel Hayes has collected, processed, and analysed (using both chemical and near-infrared techniques) a number of different compost samples.

Analysis of Compost at Celignis



Celignis Analytical can determine the following properties of Compost samples:



Lignocellulosic Properties of Compost

Cellulose Content of Compost

The composition of compost will depend on the organic material that has been used to produce it and the time and extent of the composting process. Taking the example of compost produced from horticultural waste, there will be a significant variation in composition according to the time of year. For example, in the summer the majority of garden wastes are likely to be of grasses (lawn cuttings) or the cuttings of bushes (small twigs and leaves) rather than bulky woody materials. In contrast, in the winter months the relative proportion of woody materials might be expected to increase.

In his EPA-funded research project, Celignis founder Daniel Hayes found that an increased period of comosting was associated with a lower cellulose content.

Click here to see the Celignis Analysis Packages that determine Cellulose Content

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Hemicellulose Content of Compost

The hemicellulose content of compost will depend on the organic material that has been used to produce it and the time and extent of the composting process.

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Lignin Content of Compost

In his EPA-funded research project, Celignis founder Daniel Hayes found that an increased period of composting was associated with an increased lignin content.

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Starch Content of Compost

The starch content of compost will depend on the composting time, with the value decreasing as the composting time increases.

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Uronic Acid Content of Compost

Uronic acids are present in many of the feedstocks that are used to generate compost, however we are not aware of any studies to date on the fate of these uronic acids during the composting process.

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Enzymatic Hydrolysis of Compost

We can undertake tests involving the enzymatic hydrolysis of Compost. 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 Compost

Ash Content of Compost

The ash content of compost is likely to increase with increased degradation of the organic matter.

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Heating (Calorific) Value of Compost

The heating value of compost will depend on the organic material that has been used to produce it and the time and extent of the composting process. Composts can have lesser heating values due to their high ash and moisture contents.

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Ash Melting Behaviour of Compost

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 Compost 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 Compost 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 Compost ash forms a hemisphere (i.e. the height becomes equal to half the base diameter).

Ash Flow Temperature (FT) - The temperature at which the Compost 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 Compost

Examples of major elements that may be present in Compost 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 Compost.

Click here to see the Celignis Analysis Packages that determine Major and Minor Elements

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Analysis of Compost for Anaerobic Digestion



Biomethane potential (BMP) of Compost

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 Compost. 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.



Click here to see the Celignis Analysis Packages that determine BMP

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Physical Properties of Compost



Bulk Density of Compost

At Celignis we can determine the bulk density of biomass samples, including Compost, 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 Compost

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 Compost, by following European Standard methods EN 15149- 1:2010 and EN 15149-2:2010.



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Publications on Compost By The Celignis Team

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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