• Feedstocks Analysed at Celignis
    Forest Residues

Background on Forest Residues

Wood with a smaller diameter than 70 mm (branches and the tops of trees) is generally not harvested in roundwood operations and is left on the forest floor.

Forest residues represent a highly heterogeneous mix of biomass. In addition to the tree-tops and branches there will also be a significant amount of foliage.

The constitution and total quantity of forest residues on any particular site is dependent on: the age of the tree; the species; the tree-spacings; and the wood assortment harvested. Depending on these, the amount of forest residues can vary from 50 to 100 oven dry tonnes per hectare.

The biomass obtained after thinning operations is also of relevance. Due to their small size, these trees, particularly first thinnings, are often not used in sawmills or for pulpwood.

Analysis of Forest Residues at Celignis



Celignis Analytical can determine the following properties of Forest Residues samples:



Lignocellulosic Properties of Forest Residues

Cellulose Content of Forest Residues

The composition of forestry residues will depend on: the tree species; the time of year; and the method used for collecting the residues, among other factors.

Given that foliage and bark typically contain lower cellulose contents than wood, a greater mass proportion of stem wood will favour an increased cellulose content in the harvested residues.

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Hemicellulose Content of Forest Residues

As with cellulose, the hemicellulose content of forestry residues will depend on the mass proportions that the different tree fractions (leaves, bark, tops, branches, stem wood) contribute to the total mass of harvested residues.

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Lignin Content of Forest Residues

Increased proportions of bark and stem wood in the harvested residues will favour an increased lignin content.

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Starch Content of Forest Residues

Starch can be an important constituent of forest residues as it tends to be in higher concentrations in the foliage and bark fractions of trees.

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Uronic Acid Content of Forest Residues

The uronic acid content and composition of forestry residues will depend on the mass proportions that the different tree fractions contribute to the total mass of harvested residues. For instance, bark tends to have the highest uronic acid content, followed by leaves, with lower amounts in the stem wood.

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Enzymatic Hydrolysis of Forest Residues

We can undertake tests involving the enzymatic hydrolysis of Forest Residues. 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 Forest Residues

Ash Content of Forest Residues

While most wood has a relatively low ash content, foliage can contain a significant amount of ash. Hence, a greater mass proportion of foliage in the harvested residues will lead to an increased ash content in the sample.

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Heating (Calorific) Value of Forest Residues

The heating value of forestry residues will depend on the mass proportions that the different tree fractions (leaves, bark, tops, branches, stem wood) contribute to the total mass of harvested residues.

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Ash Melting Behaviour of Forest Residues

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

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

Examples of major elements that may be present in Forest Residues 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 Forest Residues.

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Analysis of Forest Residues for Anaerobic Digestion



Biomethane potential (BMP) of Forest Residues

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 Forest Residues. 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 Forest Residues



Bulk Density of Forest Residues

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

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



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Examples of Other Feedstocks Analysed at Celignis



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