• Combustion of Biomass
    Important Analysis Methods

While anaerobic digestion is an important means of valaorising some feedstocks, and there is great potential for the biorefining of biomass to produce biobased chemicals and advanced biofuels, the main current use of biomass globally is for combustion. We have a range of analysis packages to help you determine the value of your feedstocks for the production of heat and electricity via combustion or utilisation in other thermal treatment processes (e.g. pyrolysis and gasification).

Our laboratory is equipped with a number of state-of-the art items of
equipment that allow us to determine the most important combustion-related properties of your biomass including calorific value, volatile matter, elemental composition, moisture content, ash composition and ash melting behaviour.

We recognise that it is important that you have confidence in the analytical data that you receive. That is why we follow internationally-recognised standard analysis methods and undertake all analyses in duplicate, reporting values for each of the replicates analysed, along with the average and the standard deviation. This allows us to repeat the analysis (at no extra charge) if the deviation values are high.

Moisture and ash contents are of crucial importance for combustion. This is reflected in our online, Excel, and pdf reports where all data for bioenergy-related parameters are expressed on dry-mass, as-received, and dry-ash free bases, according to standard method EN 15296:2011.

Important Parameters for Combustion

The key analytes and properties related to the combustion of biomass, and the analysis packages that Celignis offers for these, are listed below. Click on an a package for further details on it.

Moisture Content

The moisture content of biomass is a crucial efficiency parameter when biomass combustion is the main consideration, but less important in some lignocellulose hydrolysis technologies. Its determination is also necessary in most carbohydrate analytical procedures and it has a huge influence on the near infrared spectra of lignocellulosic materials.

Water is generally held in biomass in two ways - either as a free liquid and vapour that is contained in the cell cavities, or as a molecule that is bound within the cell walls.

Moisture content tends to vary widely with biomass species, age, geographic locations and genetic differences. It also varies between different anatomical fractions of the same plant and throughout the year.

The moisture content of biomass can either be measured on a wet or dry basis. The wet-basis expresses the ratio of moisture mass to the total mass of the substance whilst the dry basis expresses the ratio of the moisture mass to the mass of dry matter. All Celignis moisture data are reported using the wet-basis. Many of our thermal analysis packages (e.g. P40) report thermal properties, such as the ash content and calorific value, on both the dry and as-received (i.e. including moisture) bases. These conversions to different bases are undertaken according to standard method EN 15296:2011.

Similarly, our data regarding the biomethane potential of anaerobic digestion feedstocks are reported on as-received as well as dry bases.

Analysis Packages for Moisture Content


Ash Content

Ash is generally considered to be the residue remaining after the material has been incinerated. It therefore has no energy value and, being made up of the inorganic elements in the biomass, is of no direct value in hydrolysis technologies. High ash-contents can cause problems in many thermochemical processes (e.g. pyrolysis, gasification, and combustion).

Ash content can vary greatly between plant species, and is generally higher in agricultural residues. The ash present in plants will depend on their stage of growth, the time of year, and their location. The leaching of stored biomass may reduce the level of inorganics in some instances.

The major cations present in ashes from lignocellulosic materials are Calcium, Potassium and Magnesium. Other elements such as Manganese, Sulphur and Phosphorus are present in minor amounts. Trace constituents (such as Al, Fe, Zn, Cu, Ti, Pb, Ni, V, Co, Ag and Mo) are also found in many substrates. The anions that are usually present are Chloride, Carbonate, Sulphate and Silicate. With waste feedstocks (municipal solid wastes in particular), ashes are often more abundant and more diverse.

At Celignis with our elemental analysis methods we are able to characerise a wide range of major and minor analytes present in biomass ash. Click here to see our relevant analysis packages.

Analysis Packages for Ash Content


Analysis Packages for Ash Composition


Ash Melting Behaviour

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

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

Analysis Packages for Ash Melting Behaviour


Ultimate Analysis

The ultimate analysis of biomass will provide the mass concentrations of the major elements (carbon, oxygen, hydrogen, nitrogen and sulphur) in the sample. These concentrations will depend on the chemical composition of the biomass sample.

Lignocellulosic biomass is mainly composed of carbohydrates (in the form of the polysaccharides cellulose and hemicellulose) and lignin. Carbohydrates, having an elemental composition of (CH2O)n, will have a generally uniform carbon content of 40%, which is lower than many other biomass mass constituents such as lignin which has an average carbon content of approximately 60-65%.

Typically carbon, hydrogen, nitrogen, and sulphur can be determined in the same analytical method and the oxygen content can then be calculated as the remaining mass after the ash content has been considered.

We use an Elementar MACRO Cube unit for the ultimate analysis of samples. It allows for large sample sizes (e.g. around 40mg) to be used than many other elemental analysers, allowing us to improve the precision in the analysis of biomass and waste samples.

Analysis Packages for Ultimate Composition


Heating Value

The heating value is currently one of the most important properties of biomass given the predominance of combustion facilities over other biomass valorisation technologies.

There are several units of measurement. The caloric, or higher heating value (HHV), is independent of moisture content and reliant on the chemical composition of the material. A linear relationship exists between the heat of combustion and the carbon content of the substrate while oxygen, nitrogen and inorganic elements tend to reduce the value.

The Lower Heating Value (LHV), or effective heating value, is perhaps more relevant than the HHV in practical operations. It considers not only the energy required to vaporise the moisture of the biomass but also that necessary to vaporise the water generated when the hydrogen and oxygen elements of the biomass combine. Hydrogen content then becomes a reducing factor in the heating value.

The heating value of samples can be determined directly, by combusting the sample in a bomb calorimeter, or it can be calculated based on elemental composition. The heating value can be reported on a dry or wet basis. The wet-basis value considers the moisture content of the biomass and reduces the heating value to incorporate the latent heat of condensation.

At Celignis we use a Parr 6200 bomb calorimeter to directly determine the gross calorific value (higher heating value) of samples. The data from ultimate analysis are then used to calculate the net calorific value (lower heating value).

Analysis Packages for Calorific Value