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Analysis of Grass
Grass

Background

Grasses can be classified, according to their photosynthetic pathways, as either C3 or C4 plants. C3 grasses that could be considered as energy crops for high-capacity, low-cost production include reed canary grass and giant reed while the corresponding C4 crops include miscanthus and switchgrass. Signifcant quantities of grass biomass are also obtained in municipal areas due to horticultural activities.

Celignis founder Daniel Hayes has considerable experience in the chemical and near-infrared analysis of grasses and has characterised a large number of samples from a wide variety of species.

Components of Grasses


The above ground shoot component of grasses consists of a stem and leaves. The stems are mostly hollow, cylindrical and interrupted at intervals by swollen joints or nodes from which the leaves originate. The parts of the stem between the nodes are termed the internodes.

Rhizomes are a special type of shoot that occur in some grassy species (e.g. miscanthus). They grow underground in a horizontal manner and their internodes are usually short. The only leaves present on rhizomes are small and scale-like. Rhizomes serve as survival organs after periods of senescence and also are often used for storage.

The lower portion of the leaf forms a sheath, which protects the shoots. The second half of the leaf opens out to the leaf blade.

The proportion of biomass components vary with the species. For example, with barley and wheat straw, internodes dominate (59% and 73% of the dry mass, respectively) while leaves (including sheath and blade) constitute an intermediate, and nodes a minor portion of the aboveground dry matter.

Extractives tend to be more prevalent in grasses than woody biomass. In particular, concentrations of water-soluble carbohydrates tend to be relatively high. Glucose and fructose are the two most important free-monosaccharides that occur in grasses and can have dry matter concentrations of approximately 1-3%. More prevalent is the disaccharide sucrose, which can take up 2-8% of the dry matter in forage grasses. In certain grasses, such as perennial ryegrass (Lolium perenne) and cocksfoot (Dactylis glomerata), oligosaccharides such as raffinose and stachyose have been detected, but only in relatively small concentrations. The polysaccharide fructans tend to be the most abundant of the water soluble carbohydrates, constituting around 5-9% of the dry matter of forage grasses, although values as high as 12% have been reported for perennial ryegrass.


Analysis of Grass at Celignis


Celignis Analytical can determine the following properties of Grass samples:

If you would like us to analyse your Grass samples then please select the appropriate analysis packages from our list.

Cellulose Content of Grass

Cellulose is typically the most abundant constituent, by mass, in most grass species. However, its content can vary significantly according to: the stage of growth; the plant fraction (e.g. node, internode, leaf etc.); and the particular species and variety of grass.

Click here to see the Celignis Analysis Packages that determine cellulose content.



Hemicellulose Content of Grass

Xylans are the dominant hemicellulose type in most species. As with cellulose, the hemicellulose content of grasses can be highly variable.

Click here to see the Celignis Analysis Packages that determine hemicellulose content.



Lignin Content of Grass

The lignin content of grasses is significantly lower than that of wood, although lignin-carbohydrate associations tend to be stronger. There is particular covalent cross-linking (through phenolic acids) between arabinoxylans and lignin polymers. The cuticle contains waxes and waxy polymers that can be also be cross-linked within lignin-like phenolics.

Click here to see the Celignis Analysis Packages that determine lignin content.



Starch Content of Grass

The starch content of grasses can be high, when compared with some other biomass feedstocks. It will also vary significantly according to the growth stage of the plant.

Click here to see the Celignis Analysis Packages that determine starch content.



Uronic Acid Content of Grass

Uronic acids can be present as side chains attached to the main backbone of hemicelluloses in grasses. They are typically more abundant in the early-stages of growth. Furthermore, the concentrations of uronic acids tends to be greatest in the nodes, lower in the internodes, and at intermediate levels in the leaves.

Click here to read more about uronic acids and to see the Celignis Analysis Packages that determine uronic acid content.



Ash Content of Grass

Grasses tend to have higher ash contents than wood. Regarding the constituent elements, the epidermal cells of some species, particularly cereals, contain high levels of silica.

Click here to see the Celignis Analysis Packages that determine ash content.



Heating (Calorific) Value of Grass

Grasses tend to have lesser heating values than woods, due to their lower lignin and high ash contents. The effective heating value is also greatly dependent on the moisture content of the feedstock, which can vary significantly according to the stage of development of the plant.

Click here to see the Celignis Analysis Packages that determine heating value.



Bulk Density of Grass

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

Click here to see the Celignis Analysis Packages that determine bulk density.



Basic Density of Grass

At Celignis we can determine the basic density of some suitable biomass samples. The method requires the biomass to be in an appropriate form (chips) for density determination.

Click here to see the Celignis Analysis Packages that determine basic density.

 

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