Chemical analysis – biomass to product

Wood & pulp

Analyses include fibre content, residual alkali, sulphur compounds, oxalate, chlorides, metals, carbohydrates, lignin, tall oil, terpenes, hydroxy and volatile acids, as well as dry matter and ash.

The risk of scaling increases with high levels of extractives, leading to operational disturbances and costly maintenance. Key parameters to monitor include carbonate, sulphate, oxalate, calcium, sodium, aluminium, silicon and dry matter. These measurements support process optimisation and help prevent scaling issues.

Metal analyses include calcium, copper, iron, magnesium, manganese, potassium, sodium, cadmium and lead. For broader or more sensitive multi‑element analysis, ICP‑OES is used to quantify several metals simultaneously in process liquors, solids, extracts and ash. Common ICP‑OES targets are aluminium, barium, cobalt, chromium, phosphorus, silicon and zinc.

Gas analyses include hydrogen sulphide (H₂S), carbon dioxide (CO₂), sulphur dioxide (SO₂) and other volatile organic and inorganic substances. These measurements are essential for monitoring emissions, ensuring process control and meeting environmental requirements.

Inorganic compounds are analysed using highly sensitive methods to identify salts, metals, oxides and anions, even at very low concentrations. Both qualitative (identification) and quantitative (concentration) analysis are available. Instrumental methods such as GC‑MS, HPLC, ICP‑MS and FTIR enable detection down to ppm and ppb levels, supporting accurate trace analysis and residue control.

Microanalysis of particles and deposits: Using SEM‑EDS, solid particles, spots and incrustations can be examined to determine their composition and origin.

Process liquids

Black liquor from the kraft pulp process contains both organic and inorganic components that are analysed to optimise recovery, energy efficiency and overall process balance. Key parameters include fibre content, residual alkali, sulphur compounds, total sulphur, oxalate, chlorides, metals, carbohydrates, lignin (including molecular weight), tall oil, terpenes, hydroxy and volatile acids, as well as dry solids and ash.

White and green liquor are central to the chemical recovery cycle. White liquor is used directly in the cooking process, while green liquor forms an intermediate stage. To maintain a stable and efficient chemical balance, precise analyses are required for alkali content (total, active and effective), carbonates, sulphur components (sulphide, sulphite, sulphate and thiosulphate), total sulphur, potassium and sodium levels, chlorides and metal content.

Process water in the pulp industry is analysed for factors that influence process stability, efficiency and final product quality. Important parameters include anion content, cation demand, carboxylic and uronic acids, total ASA (alkenyl succinic anhydride), carbohydrates, lignin and the amount of optical brightener.
White water is examined for the same parameters, as well as starch.

Lime is assessed for free lime content, metal levels (Na, Mg, Ca, Mn, Fe, Al, Si, P, S) and acid‑soluble sodium.
Tall oil is evaluated using acid number, neutral substances, fatty and resin acids, water and ash content, along with total sulphur and sodium.
Soap is analysed for theoretical tall oil yield, alkali, calcium, dry content and calorific value.

Methanol and impure condensates are analysed for methanol, water, ammonium, total nitrogen, TRS components (hydrogen sulphide, methyl mercaptan, dimethyl sulphide and dimethyl disulphide) and total sulphur. Terpenoids, including monoterpenes such as α‑pinene, β‑pinene, 3‑carene and limonene, as well as mono‑, sesqui‑ and diterpenoids, are also assessed. GC‑MS screening identifies volatile compounds that affect odour, quality and environmental impact.

Organic substances

Organic acids and related substances are analysed to assess degradation and overall process quality. Common acids include levulinic acid, ethanol, glycerol, lactic acid, formic acid and acetic acid. Furan derivatives such as HMF and furfural indicate carbohydrate decomposition. These components can also be quantified in black liquor to evaluate the cooking process.

Organic compounds and extractives are analysed in forest raw materials, process liquids and by‑products. The focus includes lignans, fatty and resin acids, sterols, steryl esters, triglycerides and process chemicals such as anthraquinone. Rosin is assessed for its impact on bonding and odour. Carbon‑ and sulphur‑containing substances — including methanols, aldehydes, thiophenes and disulphides — are also included due to their relevance for process performance and environmental impact.

Organic acids are therefore an important indicator of both degradation and process stability. Levulinic acid, ethanol, glycerol, lactic acid, formic acid and acetic acid are commonly measured, while HMF and furfural provide additional information about carbohydrate breakdown. These parameters can be quantified in black liquor to support evaluation of the cooking stage.

Textile

Viscosity measurement is used to assess molecular weight and degradation in cellulose‑based textiles, particularly during recycling. Fibre analysis using light microscopy provides information on fibre type and dimensions, while SEM is used to examine morphology and identify defects.

Metal content is determined using ICP‑OES or ICP‑MS. Commonly measured metals include copper, zinc, chromium, lead, nickel, cadmium, iron, aluminium, sodium and potassium. Metal analysis is important for environmental and health considerations, and for assessing the recyclability of the material.