BMP testingAlgae and aquatic plants

Spirulina (Arthrospira) — BMP: 3 studies, weighted mean 257 m³ CH₄/t VS

Spirulina (Arthrospira) is a cyanobacterium with a very high protein content; digesting the biomass alone risks ammonia, so it is better to combine it with carbon substrates.

CH₄ ≈ 58 % (estimate)

Published 22 February 2026Updated 29 October 20263 min readFeedstockData Editorial Team

Photo David Bird / Wikimedia Commons, licence CC0 1.0, source file; changes: cropping

Weighted mean: 257m³ CH₄/t VS
Range: 190–293m³ CH₄/t VS
Records: 3studies
Publications: 3sources
Temperatures: 35 °C, 38 °Cof the test

Methane in biogas

≈55–62% CH₄

Medium methane content · ≈ 5.8 kWh/m³ of biogas

estimate from the substrate type The collected studies contain no measurement. The interval follows from the approximate composition (protein-rich (process classification)) and the yields of compound groups according to FNR.

How we calculate it and what the zones mean

Rating for biogas plants

not rated — editorial rating for biogas plants

Not rated: no dry matter or volatile solids in the data. We calculate the rating when the dry matter and volatile solids of the material are known.

Editorial rating per the methodology

Add to the co-digestion calculator CSV data

BMP curves from 3 studies

Weighted mean Individual records

Dashed lines are a model curve (first-order kinetics, B(t) = B₀·(1 − e^−kt)); the end point comes from the publication. All curves are model curves.

Cumulative methane production over the test [m³ CH₄/t VS]. The thick line is the weighted mean of all records (257); dots mark the end values given in the publications. Point at the chart to read values; click a legend item to hide or show a record.

Records and sources

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Source	BMP m³ CH₄/t VS	Temperature	Sample	Curve
Jankowska et al. (2017) DOI	190	35 °C · mesophilic	Arthrospira (Spirulina) maxima (orig.: “Spirulina maxima”): value quoted in a literature review	end point (model curve)
Mussgnug et al. (2010) DOI	293	38 °C · mesophilic	Arthrospira platensis	end point (model curve)
Chegukrishnamurthi et al. (2025) DOI	288	—	As received Spirulina biomass (experimental Gmax)	end point (model curve)
Weighted mean	257	arithmetic mean 257, SD 58

Process properties

protein-rich
nitrogen-rich
dilutes the feed (low DM)
variable composition
editorial classification

Low confidence: the description is based on general characteristics of the substrate group, not on studies of this material. Treat it as a hint to be verified.

Advantages

Methane yield in the compendium: median 288 (range 190–293) m³ CH₄/t VS, 3 records from 3 papers (weighted mean 257).

Drawbacks and risks

The high protein content of the cells causes release of ammonia, which can be toxic to the process (Sialve et al. (2009); Rajagopal et al. (2013))

Co-digestion — what to combine it with, what to watch out for

combines well
substrates: carbon-rich — e.g. Wheat straw, Maize silage (whole crop), Cereal straw (unspecified), Willow (short rotation), Cardboard and paperboard
The low C/N of algal sludge was balanced by the addition of paper: 50-60% VS of paper increased the rate of methane production, optimum C/N 20-25.^[1][2]
caution
substrates: nitrogen-rich — e.g. Pig slurry, Poultry manure, Waste activated sludge (secondary sludge), Chlorella vulgaris, Nannochloropsis salina
Algal protein releases ammonia; additional nitrogen sources increase the risk of ammonia inhibition.^[2][3]

Dosing

No source limits on the dose for this substrate.

Introduce gradually, starting with a small dose and monitoring the process (e.g. FOS/TAC, pH, gas composition).

Practical requirements

Do not dry the biomass before feeding: drying lowered biogas production to about 80% (Mussgnug et al. (2010))
Monitor ammonia (high protein) and, for marine species, sodium (Sialve et al. (2009))

Sources of the process data

The co-digestion calculator will assess a specific mixture containing this substrate.

What it is and where it comes from

Spirulina is the common name for cyanobacteria of the genus Arthrospira, mainly Arthrospira platensis and A. maxima. They are cultivated in ponds and photobioreactors around the world as food, a dietary supplement, feed and a source of the pigment phycocyanin. Despite the name, it is not an alga in the strict sense, but a cyanobacterium. In the dataset both species are combined, and one of the records concerns biomass as supplied. As a waste or by-product it appears with quality-deficient batches or after the extraction of pigments.

Properties relevant to digestion

Spirulina biomass usually contains more than half of its dry matter as protein, as well as lipids and carbohydrates. The cell wall is thin, made of murein, without cellulose, so the cells are readily accessible to enzymes and degrade faster than those of many green algae. The high protein content gives a low C/N ratio, and the released ammonia can inhibit methanogenic archaea, particularly at a high load or in thermophilic digestion. The biomass is also rich in sulphur from amino acids, which favours hydrogen sulphide. The salinity of the medium is moderate, but may accumulate.

How to read the spread of results

The records come from different studies and concern different forms: A. maxima (a value from a review), A. platensis and biomass as supplied. The differences arise from the composition of the biomass (protein, lipids, carbohydrates), which depends on cultivation and drying conditions, and from the way the sample was prepared. The substrate-to-inoculum ratio, adaptation of the inoculum to ammonia, and test temperature and duration also have an effect. With a small number of records it is not possible to determine a range typical for the whole species.

In biogas plant practice

Spirulina is not a substrate of commercial biogas plants. If waste arises at its production plants, it is best digested with materials of high C/N (straw, wastes rich in carbohydrates), with a moderate load and control of the ammonium nitrogen concentration. It is worth monitoring hydrogen sulphide in the biogas. The legal status depends on the origin of the waste and the plant's permits; cyanobacterial biomass without components of animal origin is not subject to the regulations on animal by-products.

Methodology in brief

BMP is the amount of methane obtained from volatile solids (VS) in a batch test, given in m³ CH₄ per tonne of VS (numerically the same as NmL CH₄/g VS in the publications) and converted to normal conditions (0 °C, 101.325 kPa). The weighted mean gives each publication a total weight of 1, split equally between its results for the substrate — a paper testing twenty varieties does not outweigh a paper with a single sample. In inter-laboratory programmes the unit is the laboratory (total weight 1), and within it the weight of a test grows with the number of bottles (replicates). Results after pretreatment (e.g. thermal, chemical, enzymatic) are shown separately and are not included in the mean.

Solid lines are curves measured in the tests. Where a publication gives only the final result, we draw a first-order kinetic model, B(t) = B₀·(1 − e^−kt): only the end point comes from the publication, and the shape of the curve serves purely as visualisation — do not read the production on a particular day from it. For this substrate k = 0.102 d⁻¹ was assumed (median of rate constants k reported in the sources and/or fitted to the mean measured curves).

The statistics describe the spread of published results — a descriptive compilation, not a meta-analysis or a guarantee of plant yield.

Full methodology and correction policy

Bibliography

All sources of the site: bibliography.