BMP testingAlgae and aquatic plants

Chlamydomonas reinhardtii — BMP: 2 studies, weighted mean 346 m³ CH₄/t VS

Chlamydomonas reinhardtii is a unicellular green model alga without a cellulosic cell wall, which favours its degradation in the digester.

CH₄ ≈ 58 % (estimate)

Published 9 March 2021Updated 29 October 20263 min readFeedstockData Editorial Team

Illustration: FeedstockData (AI, Google Gemini)

Weighted mean: 346m³ CH₄/t VS
Range: 306–387m³ CH₄/t VS
Records: 2studies
Publications: 2sources
Temperatures: 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 2 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 (346); 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

Download CSV

Source	BMP m³ CH₄/t VS	Temperature	Sample	Curve
Jankowska et al. (2017) DOI	306	38 °C · mesophilic	(orig.: “Chlamydomonas reinhardtii”): value quoted in a literature review · pretreatment: particle size reduction/sample preparation (MY-D: physical treatment)	end point (model curve)
Mussgnug et al. (2010) DOI	387	38 °C · mesophilic	Chlamydomonas reinhardtii	end point (model curve)
Weighted mean	346	arithmetic mean 346, SD 57

Process properties

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

Advantages

Methane yield in the compendium: median 346 (range 306-387) m³ CH₄/t VS, 2 records from 2 studies (weighted mean 346).
In a comparison of six species, Chlamydomonas reinhardtii was digested efficiently without pretreatment, and the gas contained 7-13% more methane than biogas from maize silage (Mussgnug et al. (2010))

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

Chlamydomonas reinhardtii is a unicellular, motile, freshwater green alga, one of the most important model organisms in cell biology and genetics. It grows in soil and shallow water bodies, and in laboratories it is cultivated in acetate media or in photobioreactors. It is not grown on an industrial scale for biogas, and the BMP data come from laboratory studies, including one literature review.

Properties relevant to digestion

The cells of this alga have a wall built of glycoproteins rich in hydroxyproline, not of cellulose, so they are less resistant to hydrolysis than algae with walls containing algaenan, such as Chlorella or Nannochloropsis. Algal biomass is usually rich in protein, so the C/N ratio is low, and the breakdown of proteins releases ammonia, which at a high load can inhibit methanogenic archaea. Lipids increase the methane potential, but too large an amount promotes inhibition by long-chain fatty acids. The starch content of the cells depends on the growing conditions and the growth phase.

How to read the spread of results

The composition of algal biomass is not constant: the content of protein, starch and lipids depends on the medium, light intensity, the age of the culture and nitrogen deficiency. A laboratory strain grown on acetate differs from a culture in mineral medium. The result is also affected by the form of the feed (fresh suspension, concentrated biomass, freeze-dried material), cell disruption, the substrate-to-inoculum ratio, temperature and test length. One of the values was quoted in a literature review, with a less detailed description of conditions, and with a small number of records the spread does not describe the variability of the species.

In biogas plant practice

Chlamydomonas reinhardtii is not a substrate used in biogas plants. The results are of illustrative value for the concept of digesting algal biomass, for example as the last stage of a biorefinery. In practice, algae cultivation requires investment and is costly, and separating biomass from a dilute suspension consumes energy. If the alga does reach the digester, combining it with a carbon-rich substrate is beneficial in order to lower the ammonia concentration. Legal requirements depend on the origin and manner of use of the biomass.

It should be added that results obtained for laboratory strains, including mutants with altered biomass composition, need not correspond to the wild type. In studies on the model alga, a change in the content of starch or lipids can significantly shift the methane potential.

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.