BMP testingAlgae and aquatic plantssingle study (2 samples)

Hydrodictyon reticulatum (water net) — BMP: 2 studies, weighted mean 250 m³ CH₄/t VS

Hydrodictyon reticulatum, the water net, is a filamentous freshwater alga forming blooms in nutrient-rich waters; studies are few.

CH₄ ≈ 52 % (estimate)

Published 15 March 2026Updated 29 October 20263 min readFeedstockData Editorial Team

Photo Pablo Cauã da Silva Toledo / Wikimedia Commons, licence CC BY 4.0, source file; changes: cropping

Weighted mean: 250m³ CH₄/t VS
Range: 170–330m³ CH₄/t VS
Records: 2single study (2 samples)
Publications: 1source
Temperatures: 35 °Cof the test

Methane in biogas

≈51–54% CH₄

Medium methane content · ≈ 5.2 kWh/m³ of biogas

estimate from the substrate type The collected studies contain no measurement. The interval follows from the approximate composition (carbohydrate-dominated (no protein or fat characteristics)) 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 (250); 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) · 1 DOI	170	35 °C · mesophilic	(orig.: “H.reticulatum”): value quoted in a literature review	end point (model curve)
Jankowska et al. (2017) · 2 DOI	330	35 °C · mesophilic	(orig.: “H.reticulatum”): value quoted in a literature review · pretreatment: particle size reduction/sample preparation (MY-D: physical treatment)	end point (model curve)
Weighted mean	250	arithmetic mean 250, SD 113

Process properties

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 250 (range 170-330) m³ CH₄/t VS, 2 records from 1 study (weighted mean 250).

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

Hydrodictyon reticulatum, known in English as the water net, is a green freshwater alga that forms macroscopic colonies in the form of a net of cylindrical cells. It develops in standing and slow-flowing waters rich in nutrients, where it is sometimes the cause of blooms. As biomass it is considered in the treatment of waters and water bodies. The records in the dataset come from a single literature review.

Properties relevant to digestion

The biomass of a macroalga collected from water contains a lot of water (dry matter usually very low), and its composition depends on the place of collection. The cells have a cell wall of cellulose and other polysaccharides, less resistant than in many microalgae, but requiring size reduction. The protein content can be considerable, which means a risk of ammonia in digestion without a co-substrate. The collected mass often contains sand, sediments and accompanying organisms, which contribute no methane. The seasonality of blooms limits the continuity of supply.

How to read the spread of results

Values from a single source may differ markedly, because biomass is by nature not homogeneous: it depends on the stage of bloom development, the composition of the water, the presence of epiphytes and contaminants, and on the method of preparation (fresh, dried, ground). Temperature, the substrate-to-inoculum ratio and test time also have an effect. Values quoted in a review usually have a scant description of conditions, and measurements of a small number of samples do not describe the variability of the species.

In biogas plant practice

The water net is not a commercial substrate. In practice it may appear as biomass from bloom removal, which has to be managed. Digestion is then one of the options, but it requires cleaning of sand, dewatering or thickening, and allowance for seasonality. It is worth combining it with substrates of higher dry matter. The legal status of biomass collected from waters depends on whether it is a waste, and on permits for its harvesting and management.

In practice, before considering digestion it is worth assessing whether the biomass contains heavy metals or other contaminants that algae can accumulate from water. This is significant both for the operation of the digester and for the future use of the digestate.

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

Jankowska, E.; Sahu, A.K.; Oleskowicz-Popiel, P. (2017). Biogas from microalgae: Review on microalgae's cultivation, harvesting and pretreatment for anaerobic digestion. Renewable and Sustainable Energy Reviews 75, 692–709. DOI: 10.1016/j.rser.2016.11.045 DOI

All sources of the site: bibliography.