BMP testingBy-products of the agri-food industry

Sugar beet pulp — BMP: 2 studies, weighted mean 358 m³ CH₄/t VS

Sugar beet pulp is the residue of sugar extraction from beet, rich in pectins and cellulose; a valuable feed, and in a biogas plant an easily digestible substrate with low lignin.

rating: good CH₄ ≈ 52 % (estimate)

Published 11 January 2025Updated 29 October 20263 min readFeedstockData Editorial Team

Photo Blonder1984 / Wikimedia Commons, licence CC BY-SA 3.0, source file; changes: cropping

Weighted mean: 358m³ CH₄/t VS
Range: 285–430m³ CH₄/t VS
Records: 2studies
Publications: 2sources
Temperatures: 35 °C, 38 °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

good — editorial rating for biogas plantsStable, usually accepted without a fee

Potential per tonne of fresh matter: high (82 m³ CH₄/t); no particular threats to stability. Handling costs: sand, stones, shells, fibres, floating layer.

Why? Rating factors

Potential per tonne +2

+2potential 82 m³ CH₄/t fresh matter (BMP 358 × composition per FNR (2013), Guía sobre el Biogás, Tabla 4.9: pressed beet pulp (DM 24 %, VS 95 % DM))

Process stability 0

0no factors

Handling and costs −1

−0.5sand, stones, shells — sediment in the digester
−0.5fibres, floating layer — shredding and intensive mixing

Total points: 1 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.

Editorial rating per the methodology · confidence of the rating: low · excluding market prices

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 (358); 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
Amon et al. (2007) DOI	430	38 °C · mesophilic	pressed Beet pulp Silage	end point (model curve)
Kouas et al. (2017) DOI	285	35 °C · mesophilic	beet pulp	end point (model curve)
Weighted mean	358	arithmetic mean 358, SD 102

Process properties

fibrous
carbon-rich
low in nitrogen
sand and sediment
seasonal
editorial classification

Advantages

Methane potential in the Substraty.pl BMP dataset: weighted mean 357.5 m³ CH₄/t VS (SD 102.5; 2 records, 2 sources).
Pectin-cellulosic, low in lignin; studies of sugar mill by-products (Kryvoruchko et al. 2009; Alkaya and Demirer 2011).

Drawbacks and risks

Ensiled pulp is acidic, and a large dose acidifies (Kryvoruchko et al. 2009).
Residual soil/sand from washing beets settles out.
High C/N: they require nitrogen (Alkaya and Demirer 2011).

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

combines well
substrates: high alkalinity (buffer) — e.g. Cattle manure, Pig slurry, Cattle slurry, Duck slurry, Rumen and digestive tract content
Slurry supplies N and alkalinity, balancing the high C/N of the material.^[1][2]

Dosing

No source threshold.

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

Practical requirements

Provide for removal of sand and heavy contaminants: sand is often strongly bound to organic matter and is released only in the digester, and sediments reduce its usable capacity, so a scraper or bottom drain is needed (FNR 2010, Ch. 3).

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

Sugar beet pulp arises after sugar is extracted from beet cossettes in a sugar factory. In Poland the sugar industry is well developed, and the sugar campaign runs in autumn and winter. The pulp is wet, and after pressing and drying it becomes a popular cattle feed; it can also be ensiled in clamps. In a biogas plant it appears as an additive when its price or availability is favourable, although it competes with the feed market.

Properties relevant to digestion

The dry matter of the pulp consists mainly of pectins, cellulose and hemicellulose, with a small content of lignin, protein and residual sugars. The fibrous structure is quite susceptible to enzymes, and pectins hydrolyse quickly, so the gas potential is high and degradation efficient. The risks are acidification at a high dose and the presence of sand and soil remaining after the beet is washed. Ensiled pulp contains organic acids, which lower the pH. The high C/N ratio requires the addition of nitrogen.

How to read the spread of results

The set contains several records from several sources: pressed ensiled pulp at 38 °C and pulp at 35 °C. The differences may result from the form of the material (fresh, pressed, dried, ensiled), the dry matter content, residual sugar, particle size, test duration and inoculum. Ensiling changes the composition, because part of the sugars is consumed.

In biogas plant practice

Pulp works well in co-digestion with slurry, after shredding and wetting, especially dried pulp, which must be rehydrated. Storage in a clamp is possible if the material is ensiled, and protection against leachate is necessary. Availability is seasonal, so feed planning must take the campaign period into account. As a by-product of the sugar industry, pulp has a status depending on how it is used, usually as feed or as waste.

In Poland there is competition for pulp between the feed sector and biogas plants during the campaign. In practice, biogas plants at or near sugar factories have a logistical advantage, because the material is wet and heavy, and transport costs rise quickly with distance.

Ensiled pulp available outside the campaign is particularly valuable, because it allows the supply of material to be evened out throughout the year, but it requires a well-built clamp and a film cover.

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 = 0.091 d⁻¹ was assumed (no kinetic data for the group – the median of all available rate constants k (93 values) was used).

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.