BMP testingBy-products of the agri-food industry

Grape pomace (marc) — BMP: 6 studies, weighted mean 221 m³ CH₄/t VS

Grape pomace consists of skins, seeds and remains of pulp after pressing; it contains polyphenols and lignin from the seeds, and the results from a small number of records vary widely.

CH₄ ≈ 54 % (estimate)

Published 20 June 2022Updated 29 October 20263 min readFeedstockData Editorial Team

Photo davitydave / Wikimedia Commons, licence CC BY 2.0, source file; changes: cropping

Weighted mean: 221m³ CH₄/t VS
Range: 116–360m³ CH₄/t VS
Records: 6studies
Publications: 5sources
Temperatures: 35 °C, 40 °C, 55 °Cof the test

Methane in biogas

≈52–55% CH₄

Medium methane content · ≈ 5.4 kWh/m³ of biogas

estimate from the substrate type The collected studies contain no measurement. The interval follows from the approximate composition (protein from total nitrogen (N 2.3 % DM × 6.25)) 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: the dry matter in the data refers to a sample dried for the test, not to the material as delivered. 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 6 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 (221); 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
Kassongo et al. (2021) DOI	144	35 °C · mesophilic	grape marc	end point (model curve)
Da Ros et al. (2016) · 1 DOI	347	55 °C · thermophilic	fresh grape marcs	end point (model curve)
Da Ros et al. (2016) · 2 DOI	360	55 °C · thermophilic	fermented grape marcs	end point (model curve)
Dinuccio et al. (2010) DOI	116	40 °C · mesophilic	Grape marcs	end point (model curve)
Gunaseelan (2004) DOI	283	35 °C · mesophilic	gRape vine pressings	end point (model curve)
Kouas et al. (2017) DOI	208	35 °C · mesophilic	Grape marcs	end point (model curve)
Weighted mean	221	arithmetic mean 243, SD 103

Typical composition

Dry matter (DM): 61.4% (range 61.4–61.4)
Volatile solids (VS): 92 % DM (range 90.7–93.2)
Nitrogen: 2.3 % DM

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: MY-D); dry matter: 1 determination, volatile solids: 2 determinations. DM from a single determination – indicative value.

Sources: Dinuccio et al. (2010); Gunaseelan (2004).

The composition of the raw material varies between batches — for plant calculations use an analysis of your own sample. The calculator inserts typical values automatically.

Process properties

contains inhibitors
fibrous
acidic
seasonal
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 potential in the Substraty.pl BMP dataset: weighted mean 220.9 m³ CH₄/t VS (SD 103.2; 6 records, 5 sources).
A mix of skins, seeds and stalks of variable potential.

Drawbacks and risks

Tannins and polyphenols bind proteins and inhibit microorganisms (Chen et al. 2008).
Fresh pomace acidifies.

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

Shred: shredding increases the surface available for degradation and speeds it up, but does not necessarily raise the final gas yield (FNR 2010, Ch. 3 “Triturado”).

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

Grape pomace arises after the must is pressed and makes up a significant part of the mass of the grapes processed. For white wines the pomace is obtained before fermentation and contains more sugar, whereas for red wines it ferments together with the must, so it is already fermented. In Mediterranean countries the pomace is distilled, and in Poland, where winemaking is small, the stream is small and local.

Properties relevant to digestion

Pomace consists of skins, seeds and stalks in various proportions. It contains cellulose, hemicellulose and lignin (especially in the seeds), fat in the seeds, protein, and polyphenols and tannins. Fresh pomace still contains soluble sugars, whereas fermented pomace is stripped of them and contains ethanol and acids. Tannins and polyphenols bind proteins and may inhibit microorganisms. Seeds are hard and poorly degradable without grinding. The risks are acidification in the case of fresh pomace and a higher concentration of phenols.

How to read the spread of results

The set contains several records from several sources, with a large spread of results. They include fresh and fermented pomace, a 42-day batch test and conditions of 35, 40 and 55 °C. The skin-to-seed ratio, variety, degree of fermentation, the method of drying and storage, particle size and inoculum all have an effect. The spread therefore reflects the real heterogeneity of the material.

In biogas plant practice

Pomace can be added to co-digestion after grinding, in a small share, with slurry or other wastes. Owing to seasonality it has to be stored, usually ensiled, because fresh pomace moulds quickly. Alternative uses (seed oil, polyphenol extraction, compost, feed) compete with the biogas plant. Waste from wineries is waste or a by-product depending on how it is used, which must be taken into account in the documentation.

Because of the high variability, it is worth determining the dry matter, sugar and ethanol content of each batch and assuming that fresh and fermented pomace require different dosing, because the former acidifies the feed faster, while the latter brings in acids and alcohol.

The high polyphenol content is a subject of research into their extraction before digestion, which improves the yield but raises the cost of the whole process.

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.