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BMP testingBy-products of the agri-food industrysingle study (3 samples)

Coffee mucilage — BMP: 3 studies, weighted mean 279 m³ CH₄/t VS

Coffee mucilage is the sugar- and pectin-rich layer of the coffee bean, removed in wet processing; it ferments readily, and it was studied at several temperatures.

CH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Illustration: FeedstockData (AI, Google Gemini)

Weighted mean
279m³ CH₄/t VS
Range
256–294m³ CH₄/t VS
Records
3single study (3 samples)
Publications
1source
Temperatures
21 °C, 30 °C, 37 °Cof the test

Methane in biogas

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 3 studies

Weighted mean Individual records

BMP curves: Coffee mucilageCumulative methane production over time for 3 records and the weighted mean of 279 m³ CH₄/t VS. 3 of the curves are model curves (first-order kinetics).01002003004000510152025303540time [d]m³ CH₄/t VSChala et al. (2019) · 1: 256 m³ CH₄/t VS (model curve)Chala et al. (2019) · 2: 287 m³ CH₄/t VS (model curve)Chala et al. (2019) · 3: 294 m³ CH₄/t VS (model curve)mean279

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 (279); 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
SourceBMP
m³ CH₄/t VS		TemperatureSampleCurve
Chala et al. (2019) · 1 DOI25621 °C · psychrophilicCoffee mucilage, 21 Cend point (model curve)
Chala et al. (2019) · 2 DOI28730 °C · mesophilicCoffee mucilage, 30 Cend point (model curve)
Chala et al. (2019) · 3 DOI29437 °C · mesophilicCoffee mucilage, 37 Cend point (model curve)
Weighted mean279arithmetic mean 279, SD 20

Process properties

  • easily degradable
  • acidic
  • dilutes the feed (low DM)
  • 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 279.2 m³ CH₄/t VS (SD 20.5; 3 records, 1 source).
  • A liquid, sugar-and-pectin substrate; fits into liquid mixes (Hagos et al. 2017).

Drawbacks and risks

  • Pectins may give methanol (Chen et al. 2008, organic inhibitors).

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

Dosing

No source-based threshold; dose continuously with slurry.

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

Sources of the process data

  1. Hagos et al. (2017). Anaerobic co-digestion process for biogas production: progress, challenges and perspectives. Renew. Sustain. Energy Rev.
  2. Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
  3. Chen, Cheng, Creamer (2008). Inhibition of anaerobic digestion process: A review. Bioresour. Technol.

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

What it is and where it comes from

Coffee mucilage is the gelatinous layer between the pulp and the parchment of the coffee bean. In the wet method it is removed by fermentation or mechanically, and then washed out with water, forming a liquid or semi-liquid waste with a high organic load. It arises on coffee farms in many tropical countries. In Poland this material does not occur.

Properties relevant to digestion

Mucilage consists mainly of water, simple sugars (glucose, fructose, sucrose), pectins and organic acids. It contains little lignin and protein. As a result it is very readily fermentable, and the risk is rapid acidification in the absence of a buffer. Pectins can yield methanol, and in addition mucilage contains small amounts of caffeine and polyphenols. It is a low-energy material per unit volume because of its high water content. It undergoes spontaneous fermentation quickly.

How to read the spread of results

The dataset contains several records from one study: mucilage examined at temperatures of 21, 30 and 37 °C, with similar results. This means a small dependence of the result on temperature in this range, but does not allow variability between laboratories to be assessed. The actual result is affected by the degree of ripeness of the fruit, the method of removing the mucilage (fermentation or mechanical), dilution with wash water, the inoculum and the substrate-to-inoculum ratio.

In biogas plant practice

Coffee mucilage can supplement the feed on coffee farms, together with pulp and manure. Because of its easy hydrolysis, doses should be spread over time and the pH monitored. The liquid form eases pumping, but dilutes the feed. In producing countries it is sometimes the main source of water pollution, so the biogas plant also serves a treatment function. For Poland the data are of comparative character.

Good practice is to combine mucilage with materials of higher fibre content, such as coffee husk or manure, which stabilise the process and supply buffer. Using mucilage alone as a mono-substrate risks a sudden drop in pH and the halting of methanogenesis.

It is also worth remembering that wash water contains mucilage in dilution, so the actual dry matter content of waste from the farm may be much lower than in the sample examined in the laboratory, which changes the profitability of transport and the necessary retention times.

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

  1. Chala, B.; Oechsner, H.; Müller, J. (2019). Introducing Temperature as Variable Parameter into Kinetic Models for Anaerobic Fermentation of Coffee Husk, Pulp and Mucilage. Applied Sciences 9(3), 412. DOI: 10.3390/app9030412 DOI

All sources of the site: bibliography.

Other substrates in the group “By-products of the agri-food industry”