About usContact

BMP testingBy-products of the agri-food industrysingle study (2 samples)

Green coffee processing residues — BMP: 2 studies, weighted mean 138 m³ CH₄/t VS

Dust and silverskin from green coffee processing are dry, light wastes from roasteries and bean sorting plants, with a high fibre content and a low acidification potential.

rating: neutralCH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo Michael Allen Smith@INeedCoffee from Seattle, USA / Wikimedia Commons, licence CC BY-SA 2.0, source file; changes: cropping

Weighted mean
138m³ CH₄/t VS
Range
128–148m³ CH₄/t VS
Records
2single study (2 samples)
Publications
1source
Temperatures
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

neutral — editorial rating for biogas plantsNo clear advantages — worth charging a fee for accepting it

Potential per tonne of fresh matter: moderate, but limited by the poor degradability of the organic matter (103 m³ CH₄/t); process risk: inhibitors. Handling costs: fibres, floating layer, slow degradation.

Why? Rating factors

Potential per tonne +1

  • +1potential 103 m³ CH₄/t fresh matter (BMP 138 × DM 81.9 % × VS 91.5 %); low degradability of VS (BMP 138 m³ CH₄/t VS) — points capped

Process stability −1

  • −1inhibitors: natural or residues (e.g. limonene, polyphenols, antibiotics, metals)

Handling and costs −1

  • −0.5fibres, floating layer — shredding and intensive mixing
  • −0.5slow degradation — long retention time

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

BMP curves: Green coffee processing residuesCumulative methane production over time for 2 records and the weighted mean of 138 m³ CH₄/t VS. 2 of the curves are model curves (first-order kinetics).0501001502000510152025303540time [d]m³ CH₄/t VSVelasquez-Pinas et al. (2023) · 1: 128 m³ CH₄/t VS (model curve)Velasquez-Pinas et al. (2023) · 2: 148 m³ CH₄/t VS (model curve)mean138

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 (138); 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
Velasquez-Pinas et al. (2023) · 1 DOI12837 °C · mesophilicgreen coffee filmend point (model curve)
Velasquez-Pinas et al. (2023) · 2 DOI14837 °C · mesophilicgreen coffee powderend point (model curve)
Weighted mean138arithmetic mean 138, SD 14

Typical composition

Dry matter (DM)
81.9% (range 69.7–94.1)
Volatile solids (VS)
91.5 % DM (range 90.9–92.1)

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

Sources: Velasquez-Pinas et al. (2023).

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

  • fibrous
  • high dry matter
  • contains inhibitors
  • slowly degrading
  • 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 138.0 m³ CH₄/t VS (SD 14.1; 2 records, 1 source).
  • A dry lignocellulosic waste that is easy to store (Hendriks and Zeeman 2009).

Drawbacks and risks

  • Polyphenols and caffeine may inhibit at high doses (Chen et al. 2008).
  • Dust - exclude dust generation during dosing.

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

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

  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. Hendriks, Zeeman (2009). Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresour. Technol.
  4. Chen, Cheng, Creamer (2008). Inhibition of anaerobic digestion process: A review. Bioresour. Technol.
  5. FNR (2010). Guía sobre el Biogás – Desde la producción hasta el uso (hiszp. wydanie „Leitfaden Biogas”, GIZ 2013)

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

What it is and where it comes from

Green coffee, that is, raw beans before roasting, is cleaned and sorted in processing plants and roasteries. In this process dust and the so-called silverskin are separated off: the thin membrane surrounding the bean, which partly falls away already during wet or dry processing. Small but uniform waste streams arise at coffee packing or roasting plants. Coffee processing is well developed in Poland, although in overall terms the quantities of waste are small.

Properties relevant to digestion

Silverskin is lignocellulosic in nature: it contains cellulose, hemicellulose and lignin, as well as protein and small amounts of lipids. Dust contains bean fragments and is therefore sometimes richer in protein, fat and soluble compounds. Both fractions contain caffeine, chlorogenic acid and other polyphenols, which at high concentrations can affect microbial activity, although at typical shares in the feed this effect is limited. The material is dry, light and dusty, which makes feeding difficult, and the dust can pose an explosion hazard during dry handling.

How to read the spread of results

The dataset contains several records from a single study, carried out under mesophilic conditions: one for silverskin, another for dust. Both fractions gave similar results, which suggests that in this study the type of fraction was not the main source of variability. It is not known, however, whether this conclusion generalises to other batches. The results depend on the coffee variety (arabica, robusta), the method of bean processing, the degree of size reduction, moisture and the inoculum.

In biogas plant practice

Green coffee silverskin and dust can be added to co-digestion at a small share, preferably after wetting or mixing with a liquid fraction, for example slurry. Dry dust must be protected against becoming airborne. The material is stable and tolerates storage in dry conditions well, which makes it easier to plan deliveries. Waste from food processing is waste, so its acceptance requires appropriate authorisations, and if the material is sold as a by-product, a different legal regime applies. Because of the small quantity of material its effect on the plant's balance is limited, but it can be a valuable local supplement.

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. Velasquez-Pinas, J.A.; Ampese, L.C.; Di Domenico Ziero, H.; Radis Steinmetz, R.L.; Belt, C.; Forster-Carneiro, T. (2023). Circular bioeconomy of coffee industries: Energy and techno-economic approach based on biogas and biomethane production. Journal of Cleaner Production 418, 138045. DOI: 10.1016/j.jclepro.2023.138045 DOI

All sources of the site: bibliography.

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