BMP testingBy-products of the agri-food industry

Stone-fruit stones (plum, cherry, apricot) — BMP: 3 studies, weighted mean 84 m³ CH₄/t VS

Plum, cherry and apricot stones are hard, woody wastes of fruit processing; records from several studies show how much results differ between species.

rating: negative CH₄ ≈ 52 % (estimate)

Published 20 January 2020Updated 29 October 20263 min readFeedstockData Editorial Team

Illustration: FeedstockData (AI, Google Gemini)

Weighted mean: 84m³ CH₄/t VS
Range: 31–175m³ CH₄/t VS
Records: 3studies
Publications: 3sources
Temperatures: 37 °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 (protein from total nitrogen (N 1.3 % 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

negative — editorial rating for biogas plantsMay endanger process stability — not worth taking even with a large payment

Potential per tonne of fresh matter: low, but limited by the poor degradability of the organic matter (78 m³ CH₄/t); process risk: inhibitors. Handling costs: fibres, floating layer, slow degradation. Low potential combined with process risk and handling costs.

Why? Rating factors

Potential per tonne 0

±0potential 78 m³ CH₄/t fresh matter (BMP 84 × DM 95.3 % × VS 98.5 %); low degradability of VS (BMP 84 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: −2 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.

Low potential combined with process risk and handling costs.

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

Add to the co-digestion calculator CSV data

BMP curves from 3 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 (84); 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
Carchesio et al. (2014) DOI	175	—	Plum stones	end point (model curve)
Zhao et al. (2016) DOI	31	—	Cherry (Cerasus pseudocerasus) – Seed	end point (model curve)
Shen et al. (2018) DOI	45	37 °C · mesophilic	bitter apricot kernel shell · pretreatment: particle size reduction/sample preparation (MY-D: physical treatment)	end point (model curve)
Weighted mean	84	arithmetic mean 84, SD 79

Typical composition

Dry matter (DM): 95.3% (range 95.3–95.3)
Volatile solids (VS): 98.5 % DM (range 97.7–99.2)
Nitrogen: 1.3 % DM
C/N ratio: 130.4

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: BCBPD, MY-D); dry matter: 1 determination, volatile solids: 2 determinations. C/N was calculated as the ratio of C and N content (% DM) from the same source. Samples were tested dried/air-dry – the DM refers to the material in the test, not to fresh material.

Sources: Zhao et al. (2016); Shen et al. (2018).

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
slowly degrading
low in nitrogen
carbon-rich
high dry matter
contains inhibitors
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 83.6 m³ CH₄/t VS (SD 79.2; 3 records, 3 sources).
Stone-fruit stones: a dry, durable material, no risk of acidification - does not burden the VFA system (Hendriks and Zeeman 2009).

Drawbacks and risks

The kernels contain cyanogenic glycosides - limit doses of crushed kernels (Chen et al. 2008, cyanides).

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]
combines well
substrates: protein-rich — e.g. Food waste, Municipal sewage sludge (mixed), Poultry manure, Organic fraction of municipal solid waste, Grass clippings
The high C/N of the material balances protein substrates, limiting the ammonia risk.^[1][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

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”).
Control floating crust and sediment: when solids are fed directly into the digester, the risk of their formation depends on the substrate (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

Stones of stone fruit arise in the production of juices, jams, purées, liqueurs and preserves, as well as in the drying and pitting of fruit. In Poland plum, cherry and sour cherry stones are available, and to a lesser extent apricot and peach stones. The dataset brings together records from several studies: plum stones, cherry stones and shells of bitter apricot stones. It is therefore not a single material, but several related ones, of similar structure but different properties.

Properties relevant to digestion

The stone wall is a dense, woody tissue (sclerenchyma) with a high share of lignin and cellulose, resistant to anaerobic degradation. Inside is the kernel (seed), containing fat and protein, which degrades more readily. The kernels of plum, cherry and apricot contain cyanogenic glycosides, e.g. amygdalin; in an anaerobic system they are usually not a problem at moderate doses, but with large quantities of crushed kernels caution is advisable. The whole material is dry and poor in nitrogen.

How to read the spread of results

The records differ not only in species, but also in whether whole stones (with kernel) or only the shell were tested. They come from several different studies and methods, and temperatures are not always given in the compilation. In addition, size reduction is of great importance: whole stones degrade very slowly, milled ones many times faster. The fruit variety, residual pulp on the stones and the length of the test also have an effect, because woody material usually does not reach a plateau in the typical time.

In biogas plant practice

Stones have other, better energy uses: combustion in solid-fuel boilers, production of activated carbon or bedding. In the digester they are more a problem than an advantage, because they degrade slowly, settle in the lower parts and wear agitator components. If they arrive as part of processing waste, they require separation or milling. Before introducing them in larger quantities it is worth running a BMP test and assessing whether the additional methane production justifies the cost of preparation.

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.