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BMP testingBy-products of the agri-food industry

Hazelnut residues (shell, skin) — BMP: 2 studies, weighted mean 153 m³ CH₄/t VS

Hazelnut waste (shell and skin) comprises two different fractions from processing; the shell is strongly woody, and the skin is thin and richer in polyphenols.

rating: neutralCH₄ ≈ 51 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo daryl_mitchell from Saskatoon, Saskatchewan, Canada / Wikimedia Commons, licence CC BY-SA 2.0, source file; changes: cropping

Weighted mean
153m³ CH₄/t VS
Range
40–265m³ CH₄/t VS
Records
2studies
Publications
2sources
Temperatures
37 °Cof the test

Methane in biogas

Low methane content · ≈ 5.1 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 0.1 % 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

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 (141 m³ CH₄/t); process risk: inhibitors. Handling costs: fibres, floating layer, slow degradation.

Why? Rating factors

Potential per tonne +1

  • +1potential 141 m³ CH₄/t fresh matter (BMP 153 × DM 93.2 % × VS 99.3 %); low degradability of VS (BMP 153 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: Hazelnut residues (shell, skin)Cumulative methane production over time for 2 records and the weighted mean of 153 m³ CH₄/t VS. 2 of the curves are model curves (first-order kinetics).01002003000510152025303540time [d]m³ CH₄/t VSOliva et al. (2024): 265 m³ CH₄/t VS (model curve)Shen et al. (2018): 40 m³ CH₄/t VS (model curve)mean153

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 (153); 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
Oliva et al. (2024) DOI26537 °C · mesophilicHazelnut skin (HS raw)end point (model curve)
Shen et al. (2018) DOI4037 °C · mesophilichazelnut shell · pretreatment: particle size reduction/sample preparation (MY-D: physical treatment)end point (model curve)
Weighted mean153arithmetic mean 153, SD 159

Typical composition

Dry matter (DM)
93.2% (range 93.2–93.2)
Volatile solids (VS)
99.3 % DM (range 99.3–99.3)
Nitrogen
0.1 % DM
C/N ratio
324.2

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: 1 determination. 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: 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
  • 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 152.7 m³ CH₄/t VS (SD 159.4; 2 records, 2 sources).
  • Hazelnut shell and skin: a dry, durable material, no risk of acidification - does not burden the VFA system (Hendriks and Zeeman 2009).

Drawbacks and risks

  • The skin contains polyphenols that may inhibit microorganisms (Chen et al. 2008).

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

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

  1. Hagos et al. (2017). Anaerobic co-digestion process for biogas production: progress, challenges and perspectives. Renew. Sustain. Energy Rev.
  2. Weiland (2010). Biogas production: current state and perspectives. Appl. Microbiol. Biotechnol.
  3. Rajagopal, Masse, Singh (2013). A critical review on inhibition of anaerobic digestion process by excess ammonia. Bioresour. Technol.
  4. Hendriks, Zeeman (2009). Pretreatments to enhance the digestibility of lignocellulosic biomass. 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

The hazelnut (Corylus avellana) is grown in Turkey, Italy, Spain and the USA, among others, and in Poland in orchards of smaller scale. Shelling and roasting produce several wastes: the hard shell and the thin skin covering the kernel, removed in processing. The dataset contains several records from several studies: raw skin and shell. The material thus includes two physically different fractions.

Properties relevant to digestion

The shell is a tightly packed lignocellulosic material with a high lignin share, so it decomposes slowly and only to a small extent. The skin contains polyphenols (tannins) and dietary fibre, is thinner and hydrolyses more easily. For both fractions comminution is important: the finer the particles, the more enzymes have access to the cellulose. The low protein content means a high C/N ratio. These materials are dry, so they do not introduce water.

How to read the spread of results

The result for the shell and for the skin will by nature differ, because they are different parts of the fruit. In addition, the data come from several studies, so a difference of methods and laboratories is added. The nut variety, the method of processing (raw or roasted skin), the degree of comminution, the test length and the inoculum all have an effect. In the case of the shell, decomposition does not reach a plateau within the typical test period, so a short test underestimates the potential.

In biogas plant practice

Nut shells are valued as a solid fuel and as a material for compost and bedding, so they rarely go to the digester. Hazelnut skin, a processing waste, is a more available substrate, although in a small quantity. In the mix it requires grinding and a longer retention time. Before introducing it, it is worth carrying out a BMP test and assessing the economic balance against other routes of management.

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. Oliva, A.; Tan, L.C.; Papirio, S.; Esposito, G.; Lens, P.N.L. (2024). Use of N-Methylmorpholine N-oxide (NMMO) pretreatment to enhance the bioconversion of lignocellulosic residues to methane. Biomass Conversion and Biorefinery 14(10), 11113–11130. DOI: 10.1007/s13399-022-03173-x DOI
  2. Shen, J.; Yan, H.; Zhang, R.; Liu, G.; Chen, C. (2018). Characterization and methane production of different nut residue wastes in anaerobic digestion. Renewable Energy 116, 835–841. DOI: 10.1016/j.renene.2017.09.018 DOI

All sources of the site: bibliography.

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