BMP testingFats, oils and animal by-products

Rumen and digestive tract content — BMP: 5 studies, weighted mean 280 m³ CH₄/t VS

Rumen and intestinal contents from slaughterhouses are a stream with a high fibre content and a low energy potential relative to fats. Subject to the regulations on animal by-products.

rating: good CH₄ ≈ 54 % (estimate)

Published 4 September 2024Updated 29 October 20263 min readFeedstockData Editorial Team

Illustration: FeedstockData (AI, Google Gemini)

Weighted mean: 280m³ CH₄/t VS
Range: 232–361m³ CH₄/t VS
Records: 5studies
Publications: 3sources
Temperatures: 37 °C, 38 °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 2.8 % DM × 6.25; in manure part of the N is ammonium nitrogen)) and the yields of compound groups according to FNR.

How we calculate it and what the zones mean

Rating for biogas plants

good — editorial rating for biogas plantsStable, usually accepted without a fee

Potential per tonne of fresh matter: moderate (44 m³ CH₄/t); stabilises the process (high alkalinity, supplies trace elements). Handling costs: sand, stones, shells, fibres, floating layer.

Why? Rating factors

Potential per tonne +1

+1potential 44 m³ CH₄/t fresh matter (BMP 280 × DM 17 % × VS 92 %)

Process stability +2

+1.5high alkalinity — stabilises the pH of the mixture
+0.5supplies trace elements (Co, Ni, Se, Fe)

Handling and costs −1

−0.5sand, stones, shells — sediment in the digester
−0.5fibres, floating layer — shredding and intensive mixing

Total points: 2 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.

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

Add to the co-digestion calculator CSV data

BMP curves from 5 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 (280); 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
Yoon et al. (2014) DOI	361	38 °C · mesophilic	Digestive tract content (piggery slaughterhouse)	end point (model curve)
Browne et al. (2013) DOI	238	37 °C · mesophilic	paunch grass (abattoir waste) · pretreatment: particle size reduction/sample preparation (MY-D: physical treatment)	end point (model curve)
Meneses Quelal i Pilamunga Hurtado (2023) · 1 DOI	232	—	Rumen residue (RR:WS 4:0), I:S 1:2	end point (model curve)
Meneses Quelal i Pilamunga Hurtado (2023) · 2 DOI	239	—	Rumen residue (RR:WS 4:0), I:S 1:1	end point (model curve)
Meneses Quelal i Pilamunga Hurtado (2023) · 3 DOI	251	—	Rumen residue (RR:WS 4:0), I:S 2:1	end point (model curve)
Weighted mean	280	arithmetic mean 264, SD 54

Typical composition

Dry matter (DM): 17% (range 17–17)
Volatile solids (VS): 92 % DM (range 92–92)
Nitrogen: 2.8 % DM
C/N ratio: 16.6

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. DM from a single determination – indicative value.

Sources: Browne et al. (2013).

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
sand and sediment
high alkalinity (buffer)
source of trace elements
ABP cat. 2
dilutes the feed (low DM)
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 279.9 m³ CH₄/t VS (SD 54.5; 5 records, 3 sources).
Rumen content supplies cellulolytic microflora and buffer like manure (Hejnfelt and Angelidaki 2009).

Drawbacks and risks

After partial digestion in the rumen the remaining potential is limited (Hejnfelt and Angelidaki 2009).

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

combines well
substrates: fat-rich — e.g. Food waste, Spent coffee grounds, Primary sludge, Sunflower seeds, Olive pomace / olive mill solid waste
As a diluent and buffer it lowers the LCFA concentration in a mix with fats.^[1]

Dosing

No source-based threshold. Treat like manure: the base of the feed, change in gradual steps.

Practical requirements

ABP cat. 2 (Art. 9 of Reg. 1069/2009): manure, slurry and digestive tract content may be digested without prior sterilisation if the authority does not recognise a risk of spreading a serious transmissible disease (Art. 13(e)(ii)); in that case a minimum of 70 °C for a minimum of 60 min applies (Reg. 142/2011, Annex V Ch. III Section 1), and where they are the only material of animal origin in the installation, the authority may approve other requirements (Section 2 point 3).
Provide for removal of sand and heavy contaminants: sand is often strongly bound to organic matter and is released only in the digester, and sediments reduce its usable capacity, so a scraper or bottom drain is needed (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

Digestive tract contents (rumen, intestines) are the contents removed from the rumens and intestines during slaughter, mainly of cattle and pigs. They consist of partly digested feed, mucus, cell remnants and microorganisms. The dataset contains records for digestive tract contents from a pig slaughterhouse, rumen contents and a series of samples from a study of the inoculum-to-substrate ratio. The quantity of contents depends on the size of the plant and the animals' diet.

Properties relevant to digestion

Rumen contents are rich in structural plant fibre, which has already been partly digested in the rumen, so the remaining gas potential is lower than in fresh feed, but still significant. They also contain a rich cellulolytic microflora. The material is moist, contains sand and contaminants from feed, and decomposes quickly after removal. The nitrogen and ammonia content is moderate. It has a character similar to manure, and some ABP regulations treat it in a similar way.

How to read the spread of results

The dataset contains records from different plants and species, among them a series from one study in which the inoculum-to-substrate ratio (I:S) was varied. The result depends on the animals' diet (dry feed, grass, silage), the time from slaughter to analysis, the method of storing the sample, moisture and the share of sand. In addition, the inoculum, temperature (not given for some records) and test length differ. The spread is therefore the resultant of differences in the material and in methodology.

In biogas plant practice

Digestive tract contents are an animal by-product. The rules for their use in a biogas plant depend on the category of the material and the applicable EU and national regulations; appropriate treatment, documentation and a permit for the plant are often required. Technically, care must be taken over sand separation, chopping and regularity of deliveries. It contributes fibre and buffer, and together with other slaughterhouse wastes it can form a stable mixture. The yield depends on the animals' diet, so before concluding a contract it is worth carrying out a BMP test. It is also worth remembering that digestive tract contents may contain residues of veterinary medicines and feed additives, the effect of which on the digester microflora depends on the type and concentration, so a constant source of supply makes it easier to control the 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.