# How much energy can a tannery recover from fleshings, fat and effluent sludge?

Canonical: https://senseible.earth/answers/tannery-fleshings-fat-and-sludge-energy-recovery

The European tanning reference document says digesting limed fleshings and effluent sludge can recover around 3 gigajoules (GJ) per tonne of raw hide. Burning fat from fleshings can cover 50 to 70% of a tannery's thermal energy, and one English sheepskin tannery gets 20% that way.

## The figures the document prints

- Digesting limed fleshings and waste water sludge: around 3 GJ per tonne of raw hide recovered.
- Incinerating fat from fleshings: can cover 50 to 70% of the total demand for thermal energy.
- An English sheepskin tannery gets 20% of its thermal energy from incinerating sheepskin fat.
- The document also lists aerobic and anaerobic digestion and thermal treatment of tannery waste among ways to recover energy.

## How it compares with total use

Against the survey range of 9.3 to 42 GJ per tonne of raw hide, 3 GJ is about 7% to 32% (3 / 42 and 3 / 9.3). The document does not say whether the 3 GJ is heat or electricity, or what it costs to build.

## How much fleshings there are

The document's input and output chart gives fleshings of about 70 to 350 kilograms (kg) and sludge of about 500 kg at 40% dry matter per tonne of raw hide. So the supply depends heavily on the hides and the trimming.

## What it does to your carbon records (my reading)

This is my reading, not the document's. Replacing boiler coal or oil with fat or biogas should cut the fossil fuel line. Under the Greenhouse Gas (GHG) Protocol, carbon dioxide from burning biomass is reported separately, outside the scopes, while methane and nitrous oxide from the burning are Scope 1. Whether fat and biogas count as biomass for this purpose, and how any methane leak from a digester is counted, should be checked against the standard and with your auditor or buyer before you report it.

## Example: 100 tonnes of raw hide a month

- Recovered energy at 3 GJ per tonne: 100 x 3 = 300 GJ a month
- 1 GJ = 277.8 kWh, so 300 GJ is about 83,333 kilowatt hours (kWh) of energy
- Share of an example 16.8 GJ per tonne tannery: 3 / 16.8 = 17.9%

The 100 tonnes and the 16.8 GJ are examples. 3 GJ is the document's "around" figure, with no cost or fuel type given.

## What Senseible does here

Senseible reads fuel invoices and electricity bills into records by billing period, so a fall in boiler fuel after a digester or fat burner starts shows in the monthly fuel line. It does not meter biogas or fat burnt.

- [Wood-fired boiler and biogenic carbon dioxide](https://senseible.earth/answers/kanpur-tannery-wood-fired-boiler-biogenic-co2)
- [Tannery solid waste and sludge per tonne of hide](https://senseible.earth/answers/tannery-solid-waste-and-sludge-per-tonne-raw-hide)
- [Ambur tannery boiler and effluent plant emissions](https://senseible.earth/answers/ambur-tannery-boiler-etp-emissions)

Sources: [European Commission, Integrated Pollution Prevention and Control (IPPC) Reference Document on Best Available Techniques for the Tanning of Hides and Skins, February 2003 edition (filed by the publisher as superseded)](https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-03/superseded_tan_bref-0203.pdf), [GHG Protocol Corporate Standard](https://ghgprotocol.org/corporate-standard)

Last reviewed 2026-11-06. Figures are from the February 2003 edition of the European tanning reference document, which the publisher files as superseded; its energy and effluent tables rest on European tanneries and on older studies. Check the current edition and your own records before you quote a number to a buyer.