How much of the chrome a tannery buys is lost to effluent, and what do high-exhaustion tanning and recovery change?

In conventional chrome tanning in long floats, the European tanning reference document says 30 to 50% of the chrome applied is lost with the waste water. Careful control can raise uptake to 80%, high-exhaustion methods to 90%, and recovered chrome sulphate can replace 20 to 35% of fresh chrome.

Three routes, with the document's figures

• Better control of pH, float, temperature, time and drum speed: uptake up to 80%.
• High-exhaustion chrome tanning: uptake up to 90%. Chrome salts released in spent liquors fall from 2 to 5 kilograms (kg) per tonne of raw bovine hide to 0.05 to 0.1 kg. The leftover is too dilute to recover.
• Chrome recovery by precipitation and separation: 95 to 99.9% precipitation efficiency reported. The recovered chrome sulphate can replace 20 to 35% of the fresh chrome salt, and some leathers such as splits can be tanned with 100% recovered chrome. Total chrome in the separate chrome effluent of 1 to 2 milligrams per litre, even below 1, can be reached.

How much powder goes in

For a conventional process, chrome powder is offered at 8 to 12% of the raw material weight (or of the limed split or pickled weight). That powder carries only about a quarter active material, 2 to 3% as chromium oxide. For high-exhaustion tanning the offer is 5 to 6%. So the kilograms of chrome powder on your invoice per tonne of hide is a number a buyer or auditor can check against these.

Where the document's own figures differ

The text gives 2 to 5 kg of chrome salts per tonne of raw bovine hide in spent liquors. The document's input and output chart lists chrome of 5 to 6 kg among the water outputs of a conventional process. It does not reconcile the two, and the text and chart may use different bases. Quote the one you use and say where it is from.

Cost and payback, from old data

The document says a chrome recovery unit for one medium-to-large Italian tannery was estimated at about 520,000 euros. On Greek conditions in 1990 to 1991 the maximum payback was 1.6 years. In India, two running units showed paybacks of 1 and about 1.6 years, around 1994 to 1995. The document's summary says reference years 1994 and 1995, but its detailed section gives reference year 1994 for both Indian plants and puts 1995 on a plant in Nicaragua, with a payback under 2 years. Get a current quote before you plan on these.

Why it belongs in your carbon records

Chrome and other chemicals bought are Scope 3 category 1 by kilograms on the invoices. Buying fewer kilograms per tonne of hide lowers that line. The document gives no emission factor for chrome, so the size of the change in carbon dioxide depends on the factor you use for the chrome salt.

Example: 50 tonnes of raw hide a month, offer on raw weight

• Conventional powder at 8 to 12%: 80 to 120 kg per tonne x 50 = 4,000 to 6,000 kg
• High-exhaustion powder at 5 to 6%: 50 to 60 kg per tonne x 50 = 2,500 to 3,000 kg
• Chrome salts in spent liquors: conventional 2 to 5 kg per tonne x 50 = 100 to 250 kg; high-exhaustion 0.05 to 0.1 x 50 = 2.5 to 5 kg

The 50 tonnes is an example and assumes the offer is on raw material weight, one of three bases the document names. Your supplier's product may not match the document's powder.

What Senseible does here

Senseible reads fuel invoices and electricity bills into records by billing period. Chemical purchases are not part of that, so keep chrome kilograms per month in your own sheet.

• Counting chrome and tanning chemicals in Scope 3
• Chrome or vegetable tanned: which is lower carbon?
• Leather Working Group energy and carbon data

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), GHG Protocol Corporate Value Chain (Scope 3) 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.