Does a better spray gun cut the finish a tannery buys, and by how much?
The European tanning reference document says conventional leather spraying can have an efficiency as low as 30%, while high-volume low-pressure (HVLP) and airless guns raise it up to 75%. If efficiency means the share of finish that lands on the leather, the same coat needs 60% less finish, at best.
What the document says
- Applying a surface coat is an important source of emissions of volatile organic compounds (VOC).
- Roller coating, curtain coating, HVLP and airless spray guns give less VOC than conventional operations, where efficiency can be as low as 30%.
- HVLP and airless spraying improve spraying efficiency up to 75%, against as low as 30% for conventional spraying.
- HVLP sprays a large volume of air at low pressure, so there is much less bounce-back. Existing equipment can be retrofitted, but the cost and effort depend on the system already in place.
Where it does not fit
- HVLP does not give completely satisfactory results for some articles such as upper leather and garment leather. The document says it can be used mainly for upholstery leather.
- Conventional spraying is still needed for very thin finishes, for example on aniline and aniline-type leather.
- Air abatement for VOC needs energy and produces another waste fraction.
What the efficiency number means (my reading)
The document does not define efficiency. Its mention of bounce-back suggests it is the share of sprayed finish that ends up on the leather. That is my reading. The document gives some support: its roller-coating section says waste is 3 to 5% of the amount of finish chemicals, against up to 70% by conventional spraying, and cites a United Nations Industrial Development Organization (UNIDO) figure of conventional 25 to 30%. Waste of up to 70% fits an efficiency as low as 30% on that reading. If it is right, the finish you must buy for a given dry coat is the coat divided by the efficiency, so 1 / 0.30 = 3.33 times the coat at 30% and 1 / 0.75 = 1.33 times at 75%.
Why it is a carbon question
Finish chemicals you buy are Scope 3 category 1 by kilograms on the invoice. This page is about the kilograms you buy, which a spray gun change can reduce. The document's concern is air emissions of VOC, which is a different question from the carbon dioxide in your footprint.
Example: 100,000 square feet of leather a month
- Dry coat that must end up on the leather: 10 grams per square foot (an example) = 1,000 kilograms (kg) a month
- At 30% efficiency: 1,000 / 0.30 = 3,333 kg of finish bought
- At 75% efficiency: 1,000 / 0.75 = 1,333 kg of finish bought
- Difference: 2,000 kg a month, which is 60% less at best (1 minus 0.30 / 0.75), since 75% is the document's "up to" figure
The 10 grams per square foot is an example, and the formula holds only under the reading above. Check the share of finish that lands on the leather with your own trial before you plan on this.
What Senseible does here
Senseible reads fuel invoices and electricity bills into records by billing period. Finish purchases are not part of that, so keep kilograms of coat bought per month in your own sheet.
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.