A new environmental awareness – Silvateam research

Climate change continues to be one of the greatest challenges facing nations, businesses and citizens, and will influence the way we live and work in future decades. Past and current actions, including the release of carbon dioxide (CO2) and other greenhouse gases through human activities such as the burning of fossil fuels, emissions from industrial processes and other sources of anthropogenic greenhouse gases, will have an effect on the future global climate.

Carbon dioxide is a colourless, odourless, non-toxic gas that in its solid form is known as 'dry ice'. CO2 is commercially found in fire extinguishers and carbonated beverages. While carbon dioxide occurs naturally, it is the most common of the human-made greenhouse gases and is believed to be a significant contributor to global warming.

The leather industry is very big and complex. It is not easy for the consumer to know or estimate the true value a product features and the environmental impact it has in terms of its carbon footprint, water consumption, resources and harmful substances.

The new approach

Over the past few years, Silvateam has conducted a life-cycle assessment (LCA) of its main tanning agents, such as vegetable extracts for tanning and retanning, and synthetic tannins. The main goals were to support tanneries with scientific data on the carbon footprint (CFP), and to continuously improve its processes and reduce its environmental impact.

Silvateam is the first leather chemical company certifying the carbon footprint value expressed as 'kg CO2e per kg' product analysed. LCA and quantification of key environmental indicators were evaluated too.

The methodology of calculation used is in accordance with ISO 14025:2010 Environmental labels and declarations - Type III environmental declarations - Principles and procedures.

First, Silvateam established the procedure for the definition of environmental product category rules to calculate the carbon footprint for leather chemicals. These product category rules will need to be applied in the future for LCA calculations for leather chemicals within the EPD system.

Second, a cradle-to-gate approach was applied. Site-specific data was collected for all individual processes under the financial or operational control of the organisation. This data was representative of the production processes. Production of raw materials and precursors at supplier facilities were considered too. The main results of this calculation are:

• natural tannins, such as chestnut, have a much lower impact compared with other products based on petrochemicals
• powder products are higher in carbon footprint than the corresponding liquid products, as spry drying process is energy intensive.

For example, Ritan XCR, a new generation of chestnut extract recently developed by Silvateam, presents a much lower carbon footprint compared with synthetic tannins. Basic chromium sulphate is used as reference. Thanks to its high solubility and excellent dispersion, Ritan XCR penetrates quickly during retanning and throughout the section of the leather giving a very fine and elastic grain, good fullness and roundness.

Continuous process improvement for a lower CFP

Improving customer satisfaction, providing quality products and maximising processes are continuous, never-ending objectives at Silvateam organisations. The processing of chestnut wood biomass to produce vegetable extracts is energy intensive, in terms of electricity and steam consumption. On the other hand, the production of synthetic tannins shows high CFP value is mainly due to the raw materials used.

Silvateam is working to reduce its energy impact on CFP through the construction of a biomass power station of 20MW capacity. A biomass power plant project was submitted to the local government in the past few months. Silvateam uses 100,000t a year of chestnut timber for the extraction of chestnut tannin. The supply of wood comes from an area located in a radius of 70km, of which the centre is in San Michele Mondovì (northern Italy), the headquarters of the company. The local forest produces ten times more biomass due to its spontaneous growth compared with the one harvested by Silvateam.

Direct combustion will therefore be the most efficient method of capturing the energy contained within chestnut biomass. In the biomass power plant, wood residues from tannin extraction will be burned to produce steam and thus to provide electricity and heat for internal use. Hence, renewable energy rather than fossil fuels will significantly reduce to almost half the carbon footprint of Silvateam chemical products.

The advantage of vegetable tannins

Another important aspect in the production of chestnut tannin is 'biogenic' carbon. In fact, the uptake of carbon dioxide from the atmosphere during the photosynthesis process is a unique feature of biomass. The transformation of chestnut wood biomass (and its embodied biogenic carbon) into tannin represents, in effect, a removal of CO2, via its continued storage in the product over a period of time.

In practice, the tannin stored inside leather actively sequestrates the plants carbon dioxide from the atmosphere and keeps it separated as long as the leather is not burned or has decomposed again into gases.

Specifically, The International Reference Life Cycle Data System (ILCD) handbook proposes a 100-year assessment period for carbon storage in products, to be consistent with the use of 100-year global warming potential (GWP).

There is historical evidence to support that a leather article will remain stable for more than 100 years in a given product use or end-of-life scenario and therefore the carbon embodied in the leather can be considered sequestered permanently. Egyptian vegetable tanned sandals or Roman belts are typical example of articles still present in different museums around the world.

Thanks to vegetable extracts, it will be possible to store biogenic carbon in the finished leather articles. No biogenic carbon can be stored using other chemicals. Tannins are hence bio-based products that can contribute in the reduction of CO2 levels in the atmosphere and address global warming.