Sustainability - Signature Leather

Signature Leather manufactures high quality leather gloves using British materials and traditional production techniques. Items are cut and trimmed by hand and much of the operation is minimally mechanised. In terms of the company’s commitment to sustainable production, packaging is therefore a potential hotspot and an area of current focus.

Packaging analysis: Signature Leather

Introduction

This report assesses the potential impact of replacing the current plastics used in packaging the gloves with an established bio-polymer alternative (polylactic acid). The existing and proposed packaging solutions are considered in terms of their greenhouse gas emissions (i.e. their carbon footprints) and their non-renewable energy consumption. Other aspects of the current packaging format are also considered in brief.

Existing packaging

The gloves are dispatched in single-walled cardboard boxes containing 30 pairs of gloves each. Inside each box, the pairs are individually packed in plastic zip-lock bags, of either polypropylene (PP) or low-density polyethylene (LDPE). Each bag has a small coated-paper label with size details etc. (figure 1).

The weight of each packaging material was established and used in the subsequent environmental analysis (see table 1).

	Individual weight (g)	Weight per 30 pairs (g)
Cardboard	250	250
Plastic bag	7.15	215
Paper label	0.05	1.5

Table 1: Packaging weights per 30 pairs

Figure 1: Examples of current packaging (box contains 30 pairs of gloves)

Current packaging footprint

The weights recorded in table 1 were used to calculate both the carbon footprint (figure 2) and non-renewable energy use (figure 3) of the packaging format as it currently exists:

Figure 2 and Figure 3

Figure 2: Carbon footprint of the current packaging
(per 30 pairs of gloves)

Figure 3: Non-renewable energy use of current packaging
(per 30 pairs of gloves)

The total packaging carbon footprint was 0.9 kgCO₂e per 30 pairs (irrespective of whether the plastic was assumed to be PP or LDPE). The plastic bags represented the largest proportion of the footprint (65%), while cardboard accounted for 35%. Only 0.2% was associated with the paper labels.

The non-renewable energy use of the packaging was 23 MJ per 30 pairs (for both PP and LDPE-based scenarios). The plastic bags represented 79% of the total figure and cardboard made up 21%. Paper labels only accounted for 0.1% of the total.

In both of the above cases (i.e. in terms of both greenhouse gas emissions and non-renewable energy consumption) the plastic portion of the packaging was the element with the largest environmental footprint.

Polylactic acid

Polylactic acid (PLA) is a compostable bio-polymer produced at industrial scale from corn starch by Natureworks (Nebraska, USA) or from sugarcane by Purac in Europe and Asia. Other smaller producers also exist, but these two producers currently dominate the market. PLA is used as an alternative to traditional oil-derived plastics in a wide range of applications, including packaging.

Natureworks and Purac have both published eco-profiles of their PLA which show that it compares favourably with many traditional plastics in terms of both greenhouse gas (GHG) emissions and non-renewable energy (NRE) consumption. The Natureworks data is used in this report because it provides a detailed breakdown of the analysis and has been peer-reviewed and published in the scientific literature¹.

Using the Natureworks data, the packaging footprint was recalculated assuming that the plastic bags were produced from PLA. It was assumed that the dimensions of the bags were the same as those currently in use and the different densities of the polymers were then taken into account. Energy for extrusion was factored in, although production of the Ziploc strip was excluded (in both cases) due to the lack of data about this particular production process. The results should therefore be seen as an approximation rather than as definitive numbers given the scope of the analysis.

	Carbon Footprint
	kg Co₂e	% reduction (using PLA)
PLA	0.53
PP	0.58	-8%
LDPE	0.56	-4%

	Non-renewable energy
	MJ	% reduction (using PLA)
PLA	14
PP	18	-23%
LDPE	18	-22%

Figure 2: Carbon footprint of the current packaging
(per 30 pairs of gloves)

Figure 3: Non-renewable energy use of current packaging
(per 30 pairs of gloves)

The results show that switching to PLA could reduce the GHG emissions associated with the plastic part of the packaging by 4-8% and NRE consumption by 22-23%. This translates to a reduction in the overall packaging footprint (i.e. plastic, cardboard & labels combined) of 2-5% GHGs and 18% non-renewable energy.

Note that these figures don’t take into account the end-of-life disposal of the packaging by the consumer (or retailer) – a factor that is beyond the control of Signature Leather. PLA is technically compostable, although the separation of bio-polymers from municipal waste and the industrial composting facilities needed to process them have not been widely realised as yet. Where PLA is composted, additional environmental advantages would be realised.

Cardboard

The cardboard content of the packaging is the second most significant material after plastic, both in terms of GHG emissions and NRE consumption. The boxes make up the outer shell of the packaging and as such provide an important role in terms of protection during transportation. Two alternative solutions may be worth consideration:

Figure 6: Pulp-moulded punnets and bio-plastic (thermoplastic starch) packaging peanuts

Pulp-moulded boxes made from a variety of natural and / or recycled fibres (see figure 6) are produced by a number of companies. They make attractive presentation boxes but are thought unlikely to be economically competitive to corrugated board at present.

Another option could be (traditional) plastic outer bags with bio-polymer (e.g. thermoplastic starch) packaging ‘peanuts’ as an internal protective layer. It is unclear whether this option would provide the structural resilience necessary to protect high-end garments in transit, but if so then the lighter overall weight of this option (compared to using cardboard boxes) may work favourably in terms of reduced transport emissions.

Summary

The plastic component of the current packaging format represents the most significant portion in terms of greenhouse gas emissions and non-renewable energy consumption. Switching to a bio-polymer such as PLA for the bags could reduce this, especially if composting could be ensured at end-of-life.

Corrugated cardboard has a structural integrity that may not be matched by pulp-moulded punnets or plastic transit bags. However, if these are potentially viable alternatives to the cardboard section of the packaging, an environmental comparison could be made as part of a follow up study. If this were to be the case, then the potential weight savings of using plastic over cardboard may be a decisive factor in terms of determining the result.

References

1. Vink, E., Davies, S., and Kolstad, J. The eco-profile for current Ingeo® polylactide production. Industrial Biotechnology, 2010. 6(4): p. 212-224

Acknowledgements

BEACON is funded by the European Regional Development Fund through the Welsh Government. It focuses on the development of a viable Welsh bio-economy through the expansion of green supply chains.

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