BIODEGRADABLE CARRY BAGS

Bio-plastics can be defined as plastics where part or all of the material is derived from renewable biomass resources. For the purposes of clarity we will refer to bio-based plastics as those made from plant-based molecular sources. The term ‘bio-based’ must not be confused with the term ‘biodegradable’ which refers to the natural breakdown of a material at the end of life disposal phase. Not all bio-based polymers are biodegradable and not all biodegradable polymers are bio-based; some biodegradable polymers only biodegrade under specific circumstances.

With the introduction of plant-based bio-PE as a ‘drop-in’ alternative to fossil-derived PE (offering a direct replacement to its fossil based equivalent), coupled with an increase in the production capacity of these bio-polymers, it is becoming increasingly difficult to ignore the potential that bioplastics offer to improving the sustainability of plastic products. They are making an impact on the wider plastics market, in part because:

• As a result of increased demand and finite supply there is a long term upward trend in the cost of fossil based resources. As a result demand for bio-plastics is rising strongly year on year at a rate of 20-100%.

• The resources used to make bio-polymers are predominantly annual crops (such as corn and sugar beet) or perennial cultures (such as cassava and sugarcane) and as such are considered renewable.

• Bio-based plastics present a unique opportunity to reduce greenhouse gas (GHG) emissions or even become carbon neutral.

The production costs of sugarcane bio-ethylene across the globe are summarised in Table. Overall the current production cost of bio-ethylene is between 1.1-2.3 times higher than the global average petrochemical ethylene, but ligno-cellulosic bio-ethylene is expected to reduce the gap in the near future to the point where bio-ethylene could be less expensive than fossil-based ethylene.

Table Average production cost of bio-ethylene

With regards to the cost of feedstock’s used to produce polymers the market conditions are quite variable. Currently according to the Market Price Information and Comparison of Price Indexes and IMF Commodity Price Forecasts for crude oil, sugar, and cereals, the trend in the price of oil is stable to falling, based on a growing supply of shale oil in the USA. The price of cereals is also not trending up and the price of sugar is projected to strengthen slightly. On this basis, the trend in the short term cost of oil-based ethylene is likely to be stable to falling, and the trend for bio-based ethylene from sugarcane ethanol is likely to be stable to rising.

However, large scale production of ligno-cellulosic ethanol will enable a significant fall in the cost of bio-ethylene, but as it will take at least five years to develop and construct such a plant, it must be considered that few will start up before 2020. The longer term trend (10 – 20 years) is expected to see renewable sources of bio-ethylene remain more stable and exhaustible sources of oil-ethylene follow a rising trend as supplies dwindle. However, there is no guarantee on the predicted costs into the future as has been shown with the impact of shale gas in recent years.

Total world petroleum-based ethylene production capacity (including oil-based naphtha and ethane, propane and butane (natural gas liquids (NGLs)) reached 138 million tons per year (Mtpa) in 2011. The global demand for ethylene is expected to increase at a higher rate than the gross domestic product (GDP) rate of 3.9% through to 2020.

Another bio-based polymer, Poly Lactic Acid (PLA) initially led bio-based plastic production globally, but Braskem became the world’s leading bio-based plastic producer when its 200,000 tons per year bio-PE plant, based in Brazil, started up in 2011. One of the key attributes of bio-PE is that it’s a ‘drop-in’ replacement for oil-based PE and as such there is no obvious technical obstacle to growth of demand in the market. Bio-PE has quickly attracted the attention of leading brands such as Procter and Gamble who were early adopters, announcing their bio-HDPE bottle for Pantene shampoo in April 2011. It is understood that Braskem’s production is currently sold out to these premium end users, and there is no other bio-PE producer available in the market at present. This is a potential constraint on the introduction of bio-PE for SUPCBs in the short term.

Although SUPCBs are a much lower value product than those which currently use bio-PE they also have very low material content so the additional cost of converting them from oil-based PE to bioPE is likely to be very small when compared to the expected 5p charge for SUPCBs in England.

The current world production capacity of bio-ethylene monomer is about 375 kilotons per annum (ktpa), of which 200 ktpa are used for producing bio-PE polymer. The capacity and status of known plants and projects, based on information from multiple sources, are shown in Table.

Table Capacity and status of known plants and projects (bio-PE and bio-E)

Biodegradable (PE) plastic bags own almost the same qualities as ordinary plastic bags. Biodegradable plastic bags differ mainly through its composability (biological reduction).The underlying technology is based on special additives which, if incorporated into standard PE resins, are purported to accelerate the degradation of the film products. Degradable PE films can help lessen the problem of plastic wastes. By using degradable plastics, farmers can protect their horticultural crops from harsh elements like too much sun, wind, rain, and diseases, without significant negative effect on yield, quality, and heavy metal content of these crops as well as on soil properties.