Most of the cement factories are confronted with the question of using Paper (Kraft) Bags or Poly Propylene Bags in their packing line.
The basic parameters of the two options are compared in the table below:
| Kraft paper bag | Laminated polypropylene (PP) woven bag | ||
| 1 | moisture-proof | Strong moisture absorption, water permeates layer by layer, deformation after wetting, high requirement for stacking. | Isolated from moisture erosion in normal temperature, water absorption below 0.01% in 24 hours, low moisture permeability |
| 2 | EnvironmentalProtection | 24 trees was logged for making 1 ton of paper 8-20 tons of water was consumed for 1 ton of paper with subsequent severe water pollution | Byproduct of crude oil refining 100% recyclable few water demand in manufacture, mainly Recycling water |
| 3 | Cost | Manufacture: large water consumptionWastewater handling: should be processed by special apparatus, increasing expenditure and energy consumption
Logistics: nearly twice heavier than laminated woven bag, uneconomical cost in transportation Recycling: same proceed with manufacture with large water consumption, high resources cost and heavy pollution, increase wastewater handling cost. Recycling less than Procurement cost: higher unit price than laminated woven bag |
Manufacture: few water consumption, barelogistics: nearly twice lighter than Kraft paper bag, cost-effectiveness in transportation
recycling: recycling used bags for direct re-use, recycling more than 6 times, energy-saving to the maximum procurement cost: relatively lower unit price than Kraft paper |
| 4 | strength | Easily to be broken while drop test or unloading if the paper sizes are not uniform through multiple layer | High elongation and strength of weft and warp |
| 5 | Tear and wearresistance | High friction between bags in stacking resistance | With only about 0.12 rub coefficient between pp woven bags, convenient for unloading |
| 6 | Recycling | Could be recycled about 3 times, functionality decreases with increasing recycling times recycling rate is 21% | Simple recycling process, energy-saving, recycling more than 6 times no limits for recycling times, few influences in functionality High recycling rate |
Environment in the green – finances in the black
The economical use of raw material, the extremely low breakage rate, the recyclability or reusability of the sacks: Each ecological advantage is also reflected as an economical advantage. As a result of the material characteristics and the special production process, the weight of an average 50 kg AD*STAR® cement sack can be as low as 75g. A comparable 3-layer paper bag will weigh about 180g and a PE-film bag 150g. An economical use of raw material not only helps minimize cost, it is also a valuable contribution to the preservation of our environment.
AD*STAR® for ecology and economy:
The impressive reduction of the breakage rate when compared with conventionally used paper sacks has both an environmental and an economical effect: First, the risk of contaminating earth and water with the filling material is nearly zero. In addition, the savings potential is enormous when you act on the assumption that realistic breakage rates in the life cycle of paper bags (filling, conveying, palletizing, stacking, loading, transporting, unloading, …) are about 5%.
Marketable and recyclable:
What is more, most of the breakage occurs not within the cement plants but outside at the distributor and end customer during transport and handling. This is the reason why so many customers ask for the AD*STAR® bag by name! Offering and advertising AD*STAR® bags can give you a huge marketing advantage over your competitors and help you sell your production.
Even after emptying, AD*STAR® bags are a resource. Recycling is one option because polypropylene is fully recyclable into resin; another possibility is intrusion, also a recycling technology, by which household-grade plastic waste is processed into quality moulded products. There is always the option of burning the sacks to recover the very high calorific value which is almost as high as the energy value of fuel oil. Cement plants all over the world supplement oil and coal with secondary fuels to achieve savings of up to 30% of primary fuels.
However, often this is not going to happen because in many countries, second-hand woven bags are in demand for a variety of practical uses, from growing vegetables to covering roofs.
A practical example:
By switching over from paper sacks to AD*STAR®, a Tunisian cement plant was able to reduce the in-house breakage rate from 5% to 0.25%. Given an annual demand of around 160 million sacks for the whole country and a price of about € 2,50 per 50 kg bag of cement, changing over to AD*STAR®-Sacks could save €19 million a year – the equivalent of 8 million sacks and around 380,000 tons of cement.
Not to mention the loss that could be prevented outside the plant of origin…
