Environmental effects from a recycling rate increase of cardboard of aseptic packaging system for milk using life cycle approach

Abstract

Despite the well-known advantages of recycling materials to reduce solid waste or save natural resources, the recycling stage is an additional process within the life cycle that has its own energy and input requirements, as well as specific emissions. The objective of the present paper is to analyze the life cycle inventory associated with the increase in recycling rate (from 2% up to 22% at present) of the cardboard contained in the aseptic packaging for long-life milk. The main aspects of the manufacturing of the Tetra Pak aseptic package, including the filling of the product, the distribution of the conditioned product, up to the final disposal and recycling rates, were considered. This study was conducted in accordance with the general directives of the ISO 14040 series. The packaging material system was assessed using 1000 liters of milk as a functional unit, in a packaging system containing 12 units of 1 L cartons each, placed on a corrugated paperboard tray wrapped in polyethylene shrink film and arranged onto one-way wooden pallets. Brazilian inventories for energy, carton, corrugated paperboard and aluminum, based on site-collected data were employed. The final disposal of used packages was modeled using the Average Brazilian Municipal Solid Waste Management data collected for the purpose of the census of the year 2000. Comparison of the total energy consumption throughout the whole life cycle of two recycling scenarios (i.e. different recycling rates) analyzed shows that the higher recycling rate led to a 6% reduction of the total energy requirement for the long-life milk package material system. The most significant reductions in the consumption of natural resources were: 8% water, 11% wood and 10% land use savings. Greenhouse gases were the main reduced air emissions and contributed with a reduction of 9.7% in GWP. Most water emissions were reduced: 10% COD, 9% BOD and 6% TSS. A unique drawback directly caused by the increase of the recycling rate was an increase of 14.4 g in TDS emissions (57%). The reduction in energy requirements are related and limited to the proportionality among the different materials that make up the packaging system. Most emission reductions result from the replacement of virgin materials with recycled materials in the packaging system. Although the average balance of water emissions is positive, the need to improve wastewater treatment processes in the paper recycling plants to reduce TDS is highlighted as a key issue. It may be concluded that the increase in the recycling rate brings about a series of benefits in terms of reduction of energy and natural resource consumption, air pollutants and most water emissions. In this case, the increase of the recycling rate improved the overall environmental performance of the aseptic Tetra Pak system for milk. The authors are currently analyzing alternative recycling scenarios that will enable one to evaluate maximum reduction in GWP. Further studies could include the agriculture stages, livestock and consumer phase to broaden the environmental evaluation.