A recent study investigated the environmental impact of the disposal of construction waste in Catalonia, Spain. The study suggests that the best options are to recycle construction waste where possible, incinerate the rest and landfill when there is no other option. These findings are in line with the waste hierarchy specified in the Waste Framework Directive1.
About 6.3 million tonnes of construction waste were generated in Catalonia in 2003, most of which was disposed of in landfills. Since then, efforts to reduce waste through improved design and technology and better disposal alternatives have been implemented.
By considering the entire life cycle of a product or a process from its origin to its final disposal (Life Cycle Assessment), the study investigated the environmental benefits of three disposal options: landfilling, recycling and incineration. Waste was classified according to the source of the construction material. Materials derived from the construction process itself were grouped as stone, metals, timber, plastic and other construction wastes. Packaging material was grouped into timber, plastics, and paper and cardboard.
A number of indicators were used to estimate the environmental impacts of the construction waste. Among these was the Global Warming Potential (GWP), which is used to compare the warming potentials of different greenhouses gases. In addition, eco-efficiency indicators provided information on the use of resources, consumption of renewable and non-renewable energy and overall water use.
Waste management is regulated at EU level2, as well as through national and regional legislation. In Catalonia, the EU funded project LIFE98 ENV/E/351 3, which promotes sustainable waste management in the construction industry. This study was conducted in response to the LIFE project and used the same waste stream classification system.
Overall, the results suggest recycling is the most environmentally friendly way to dispose construction waste, followed by incineration and landfill. By recycling materials, environmental impacts associated with producing new materials are avoided and this benefit outweighs the negative environmental effects caused by the recycling process itself and transporting waste to the recycling plant. Recycling timber and plastics from the construction process and especially packaging materials provides major environmental benefits.
In landfill sites, stone waste from the construction process has the biggest environmental impact due to the large volumes. The next highest impact is caused by metals, followed by plastics, timber and other materials. Contaminants released from metals in landfill sites were shown to be particularly toxic to terrestrial and freshwater ecosystems. All categories of packaging materials in landfills had significant negative environmental impacts.
For the incineration scenario, the study offered a mixed picture. Depending on the indicator chosen, incineration of different categories of waste either produced environmental benefits or had a negative impact on the environment. The researchers suggest that the importance of different impacts should be considered when deciding whether certain wastes should be incinerated.
In addition, the researchers considered the influence of transport on the GWP indicator. Recycling and incineration of construction wastes are better than landfill, even for long distances to waste disposal centres: stone and timber wastes are more suitable for recycling when the recycling plant is close to the building site. However, the re-use of stone as a gravel replacement on building sites is the best environmental option for stone waste.
Source: Ortiz, O., Pasqualino, J.C., Castells, F. (2010). Environmental performance of construction waste: Comparing three scenarios from a case study in Catalonia, Spain. Waste Management. 30: 646-654.