Reducing waste in the construction industry

Dr Domingo emphasises the importance of thinking about construction waste at all stages of a building’s life cycle. ‘Almost all materials can be either reused or recycled; it depends on how you manage things,’ she says. ‘But it is not something that we can do during construction only: it should start much earlier. For example, if your design is not standardised then there will be a lot of offcuts, but if you can standardise, then a lot of waste can be reduced. Instead of putting packaging into a skip, introduce a system for suppliers to take it back and reuse it.’

Some contractors, she notes, put their surplus building supplies in special bins for the community to take. ‘All this can help to reduce a lot of waste. It is still not as popular as it should be, but there are some contractors who are really into the zero carbon mandate. It’s part of corporate social responsibility and it is a very good way of saving the environment, too.’

Perhaps surprisingly, in New Zealand, it is not yet usual to separate waste on building sites. ‘Everything goes into a single skip and the waste management company takes it to the processing plants. There, they try to sort it, but it can be much more effective and efficient to introduce onsite waste management.’ This is the case in overseas countries – in the UK, for example, it is mandatory for projects over £300,000 to have a site waste management plan. These plans require contractors to describe each waste type expected to be produced, in what quantities, and the waste management action plan for the different waste types, including reusing, recycling, recovery and disposal.

Fortunately, a number of councils are working towards achieving this here, too, and Dr Domingo is creating a tool to make things easier. ‘If we are going towards site waste management plans, the first step is to figure out how much waste a project is going to generate. Auckland Council approached me after they saw one of the articles that I did with one of my students, where we worked on a model to predict construction waste generation based on a design. They funded us to develop an online waste calculator for designers and contractors to enter the dimensions of a design and predict the amount of waste.’

The calculator is still in development, she adds, but the industry is eager to use it. ‘They are keen to develop it further to predict not only the total amount of waste produced in a project but also the amount of waste generated from different materials at various stages in the project.’ Currently, Dr Domingo has waste data from about 200 housing projects around New Zealand and is gathering more in order to build confidence into her figures. Then, she says, ‘the government or councils can use the calculator to benchmark projects as well, especially if they are going towards site waste management plans’.

Dr Domingo has also been investigating industry awareness of New Zealand’s zero carbon initiative and the availability of resources around it. A survey of professionals, including quantity surveyors, project managers and engineers, showed that about 15 to 20 per cent were not aware of the zero carbon initiative, even though most of them knew about the Paris Agreement. ‘That is why upskilling of industry professionals is important.’

Another research project explores early design management to reduce carbon emissions. The building industry produces one-fifth of carbon emissions in the country, and currently, there is no push to identify low-carbon materials. ‘Most building products come from overseas, and obviously, the carbon footprint is much higher when we import materials rather than use locally produced ones,’ says Dr Domingo, ‘so early design management is important in achieving net zero carbon.’