The city of Palo Alto has recently created an ordinance that would require large buildings to be deconstructed—rather than demolished—in an effort to curb construction and demolition waste. When buildings are demolished, most components are lost to landfill, significantly contributing to greenhouse gas emissions. The new ordinance aims to tackle these emissions by prioritising the reuse, recycling and composting of building components. While the project is in early stages and will not ramp up its requirements until 2023, it has already seen some success, with approximately 25% of buildings currently deconstructed rather than demolished. Further success is likely, based on data from Portland, Oregon, which implemented a similar law in 2016 and has seen marked improvements in air pollution, job creation and waste diversion.

The two largest components of landfill waste are food waste and construction and demolition waste—the latter making up more than 40% of landfilled debris in Palo Alto. On a global scale, construction and demolition debris comprises about 19 000 tons of landfill waste each year. Traditional demolition is often the go-to, as it takes on average just a few days, requires only two or three workers, and costs approximately six to ten euros per square foot. Disassembling buildings in a methodical manner, so that the components can be recycled and reused, is a longer, more expensive process: a crew of four to eight workers is needed for up to two weeks, and costs range from 18 to 28 euros per square foot.

In response to the massive amount of waste stemming from demolition, the city of Palo Alto will entirely ban construction workers from demolishing buildings, instead requiring them to disassemble structures in the reverse order of construction. Contractors will then complete a ‘salvage survey’, where all materials that can be recycled and reused are clearly listed; components will then be sorted accordingly in blue and green containers, and taken to city-approved recovery stations. This deconstruction will allow for a hierarchy of uses to fall into place, which would prioritise reuse, followed by recycling and composting. A range of materials can almost always be reused: appliances, cabinets, lumber, windows, doors, electric and plumbing fixtures and hardwood flooring. If recovered in good condition, tiles, bricks and wood can often be reused. If blocks or bricks are recovered misshapen, they can still be turned into ‘base rock’ and used as underlayment for roads; similarly, damaged wood can be shredded and composted. 

Before the new policy was set into motion, the city conducted a pilot, deconstructing a 2 500 square foot city-owned building. The process generated about 184 tons of material. 4% was able to be directly reused, 93% recycled, and only 3% disposed of in landfill. Since 2016, success has grown: a quarter of houses in Palo Alto were deconstructed rather than demolished—the new policy aims to expand this success, eventually diverting 95% of construction waste from landfills by 2030. The city is still in its initial phases of implementation; the policy will have a broader reach in 2022, when it will be applicable to all projects valued over 85 000 euros, and 2023, when that number will decrease by 50%. The programme is projected to help divert 7 930 tonnes of waste annually, reducing the city’s greenhouse gas emissions by 22 300 metric tonnes per year. While there have been concerns from stakeholders regarding the market for salvaged building components, the policy has also seen support from construction companies as well as non-profit organisations.