What is 'bio-based' construction and how could it help cities get to net zero?

Over half the global population lives in cities and by 2050 this is expected to rise to 70%. All these people will need somewhere to live and work with an infrastructure that supports them and their families.

That’s not only good news for the construction industry, but could be good news for the environment too. If just a small percentage of these buildings are constructed using sustainable bio-based materials, it could significantly reduce carbon emissions, boost carbon storage and help us reach net zero. Bio-based materials are materials intentionally made from substances derived from living organisms, such as timber derived from trees.

Nature is already helping to build our cities. Bio-based construction is catching on among early adopters keen to ensure that buildings have minimal impact on the environment. It’s hoped that these proof-of-concept buildings will help biomaterials to be widely adopted.

Set to be the tallest timber building in Africa at 96m high, the Burj Zanzibar is due to get under construction in Fumba Town. Bringing the forest to the city, it will be built from locally sourced glue laminated timber columns and cross-laminated timber (CLT) slabs, creating local jobs across rural and urban areas. Sales of the high-end Burj apartments will help fund a surrounding low-rise development of affordable housing in Fumba Town, built with sustainable timber and following the same principles. Its design cools the interior climate, reducing the need for electricity-intensive air-conditioning.

Work is ongoing to make sustainable mass timber a go-to construction material in the Global North too. Plans have been unveiled to build what could be the world’s biggest wooden city. Stockholm Wood City will be built in Sickla, an area in the south of the Swedish capital. Construction on the 250,000-square-metre site will begin in 2025 and, when complete, it will contain 2,000 homes and 7,000 offices, along with restaurants and shops. The wooden city further incorporates natural elements, such as green roofs, in its design.

Climate-smart forests offer a remarkable solution to the urban expansion problem, as their supply of timber can be continually replenished through tree replanting, which sequesters or absorbs carbon from the atmosphere as trees grow. That carbon is then stored within the trees, the forest plant matter and the soil, creating a huge carbon sink. Forest materials continue storing carbon even when they are made into something else, whether that be the frame of a building or a cupboard. As part of a circular economy: when that building or cupboard reaches the end of its use, its biomaterials can be repurposed again, perhaps as a fence, keeping its carbon locked in.

Right now, the construction industry accounts for around 39% of energy and process-related global CO2 emissions. If new urban areas can store carbon, rather than emit it, they become key to halting climate change and reducing climate disasters, such as floods. Where a typical steel and concrete building is expected to produce 2,000 metric tons of CO2 emissions, an equivalent mass timber building can match this in carbon storage.

And, while timber serves as a prominent sustainable carbon storage material, other options are emerging too. Algae is utilised in Algae Building Technology (ABT) to heat buildings through innovative facades; fungi is employed in mycelium composite construction materials for sustainable insulation, panels, flooring and furniture; and hemp is transformed into bricks. Although further research and development is necessary before these materials reach the mass market, their potential is immense.

Scaling up the use of bio-based building materials not only benefits the environment, but also stimulates local economies, job creation, biodiversity and reforestation efforts. The Climate Smart Forest Economy Program (CSFEP) is a global initiative aiming to generate and disseminate knowledge about how forests and forest products can be used to benefit the climate and support the economy and social needs of local communities. One of the many projects it supports is in Kenya. Architecture, engineering and construction firm BuildX is working with CSFEP to promote the use of local sustainable mass timber, develop a regional value chain and scale sustainable forest management in Kenya, Tanzania and Uganda. BuildX’s Model for Decarbonised Urban Living (MODUL) is a cross-laminated timber flat-pack urban housing system. Focused on low-income and middle-income housing, it’s designed to provide affordable, sustainable housing at scale.

Despite the tremendous potential of bio-based materials, several barriers exist on the path to widespread adoption. Convincing stakeholders, such as developers, architects, engineers, investors, insurers, governments and policymakers, to embrace natural materials in construction is a significant challenge and there are many myths prevalent in the demand sector. Built by Nature (BbN), however, is setting out to tackle just this with the release of the Debunking Timber Myths booklet. BbN is a network and grant fund working to create a future in which buildings work in unison with nature. It’s on a mission to increase the market demand for mass timber and bio-based materials and remove the barriers to market scaling. Much research has already been carried out into the use of bio-based materials in construction; now BbN is playing a vital role in consolidating and dispersing that knowledge to speed up implementation in local contexts.

As well as stimulating demand, history shows us that policy and regulation are instrumental in pushing through industrial change. Some governments have already taken the lead on this. The French government, for example, has ruled that any public construction project financed by the state must contain at least 50% bio-materials. While Amsterdam has stated that 20% of the city’s housing projects must be constructed from bio-based materials from 2025.

Bio-material prices often deter their use, but a burgeoning sustainable forest economy, grown close to locations where there is demand for its products will create economies of scale and bring down production and transportation costs. Already the cost of wood can be less than expected, because mass timber buildings can be largely prefabricated off-site and built faster than traditional fossil-fuel-intensive builds. The Stora Enso company HQ in Finland, for example, now under construction using mass timber, is forecast to reduce emissions by 2,795 tCO2, when compared to a similar building made of steel. And, as large parts of the construction are fabricated off-site, this should reduce build times while reducing noise, pollution and accidents on site too.

The construction industry often talks about its commitment to meeting various environmental and social governance goals and reducing its carbon footprint. However, like many industries its struggles with inertia, fragmentation, risk adversity and a lack of dedicated funding to harness the full potential of nature. It now needs to turn plans into actions and use proven solutions, backed by data, across its supply chains to show it is decarbonising.

Find out more about the work CSFEP and BbN are doing