Simple changes in urban planning can reduce carbon emissions and increase carbon storage, offering readymade tools to help meet emissions targets. By combining complementary approaches, cities can build a sustainable infrastructure and encourage environmentally friendly development.
'We need to have design and cultural approaches that work for sustainability and mitigation in the built environment instead of limiting ourselves to economic and technical tools,' says Matti Kuittinen, an adjunct professor at Aalto University and senior specialist at Finland's Ministry of the Environment.
Construction and building receive less attention for their emissions than other industries, such as air travel, but they account for about 40% of primary energy demand worldwide and generate one-third of global greenhouse gas emissions – tenfold more than air traffic. Improved insulation and more efficient heating systems have altered the energy budget of buildings, and roughly half of the carbon emissions of zero-energy buildings happen before their use.
Building with wood instead of concrete would require fewer industrially produced, carbon-intensive materials, meaning lower emissions. Wood-based buildings also serve as carbon storage, trapping carbon which might be released back into the atmosphere from shorter-lived wood-based products.
Research by Seppo Junnila's team at Aalto University showed that using wood to build 80 percent of new residential buildings in Europe would sequester 55 million tons of carbon dioxide per year, equivalent to nearly half of the annual emissions of Europe's cement industry. Evidence also shows wood-based construction can be a smart investment. A second study found that wooden houses are more economically valuable than houses built of other materials, with wood-based houses in Helsinki being 10% more expensive than other houses in the same or similar neighbourhoods.
'Buyers are willing to pay more for an eco-friendly choice, even if they can't afford to live in the most expensive neighbourhoods of the city,' says Junnila. 'The good news is that some international investment companies have already realised the potential of timber construction, and we can only expect this interest to grow.'
Urban green spaces offer another avenue for storing carbon, but currently there are no standards to evaluate the contribution of green infrastructure in climate budgets. 'We need to empower landscape designers to play their part in carbon mitigation in the built environment,' explains Kuittinen, 'but they can't do that if they don't know how effective or ineffective the living products they work with are.'
Kuittinen's team assessed existing carbon footprint standards to determine how they should be developed for plants and soil. One of the challenges is that the carbon storage potential of plants changes as they grow. The team analysed how the flow of carbon changes in soil and plants over their lifespan and proposed ways to translate these flows in standardised industry reporting formats.
'It's a new frontier. We're pointing out a knowledge gap that needs to be filled,' says Kuittinen, calling for 'not all hands on deck but all plants on deck.'
Once the carbon footprint of green infrastructure can be accounted for, it can be included directly in urban planning and policymaking. 'It's a simple, wide-reaching solution that can make real impact. This is an area that needs real attention from decision-makers in the European Union and elsewhere,' says Kuittinen.
Aalto University experts are available to comment on following topics:
Building with wood
Seppo Junnila is a professor of real estate business. He has also been a visiting scholar in the University of California at Berkeley and Stanford University and has worked in the consulting industry. His research focuses on management and innovation, sustainable real estate, industrial ecology and lean management in real estate and services industries.
Carbon budgets and urban green spaces
Matti Kuittinen is a professor of resource-efficient construction who focuses on combining architecture, engineering, and ecology for climate change mitigation. He is also a senior advisor to the Finnish Ministry of the Environment, where he helps develop policies related to the circular economy and methods for whole life cycle carbon assessment in the built environment.
Biochar
Mikko Jalas is a senior lecturer of practice who works on sustainable design. His research focuses on sustainable consumption practices and policies to steer energy use and consumption patterns. He co-leads Carbon Lane, one of the first projects in the world to pilot the use of biochar in urban parks - an approach that could help cities easily reduce their carbon footprint. Jalas has also studied and been involved with citizen and DIY projects related to climate mitigation and carbon sequestration.