The challenge:

More than 300 UK local authorities have declared climate emergencies. The IPCC has published its special report on 1.5°C, and the Climate Change Act was published way back in 2008, but there’s still a significant gap between what’s needed for the UK to meet its own legally binding climate targets, and current national policy.

Bioregional has been working with a number of local authorities to bridge that gap by creating net-zero local plans.

• Download the Greater Cambridge Net-zero Carbon Evidence Base >>
• Download the Central Lincolnshire Local Plan >>

How we helped:

Working with partners Etude, Currie & Brown, Mode Transport, Bioregional created evidence bases and policy wording for net-zero local plans for Central Lincolnshire and Greater Cambridge. As part of that extensive work, we established the spatial implications of proposed growth, across alternative locations and at differing densities.

We created a tool that allows local authorities to model the annual carbon footprint that would be generated by new development, depending on where that development takes place and what policies are applied to it.

For Greater Cambridge, we worked with the local planning authority to establish six categories of location (from dense urban areas through to dispersed villages). Location matters for carbon, mainly because of the transport habits that the new residents or workers will develop, depending on the distance they need to travel for their daily needs and the public transport service available locally. But beyond that, different locations vary in the size of development that tends to be built, and the amount of new infrastructure that must be built alongside new homes. For example, residents of new homes in urban areas can (to some extent) make use of existing schools, healthcare and so on, while new homes in less well-served areas often need more new infrastructure to be built. This implies more carbon emissions to build and operate that new infrastructure.

Our tool also models various net-zero carbon policies on top of the location - eg, best-in-class energy efficiency; replacing gas boilers with heat pumps; adding on-site PV; reducing the embodied carbon, and various measures to promote sustainable transport (walking, cycling, public transport and electric vehicles). Our tool gives local authorities the ability to dial up or dial down their policy choices, and rearrange the spatial distribution of the new development, in order to understand the least carbon-intensive options for new growth.

To build the tool, we plugged in the detailed characteristics that would define each of the six spatial categories. To do this we gathered real-life data for representative locations in Greater Cambridge, on various topics including typical types and sizes of development, types and amounts of non-residential buildings and infrastructure needed to serve new homes, typical numbers of people per household in different sizes and types of home, and transport patterns (which depend on type of transport available, and distance that people have to travel). We combined this with data on the carbon emissions of various activities such as grid electricity (current and future) and other fuel types, transport in the local area, and industry benchmarks for embodied carbon of typical new buildings (current, and future recommended targets).

Our starting point is to model one home in each spatial location, which gives us the annual carbon data in its rawest form. We model this twice – firstly with business-as-usual construction and transport practices as they stand today, and secondly with all the zero-carbon policies implemented to a reasonable level. As you can see in the graph below, the key takeaway is that zero-carbon policies have the potential to create a large positive impact, as well as the choice of location.

But the graph also shows another important fact: in a location where cars will realistically be the main transport choice, even with ‘zero carbon’ policies applied, the transport carbon is so high that this is still a worse option than if this new home were in a dense urban area or public transport corridor even without zero carbon policies.

But in reality, new homes will be spread across many types of location. Depending on the amount of land expected to become available, the local plan needs to decide how each type of location should be allocated a share of the housing growth that the plan is required to accommodate.

Therefore, we mapped eight different growth options for Greater Cambridge – each of which is a different combination of spatial locations, with each location receiving varying proportions of the new homes. Each of these options is named for the type of location that would receive the largest share of growth. We then compared business-as-usual vs zero-carbon policy.

The impact

Our tool helps local authorities easily identify the lowest-carbon route for new developments, and gives them an accurate insight into where the remaining carbon emissions will come from.

With Greater Cambridge as an example, the tool helped illustrate that in a medium-growth scenario, and with zero-carbon policies applied, emissions from building energy use almost completely disappear and transport and embodied carbon become the dominant sources of emissions.

For Central Lincolnshire, the local plan recommended allocating its spatial growth sites based principally on reducing transport emissions and protecting green infrastructure as a carbon sink. Any new growth that is necessary in a location where most trips will be by car should be required to provide electric vehicle charging infrastructure to support all of these.

In the case of Greater Cambridge, our work showed that unless maximum growth is pursued, the new growth will represent a relatively small increase in existing annual emissions already caused by lifestyles in the region. This is the case in all eight spatial options, except the ‘villages’ option.

With ‘Medium growth – zero carbon policies’, the increase in existing emissions could be as little as 1% if the ‘urban densification’ option is chosen, or 2% if the highest-carbon non-village option is chosen (option 8, ‘expanded growth area’).If the ‘villages’ option is chosen, even with zero-carbon policies applied, this would result in an increase of 4.2% in Greater Cambridge’s existing annual carbon dioxide emissions, due to the heavy use of cars that is created by rural living (even though our ‘zero-carbon policy’ includes a much higher rate of electric vehicle use than today).

Ultimately, in the case of Greater Cambridge, if choosing a spatial option purely based on climate impact, we established that the best choice would be urban locations or public transport corridors, and to apply zero-carbon policies to ensure the new buildings have such little need for energy that they can mostly meet this demand with solar panels on their own roofs.

While it is absolutely crucial to build the homes of the future in a truly sustainable way, it is equally important to view any new developments within the context of the overall emissions that a local authority can influence – which includes the huge retrofit challenge. To help address this, Bioregional has also worked with Cambridge City Council to create a comprehensive retrofit guide for homeowners and landlords.

• Download the Greater Cambridge Net-zero Carbon Evidence Base >>
• Download the Central Lincolnshire Local Plan >>

Interested in our Sustainability consultancy services for local authorities?  

Get in touch with Ronan Leyden, Director of Consultancy below, or click here to learn more about how we can help your local authority meet its climate challenges.

_{Additional image credits: Dorin Seremet, James Feaver, Andrey Zaychuk, and Phil Hearing, all via Unsplash}