The Green Urbanist

#1: Zero Carbon Britain

June 28, 2020 Ross O'Ceallaigh
The Green Urbanist
#1: Zero Carbon Britain
The Green Urbanist
#1: Zero Carbon Britain
Jun 28, 2020
Ross O'Ceallaigh

In this episode, I take a look at one scenario for Britain achieving zero carbon emissions put forward by the Centre for Alternative Energy (CAT) in their report called Zero Carbon Britain.

CAT describe the report like this:
"Incorporating work from the last 12 years of Zero Carbon Britain research and the latest scientific and technological developments, the report presents a technically feasible scenario showcasing a future Zero Carbon Britain using only proven technology."

I present a summary of the report with a focus on the elements of most interest to urbanists. Think of it as a primer for understanding the high level actions that need to be taken as we transition to zero carbon emissions.

Read the full report here:

Follow the podcast on social media

Intro music by Tanoi

Show Notes Transcript

In this episode, I take a look at one scenario for Britain achieving zero carbon emissions put forward by the Centre for Alternative Energy (CAT) in their report called Zero Carbon Britain.

CAT describe the report like this:
"Incorporating work from the last 12 years of Zero Carbon Britain research and the latest scientific and technological developments, the report presents a technically feasible scenario showcasing a future Zero Carbon Britain using only proven technology."

I present a summary of the report with a focus on the elements of most interest to urbanists. Think of it as a primer for understanding the high level actions that need to be taken as we transition to zero carbon emissions.

Read the full report here:

Follow the podcast on social media

Intro music by Tanoi

Today's episode is about Zero Carbon, making sense of the confusing and conflicting arguments around the concept, and asking what does a zero carbon world look like and what role do urbanists have in achieving this?

Last year, the UK signed into law that it would reduce its greenhouse gas emissions to zero by 2050. Yet, for many people this is not soon enough, and the recent major demonstrations by climate activists around the world has brought Zero Carbon into the media spotlight.

The question is, what does Zero Carbon really mean and how do we get there?

There are many different ideas about this. Some people think we can continue business as usual and invent our way out of the problem. Some people think that the push for economic growth is the problem and we need a massive roll back of our modern, carbon-intensive way of life. 

Because nobody has reached Zero Carbon before, there is no road map, no accepted way of achieving it. In fact there is likely many different paths to Zero Carbon, and these vary for each country and each organisation

What I would like to present today is just one scenario for the United Kingdom reaching Zero Carbon, put forward by the Centre for Alternative Technology in Wales, also known as CAT, in their report titled Zero Carbon Britain. This report takes a very balanced approach and comes up with a realistic solution for achieving this goal. Again, it is not the only way, but it has been really helpful in shaping my understanding of everything that needs to happen to reach Net Zero. And although the focus is on Britain, there are lessons in here for other countries too. You can read the full report at I have no affiliation with CAT, I am just a fan.

I cover a lot of different topics in this episode in a very general way. The idea is to start with an overview to show you how the jigsaw pieces fit together.  Then in subsequent episodes I will deep dive into specific topics to better understand their role.

When we say Zero Carbon, what we really mean is No Net Release of Greenhouse Gases into the Atmosphere. But carbon dioxide is kind of the big one, so we tend to translate other greenhouse gases into Co2 Equivalent just so we can talk about everything at once. So I will be using the phrase Zero Carbon but it encapsulates all the other nasty gases too.

Remember that we're talking about Net Zero Carbon, so it's not about never releasing any carbon into the atmosphere, it means that if you do release some, you need to capture it, so the result is technically zero. 

We have to understand that ending carbon emissions is just one element of fixing our problems. It doesn't necessarily deal with things like plastic waste in the ocean, the extinction of animal species or the quality of our environments, both urban and natural. However, the challenge of reaching Zero Carbon is also an opportunity to solve many of our other problems, and I will touch on some of these synergies throughout the podcast

Let's move on to the main event - what does this Zero Carbon Britain study propose?

The study sets itself rules to follow, which shape the outcomes. The key ones are:

  • Only use technology that is available now and currently in use, or that have been demonstrated to work.
  • Supply our energy with 100% renewable technology with no nuclear component. This is because nuclear energy production produces waste and that waste needs to be stored safely for thousands of years. Plus every few decades one of them seems to blow up and let's just do without that entirely.
  • Rule out geoengineering options that are dangerous or have not been proven to work. However, that does leave us with the old fashioned methods of planting forests and the newer proven methods of carbon capture and storage.

Okay so we've laid the ground rules. The study also has a set of aims, which basically ensures that life can continue in a fairly normal way, albeit with some changes, under a Zero Carbon scenario. These are:

  • Make sure energy supply meets energy demand at all times. This is one of the big problems of renewables, if the wind isn't blowing or the sun isn't shining, then there's no energy. Well, we have to figure out a way of making that work.
  • Only rely on energy we produce in the UK - so no buying energy from elsewhere.
  • Ensure that the food we produce feeds the population sufficiently and healthily - and we'll talk about agriculture and diet later.
  • Must not reduce the areas for wildlife and conservation - so you can't just turn the lake district into a giant solar farm and call it a day.

So, that's what I mean when I say this is a realistic and balanced approach to reaching Net Zero. And actually the solution for achieving Net Zero in the UK is relatively simple. There are three stages:

  • Power Down - reduce energy use
  • Power Up - switch to renewables
  • Land Use Change

I'm going to present a simplified version and focus on the aspects that urbanists and designers will be most interested in.

So, Stage 1: Power Down

By reducing our use of energy and using energy more efficiently, we can reduce the UK's energy use by 60% overall and that makes it much easier to provide that energy in the form of renewables, so that's why this is the first step.

The two big ones we can go after are energy associated with transport and with building

Transport is 40% of UK energy use and fully half of that is for road transport vehicles with aviation and freight being the other two big contributors.

In reducing these emissions, there is a behaviour change element and a technological element. The behaviour change element is facilitating and encouraging people to travel less, for instance by working from home and conducting more communication by phone and video rather than in person. We can also get more people walking, cycling and taking public transport by improving the facilities and infrastructure  for these things. The report also promotes the need for car pooling to reduce the total number of cars on the road.

So as urbanists we need to push for the principles of good urbanism. Compact cities with friendly streets that people want to walk and cycle on, and reliable, enjoyable public transport. There is likely a carrot and stick element to this, for instance through congestion charging or parking levies, to discourage people from driving.

Now, the assumptions behind how much behaviour change you can get is actually really sensible. The report assumes that the distance travelled per person reduces by 13%. Public transport increases by 14%, car travel reduces by about 20%. There's nothing drastic here. It is totally within the realms of possibility to achieve with a concerted effort over the next 10 years.

The technological side of this is the shift to all vehicles being electric. This is going to happen anyway. It's written into law in many countries now that at a certain time, non-electric vehicles can no longer be sold. So it's really just a question of when. The other big challenge is aviation, because planes not only run on fossil fuels, but they burn high in the atmosphere where the effects are even worse. There doesn't seem to be any viable electric planes on the horizon so the solution here is to switch to using biofuel and synthetic fuels, which can be produced in a carbon neutral way. I'll discuss this more in the next section on energy provision.

The next big contributor that we can target is the energy use in buildings. Energy used by buildings are 40% of the UK's energy use. In the UK and in other northern countries the big contributor to that is heating. In warmer climates, air conditioning would be the big energy suck. Other things like electronic devices and cooking are actually a small percentage. And so the big challenge of reducing energy use is that the vast majority of our building stock for the next many decades is already existing.

What we have to do is retrofit all exiting buildings to improve insulation and reduce draughts. If you retrofit all existing buildings to a high standard, you can reduce heating demand by 50-60%. Of course it would be hugely expensive and logistically mind boggling. We're talking about a nation-wide government subsidised scheme for systematically retrofitting every single house, office and shop. But the gains you get are that you have to invest less in renewable energies down the line, because we need less of them. And also you get an increase in the quality of life and health for vulnerable people who can't afford to heat their homes adequately.

As for new buildings, the study proposes that they should be Passivhaus as standard. Some people would think that is outrageous but the fact is if you build a poorly performing building now then someone will just have to retrofit in 10 years time. So it pays to get ahead of this. If you do all of this you can reduce energy demand for building by 47%.

So those are the headlines from the Power Down element of this plan. There are lots more details in the report, including some stuff on Industry that I haven't gotten into here.

We're moving on to Stage 2 of the Zero Carbon Britain strategy. This is Power Up - switch to renewables. In Stage 1, we drastically reduced the amount of energy we need. Now, it is more feasible to switch all of that energy supply to renewables.

Let's star by saying that 80% of the UK's greenhouse gas emissions are from burning fossil fuels. That puts in perspective how pressing it is to decarbonise the grid. Most of our energy mix is oil, natural gas and a little bit of coal. Nuclear energy contributes a good chunk but one of the rules of this study is to get rid of nuclear because it has its own problems. Currently less than 5% of our energy mix is from wind, solar and marine renewable energy source

So what's solution to this. One of the issues with renewable energy is that its inconsistent. When its not windy or sunny, there are dips in the supply of energy. So the solution to this is diversification. You don't just rely on one type, you have to invest in a wide variety of generation methods. And this also includes things like burning biomass and geothermal energy, which is more reliable. Now, that being said, you have to play to your strengths. In the north and west of the UK and Ireland, we are...blessed with high wind speeds. Whats more, wind speeds are higher off the coast than they are on land, so off shore wind farms hold the most promise for this part of the world. If you're in the middle east or California, then solar energy would be your big contributor.

Remember also that one of the goals of the study is to make sure that energy demand is met at all times, so you don't have moments where you can't make a cup of tea because its a calm cloudy day.

So, bearing all that in mind, the energy mix proposed within this study is about 50% wind power, with the remainder made up of wave and tidal, solar, geothermal, hydro power, ambient heat and biomass. Of all of these, biomass is a really key one. Biomass is essentially just organic material like trees, which you can grow, chop down, store and then burn for energy when you need it. When it burns, it releases CO2 but it only releases the same amount of CO2 it absorbed as it was growing so technically there's no additional emissions - that's what I mean by Net Zero Carbon. Biomass can also be used to create biofuels, which can be stored for later use or used in particular technologies that can't run on electricity. Then on top of this, we need to deploy ways of storing energy for when demand is high but supply is low, for instance on a cold winter evening with no wind. There are lots of ways to do this, like batteries, heat storage tanks, biogas and synthetic gas. It's just another piece of the puzzle and it may have some interesting impacts on urbanists if cities need to be retrofitted with this storage infrastructure.

Okay, so far we have cut our energy demand down and we're supplying all of that through renewables. That brings us to a 90% reduction in greenhouse gas emissions. The last 10% is largely to do with how we manage our land on a macro scale.

Stage 3 is Land Use Change

Let's look at the existing land cover in the UK. There are 66 million people on this little island and it can feel very urbanised. However, only about 5% of the total land area is urban area. In fact, almost half of all the land in the UK is grassland for livestock. About another 10% is crop land growing food to feed livestock. And about 10% is agricultural land growing fruits, vegetables and grains for us.

Now, you've probably heard that livestock contributes to greenhouse gas emissions through producing methane, and that's true. It's a relatively small percentage when you consider transport and heating buildings and all that. But if we want to get to Net Zero, then we'll have to reduce that. 

I think the bigger issue with livestock, and cows in particular, is just how much space they take up to produce essentially two product, meat an dairy. Calorie for calorie, its very inefficient compared to growing crops. But it's tricky because actually grasslands tend to have very rich soils that act as carbon storage. So if you convert that to arable land and you plough it. then you release all that carbon into the atmosphere.

Another issue is that the landcover in the UK has become so monocultural that we've seen huge losses of habitat and biodiversity. As biodiversity reduces, the productivity of agriculture land reduces too. The whole system is connected. So we need to be expanding the amount of unmanaged land for wildlife and biodiversity.

Another issue is that as part of our renewable energy strategy, we want to grow biomass. We need to find land to do that. Another issue is that we want to plant trees to sequester carbon.

So, it is clear that to make room for all of these very necessary things, we have to give over a lot of land that is currently used for livestock. What this study calculates is that we should reduce the land for livestock by 75%, and covert that land to growing biomass, planting forests and restoring peatland for carbon capture, and rewilding land for the purpose of biodiversity.

Remember earlier I said that we use as much crop land to grow feed for livestock as we do to grow crops for ourselves? Well if there are less livestock, then there is also less need to grow food for livestock so we can use that land to grow food for us, making the UK more self-reliant when it comes to food and reducing the need to import things like fruit and veg, which have a large carbon footprint.

Now, reducing our production of meat and dairy to a quarter of what it is obviously has huge implications for our diets and raises questions around equality and health. I could talk about this for hours but instead, I'll dedicate a whole episode to this, which will be released next month.

By making those land use changes, we have reduced emissions relating to agriculture, we've created space for growing biomass for energy and we've increased our land for natural carbon capture. After all that, we are officially at Net Zero Carbon.

If you are feeling bowled over by how much work is needed and how expensive all of this will be to achieve, then I would like to leave you with a quote from Simon Wren Lewis, who is an Oxford Economist.

"No one in 100 years’ time who suffers the catastrophic and irreversible impact of climate change is going to console themselves that at least they did not increase the national debt. Humanity will not come to an end if we double debt to GDP ratios, but it could if we fail to combat climate change.”