12 Feb 2020

The risks we face

Back in November 2019, I blogged about plate tectonics and, in particular, how we live - and die -with the earthquakes, tsunamis and volcanoes that result from us living on an unstable planetary surface. It set me thinking more about the more general risks we face and how we can categorise them.

Plate tectonics covers the below-ground risk. But what about things dropping on our heads from outer space? These could be solid, like meteorites or asteroids, but they could also be unwelcome rays from the Sun or elsewhere. We don't see much evidence of these risks but they do happen and very occasionally they can be very deadly. A single huge collision with another heavenly body 65 billion years ago is believed to have been  responsible for the extinction of the dinosaurs.

The third field of risk is atmospheric. The Earth's surface is surrounded by a relatively thin layer of gases which we depend on for life. As the Earth both rotates and tilts on its access, the resulting winds and weather patterns cause all manner of mayhem at the surface. Think Droughts. Storms and Hurricanes. Monsoons. Flooding. Extreme temperatures. Fog. Snow. Ice. Fires (albeit at one stage removed but remember that oxygen is an essential component of fire).

The atmosphere also dictates which life forms, if any, will occupy the surface. No rain = dessert. Frozen rain = snow = Arctic like conditions and glaciers. Lots of heat and rain = jungles. Lots of rain and coolish temperatures = Manchester.

We interact with our atmosphere in ways we don't with the ground beneath or space above. For instance, we can turn fog into smog by adding burnt carbon to the atmosphere. And we can alter the characteristics of the atmosphere itself by tinkering with its component gases. In particular, with carbon dioxide which, despite being only a trace gas making up just 0.04% of the Earth's atmosphere, is known to act as a thermostat for global temperatures.

A more nuanced example of this was our production of CFCs, a 20th century phenomenon, which then drifted into the upper atmosphere and reacted with ozone. This resulted in large holes in the ozone layer which acted as a dampening layer for incoming solar radiation. This made sunshine a far more dangerous factor for those outdoors and led to increases in skin cancer. The Montreal Protocol, in 1987, was a fine example of nations working together to ban the use of CFCs and to bring about a gradual repair of the ozone layer.

An even more nuanced example would be the current fear about the spread of the cornonavirus from China. The atmosphere carries with it not just the threat of challenging external weather conditions, but also as a carrier of communicable diseases.

So there you have it. We live on a Planet with an unstable surface, subject to bombardment by things from outer space and dependent on a thin zone of gases which behave in a somewhat chaotic manner, and which we have started to use as a waste dump.

Having said that, it's a beautiful morning here in Cambridge and it's good to sometimes feel that Earth is not such a bad place to be posited on for a while.

1 Feb 2020

Carbon-free electricity

The race is on to produce zero carbon electricity, which is the most straightforward way of slowing/stopping climate change. But how realistic is this goal, and how long will it take? Here's a summary of the situation in the UK.

When we say 'zero carbon electricity' we are referring to how electricity is made, not what's in it. Using fossil fuels to make electricity (the traditional method, if you like) burns lots of carbon which releases loads of carbon dioxide (CO2) into the atmosphere. Renewable technologies, hydro power and nuclear power produce electricity without burning any carbon and are therefore said to be zero carbon. The electricity we now use is from a mix of sources and therefore can be said to have a carbon intensity factor, depending on how much is derived from fossil fuels (carbon) and how much from zero carbon sources. The higher the proportion from fossil fuels, the greater the carbon intensity is said to be.

The standard measurement (or metric) used to express the carbon intensity of electricity is grams of CO2 equivalent per kWh (kilowatt hour) of power, written XXXgCO2ee/kWh. The word "equivalent" is in here because other climate changing gases (notably methane) are also released during the production processes and these have to be taken into account when considering the global warming effect of the different gases. It's a complex field and the maths is not quite as straighforward as we might hope for. Methane has a large global warming footprint, but only stays in the atmosphere for a few years, unlike CO2 which hangs around for centuries before slowly being absorbed by the oceans.

When we first started making electricity on a commercial scale, the preferred method of production was to use coal-fired power stations to drive huge turbines. Coal-fired electricity has a very high carbon intensity factor, as it releases masses of CO2: anywhere from 750 to 1,000g/kWh, depending on the type of coal and the efficiency of the plant. Coal also happens to be a dirty, toxic fuel which poisons a lot of people, but that is not what concerns us here. Using gas to make electricity is a much better option than coal (and it's cleaner) but it still produces a lot of CO2 —  it scores between 380 and 480g CO2ee/kWh/kWh.

In contrast, with the notable exception of biomass, all the non-fossil fuel production methods are zero-carbon. That doesn't mean there aren't other issues surrounding their use: nuclear power maybe zero-carbon but it is not zero-problem (Chernobyl, Fukashima etc). But from a carbon intensity point of view, they all score zero. Or 0g CO2ee/kWh. To be pedantic, there are carbon costs with renewables but they are solely to do with the construction or manufacture of the equipment — known as embodied carbon.

The carbon intensity of fuel table can be summarised thus (all in g CO2ee/kWh):
Lignite: 850 - 1100
Coal: 750 - 1000
Oil: 550 - 700
Natural gas: 380 - 480
Biomass: 50 upwards
Nuclear: 0
Wind, solar: 0
Hydroelectric: 0

More details via Google or Wikipedia but a good source is here.

The history of UK electricity production shows the carbon intensity was high, at around 700g CO2ee/kWh in the 1970s when it was almost all produced by coal-fired power stations. As the switch to gas took place over the following decades, the intensity falls to around 450g CO2ee/kWh. Here is a useful summary of the situation up till 2015.  However, since 2015, the rate of change has accelerated dramatically, as you can follow here. The principle reason for this is the switch to offshore wind farms, which have had a massive effect. Maybe because it is happening out at sea, we are only barely aware of this major infrastructural change. Other factors include decreasing demand for electricity overall (which makes it easier to drop coal from the energy sources), an uptake in solar PV and a switch from coal to biomass as the huge Drax power station in Yorkshire which alone accounts for around 8% of the UK electricity demand. Currently UK electricity averages around 230g CO2ee/kWh

What it means is that electricity has gone from being a much higher carbon intensity than gas to becoming much the lowest carbon intensity power source, all in the past five years. And it is due to head lower still over the next 15 years, as we move to decarbonise the grid. Electricity is, however, over three times the price of natural gas, so a switch to electric heating is still unlikely any time soon, especially as the cost of heat pumps, the obvious technology to employ here is way more than a standard gas boiler.

I for one hadn't realised quite how quickly this change would take place and as a result fitted a gas condensing boiler in our new home - a decision made in 2017 - on the basis that we had done everything possible to minimise the heat load and that, as electricity released rather more CO than gas, it made sense to go with the cheaper power source.

The government has recently published the Future Homes Standard which is a mixed bag of proposals outlining measures to decarbonise our housing over the coming decade. It's received a very lukewarm review from almost every commentator, but the headline move contained in the proposals is that ‘new homes should not be connected to the gas grid from 2025’. 

Given the huge change in the mix of energy sources we are using to make electricity, this single proposal will rank as the most significant decarbonising measure we have ever taken.