Where does your renewable energy come from?

Did you know that the renewable energy you are paying for with your green energy tariff does not actually have to be generated in this country - or even supplied to this country? For example it is quite possible your green electricity usage has been matched with generation in Italy. In the year to April 2019, 16 TWh of renewable energy certificates were imported into this country, almost half from Italy. This only adds around 15% to the green energy generated in the UK - but it does make you wonder if it is worth getting a green energy tariff at all. Fortunately some electricity companies either generate their own or buy direct from UK generators.

How, why and how far we travel: trends since 2002

The National Travel Survey for 2018 has been published - you may have noticed the reporting on aircraft travel. I have been looking at other aspects of our travel patterns: why we travel, how and how far. There are some interesting changes since 2002:

• Walking distance has hardly changed but we are cycling more
• All other modes of transport are down except for rail travel
• Business related travel, shopping and visiting friends all substantially down

The survey allows us to see more detail than this. For example, between 2005 and 2015 we walked less and less. In 2015 we took 15% less trips than in 2002 (though on average they were longer then now). Then we reversed those changes in the last three years. In contrast, for cycling we make no more trips now than before but we go 60% further each time and this trend has been fairly steady through the whole period.

Hoarding electrical stuff harms the environment.

Do you have a drawer full of old mobile phones and other electrical/electronic stuff? If so, why haven’t you recycled them? Hoarding damages the environment.

I was pleasantly surprised that Apple actually paid me £94 for my old Mac Mini when I bought a new one a few months ago. However even without a financial incentive it is good to recycle. It helps the circular economy - otherwise there is nothing for it to work on.

If I was on the citizen's assembly for Cambridge transport ...

The Greater Cambridge Partnership did not get a clear message from the survey they ran earlier this year so now they are running a citizen's assembly. I thoroughly approve - if done well a citizen's assembly allows for a representative panel of ordinary people to hear evidence from a range of experts and consider a topic in depth. Transport is a complex problem because different people have different needs and it is hard to satisfy everyone. Using your own car is always going to be more convenient if you have one - as long as the traffic is actually flowing rather than in gridlock. I would want to see evidence for solutions that will bring benefits to most people at least some of the time.

I believe the invites have gone out and I have not got one so I won't be able to take part. However, if I were, this is what I would like to discuss while on the panel.

Surprising results of air tightness tests in new homes

No-one wants to live in a draughty home. They are uncomfortable to sit in and have high energy bills. Building regulations have stringent rules about ventilation levels and air tightness - but there is strong evidence to suggest that they are not working very well. New homes are often much more draughty than they should be, and adding an extension to an existing home can introduce draughts in the main part of the house, if not done properly. This post draws on evidence from a study by UCL researchers of 144,000 air tightness certificates lodged with the ATTMA database (Air Tightness Testing and Measurement Association) [1]. Also I have included anecdotal evidence reported to me by Paul Buckingham of Sustainable Lifestyles Ltd and others.

How is a house like 3/4 of a cow?

One way to decarbonise our home heating is to use anaerobic digestion (AD) to process biomass (such as grass) into biogas. So we can grow grass as cattle feed or to heat our homes. How do cows and houses compare in terms of grass demand? Here is a back of the envelope calculation - and the conclusion is: one house is about 0.75 cows. Based on this (rough) figure, if we repurposed all our land that currently supports sheep and cattle to grow grass for biogas, we could supply about 13 million households, a little less than half the current number in the UK (27 million) [1].

The grass these cows are eating could be used to heat our homes instead.

Low carbon heating in real houses

The quick way to get to low carbon heating is to replace our gas boilers with heat pumps. We don’t have to wait for low carbon gas or district heating infrastructure to be installed - we can do it tomorrow. However, it isn’t always that easy. The Energy Systems Catapult (ESC) have done a fantastic job of modelling how this could work in five real homes [1]. They envisage a staged conversion in each case, usually starting with fabric upgrades and moving on to a heat pump (or district heating) later on, over 10-15 years. Each house (two semi detached, two terraced and one detached) has its own story, but I am not going to worry about the paths, just about the end points. Interestingly, in two cases they envisage keeping a boiler in place as well as the heat pump, running the heating in a hybrid scenario.