I've been playing about with DECC's 2050 calculator and I wondered if BH readers (if any of you are still popping by) to take a look at something.
I'm interested in how it handles bioenergy. Here's how the relevant help screen describes the process.
In 2007, the UK used 4000 km2 of land to grow energy crops, which is less than 2% of the country. For comparison, 174 000 km2 of land was used for arable crops, livestock, and fallow land. The 2050 Calculator contains two options relating to agricultural biomass and land use: land use management (described here) and livestock management (described on another page).
In his book, Mackay uses a value of 244,000 km2 for the area of the UK, so "less than 2%" is correct.
Near the bottom of the screen the power output from this 4000 km2 is given at 8 TWh. That's 0.002 TWh/km2, a number that is similar to the value you can derive from the text of the book (24 kWh/person/day, 59,500,000 people, 244,000 km2 gives a value of 0.0028 TWh/km2, and Mackay admits this is optimistic).
Then look what happens when you move the slider for land dedicated to bioenergy. Take Level 4, for example. According to the help text.
Level 4Level 4 assumes that the UK has a strong domestic bioenergy production focus, with 17% of the country planted with energy crops. There is extensive carbon capture through forestry, and highly effective management and collection of waste materials for bioenergy use. The resulting energy available in 2050 is 545 TWh/y.
Using our figure of 0.002 TWh/km2, 545 TWh will require 272,500 km2 of land. Which is to say pretty much the whole of the UK.
Can anyone explain why DECC thinks it will only take 17%? Or is my maths wrong somewhere?
Note:
If you want to get to the relevant place on the calculator, start it up, click "Overview" in the bottom left hand corner of the screen and then the "Supply" tab in the top right. Scroll down the list of options on this tab. Near the bottom, you will see "Land dedicated to bioenergy" with a slider that allows you to make your selection. The help screen is available by clicking the "i" button just above the slider.