How much of the UK's arable land will be needed to make it's biofuel?

According to this story on today's BBC news website the UK government is set to mandate the proportion of ethanol in standard petrol is increased from 5% to 10%.  The 5% grade is known as E5 and the new grade will be known as E10.

So, how much of the UK's arable land would be needed to make this, if it were made here?

The article says "Ethanol is a kind of alcohol manufactured from plants, including sugar beet and wheat".  Since sugar beet can be grown successfully in the UK, and it has a higher ethanol yield than wheat per square metre, I'm going to assume that we make the ethanol entirely from sugar beet.  So let's see if we can work out what proportion of the UK's 60,000 sq km arable land would be needed to power 10% of it's vehicle miles:

In [1]: beet_ton_per_sq_km_per_year = 1320
In [2]: litre_biofuel_per_ton_beet = 108
In [3]: litre_biofuel_per_sq_km_per_year = beet_ton_per_sq_km_per_year*litre_biofuel_per_ton_beet
In [4]: gallon_biofuel_per_sq_km_per_year = litre_biofuel_per_sq_km_per_year / (8 *0.568)
In [5]: av_mpg = 38.8
In [6]: miles_per_sq_km_per_year = av_mpg * gallon_biofuel_per_sq_km_per_year
In [7]: vehicle_miles_uk_per_year = 350e9
In [8]: sq_km_beet_needed = vehicle_miles_uk_per_year/miles_per_sq_km_per_year
In [9]: sq_km_arable_uk = 60000
In [10]: uk_arable_needed_percent = sq_km_beet_needed *100 /sq_km_arable_uk
In [11]: percent_uk_arable_needed_for_E10_fuel = uk_arable_needed_percent * 10/100
In [12]: percent_uk_arable_needed_for_E10_fuel

Out[12]: 47.92098148340989

Yup, only 48%

It would take nearly half of our arable land to create the ethanol in the E10 if we made our own biofuel.  It would take nearly 5 UK's if we went all the way to E100!

Is biofuel madness?

According to Mike Berners Lee in "There is no Planet B" one square metre in California could, in one year, produce enough biofuel to power a small car 1 mile.  Alternatively, if you place photo voltaic cells on it, it could power an electric car 1000 miles or an electric bike 20,000 miles.  So, perhaps it would be better for the government to ramp up the electrification of private (and public) transport, and to encourage more walking and cycling.

(Apologies to Mike for stealing the question "Is biofuel madness?" from a chapter title in his book!)