The fat of the land

by Simon Handby in Your car on 10.07.07

It seems there’s no getting away from the biofuel debate. The BBC recently reported how demand for oil crops was affecting agricultural markets, and on the ‘wonder plant’ jatropha, which could soon be powering Indian cars and buses.

Chief among the concerns over biofuel is the need either to earmark food-producing land for fuel crops, or to clear and convert land occupied by other ecosystems such as rainforest. With some commentators predicting an energy crisis, and everyone wondering where our biofuel is coming from, there seems to be a need for some radical thinking.

We wondered; you can grow your own food, so why not your own fuel? Do it yourself biofuel isn’t a new concept, but how much land would you actually need? The answer is surprisingly little, or at least, that’s how it seemed at first.

Our rough calculations (see below) suggest that you could power a typical family diesel with just 1.6 acres of oilseed rape. Bill Bryson says that the UK has an acre for every person who lives here, but how big is the average UK garden? We couldn’t find a definitive answer, so we’ve asked the Office of National Statistics if they can help.

In the meantime, we’ve seen estimates ranging from 270-500 square metres – about 1/16 to 1/8 of an acre. Even using the most generous estimate, a typical garden could only grow enough oilseed to slake 8% of the average diesel’s yearly thirst; a fairly limp 670 miles.

Sadly, it’s enough to shatter our utopian visions of a new generation of self-sufficient Tom and Barbara Goods, which leaves us back at square one. As we said; there’s no getting away from this debate.

The science bit

We used figures for oil yields from Wikipedia, which says that the yield from oilseed rape is 127 gallons per acre per year. Journey to Forever quotes the same figures, and adds that each litre of vegetable oil will produce about 0.8 litres of biodiesel.

We took Ford’s Focus as a typical small family hatchback. There are three diesel models in the range so we chose the middle, 1.8 Duratorq TDCi. Its combined cycle fuel consumption is 54.3 miles per gallon.

According to the IAM Motoring Trust, the average privately-owned UK car travels 8,700 miles in a year.

Covering 8,700 miles at 54.3 miles per gallon would require 160 gallons of diesel. You’d need 200 gallons of rapeseed oil to create this much biodiesel, which you’d need just under 1.6 acres of land to grow.

It’s worth pointing out that this isn’t the most scientific calculation ever, and that the amount of biodiesel you could produce would depend on your crop yields and how reliably you could create good-quality biodiesel.

IMAGE by Flickr user net_efekt