Rudolf Diesel experimented with vegetable oils when he built the first diesel engine in the 1890s. During the second World War, the French used sunflower and rapeseed oil as ersatz petrol. In the colonies, French soldiers discovered that palm and coconut oil made excellent fuel for army lorries.
Drawing on these folk memories, a group of 20 ecologist artisans and farmers in the Lot-et-Garonne department of south-western France set up ValΘnergol in 1996.
"We wanted to prove it's possible to produce energy without supervision by the government or oil companies," says its director, Mr Alain Juste.
Like a hundred other vehicles in the area, the exhaust of his sunflower-powered Renault 21 smells like frying chips. ValΘnergol stands for "Valorisation ΘnergΘtique des olΘagineux", but if the French government has its way, the energy potential of natural vegetable oils may never be realised.
The national customs and excise authority has filed a suit against the ecologists and last month a tribunal in Agen slapped a Fr 33,000 (£3,962) fine on Mr Juste and his friends for selling "at least 10,000 litres of sunflower oil" without paying the TIPP (domestic tax on petroleum products).
The TIPP brings a staggering Fr 160 billion (£19.2 billion) to government coffers each year, so the finance ministry and oil companies stand to lose heavily if every farmer with a field of sunflowers makes his own fuel.
All it takes, Mr Juste says, is a Fr 30,000 (£3,601) press, a couple of plastic tanks and a few hundred coffee filters. The end product costs only Fr 4 (48p) a litre, compared to Fr 5 (60p) for a litre of diesel.
The fine levied against ValΘnergol is all the more unfair because bio-fuels are supposed to be exempt from fuel tax. The main beneficiary of the exemption is Diester, the officially approved bio-fuel produced in three French chemical factories from sunflower and rape seed oil.
When the 1992 Common Agricultural Policy reform left vast stretches of land fallow, oil companies teamed up with farmers whose land was authorised for industrial use to produce government-subsidised Diester.
Unlike the much cheaper sunflower oil, Diester can be used in new, fuel injection engines. Nonetheless, 10 million older vehicles in France could be sunflower powered.
But the anti-sunflower lobby is winning. Back in 1993, the prime minister commissioned a former chairman of Renault and former deputy chairman of the Elf oil company, Raymond Levy, to study the potential of sunflower oil.
The natural fuel "mucks up the cylinders" and "deteriorates the quality of the lubricants", Mr Levy concluded. A scientific thesis which maintained the opposite was ignored.
"I've seen them fuel up and drive - it works very well," protests Alexandre Garcia, the Le Monde correspondent who investigated the ValΘnergol case.
Mr Garcia is convinced that the state, the oil companies and farmers involved in Diester production have conspired to sabotage cheap, non-polluting sunflower oil.
