By Tim Hirsch
Environment reporter, Brasilia
Biofuels should only be produced if they meet strict environmental standards, an international group of lawmakers have concluded.
The legislators said the fuels also had to deliver significant savings of greenhouse gas emissions.
If such criteria were met, they said there should be an urgent review of the tariffs that currently block imports into markets such as the EU and US.
The forum was hosted by Brazil, one of the world's biggest biofuel producers.
Biofuels have become a highly controversial issue, with claims that the rapid expansion of energy crops could threaten global food security, and add further pressure to sensitive ecosystems including rainforests.
It is also argued that in some cases the benefits to the climate of burning plant material instead of fossil fuels are outweighed by the energy needed to produce and transport biofuels, and by the release of carbon from soils by changes in land use.
The gathering of legislators from the Group of Eight (G8) richest economies and five key developing countries heard repeated claims from its Brazilian hosts, led by President Luis Inacio Lula da Silva, that ethanol made from sugar cane was highly efficient.
Biofuels can be made from wheat, rape seed and sugar cane
They added that it could also be produced without serious negative impacts on ecosystems or threatening food supply.
Brazil has been using ethanol to power its vehicles since the 1970s and is now hoping to reap major economic benefits from global demand for alternatives to oil.
The meeting failed to agree a final policy statement on biofuels, with some delegations led by France and Germany reluctant to abandon trade restrictions before a system of strict certification of sustainability was in place.
But there was consensus on the main elements of the tests that should be placed on biofuels.
These included that they should not be made from materials grown on land with recognised value for biodiversity.
Also, that the greenhouse gas emissions involved in their production and use should be significantly less than those produced by fossil fuels.
That would place in doubt many fuels such as biodiesel from palm oil that has been implicated in the destruction of Indonesian rainforests.
Many forms of biofuel production in colder countries would also be in doubt, where the energy benefits have been questioned.
Although sugar cane is not grown in significant quantities in the Amazon region, some environmental groups will also question whether Brazilian ethanol would meet these criteria.
Much of the recent expansion of sugar cane plantations has been in the highly bio-diverse savannah region of the country.
Activists claim the dash for biofuels is causing more harm than good
The supporters of Brazilian ethanol argue, however, that huge areas of degraded cattle pasture are available to grow the crop, and that expansion of biofuel production does not require significant conversion of native ecosystems.
The meeting also failed to agree a framework for a new global agreement on measures to tackle climate change beyond 2012, with the Chinese delegation apparently reluctant to pre-empt the position of its government in forthcoming negotiations.
Lord Jay, the former head of the British Foreign Office, who had led the efforts to agree the framework, said there had been consensus over his claim that a massive increase was needed in the funds available to poorer countries to cope with the impacts of climate change.