6 October 1995

Biodiesel kinder to water life

BIODIESEL is much less likely to damage pond and river life than conventional diesel fuel.

A ministry-funded study by the Centre for Aquatic Plant Management found rape methyl ester is roughly 100 times less toxic to a range of algae than standard mineral-based diesel.

The oilseed rape-based fuel is also much less poisonous to water fleas, snails and pondweeds, the CAPMs Jonathan Newman told a meeting of the Arable Research Institute Research Association.

The work at Sonning, Berks, reflects official recognition of the need for a less polluting fuel for diesel-engined boats on inland waterways, explained Dr Newman.

The experiments compared the effect of various concentrations of the two fuels in water. Thick oil slicks typically leave concentrations of 1-10g/litre, said Dr Newman. The tests used 1g/litre as the lowest "dose" and up to 200g/litre – a 20% solution – forming a "fairly thick layer".

Even at the high level one common algal species – Chlorella vulgaris – continued to grow in the biodiesel mix. Another species was killed by all rates of standard diesel but survived biodiesel at up to 100g/litre.

Snails and Daphnia, the water flea, died even at the lowest dose of standard diesel (1g/litre) after just 24 hours. But there were still 10% alive at a biodiesel dose rate 100 times higher a day later.

One type of surface duckweed seemed relatively unaffected by either fuel, but another was killed by the conventional diesel. Canadian pondweed was soon killed by standard diesel deposits accumulating in the sediment, but was still growing in biodiesel-treated water a fortnight later.

Most of the biodiesel was usually undetectable within 10-14 days, said Dr Newman. It breaks down into compounds which occur naturally in waterways.