HELP save the Sumatran tiger while you buy your carrots.

That is the promise from an Oxford social enterprise which sells refills of environmentally-friendly washing up liquid.

Husband and wife team Rina Melendez and Paul Godden, who run SESI Food and Household Refills, have set up one of their refill stations on the travelling 'veg van' of local food co-op Cultivate.

When Cultivate customers visit the van's Thursday afternoon stop outside the Rusty Bike pub on Magdalen Road, they will also now be able to top up on sustainable laundry liquid, fabric conditioner and spiced ginger-scented washing up liquid.

All of the products are produced for SESI by a family firm in Northampton called Ideal Manufacturing.

The ingredients are almost entirely from the UK, except for lemons and lavender from Europe, and none of them are harmful to the environment.

SESI takes special pride in the fact that none of their ingredients are grown in monocultures: massive single-crop farms which are often harmful to biodiversity, including the palm oil plantations which have destroyed the habitat of the Sumatran tiger.

Palm oil, a popular ingredient of many household detergents, does not feature in SESI products.

What's more, SESI does not sell any of its products in bottles: customers have to bring their own containers.

Since it was set up in 2006, the organisation estimates that it has saved 40,000 containers from landfill.

Mrs Melendez and Mr Godden, who live with their two children in Littlemore, started SESI with a refill station at East Oxford Farmers' and Community Market every Saturday morning, where they still food refills such as flour, lentils, olive oil and vinegar.

The scheme was a hit, and the money they made was reinvested to diversify into detergents.

They now employ four staff alongside the six volunteer team members and have refill stations at South Oxford Farmers' Market and the Talking Shop market at Sandford-on-Thames village hall.

Mrs Melendez said they would see how popular the Cultivate refill station was on a Thursday and consider whether to extend it to the van's other weekly stops around the city.

She said: "We've already saved 40,000 bottles from landfill and hopefully if everything goes well, the new station at Cultivate will save a lot more."

According to Greenpeace, the UK uses 35 million plastic bottles each day and up to 16 million of those are not recycled, ending up in landfill or as litter.

Cultivate's Katie Herring, who runs the veg van on a Thursday afternoon, said the SESI ethos fit perfectly with that of the co-op.

She said: "We are all about promoting locally-sourced products so it is great to partner with SESI – we can help reduce waste at the same time."