Originally founded in 2014 with the mission to introduce merino wool to the world of footwear, Allbirds has fast become known for its eco-credentials. The brand announced a partnership with Adidas in 2020, with the mission to create a trainer with the "lowest ever carbon footprint". The result? The Adizero x Allbirds 2.94 CO2e – the lowest carbon emissions performance running shoe Adidas has ever created. As well as using wool, the brand uses Tencel, which comes from FSC-certified forests, alongside bio-plastics and natural rubber. Each sneaker also comes with a label telling you its carbon footprint, which is offset by the company.