Check out their website and their article in the features section...They are really doing quite a lot for the environment and their community. Purchases of Belu water fund clean water initiatives in the UK (local to Belu) and abroad (India, Mali), They're going to fund a garbage filter for the Thames and have supplied hand pumps to rural villages in India.
Belu also points out that shipping water from Fiji to the UK is insane. The carbon footprint of shipping is huge. So Belu went to the trouble to find water sources in the UK. I think it's a very admirable effort. i just wish Poland Spring would do the same.
On the flip side...corn is better than oil and is technically renewable...but it is usually grown with petrochemical fertilizers. The next step would be to make the growing greener. Belu points out that the bio-plastic can be made from potatoes, beets...really, anything with carbs and sugars. Corn does grow fast, though. Plus this article from Columbia University's news service points out that corn plastics use 20-30% less petroleum overall than PET. So that's great.
This project really seems to have taken a village; looking at their supporters page you can see that they were helped by local design schools and water charities, among others. Parson's in the US seems to be leading the way on this...I hope other schools follow suit and find worthy projects to contribute to.