Taking a strategy that's been in use by bargain cereal brands, U.K. grocery chain Sainsbury's has started stocking cereal that is packaged only in bags, without cardboard boxes.

The retailer is starting the transition to box-free cereal with its own line of products, starting with its Rice Pops cereal. Eventually, the company hopes to switch to bag-only packaging for all of its cereal.

Sainsbury's started with Rice Pops because the bits of cereal are less likely to break apart when the bags are handled that other, more fragile cereals. The company is next testing out how its Fruit and Fibre cereal stands up in the new packaging.

Sainsbury's plans to cut its packaging by one-third by 2015, and has developed a number of tactics to make that reduction. The company sells milk packaged in bags instead of bottles (a 75 percent packaging reduction) and has redesigned some fruit and vegetable packaging to eliminate or reduce plastic.