Using a bike with a trailer attached for doing shopping has a number of advantages. Typically half the embedded energy in a product (all the energy taken to grow, transport and package a product) is generated by the buyer driving to the supermarket or farmers markets to collect the produce. Biking to a market is an obvious solution but carrying enough stuff in panniers can be a problem. A trailer can easily handle a weeks shopping for an average family and most people find it much more fun and social than taking a car shopping, as well as saving money and carbon emissions.
Steven Muir has been making trailers specifically designed for shopping, which use a variety of bins made from fully recycled plastic, including the obsolete Christchurch recycling crates. The bins are placed in the shopping trolley and products are placed directly into them at the checkout, eliminating any need for shopping bags plastic or otherwise.
If you live in Christchurch you can try a trailer for free for a month, and get a variety of kitset trailers with instructions for building your own, or get a fully made trailer. Details on www.cycletrailers.co.nz email: firstname.lastname@example.org