I was planning to buy a toy. I can buy it online and in local shop next door. Price is (including shipping in case of online shop) more or less the same. Is one more sustainable than the other?
TLDR: in this particular case, where the buyer lives very close to the shop, it's likely that buying in a brick-and-mortar shop has a lower carbon footprint compared to buying online. Online shopping may become greener when the distance to the shop is more than 14 - 50km (depending on your shopping behavior and on which scientific study you consult).
First of all, the answer given by Maxfield Solar raises a very good point saying that
- you should make a distinction between sustainability and environmental impact and
- it's very difficult to go into a specific situation because we don't know all relevant details.
This being said, there have been a number of interesting scientific studies about shopping online versus shopping in a brick-and-mortar shop.
Important factors to consider are:
- method of transportation (for both the consumer and the retailer),
- distance to the brick-and-mortar shop,
- number of items that are bought in one go,
- consumer shopping behavior (e.g. orientation trips, time spent browsing online, ordering express delivery, number of items that are returned),
- missed deliveries (e.g. when a delivery truck tries to deliver a package multiple times, but the recipient is not at home).
Some conclusions you often encounter in those studies:
- Transportation is the biggest contributor to carbon emissions
- Delivery trucks are more efficient per item compared to the average consumer's car because trucks optimize routing and deliver multiple items to various places in one go. Consequently driving to a brick-and-mortar store yourself usually just adds to the carbon footprint of a product.
- Express delivery (often by air) and returned items can both have a significant impact on the total carbon footprint
- Brick-and-mortar shops use more electricity and storage space compared to one central location used in online shopping.
- Online shopping uses more packaging
There is one study which seems to be particularly relevant for this case. Looking at carbon footprint, this German study done in 2012 has found that
online retailing causes lower CO2 emissions under many conditions. Nevertheless, the brick-and-mortar channel is more environmentally friendly when travel distances are small. The radius for which brick-and-mortar shopping has an advantage increases when returns, shifts in the use of public transport and information behavior are also considered.
I don't have access to the full article, but I did find this online article where more details where provided:
At short distances—less than 8.6 miles or 14 km one-way—in-store shoppers slightly edged out online customers per transaction, about 73.8 g CO2 vs 77.9 g CO2. But over that, online shoppers’ footprints remained relatively stable while store goers emissions skyrocketed to as high as 451.4 g CO2 per transaction if they had to travel over 62 miles or 100 km.
In an older Swedish study done in 1999 which was quoted here they found somewhat similar results with slightly different numbers:
one e-commerce delivery replaces 3.5 traditional shopping trips, if more that 25 orders are delivered at a time, and if travel distance is longer than 50 km
Note that different studies make different assumptions and use different cut-off rules (what is and isn't included in the measurements). As a result a definitive answer cannot be given.
Weideli, D. (2013) "Environmental Analysis of US Online Shopping", Master Thesis Ecole Polytechnique Fédérale de Lausanne, carried out at MIT Center for Transportation & Logistics Available at http://ctl.mit.edu/library/environmental_analysis_us_online_shopping
Wiese, A. et al. (2012) "Transport-related CO2 effects of online and brick-and-mortar shopping: a comparison and sensitivity analysis of clothing retailing", in Transportation Research Part D: Transport and Environment, Vol. 17, Issue 6, pp 473-477. Available via http://www.sciencedirect.com/science/article/pii/S1361920912000521
Plepys, A. (2002) "The Grey Side of ICT", Environmental Impact Assessment Review, Vol. 22, No. 5, pp 509-523. Available at SSRN: http://ssrn.com/abstract=1799327
It depends on your definition of sustainable. Your question doesn't have an absolute answer as stated. Sustainable can refer to an individual, a community, a region, a country, or civilization as a whole. It is also used to make reference to the effect on the environment (which can become very controversial).
If you make your money from the local community (which is true for most of us) then the more of your money you spend locally, the better the local economy grows and in turn, your livelihood may be more sustainable. Therefore, if your definition is more of a personal sustainability or a local sustainability then buying locally is the correct answer.
If you make your money online, you may not care about local sustainability but you may want to consider the environment. This is where it becomes more complicated. When you buy in bulk (such as the local retail) a whole bunch of merchandise is shipped at the same time (less impact per item). However, the local retailer "may" have additional environmental impact such as his heating, cooling, etc. If you want to get that detailed, you can also investigate the online store to see if they also have a storefront which may impact the environment, if either of the retailers have solar or use the income to help, etc. As you can see, it becomes very complicated (and sometimes impossible) to know for sure what the best option is to be environmentally sustainable.
The truth is that most people will have a preference. So then they use the arguments which support their view.
The ultimate two questions for the hard core who want to be really sustainable would be: "Do I really need the item in question?" or "Does the item in question improve my sustainability?"