23

This question is addressed in a paper by Shibahara et al, 2013 (doi:10.2208/jscejipm.68.I_285). They don't discuss walking, but they do discuss bicycling, which I suppose is a more realistic method for commuting (for example, I bike the 8 miles to work but I've never walked it). The authors analyzed taxi, gas cars (GV), electric cars (EV), bus rapid transit ...


19

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 ...


12

Not sustainable at all because they use helium for lift. Currently we can't manufacture helium in meaningful quantities, so the helium we get comes from fossil fuel extraction "natural gas" as it comes out of the ground contains all sorts of gases including helium. The US government has long funded some gas extraction/purification plants collect and purify ...


12

If we diverge slightly from the request for CO_2 per passenger km, and look at energy use per passenger km, then David MacKay's book "Without Hot Air" has a rather good chart. Pulling from that the methods by which one might plausibly cross the atlantic (figures are approximate, as I'm reading them off the vertical scale): A Boeing 747: 52 kWh per 100 ...


11

While this doesn't fully answer the question in terms of ecological impact, David MacKay provides a good chart of the energy use of various modes of transport, here. I'll extract some figures from it (they're approximate, from me reading off the vertical axis). They refer to typical occupancy unless otherwise stated. Note that, as pointed out by a ...


11

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 ...


9

Air is much more energy intensive. Gucwa and Schaefer looked at the impact of scale on energy intensity in freight transportation, and the chart below is taken from that paper. They looked at varying loads, across four modes - the line in the lower left is trucks, the cluster above it is air, the long spread-out light grey dots in the bottom-right is ships, ...


9

From the first search I tried the first result says: According to the Second IMO GHG Study 2009, which is the most comprehensive and authoritative assessment of the level of GHG emitted by ships, international shipping was estimated to have emitted 870 million tonnes, or about 2.7% of the global man-made emissions of CO2 in 2007. Exhaust gases are the ...


7

Each has pros and cons. Trolleybuses require less infrastructure (no steel tracks), and don't need the road dug up. Light rail typically (with few exceptions - Curitiba being the notable counter-example) offers much higher capacity for a given land-take: it requires a narrower corridor and it carries more people per metre lane width per minute; and has ...


7

To encourage people to not use of purchase cars develop a public transportation system that is easily accessible by the to public and caters to the needs of the public so that people will use it. Additionally, the energy source for the public transport system must be electricity. Anything that is combustible, even bio fuels, will maintain a certain level of ...


7

I think that you can assume, worst case, that your car will be no worse than the 10-15 seconds break-even given in the linked answer. Since your car is engineered for start-stop, if there are easy improvements to be made to minimize the cost of restarting then the manufacturer may have made them, but in any case it should be no worse than average. The ...


7

Unfortunately there are not many studies available on this subject and, as you wrote, the answer depends a lot on the country and on the city. This article on the Guardian analyses the study Impacts of home shopping on vehicle operations and greenhouse gas emissions: multi-year regional study. This study investigates the effects of home shopping on vehicle ...


6

I have been using this method for years, on both my Toyota and my Ford Explorer. I save lots of gas, nothing has ever happened to my batteries, and have never had a mechanical problem. You need to use common sense. I typically shut it off when it's a long light and I'm in a long line, railroad crossings, and any other situation where it's going to be at ...


6

According to this answer over on mechanics.SE, below a certain engine RPM, your vehicle automatically disengages the torque converter. That is to say, when stopped, there isn't a fundamental difference between having the transmission in drive or neutral. On the other hand, shifting back and forth each time you're at a stop light does cause a bit of wear, ...


6

I am not able to find any studies comparing the energy consumption. But if we look at a paper investigating emissions directly, which one could argue is an even better proxy for sustainability than energy, it seems that although the emissions from construction for railways is more than twice as large as that from the construction of airports, on a passenger-...


6

Carbon offsets aren't a perfect solution by any means, but provided the activity being funded by the offset is genuine and sensible for the long term, carbon offsets could certainly be considered to be a good solution. For example, if you help fund technology that reduces fossil fuel use that wouldn't otherwise have been able to be funded, then you could ...


6

CO2 is produced by burning the carbon in the fuel, so if your driving style causes you to use twice as much fuel, you will produce twice as much CO2. Driving aggressively can have a big impact on fuel consumption. It's hard to quantify, but a 50% increase in fuel consumption and CO2 emissions is certainly possible. Conversely, the CO2 emissions will be ...


6

Cars, buses, trains, and planes: comparison including infrastructure "Life-cycle Environmental Inventory of Passenger Transportation in the United States", a 2008 PhD dissertation, provides a comparison of various passenger vehicles, buses, commuter rail, and air travel. The results were summarized in an article in Environmental Research Letters, "...


6

The best list is probably wikipedia: Phase-out of fossil fuel vehicles There is a good review from the World Economic Forum here, dated 2017, which discusses some of the different approaches taken, which I've summarized here: UK: Ban production of petrol and diesel cars by 2040 (since changed to 2035); France: Ban sale of petrol and diesel cars by 2040; ...


6

The Umweltbundesamt (sort of German EPA, I figure) recently released a new study on the "Ecologisation of online shopping" - which obviously is in German. Anyway, core findings are that individual shopping using your own car is the worst (CO2-wise) with 600 to 1100 g CO2 (for a 5 km ride to the store), while delivery is better due to optimized ...


5

Air or water? Should engineers bend their energies on improving air travel or sea travel? Air. Regardless of sustainability, people who are used to hypermobility will not easily accept that mobility to be taken away. There is work going on on electric aircraft. Current batteries have insufficient energy density, but energy density is increasing rapidly. ...


5

Unfortunately--and I realize this is not very helpful--the best choice in terms of carbon footprint is almost certainly not to go. It's a good point that freighters are likely to be much more efficient per passenger than cruise ships, but when comparing them to airplanes, you have to keep in mind what's being brought along to accommodate the passenger, not ...


5

KubaFYI, in light of the update you made to your question, I am submitting a second answer for your consideration. The title of the question is "How can I make my family understand my CO2-emissions-related hesitation to fly in order to spend time with them?" In the update you say that "This question was meant to be ... more about how to negotiate a ...


5

Three routes: A: Your van has all your worldly possessions. B: In addition you have a place you can store stuff. C: Use a car towable R.V. A: Everything is in your van. Consider removing the back doors and buiding a box that fits into this space. The back panel folds down to make a table. A propane tank and a gas stove is how you cook. Or you have ...


5

It depends on how you define "pollution". Cargo ships use some of the dirtiest fuels available: bunker fuel is basically what's left over after you refine all the good stuff out of crude oil. It's got all sorts of contaminants that something like gasoline or jet fuel doesn't have. On top of that, there are basically no regulations on emissions by ...


4

short answer: yes, it's better than driving a fossil-fuel car. Long answer: it may seem to make less sense if you only consider a very small range of impacts, where all of the costs are visible, but only some of the benefits. Only when you zoom out to the long-term system level do you capture all of the benefits. And there are even better alternatives. ...


4

The key thing is: what can you buy second hand at your destination. Not just "what is available", but "what are you actually willing to buy second hand" and "what about the other people involved". It's all very well saying "I will buy a second hand couch" but if your mother disowns you for throwing out the couch she gave you, or your partner refuses to buy ...


4

Plant a lot of trees -- assuming you mean partciulate pollution: See for example Estimating the removal of atmospheric particulate pollution by the urban tree canopy of London, under current and future environments, Tallis et al. 2011


4

Another option that could be explored (and indeed is, to a limited extent) is the increased use of airships. Being neutrally buoyant, they need much less energy per trip, and the propulsion could be provided by solar power (they also have a large area on top of the envelope to hold solar cells). The downside, of course, is the need for large amounts of ...


4

The question has the carbon-footprint tag so this answer will focus on this aspect. Considering that the great majority of an airline's total fuel consumption is driven by the aircraft consumption we can probably ignore the other operations (maintenance, vehicules, building efficiency, ...) since they are relatively small. There is a great wikipedia page ...


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