13 votes

Are fuel cell electricity generators a sustainable way of making electricity?

No. There is no readily available supply of net-positive-energy hydrogen on Earth, where most human power usage takes place. Hydrogen fuel cells may be a useful component of a total energy system ...
user avatar
10 votes
Accepted

What is the most environmentally-friendly fuel source (e.g. wood, coal, oils, alcohols) for campfire cooking?

Solar thermal Given your limited criteria, solar thermal is in fact the ideal solution. I assume you say that "[solar] heating is so inefficient and the materials for solar panels introduce a can of ...
user avatar
  • 360
9 votes
Accepted

Impact on environment: a million horses vs a million cars

In large numbers, horses are more problematic than cars. According to Eric Morris, in 1898 delegates from around the world gathered to discuss urban planning. The issue they were "desperate" to solve ...
user avatar
  • 3,207
7 votes
Accepted

Size of wood lot required for cooking/heating (US west coast)?

OK, one possible setup (and assuming both my math and memory are right, neither of which is certain): Planting Douglas Fir, which is fairly fast growing (one to two feet a year) and a good wood for ...
user avatar
  • 186
7 votes

Can alloy wheels (for a car) pay for themselves through fuel savings?

A quick look doesn't show a clearcut weight difference. The claim is more for a 'rounder' wheel and a 'stiffer wheel' First order approximation fuel economy depends on the weight of the vehicle, ...
user avatar
6 votes

Oxyhydrogen as home heating method

You will always put more energy into generating this gas mixture than you will get back by burning it. The second law of thermodynamics (which for this context can simply be thought of as saying that ...
user avatar
  • 3,621
6 votes

How effective is turning a car's engine off while standing at a traffic light?

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 ...
user avatar
6 votes
Accepted

Is it better to use propane or natural gas as a heating fuel?

There is probably not a lot in the choice but some considerations are listed below. A significant consideration is that while Propane is superior environmentally, individual purchasing decisions are ...
user avatar
6 votes
Accepted

Does putting an automatic car in neutral when stopped help save petrol?

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 ...
user avatar
  • 11.3k
6 votes
Accepted

Is flying more sustainable than taking the train?

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 ...
user avatar
6 votes

To what extent do CO2 emissions from motor vehicles vary?

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 ...
user avatar
  • 294
6 votes

Efficiency of delivery services vs individuals travelling to purchase items?

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 ...
user avatar
  • 587
5 votes

Are we running out of fuel?

No, we're not running out of fuel. Peak oil never made sense as a problem, and still doesn't. I know that's an inconvenient truth for anyone who'd vested a lot of time and effort into the question of ...
user avatar
  • 14.6k
5 votes

Impact on environment: a million horses vs a million cars

I think the main problem is that commuting is almost never "eco-friendly". There's a lot of energy that's needed to carry your behind (and your carriage) from your home to your workplace. I think the ...
user avatar
  • 5,923
4 votes

Can chip tuning make a car more fuel-effective?

Yes, many tuning stations offer a range of options. The most popular is to offer power upgrades, usually at the expense of fuel economy, for example improving fuel/air/compression balance at low ...
user avatar
4 votes
Accepted

How efficient are tiny cars compared to others?

In the USA the Daimler/Mercedes "Smart" Fortwo car is the obvious choice, rated at 41mpg on the highway. Those look silly but are quite safe and very fuel efficient, as well and being ridiculously ...
user avatar
  • 3,755
4 votes

Size of wood lot required for cooking/heating (US west coast)?

I've done this calc for my farm here in Alberta. I know that it takes 5 cords a year to heat my house. The average lifespan of trembling aspen is about 40 years. At that point it's about 40 feet ...
user avatar
4 votes
Accepted

How to choose a more sustainable vacation option?

The issue here is using the word "sustainable" as something like "healthy" - the more the better - when it actually refers to a balance between, say, resources used and resources generated. If I buy a ...
user avatar
  • 1,807
4 votes

Carbon emissions from Ethanol car fuel

There are a ton of different factors to take into consideration here. Lets make sure we keep net GHGe and tailpipe GHGe separate here. Net GHGe Net GHGe: Since 2015, satellite observation as well as ...
user avatar
3 votes

How to choose a more sustainable vacation option?

Instead of comparing the impact of each travelling modality with 1 traveller, you want to compare modalities per passenger-kilometer or passenger-mile with average load. This means that you divide the ...
user avatar
  • 14.1k
3 votes

Oxyhydrogen as home heating method

It is appealing to use wind or PV whenever they are available, and to have heating when it is required - and something is required to help those align in time. Using the energy to synthesise storable ...
user avatar
  • 14.6k
3 votes

Fuel efficiency when decelerating on a hill

Generally a driver doesn't know the exact angle of the hill at any point in time, nor do they generally know the exact combination of gear and gas-pedal that will be the most efficient. Maybe some ...
user avatar
3 votes

Is it better to use propane or natural gas as a heating fuel?

Depending on where you are, the natural gas may be mostly propane ;-) The answer from Russel McMahon gives an excellent summary of the chemistry. However, I suspect that the differences there will ...
user avatar
  • 3,621
3 votes
Accepted

Burning wood efficiently via rocket stove

Yes. Moz's comment is correct. When burning wood, you are in essence just shortcutting the rot process. Which means that instead of fungi and bacteria and bugs getting lunch, you get warm. These ...
user avatar
3 votes

Can alloy wheels (for a car) pay for themselves through fuel savings?

Theory The calculation in the other answer is rather naive. I haven't done the calculation myself, but there are a few things to consider. First of all, lighter wheels mean more than just lower ...
user avatar
  • 131
3 votes

Why are new cars being built in the UK / europe without Start-Stop technology when it seems it can lower pollution?

The simple answer is because any feature costs money, so car makers won't include it unless they're forced to. On some models it's available as an option for extra cost - which relies on the purchaser ...
user avatar
  • 2,037
3 votes
Accepted

EU Real Driving Emissions testing (RDE) - does it factor in real driver behaviour and the inefficient driving habits they often exhibit?

Under RDE [Real Driving Emissions test], a car is driven on public roads and over a wide range of different conditions..... Conditions include: Low and high altitudes Year-round temperatures ...
user avatar
  • 14.1k
3 votes
Accepted

How feasible is a city with no cars and no streets?

This is simply a fancily designed chain of cities based on the about 40 years old idea of the "compact city". The idea is to reduce urban sprawl, reduce traffic and improve living conditions....
user avatar
  • 587
2 votes

Are electric cars as environmentally friendly as we think they are?

The answer to this depends on your assumed alternative. Electric vehicles are better than some traditional gas-fueled cars, but hybrids can have an even larger footprint than efficient combustion ...
user avatar
2 votes

How effective is turning a car's engine off while standing at a traffic light?

My 95 Accord MT went from ~28.5mpg to ~32mpg easily from mostly shutting off at stoplights, even as little as 7sec or more. About 10%-12% increase in mpg. I also use engine breaking and conserve ...
user avatar
  • 21

Only top scored, non community-wiki answers of a minimum length are eligible