We risked running low on fuel today, and saw the car sputter briefly while going up a hill. Made it to the gas station fine, in fact with a gallon to spare, it seems.

I've been thinking more about environmental economics since I blogged about retail carbon credits. I was surprised about how cheap (some would say unrealisticly cheap) wholesale credits are -- about $2.20 per tonne of CO2. (Update: This price keeps changing. The U.S. price is clearly out of whack down to just 25 cents per tonne in 2009. The European price has declined too, from $20/tonne when I wrote this to $14/tonne in fall 2009.)

Today, many of my friends have bought a car like the Toyota Prius, feeling they are doing their bit to help the environment by burning less gas. The Prius costs around $3,000-$6,000 more than a comparable old-style engine car (in part because high demand keeps the price high), and the savings on gasoline don't justify it on a financial basis unless you do nothing but drive all day. So the main reason to buy it is to help the environment and to make a statement before your peer group. The Camry Hybrid, which gets 32mpg instead of 23mpg costs about $5,000 more than the regular Camry.)

Problem is, there's an argument that you're hurting the environment, counterintuitive as that sounds. And no, it's not just the unanswered questions about recycling the fancy batteries in the Prius when they fade, where fairly positive results have been returned so far. Read on...

After we picked up our rental car in Darwin in the Northern Territory of Australia, the blasting heat told us we would like a cooler full of drinks on our 3 day road trip through the outback. So we stopped at a Woolworths and picked up one of those terrible foam coolers, ice and some drinks. There was no bar code on the cooler so we wasted what seemed like 10 minutes in the checkout because the clerk wasn't authorized to ring up an item as general merchandise. (Hint to stores: I know you're scared of your cashiers stealing from you but this is ridiculous.)

You may have heard of the idea of pollution credit trading. I've been pointed to two firms that are selling CO2 credits on the retail level for individuals, to offset the output from driving a car, heating a house etc.

I'll get into the details on how it works a bit below, but if you have a car like mine that is putting out 5 metric tons of CO2 each year, you can for a low price (about $50, which includes a whopping markup) pay a factory somewhere to cut their own output by 5 tons, meaning that net, you are causing zero emissions. Which means you are reducing total emissions by a lot more than you would by switching to a Prius, and you are doing it at a vastly lower cost. (This doesn't mean you shouldn't drive a Prius, it just means this is a lot more effective.)

Normally pollution credits are traded only by the big boys, trading contracts with hundreds or thousands of tonnes of emissions. The retail firms are letting small players get in the game.

This is a fabulous idea, in theory at least, and also a great, if sneaky gift idea. After all, if you buy the gift of not polluting for your loved one all they get is a bumper sticker and a good feeling. At least it's better than giving to The Human Fund in their name.

Here's the catch. I went and priced the credits, and while www.certifiedcleancar.com wanted $50 to credit my car, the actual price of credits on the Chicago Climate Exchange is about $2.16 per tonne of CO2, or about $8 for my actual output as they calculated it. One expects some markup, of course, and even some profit for the company selling the retail credits, but this is nuts. I called the other company, Terrapass and got reasonably frank answers. First of all, they claim they invest more in wind power and other truly non-polluting forms of energy more than they just buy carbon credits. Secondly, this is still a small volume thing, and most of the costs are not the credits, but the $20,000 or so to become a member of the exchange, or so I was told. And of course, in small volumes, administrative costs can swamp the real costs.

Another outfit I found is carbonfund.org which is non-profit and cheaper. In some sense since people buy these out of guilt rather than compulsion (they were meant to be forced on polluters to give money to non polluters and make a market) non-profit might make sense, but they are also supposed to be a real market.

Still, if I pay $50, I would love for my $50 to mostly go to reducing pollution, not mostly to administration. Usually when exchanges are expensive there are members who will trade for you at much more modest markups. The folks at Terrapass said they were not yet profitable at the current prices.

And it is such a good idea. Read below for more on pollution credits.

Recently, I discovered something that others have known for a while but many don't know. Namely that effectively all modern cars that say they should use Premium (high-octane) gasoline run perfectly fine on regular. Since the early 90s, cars have had more advanced carb/fuel-injector systems which adjust to the octane of the gas and don't knock. Like an idiot, I've been filling my car with premium. The engineers at all the major car vendors have confirmed this.

Many are commenting on the gasoline shortages and price increases involved with hurricane evacuation and other emergencies. Some people can't get gas to get out of the city. Others full up giant tanks even when they don't need it. Stations raise prices as supply drops and demand increases, as per the normal rules of the market. Some suggest the stations be price-controlled to stop this, but that would only result in even more gas hoarding by the public.

Every time I take an RV trip (ie. each Burning Man) I come up with more observations. The biggest one is that it cost $360 in gasoline to go from the bay area to the black rock desert, about 800 miles. And that's at a price still well below world price. The RV owner said he was planning to get out of the business, people no longer want to pay the gas price.

I recently picked up a surplus battery-powered motor assist for a bicycle, and it's a lot of fun. Due to lower power you have to start peddling to 3mph and then it can run the bike for 10 miles at 10mph (for normal weight people, not me.)

Mapping programs, and fancy GPSs come with map databases that will, among other things, plot routes for you and estimate the time to travel them. That's great, but they are often wrong in a number of ways. Sometimes the streets are wrong (missing, really just a trail, etc.) and they just do a rough estimation of travel time.

Ok, this idea will make no sense to those who have not gone RV camping. RVs have 3 water tanks -- one for fresh water, one for the toilet sewage (known as "black water") and one for the other drains (shower, sinks) known as "grey water." When you camp in unserviced campsites for a while you become very aware of the capacities of your tanks.

However, the RV uses the fresh water tank to "flush" the toilet. It seems to me that with a small extra water pump, one could use the grey water, or a mixture -- grey with a final spurt of fresh to rinse the bowl.

RVs don't really flush the toilet, that would use way too much water. You rinse the bowl after #1 and you pre-fill the bowl before #2 and rinse later.

Having completed a long fly-n-drive road trip, I have some lessons and observations.

1. If you will be driving a lot, use a rental car even if leaving your own city. We put 3000 miles on our rental car for $300 -- far less than the depreciation cost would have been on my own car.

2. It's great to have a cooler in the car, you can buy perishables and get cold drinks when you want them, but forget about those $5 styrofoam coolers for any long trip. Within a few days ours was leaking, we fixed it by putting a plastic bag inside and out, but they are not very sturdy. There are collapsible coolers and we have one but didn't have luggage room. You can buy a cheap solid cooler for under $20 at wal-mart or Costco, but it seems wasteful to throw it away. If you have extra luggage, you can fill a cooler with stuff, duct tape it and check it as luggage, however.

Perhaps this is one of those ideas that some car has implemented and I haven't yet seen it. As many people know, in several years ago a number of cars arranged so that their interior lights would not go off immediately when you closed up the car. This gives you the ability to still see shortly after closing up the car and walking away.

Of course this also drives people nuts, because in many cases you can't tell if the lights stayed on because you didn't close a door properly, and you would end up waiting around to see if they would go off.

RVs come in all sizes, from 40' bus to towable pop-up. But what about inflatable in a trunk in the back of a minivan?

Setting up and tearing down tented campsites is a pain, and there are instant-setup tents and even some inflatable tents. But what about a super-duper inflatable tent, designed for car-camping.

First entry in a while due to trip to Burning Man ... more on that later. This time I returned to RV rental, after 2 years in a tent, so I thought I would make some notes on that.

Ok, I'll admit this is a crazy idea, not likely to ever see the light of day, but it's worth throwing out as an exercise. It is often said we should keep the speed limit low to encourage good fuel economy.

What if there were no speed limit, but instead a "fuel limit." For example, 2 gallons of gas per hour.

I'm not the only one to have thought of this, but as yet no real work has been done. How about a hybrid car powered with a Stirling Engine? (Not spelled Sterling, btw.)

The Stirling is more efficient than the internal combustion or diesel engine, and it's also a lot quieter. Sounds great, but it's not good for cars because it can't rev up quickly and it takes about 5 minutes to get the engine hot enough to run well. We want our cars to start the minute we put the key in.

Commodities traders buy gasoline futures all the time. Could they work at the gas pump? Imagine a big gas chain willing to sell you future gas today. You would buy a coupon, good for 15 galons of gas in August, the month you plan a big family trip in the minivan. You're afraid the high prices in the future might hurt the trip, you can be protected against them. The futures might even cost less than gas at the pump today due to widespread belief that supplies will open up. In times of heavy fear they would cost less.

I've often wondered why, when you have an electric train line that has a terminus as the main destination, you can't give everybody an express train.

To do this, imagine for the commute home, a 5 car train starts downtown. It leaves and expresses a few stops down the line. (A local car leaves after to handle the stops close to downtown.) When it gets to point one, with sufficient warnings and many safeguards, it decouples, and the rear car brakes to stop at the first of its stations.

Carpool lanes exist to reward those who work to reduce congestion and pollution with a faster trip. I know that's good every time I look out my window and can't see the hills for the haze. Some areas allow zero-emission-vehicles (electric cars etc.) to also use carpool lanes with a solo driver, reducing pollution if not congestion.

Proposals have been made to also allow solo drivers of hybrid cars into the lanes, as well as solo drivers who simply pay a fat fee for a permit. Let me propose an interesting variant of these payment ideas.

Pardon the local entry boring to those outside this valley.

San Jose is seeking something "distinctive" for the airport remodel. Let me suggest something I have not seen anywhere else, something that would say something about the area.