John Mott-Smith Credit: Davis Enterprise

This column by John Mott-Smith, a member of Cool Davis, is cross-posted from the Davis Enterprise.

The last column was (in part) about how important it is to reduce greenhouse gas emissions from vehicles if we are to reach our emission reduction target of 80 percent below 1990 levels by 2050. On average, cars put about a pound of carbon dioxide into the atmosphere for every mile driven, and all of our cars and trucks collectively are responsible for about 40 percent of greenhouse gas emissions in the United States.

Efforts to reduce these emissions have focused on the car (making them smaller and lighter, and increasing the miles they get per gallon), the fuel (developing electric cars, introducing ethanol into gasoline, etc.) and the driver (better driving techniques, and walking, biking or taking a bus more often).

Decisions about the first two (cars and fuel) are being made “upstream” from us through laws and regulations, but the third, reducing “vehicle miles traveled” by decreasing the number and length of trips made in a car, is mostly up to us as individuals.

But, and this was the point I was trying to make in the previous column, land-use decisions by local governments also play a part. For example, new construction doesn’t have to sprawl all over the countryside but instead can be infill development with higher densities and easy access to transit lines, shopping and schools.

At a recent conference of state energy experts and officials, it was stated that the average number of miles generated by a residence each year varies according to whether the home is in a suburban area (28,999 miles), a “smart growth” community (17,000 to 23,000) or a typical urban/city environment (10,000 to 16,000). The more dense, the fewer miles.

But, what do we do with all the existing neighborhoods where it’s possible but not practical for most people to walk or bike to a grocery store?

The solution posed by the last column was to gradually increase density in existing residential areas while at the same time introducing small-scale commercial amenities to transform neighborhoods into what they used to be before the car took over the planning process: walkable.

Another possible way to envision the future is to change the challenge from reducing vehicle miles traveled to reducing miles based on fossil fuels. In this conceptualization, rather than densifying neighborhoods, the task would be to increase the number of electric (or hybrid) vehicles that don’t directly contribute to greenhouse gas emissions.

If, for example, either through consumer choice, public policy or a combination of the two, every garage, or at least a high percentage, housed electric vehicles, it would matter much less how many miles those vehicles traveled.

Producing electricity currently (no pun intended) results in some greenhouse gas emissions from power plants, but less and less as the utilities increase the amount of power produced from renewable sources.

Moreover, a recent study calculates that an electric vehicle powered by the U.S. grid travels almost twice as far per unit of energy used as does a car using gasoline derived from oil. The difference is even greater if the comparison is with California’s electricity supply, which is based on a much higher percentage of renewables than the country as a whole.

Going a step further, imagine that each garage has on its roof a photovoltaic array. In this scenario, in order to reduce greenhouse gas emissions, there would be no need to tinker with land-use issues such as density and mixed use since the entire vehicle miles traveled would be without emissions. There still may be good reasons to increase density, promote mixed use and plan development along transit lines, but reducing greenhouse gas emissions wouldn’t be at the top of the list.

A beauty of solar power, as compared to development of fossil fuels, is that once a solar array is built and installed, there’s no fuel cost (the sunlight is free) or greenhouse gas emissions. Solarizing residential energy use is a huge challenge in and of itself, but the opportunity to also solarize the transportation system has a huge upside.

A beauty of solar power, as compared to development of fossil fuels, is that once a solar array is built and installed, there’s no fuel cost (the sunlight is free) or greenhouse gas emissions.

There may be real problems to be overcome with a decentralized system of electricity production, including grid capacity and design of the transmission and distribution system, but these are not unsolvable.

A bigger issue might be that for many people, rooftop (or garage-top) solar systems may not be practical. For example, many homeowners enjoy the shade of mature trees that block the sun’s rays and keep the building cool. Other folks rent or live in apartments and don’t have, for lack of a better term, “a roof of their own” upon which to place a solar system.

There are, currently, both technical and regulatory barriers to construction of “solar farms” or “solar parks” that would permit anyone to “purchase” a portion of a large array that is located, for example, over a parking lot, or just outside of town, or on a building with a large roof area (such as a school or warehouse).

These barriers are also, given the will, not unsolvable, especially when compared to the potential for greenhouse gas reduction.