The following information comes from the US Department of Energy, using data from 2005 for US emissions.[source]
The total emissions of CO2 for the US weighed in at 6009 million metric tons. The main contributors that are amenable to replacement are as follows:
|Electricity generation from fossil fuels||2375 MMT|
|Residential use of natural gas||262 MMT|
|Gasoline motor fuel||1171 MMT|
The remaining 2291 MMT is spread over a large range of agricultural, residential, industrial, and transportation applications and miscellaneous applications such as road pavements. Some improvements can be sought here, but most of the users already are economically motivated to reduce energy consumption, so we should only count on modest improvements. Here's a plot that shows where all the greenhouse gases are coming from in the US:[source]
Out of all these, electricity generation is where the greatest savings can be made, accounting for 40% of the total CO2 emissions.Taking CO2 emissions as a whole, there are four options available: carbon sequestration, conservation, renewable energy, and nuclear energy. We'll cover the first two in this article.
1) Carbon Sequestration
It is possible that the CO2 could be captured and stored in some geological formation.
The problems with sequestration are that it's very expensive to pipe the CO2 from the power plant to the formation and pump it deep into the ground, and there's no way to be sure the CO2 will stay there. The scheme du jour is to bubble the gas into saline aquifers and hope the CO2 will form stable minerals there. No one knows what the capacity of the available aquifers is, or how to find out.
Improving energy codes has gone a long way toward reducing greenhouse gases. Americans are using only as much energy per capita as they were ten years ago and twenty years ago. Meanwhile, energy consumption per dollar of domestic product has dropped about 40% since 1980. Of course, the US has shifted away from manufacturing toward importation in that same period, which accounts for some of the savings. Nonetheless, it's clear that energy codes can play a part in greenhouse-gas reduction.[source]
It can be stated with no fear of contradiction that people who live in affluent countries could reduce their energy consumption by large amounts. The problem with this solution is that there is a huge difference between can-do and will-do. People for the most part don't know how to quantify energy consumption. People drive motorhomes and put in compact fluorescent lights to balance their carbon footprints. People live in 8000-square-foot houses but recycle their wine bottles so it's all okay. An energy plan that depends on people giving up their big houses and their flying trips around the world and their motorhomes or boats or personal aircraft needs to be studied carefully.
What happened in the past was that alternative-energy advocates assured everyone that using fossil fuels was perfectly acceptable because new energy sources would meet the world's energy needs and switching over was only a matter of making some simple political decisions. But it turned out that the new energy sources weren't adequate for the task and continuing to use fossil fuels had tragic results.
In the next article we should look at some of those alternative energy sources and see what their limitations are.