We talk about greenhouse gas emissions but how much of that is due to the USA energy consumption. All of this info is from the Energy Information Administration total energy environment section. We will just look at the USA for now and expand to the rest of the world in a future article. We have three main sources of GHG (greenhouse gas) emissions.
The first is coal of which 90% is used to generate electricity and the rest for industry. The total usage is decreasing and the planning is to eventually go to zero coal consumption.
The second is petroleum of which almost 75% is used to fuel engines and the rest is used for a wide variety of purposes — some of which, such as lubricating oil, also involves engines.
The third is natural gas which is used for a wide variety of purposes but mostly space heating, water heating, and electricity generation. Natural gas can completely replace coal and can replace petroleum in several applications. The chart below shows the tons of CO2 emitted per year by each of the three sources since 1974.
It is apparent that total emissions peaked in 2007 (when coal burning peaked) and has fallen in step with coal burning reductions. To calculate the emissions the EIA uses CO2 coefficients where the units are million metric tons of CO2 per quadrillion BTUs. The relative amounts are interesting and explain why replacing coal or petroleum with natural gas results in a CO2 emissions reduction.
- Coal is 95
- Petroleum is 73
- Natural gas is 53
Just replacing coal with natural gas for electricity generation reduces the CO2 emissions by 50% but this works only until coal usage reaches zero. The coal emissions are about 1,000 million tons and replacing all coal burning with natural gas means a total emissions reduction of 500 million tons (5,000 million tons total to 4,500 million tons).
The next chart breaks down the petroleum emissions by type. Number one is gasoline at almost half of all emissions and number two is distillate fuel oil (this is mostly diesel fuel and some home heating fuel) at about one third.
Jet fuel gets a lot of attention in the press but is a rather modest CO2 source. Residual fuel oil was, in the far past, used to generate electricity and create industrial process heat. Now what little is made gets burned in large cargo ships when in international waters where high sulfur fuel is legal. Burning RFO is illegal in US and EU waters so the cargo ships carry some distilled fuel oil, which has low sulfur content, when in regulated areas.
With this information we can evaluate the various efforts and ideas to reduce emissions. Coal is simple and needs to be replaced with wind, solar, and storage. Any remaining industrial usage needs to be replaced by, at worst, natural gas. The good news is that we are over half way to accomplishing that goal.
Petroleum is more complicated and, while refineries can do a lot more magic to convert crude into products, I don’t know anything about refinery operation or chemistry. There are very likely things made of crude that will be a challenge to replace but that is why chemists will play an important role. The road and railroad vehicle fuel will be replaced by electricity in some manner. Airplanes and ships will, in my opinion, switch to renewable liquid fuels such as methanol and ethanol. If gasoline fueled cars are replaced by EVs we will have a lot of spare ethanol production that can perhaps be used to replace much of the jet fuel.
Natural gas that is used for space and water heating will be replaced with electric heat pumps as is starting to happen now. Much of the natural gas burned to generate electricity can be replaced by wind and solar. By doing these things then the majority of CO2 emissions can be eliminated with no new technology breakthroughs required — we just commit to using what we have to transition our energy system. The best part that we can play right now is to vote in November and take overwhelming control of the House and Senate.
