* Fracking pollutes local groundwater, causes earthquakes in places far from fault lines, uses scarce freshwater resources that could otherwise provide water for people, animals and plants, pollutes the areas where drilling takes place, and is one of the most hazardous industries for workers (in part because worker safety in the industry is regulated by underfunded OSHA instead of adequately funded MSHA). Setting up drilling sites can destroy natural habitats.
But, fracking increases the supply of oil and natural gas at lower prices than conventional extraction methods. This lowers the price of oil and natural gas which have consequences discussed below, reduces U.S. dependency on foreign oil which frees us to oppose abhorrent practices of oil rich countries, and boosts the U.S. economy not only because oil and gas prices are lower, but also because oil and gas production jobs are in the U.S. and not elsewhere.
* High petroleum (i.e. oil and gasoline and diesel) prices encourage energy conservation measures like fuel efficient cars and encourage oil users in industrial and home heating uses to switch to alternative fuels that are cleaner like natural gas and non-coal derived electricity. Moving away from oil reduces air pollution, from oil spills at sea and on land, and slows man made climate change leading to global warming.
High oil prices also drive up the costs of fertilizer and pesticides which makes organic farming economically competitive with conventional farming.
There is a limited world supply of oil, someday we will run out, and that could be a huge problem for our economy if we don't transition away from it.
But, high oil prices also provides more funds to oil rich despots and conservative elites in the Middle East like Saudi Arabia and Iran whose funds are the lifeblood of ISIS and fundamentalism Islam, it funds economically irrational authoritarians in Venezuela, it funds conservative Evangelical Christians in places like Texas, and it allows governments in places like Mexico to rely on natural resources as a crutch instead of focusing on building a productive middle class.
High oil prices slow down the economy and sends U.S. money out of the country. Low oil prices lead to economic growth, lower real prices, and easy the lives of the working and middle class.
* Natural gas is the least polluting fossil fuel when used, by far, although extracting it (often via fracking) can lead to environmental harms, and the total production process including transporting natural gas by pipelines lead to far fewer injuries, although occasionally natural gas leaks can lead to huge explosions anywhere it is used.
Natural gas is a cleaner alternative to heating oil, it is a cheaper fuel for heating homes and offices than electricity, it is a cleaner fuel for generating baseline electricity than coal, and a cleaner alternative to gasoline and diesel in converted vehicles.
Natural gas used in the U.S. is mostly produced in North America, which reduces U.S. economic dependency upon and the need to politically defer to politically questionable overseas and Latin American suppliers who are largely also oil suppliers.
Lower natural gas prices boost the economy and encourage energy users to switch to natural gas from more polluting fuels.
While we are less close to running out of natural gas than we are to running out of oil, the global supply of natural gas is also finite, so in the long term we need to transition away from it.
* Pipelines pose risks of environmental harm when they break and spill oil or flare natural gas, for example, poisoning water supplies and destroying habitats, and they can cross environmentally and culturally sensitive areas without much flexibility. But, pipelines are generally safer in terms of accidents, less likely to cause environmental harm, and cheaper than transporting oil or natural gas by truck, by train or by ship, and rail lines and roads pose similar habitat concerns.
* Coal is the most polluting fossil fuel. Mining it is dangerous to workers. Transporting it by truck or train or boat causes more deaths and prevents rail traffic from being used for alternative means of transportation. A huge share of all train and river barge transportation is of coal. Most coal is strip mined which completely destroys habitats. Mined coal is accompanied by a host of toxic and radioactive wastes that poison ground water and the land where it is stored. Coal creates more air pollution than any other form of fossil fuel speeding man made climate change leading to global warming. The number of deaths caused by air pollution from coal is immense.
Coal is more awkward to use, due to its solid form, than oil or natural gas or electricity. It is predominantly used by utilities to generate electricity, although it is also used in coke form, in steel production, and in a few other minor uses.
Coal's main advantages are that it is the most abundant fossil fuel, it has historically been cheap (until pollution mitigation or carbon taxes and pollution related illnesses are considered), its prices have been stable over time, it created good paying domestic jobs and it doesn't have to be imported increasing energy independence.
If oil and natural gas are sufficiently expensive, it is possible to create synthetic liquid and synthetic gas alternatives to oil and natural gas from coal (the Nazi regime did so briefly at the end of World War II and a few proof of concept plants were established when oil prices were $100 a barrel). These processes could postpone the need to transition the economy away from oil and natural gas as those resources run out and limit price increases when and if supplies of oil and gas grow scarce.
* Biomass, biodiesel, ethanol and incineration of trash as energy sources, unlike traditional fossil fuels, are renewable and could provide supplies of fossil fuels in applications like lubricants, plastics, nylons, aircraft fuel, farm equipment fuel, fertilizers, pesticides, fuel for fishing boats, and the like that have no good alternatives when oil supplies run out. Many of these recycle waste into valuable energy, reduce dependency on foreign oil and reduce oil prices somewhat.
But, these sources are frequently as polluting when used as oil and coal, trash incineration as as awkward or more so than coal as a solid fuel source, and there is a limited supply of recycled grease and other combustible wastes that can be made into biodiesel.
You can grow plants specifically for the purpose of creating fuel oils, but this drives up the price of food that could be grown with the same resources, and it is basically not viable to generate more than a modest fraction of current oil consumption this way even with maximally efficient food production.
* Co-generation is a system that uses waste heat from generating fossil fuels or nuclear power for space heating in nearby buildings, making systems more efficient. But, it only works in close proximity to power plants.
* Geothermal energy (basically tapping into the same kind of heat from the Earth that generates hot springs and geysers) is renewable, doesn't create any pollution that wouldn't be created already, and can be reasonably cost effective. But, there are only a few isolated places where it is available as a natural resource, it isn't abundant enough to export for long distances and use as a major share of total energy supplies, and geothermal energy facilities make natural wonders like hot springs and geysers less vibrant.
* Nuclear fission has immense energy density, so the amount of fuel that needs to be mined, transported to power plants, and stored at power plants is stunningly tiny compared to any form of fossil fuel. Nuclear fission plants need to be refueled only on the order of once per one to three decades. These plants generate no air pollution when working properly. The number of worker injuries and injuries to the public associated with mining uranium and transporting it are tiny relative to any fossil fuel. There is basically no radiation risk to neighbors or workers in a nuclear fission plant when it is operating properly. And, the fuel costs of a nuclear power plant are quite low.
The main down sides to nuclear fission power are:
1. It is pretty much useless for any purpose other than generating electricity that is added to the grid, although if designed properly, waste heat can be utilized productively rather than constituting heat pollution to local rivers and clouds. This is mostly a question of scale. Nuclear power plants can be made small enough for a large submarine (ca. 8,000 tons), or ship, or as a village power plant, but not small enough to put in a car, truck, aircraft or locomotive on a train.
2. Nuclear power does impose demands on local water supplies in most plant designs.
3. Because the technology is relatively new, because public safety concerns are great (whether this is justified or not), and because there hasn't been much mass production of plants on the same design, nuclear power plants are the most expensive kind of power plant to design and build.
4. Public fear of radioactive materials has led to fierce opposition to sensible nuclear waste storage facilities for high and low level nuclear wastes, and unrealistic demands on nuclear waste storage facility standards that have left far more troublesome interim solutions in place. The U.S. has also been slow to adopt uranium reprocessing technologies that would greatly reduce the amount of high level nuclear waste in existence by recycling rather than throwing away a valuable potential source of nuclear fission energy.
5. Nuclear power plant fuel and high level nuclear waste must be carefully guarded against diversion by terrorists or rogue nations to create catastrophically deadly nuclear weapons.
6. While the failure of a nuclear power plant is extremely rare and can be mitigated with good future nuclear power plant design, it can't be reduced entirely to zero and there have been a handful of nuclear power plant failures in history. In the U.S., the most famous, which led to very little lost human life was the Three Mile Island incident. The Chernobyl plant failure in the Ukraine (where mitigation measures were recently upgraded with a protective steel "barn" over the melted down plant) was very serious in terms of lost lives, health impacts and lost use of property, however, and the Fukushima plant failure in Japan, at a quite high risk location, has likewise caused non-negligible impacts.
In sum, nuclear fission power is plagued with exaggerated public fears of the danger it poses while more mundane fossil fuels are actually far more harmful to human life, but it does have to be carefully managed and the supply of nuclear fuel while currently abundant relative to demand, is also not infinite.
* Nuclear fusion power plants involve some of the same issues of fuel (deuterium and tritium) security although less intensely, but fuel would still be cheap and energy density would still be high. It would not have the same risks of meltdown or nuclear waste that a fission plant does even though it could give rise to a one time explosion if there was massive plant failure with a localized impact that could be mitigated with good land use. Like nuclear fission, it would only be useful for generating electricity on a power plant scale.
It would be cheap, but the costs of building a nuclear fusion power plant, potentially requiring rare or toxic materials, would still be very high, preventing a nuclear fusion power plant from generating "too cheap to meter" electricity, even if fuel and operating costs were negligible. It could be price competitive, but not dramatically cheaper. But, it would be a permanent, sustainable solution to running out of both fossil fuels and uranium.
The main problem with nuclear fusion is that while we understand the physics governing it more or less perfectly in theory, and can make nuclear fusion bombs, we can not managed to engineer any sustained net power producing nuclear fusion electrical power plant and realistically, it could be many decades before we can, if ever.
* Hydropower is renewable, generates no air pollution, doesn't use anything toxic or produce waste to generate electricity, which is the sole kind of energy it can generate. It can be used as a 24 hour baseline electricity source.
But, there are limited supplies of it because there are only so many rivers that can be effectively dammed. In the arid west, dams are already valuable as a way to manage scarce water resources, but dams also flood large areas of otherwise useful land and destroy not only the ecologies of the flooded areas but also the ecologies that had depended upon free flowing rivers.
* Tidal power in principle provides essentially all of the clean energy benefit of hydropower, apart from being a little bit less of a 24 hour power source, without flooding large areas of useful land. But, they are extremely technologically challenging to put in place and every system must be custom, with only a couple of facilities that are current viable, and it can disrupt sensitive tidal ecosystems. Obviously, it can only add to the grid in coastal locations.
* Wind power is renewable, non-polluting, cost effective in large areas, intermittent but more reliable than solar in many areas, has a modest land footprint, and not ultra-hazardous in any respect. It needs to be paired with batteries or another baseline electricity source, and is can pose a hazard to some kinds of birds. Wind power is rapidly making up a much larger part of the total electric grid.
* Sails and kites with modern designs can reduce fuel demands greatly for ships making transoceanic trips, particularly is speed is not at a high premium.
* Photovoltaic solar power is attractive in a few places as a source of utility electricity in the Southwest, where supplies of solar power also coincide with air conditioning driven demand for electricity to a significant extent, since days in the Southwest got hot, but nights rapidly cool. It is also a good niche source of electricity in places were a larger electrical grid is not available, and is an expensive, but decentralized partial power source for homes and businesses connected to the electrical grid, especially when reverse metering is available.
Prices for solar electricity generation have plummeted with technological advances (although tax subsidies have clouded the issue of price).
Solar electricity is renewable and the fuel is free. Some solar cell production methods use toxic or scarce materials, and solar cells can take up lots of space and can break and need to be replaced over time.
Critically, photovoltaic power systems don't work when its dark, and have degraded performance where days are shorter and cloudy days are common, making it less attractive cost wise in those places. And, it isn't a viable source for 24 hour baseline power without being joined to some efficient and large scale power storage technology, or having a backup alternative power source (like nuclear or natural gas power electricity).
* Heat solar power is a simpler and more efficient use of solar power for water heating and space heating, especially when reaching a boiling point is not necessary. This includes solar hot water heaters, solar pool heating, and passive solar arrangements to use the sun to reduce heating needs in buildings.
* Energy conservation is a good substitute for energy consumption and great progress is being made in reducing the energy consumed on lights (due to LEDs and motion detectors), electronics (due to solid state computer memorized and reduced size computer chips), heating and cooling (due to insulation, and ground heat exchange systems), and vehicles (due to lower weight materials, regenerative braking, and reduced energy consumption at idle, especially by hybrid and electric vehicles). In transportation, the most overlooked way to increase fuel efficiency is to increase passenger occupancy in vehicles, which makes old school buses as energy efficient as a top of the line hybrid vehicle.
* Plug in electric vehicles and electrically powered rail systems make it possible to substitute gasoline and diesel (and to a lesser extent natural gas) for electricity off the grid which is increasingly become cleaner, more renewable and has less rapidly fluctuating prices. Electrically powered urban rail systems have basically no downsides relative to conventionally fueled locomotives, high speed rail operates on the same basis, and freight rail could be relatively easily adapted to be electrically powered with existing technology.
Notably, it takes considerable electricity to refine crude oil into gasoline or diesel fuel, so converting cars and trucks and buses to electricity will have less impact by increasing overall electricity demand than one might expect.
* The need for better energy storage systems (batteries and battery substitutes) in terms of cost, range, energy density, rechargeability, and environmental soundness of their construction, is pretty much the exclusive barrier to widespread conversion to electric cars and trucks, and also, at another scale, to conversion to renewable but intermittent power sources for the electrical grid. Existing batteries needed for an electric car are expensive, have limited range, can take a long time to recharge, and can require toxic or scarce materials to make.