question: What is the most viable alternative to fossil fuel and why has it not already replaced conventional fuels?
comment: The answer to the first question isn't yet settled for grid-scale power generation. It looks like a combination of solar and wind are the best bets, but nuclear is still in the running. And there's always the possibility that workable fusion becomes a thing. But all of those have open questions: for solar and wind, availability is still unanswered. Probably a combination of distributed generation (the wind is always blowing somewhere) and energy storage (batteries, pumped hydro, compressed air), but it's still evolving. For nuclear, safety and waste management questions still dominate - along with, crucially, financing. A nuclear plant is an enormous capital expense, and the breakeven point is decades out. Fusion continues to be twenty years out, but there's always the possibility that there's a sudden increase in funding and the timetable accelerates. And all that is also part of the answer to the second question: since we haven't settled on a solution, we also haven't rolled it out. But even if we did, the sheer scale of the problem makes it a multi-decadal effort. There are an awful lot of fossil fuel plants still operating, and there's only so fast we can build windmills, solar panels, and nuclear plants. Meanwhile, there's no appetite for dramatically curbing our energy use, so they all need to keep operating until their capacity has been made up for from other sources. When it comes to other fossil fuel uses - vehicles, mostly - it's a similar question. While it certainly seems likely that electric is the future, that's not a guarantee. Hydrogen is still being worked on as a replacement fuel (to be clear, I personally don't think it's a plausibly viable solution, but many people both smarter and better educated in the area than I am think it is). And again, even if we all decided that electric was definitely the way forward (and somehow solved the problem of energy density for airplanes and cost for cargo ships), it would be a multi-decadal effort to replace the entire fleet with electric vehicles. Even the most aggressive car buyers don't typically buy a new car more often than once every three years, and that period can't really start until there's the manufacturing capacity to meet the demand. Meanwhile, the people who buy new cars every three years rely on a secondary market for the car to be sold into. The average age of cars on the road in the U.S. is something like eleven years, IIRC, and the US consumer is (on average) more aggressive in buying new cars than most of the world. In short - we don't actually know what the most viable alternative is, and even if we did, it's a huge undertaking to rip and replace all the deployed infrastructure.
passages: One of the more promising energy alternatives is the use of inedible feed stocks and biomass for carbon dioxide capture as well as biofuel. While these processes are not without problems, they are currently in practice around the world. Biodiesels are being produced by several companies and source of great research at several universities. Some of the most common and promising processes of conversion of renewable lipids into usable fuels is through hydrotreating and decarboxylation.
  
  Section::::Environmental effects.
   The use of fossil fuels in the 18th and 19th Century set the stage for the Industrial Revolution.
  
  Fossil fuels make up the bulk of the world's current primary energy sources. In 2005, 81% of the world's energy needs was met from fossil sources. The technology and infrastructure already exist for the use of fossil fuels. Liquid fuels derived from petroleum deliver a great deal of usable energy per unit of weight or volume, which is advantageous when compared with lower energy density sources such as a battery. Fossil fuels are currently economical for decentralised energy use.
   Alternatives to fossil fuel power plants include nuclear power, solar power, geothermal power, wind power, hydropower, biomass power plants and other renewable energies (see non-carbon economy). Most of these are proven technologies on an industrial scale, but others are still in prototype form.
  
  Some countries only include the cost to produce the electrical energy, and do not take into account the social cost of carbon or the indirect costs associated with the many pollutants created by burning coal(e.g. increased hospital admissions due to respiratory diseases caused by fine smoke particles).
   Fossil fuels were rapidly adopted during the Industrial Revolution, because they were more concentrated and flexible than traditional energy sources, such as water power. They have become a pivotal part of our contemporary society, with most countries in the world burning fossil fuels in order to produce power.
  
  Currently the trend has been towards renewable fuels, such as biofuels like alcohols.
  
  Section::::Chemical.
   The principle of supply and demand holds that as hydrocarbon supplies diminish, prices will rise. Therefore, higher prices will lead to increased alternative, renewable energy supplies as previously uneconomic sources become sufficiently economical to exploit. Artificial gasolines and other renewable energy sources currently require more expensive production and processing technologies than conventional petroleum reserves, but may become economically viable in the near future.
  
  Different alternative sources of energy include nuclear, hydroelectric, solar, wind, and geothermal.
   Section::::Alternative Sources of Energy.:Hydroelectricity.
  
  In 2015, hydroelectric energy generated 16.6% of the world's total electricity and 70% of all renewable electricity. In Europe and North America environmental concerns around land flooded by large reservoirs ended 30 years of dam construction in the 1990s. Since then large dams and reservoirs continue to be built in countries like China, Brazil and India. Run-of-the-river hydroelectricity and small hydro have become popular alternatives to conventional dams that may create reservoirs in environmentally sensitive areas.
  
  Section::::Alternative Sources of Energy.:Wind power.
   Concerns over pollution and greenhouse gases have spurred the search for sustainable alternatives to our current fuel use. For example, biogas from anaerobic digestion of plant waste can be stored to produce heat or electricity. The global reduction of greenhouse gases requires the adoption of energy conservation as well as sustainable generation. That environmental harm reduction involves global changes such as:
  
  BULLET::::- reducing air pollution and methane from biomass
  
  BULLET::::- virtually eliminating fossil fuels for vehicles, heat and electricity, left in the ground.
  
  BULLET::::- wide spread use of public transport, battery and fuel cell vehicles
  
  BULLET::::- more wind/solar/water generated electricity
   Conventional COG is produced from the many underground natural gas reserves are in widespread production worldwide today. New technologies such as horizontal drilling and hydraulic fracturing to economically access unconventional gas resources, appear to have increased the supply of natural gas in a fundamental way.
   Second-generation biofuels technologies are able to manufacture biofuels from inedible biomass and could hence prevent conversion of food into fuel." As of July 2010, there is one commercial second-generation (2G) ethanol plant Inbicon Biomass Refinery, which is operating in Denmark.
  
  Section::::History.:Coal gasification as an alternative to petroleum.
  
  In the 1970s, President Jimmy Carter's administration advocated coal gasification as an alternative to expensive imported oil. The program, including the Synthetic Fuels Corporation was scrapped when petroleum prices plummeted in the 1980s. The carbon footprint and environmental impact of coal gasification are both very high.
  
  Section::::Existing types of alternative energy.
   In oil producing countries with little refinery capacity, oil is sometimes burned to produce electricity. Renewable energy technologies such as solar power, wind power, micro hydro, biomass and biofuels are used, but the primary alternatives remain large-scale hydroelectricity, nuclear and coal-fired generation.
  
  Section::::Future production.
  
  Consumption in the twentieth and twenty-first centuries has been abundantly pushed by automobile sector growth. The 1985–2003 oil glut even fueled the sales of low fuel economy vehicles in OECD countries. The 2008 economic crisis seems to have had some impact on the sales of such vehicles; still, in 2008 oil consumption showed a small increase.
   Section::::Fossil fuels.
  
  Fossil fuel ("primary non-renewable fossil") sources burn coal or hydrocarbon fuels, which are the remains of the decomposition of plants and animals. There are three main types of fossil fuels: coal, petroleum, and natural gas. Another fossil fuel, liquefied petroleum gas (LPG), is principally derived from the production of natural gas. Heat from burning fossil fuel is used either directly for space heating and process heating, or converted to mechanical energy for vehicles, industrial processes, or electrical power generation. These fossil fuels are part of the carbon cycle and thus allow stored solar energy to be used today.
   Renewable energy is generated from natural resources—such as sunlight, wind, rain, tides and geothermal heat—which are renewable (naturally replenished). When comparing the processes for producing energy, there remain several fundamental differences between renewable energy and fossil fuels. The process of producing oil, coal, or natural gas fuel is a difficult and demanding process that requires a great deal of complex equipment, physical and chemical processes. On the other hand, alternative energy can be widely produced with basic equipment and natural processes. Wood, the most renewable and available alternative fuel, emits the same amount of carbon when burned as would be emitted if it degraded naturally. Nuclear power is an alternative to fossil fuels that is non-renewable, like fossil fuels, nuclear ones are a finite resource.
   Various biofuels such as biodiesel, vegetable oil, alcohol fuels, or biomass can replace fossil fuels. Various chemical processes can convert the carbon and hydrogen in coal, natural gas, plant and animal biomass and organic wastes into short hydrocarbons suitable as replacements for existing hydrocarbon fuels. Examples are Fischer–Tropsch diesel, methanol, dimethyl ether and syngas. This diesel source was used extensively in World War II in Germany, which faced limited access to crude oil supplies. South Africa produces most of the country's diesel from coal for similar reasons. A long term oil price above US$35/bbl may make such large scale synthetic liquid fuels economical.
   Combined heat and power (CHP), also known as cogeneration, is the use of a thermal power station to provide both electric power and heat (the latter being used, for example, for district heating purposes). This technology is practiced not only for domestic heating (low temperature) but also for industrial process heat, which is often high temperature heat. Calculations show that Combined Heat and Power District Heating (CHPDH) is the cheapest method in reducing (but not eliminating) carbon emissions, if conventional fossil fuels remain to be burned.
  
  Section::::Environmental impacts.
   The available alternatives to biomass fuels do not offer much improvement. Kerosene is imported at significant expense, and is burnt with a wick stove that does not combust the fuel efficiently and tips or spills easily. The projected retail cost of ethanol is lower than that of government-subsidized kerosene in Ethiopia today. Kerosene stoves are also prone to flare ups and explosions; accidental kerosene fires cause many injuries and deaths each year. Kerosene releases carcinogenic emissions and is often poorly refined or adulterated by the time it is acquired for domestic use. Liquified petroleum gas (LPG) burns cleanly but is expensive and cannot be produced locally. Charcoal, a processed biomass fuel, burns with less smoke, but emits carbon monoxide. Meanwhile, coal produces all of the dangerous emissions of traditional biomass fuels and depending on its quality, also produces sulfur oxides and toxic elements such as arsenic, lead, fluorine, and mercury.
   It has become popular among coal power stations, which switch from coal to biomass in order to convert to renewable energy generation without wasting existing generating plant and infrastructure. Biomass most often refers to plants or plant-based materials that are not used for food or feed, and are specifically called nitrocellulose biomass.[2] As an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of bio-fuel.
  
  Section::::Bio-fuel.:Algae-based fuels.
   Section::::Alternative Sources of Energy.:Biofuels.
  
  Biofuels, in the form of liquid fuels derived from plant materials, are entering the market. However, many of the biofuels that are currently being supplied have been criticised for their adverse impacts on the natural environment, food security, and land use.
  
  Section::::Alternative Sources of Energy.:Biomass.
   Heavy fuel oil was once a significant source of energy for electric power generation. After oil price increases of the 1970's, oil was displaced by coal and later natural gas. Distillate oil is still important as the fuel source for diesel engine power plants used especially in isolated communities not interconnected to a grid. Liquid fuels may also be used by gas turbine power plants, especially for peaking or emergency service. Of the three fossil fuel sources, oil has the advantages of easier transportation and handling than solid coal, and easier on-site storage than natural gas.
  
  Section::::Combined heat and power.
   Renewable energy alternatives also exist. These include solar energy, wind energy, geothermal and hydroelectricity as well as other sources. These sources are said to have much lower emissions, and almost minimal secondary by products. The production of renewable energy is projected to grow in nearly every region in the World. Natural gas is also seen as a potential alternative to oil. Natural gas is much cleaner than oil in terms of emissions. However natural gas has its limitation in terms of mass production. For example, in order to switch from crude oil to natural gas there are technical and network changes that need to occur before the implementation can be complete. Two possible strategies are to first develop the end use technology first or second is to completely change the fuel infrastructure.
   In very small vehicles, the power demand decreases, so human power can be employed to make a significant improvement in battery life. Two such commercially made vehicles are the Sinclair C5 and TWIKE.
  
  Section::::Comparative assessment of fossil and alternative fuels.
   Section::::See also.
  
  BULLET::::- Abiogenic petroleum origin proposes that petroleum is not a fossil fuel
  
  BULLET::::- Bioremediation
  
  BULLET::::- Carbon bubble
  
  BULLET::::- Environmental impact of the energy industry
  
  BULLET::::- Fossil Fools Day
  
  BULLET::::- Fossil Fuel Beta
  
  BULLET::::- Fossil fuel divestment
  
  BULLET::::- Fossil fuel drilling
  
  BULLET::::- Fossil fuel exporters
  
  BULLET::::- Fossil fuel phase-out
  
  BULLET::::- Fossil fuels lobby
  
  BULLET::::- Fugitive gas emissions
  
  BULLET::::- Hydraulic fracturing
  
  BULLET::::- Liquefied petroleum gas
  
  BULLET::::- Low-carbon power
  
  BULLET::::- Peak coal
  
  BULLET::::- Peak gas
  
  BULLET::::- Petroleum industry
  
  BULLET::::- Resource decoupling
  
  BULLET::::- Shale gas
  
  BULLET::::- Oil shale
  
  Section::::Further reading.
   Prior to the latter half of the 18th century, windmills and watermills provided the energy needed for industry such as milling flour, sawing wood or pumping water, and burning wood or peat provided domestic heat. The widescale use of fossil fuels, coal at first and petroleum later, to fire steam engines enabled the Industrial Revolution. At the same time, gas lights using natural gas or coal gas were coming into wide use. The invention of the internal combustion engine and its use in automobiles and trucks greatly increased the demand for gasoline and diesel oil, both made from fossil fuels. Other forms of transportation, railways and aircraft, also required fossil fuels. The other major use for fossil fuels is in generating electricity and as feedstock for the petrochemical industry. Tar, a leftover of petroleum extraction, is used in construction of roads.
   Fossil fuels are of great importance because they can be burned (oxidized to carbon dioxide and water), producing significant amounts of energy per unit mass. The use of coal as a fuel predates recorded history. Coal was used to run furnaces for the melting of metal ore. Semi-solid hydrocarbons from seeps were also burned in ancient times, but these materials were mostly used for waterproofing and embalming.
  
  Commercial exploitation of petroleum began in the 19th century, largely to replace oils from animal sources (notably whale oil) for use in oil lamps.
   Bio-fuels are also considered a renewable source. Although renewable energy is used mostly to generate electricity, it is often assumed that some form of renewable energy or a percentage is used to create alternative fuels.
  
  Research is ongoing into finding more suitable bio-fuel crops and improving the oil yields of these crops. Using the current yields, vast amounts of land and fresh water would be needed to produce enough oil to completely replace fossil fuel usage.
  
  Section::::Bio-fuel.:Biomass.
  
  Biomass in the energy production industry is living and recently dead biological material which can be used as fuel or for industrial production.
   Micro-hydro configured into mini-grids also provide power. Over 44 million households use biogas made in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cookstoves. Clean liquid fuel sourced from renewable feedstocks are used for cooking and lighting in energy-poor areas of the developing world. Alcohol fuels (ethanol and methanol) can be produced sustainably from non-food sugary, starchy, and cellulostic feedstocks. Project Gaia, Inc. and CleanStar Mozambique are implementing clean cooking programs with liquid ethanol stoves in Ethiopia, Kenya, Nigeria and Mozambique.
  