Bio-diesel, wind, solar, bio-gas all are renewable.

Charging mobile phones with sound, like chants from at football ground, could become a reality, according to a new collaboration between scientists from Queen Mary University of London (QMUL) and Microsoft.The team used the key properties of zinc oxide, a material that when squashed or stretched creates a voltage by converting energy from motion into electrical energy, in the form of nanorods.The nanorods can be coated onto various surfaces in different locations making the energy harvesting quite versatile. When this surface is squashed or stretched, the nanorods then generate a high voltage.The nanorods respond to vibration and movement created by everyday sound, such as our voices. Electrical contacts on both sides of the rods are then used to harvest the voltage to charge a phone.

http://www.qmul.ac.uk/media/news/items/se/137892.html

Pinoy teen invents electricity-generating shoes

https://ph.news.yahoo.com/pinoy-teen-invents-electricity-generating-shoes-034836180.html

Any renewable energy is good. Choice depends on country/region natural resources, financial and intellectual potential.   

I a agree with @Viadimir, and according to @Lala, I add it's depend on the availibility and behavior of the community and as @Saeed as well

Regarding the big picture, @Vladimir is correct.

Germany has started a very ambitious program to harness 'renewables'.  The most important problem is the development of an appropriate grid system, which reaches from the points of generating to the consumers. Although most people welcome renewable energy consumption, they refuse to have huge overhead lines at the horizon or in their backyards.

Bio-energy will cause severe problems because cultivated areas are used for industrial purposes and not for food production. Given the underfeeding in many areas and the increase in population worldwide, the need for more cultivated land is obvious.

A £1bn plan to build the world's first power-generating tidal lagoon in Swansea Bay has been given a boost as the UK government revealed further discussions with the developers.

http://www.bbc.com/news/uk-wales-south-west-wales-30283203

The ones that hold the potentials of being reliable clean alternatives are fuel cells that will power automobiles; Hydroelectric, solar energy, geothermal, tidal etc. Nuclear power could be dependable if NP stations if they are placed at geologically stable locations

Researchers use waste slag to create energy and cut emissions

http://phys.org/news/2014-08-slag-energy-emissions.html

Of course biofuel holds a big potentials not only as an alternative energy source but also waste handling alternative.

Perspiration Power: Scientists Turn Sweat Into Electrical Energy

http://commonhealth.wbur.org/2014/08/sweat-power-exercise-energy

Individual efforts are going to make the difference like reducing the demand,changing personnel attitude, switching to eco-friendly energy sources like solar, hydro and wind  etc, and above all the sincerity while using these resources of mother earth.

The question can be better framed as "What are the alternative energy sources to address climate and local environmental challenges" since it is debatable whether fossil fuel are diminishing. The latest IPCC Assessment http://www.ipcc.ch/report/ar5/wg3/ has a good review of various technology options

To my opinion, the nuclear energy would be, but our society is not ready for running it safely. Nuclear fusion has a perspective only in several decades if ever and it is not so clean as presented, while using the D+T reaction. So the next step for nuclear fusion, once managing the D+T reaction, would be to manage other reactions that do not use radioactive materials as fuel (check Wikipedia on nuclear fusion, there is the whole list).

The renewable sources like wind and sunlight alone are not sufficient. The developed world needs a stable basis (in time) to cover up the periods when there is no wind and/or no sun (e.g. calm nights, both missing). An alternative is to produce hydrogen and use it as CO2-neutral fuel (oxidation produces water that can be drained). But hydrogen tanks are still a risky technology although their hazards are located to the storage cells only (no pollution hundreds of km away) "just" a huge explosion capable of killing and gravely injuring many people.

I had also following ideas:

(1) Solar panels floating on the oceans' surface and producing hydrogen to be transported by ships to ports equipped with pipework systems distributing the hydrogen in the continental areas. The solar platforms could be intelligent in the way of following sunny places around the equator and avoiding storms and hurricanes.

(2) The same as (1) but with genetically modified algae that would produce some higher hydrocarbon fuel (propane, butane, etc., less risky than pure hydrogen and not needing energy-consuming liquefaction and cryogenic systems).

If you look into the history, the brightest periods occurred when there was plenty of food and energy available and mild climate. So I do not share the left-green approach of saving. It is not sustainable in long term so as all political systems pursued by the left political wing (socialism failed every time and everywhere and, in total, Marxist ideas killed dozens of millions of people (gulags, Red Khmers) and destroyed lives of billions of people. Venezuela that had the means to finance the Chavez's socialism by exporting petrol is now heading a default; these are not intellectual debates, these are results of costly "experiments", both in terms of material resources and in terms of human lives. And greens are like water melons: Green outside, red inside. A "fanatic idea", no matter whether it is protection of the environment or the interests of the working class always finds an "excuse" for killing and devastating, sooner or later but always.) Of course new energy-saving technologies like LED lamps are more than welcome. I have LED lamps everywhere in my house. I wash and iron my clothes only outside the peak hours (night, weekends). My refrigerator is set to +7°C, and I do not eat frozen food but just in case I have a deep freezer set to the highest temperature possible: -16°C, although I could go down to -32°C but why?

Hoping to inspire you,

http://cern.ch/pvojtyla

Subash, although your framed version is equally important, Lala's context of alternative energy in the face of diminishing fossil fuel reserves addresses a different concern. Dependence on fossil fuel does not only exacerbate the woes of global climate change but will lead the world to stagnating economies without adequate energy to support current and future needs if fossil fuel runs out. The direct sustainability question to the dependency on fossil fuel is whether future supplies will match demands and that ugly reality may even set in earlier than the purported Apocalyptic consequences  of global warming and climate change. Thus searching for other alternatives is the stone that's sure to kill many birds.

Of course I share your worries about the climate change although ICCP becoming a political organization lost its credibility for me (how can one vote about scientific results???!!!). I also agree that petrol is too fine for being burnt. We need plastics, medicaments, bio-degradable packages and materials in general etc., all made of petrol.

Do not feel hurt by my criticism of the present green and other Marxist ideologies. I know what I talk about. My father was killed by KGB in 1968 during the Soviet occupation of the former Czechoslovakia (the Prague spring) four days before Christmas. My mother stayed alone with four kids in a politically hostile environment for some 30 years; I was four at that time. And I could observe both political systems working already being adult, socialism like in the former Czechoslovakia and capitalism like in Switzerland 20 years ago. Now, Marxist ideas gain even in Switzerland and I see them as the true source of the decline of the Western world that we can observe at present. But this is a scientific forum so I'll stop all discussions as this. Everyone who is adult and experienced shall think twice whom to vote and why. Political parties are not football clubs with fans following them with enthusiasm no matter how they perform.

EIA expects continued growth in utility-scale solar power generation, which is projected to average almost 80 gigawatthours (GWh) per day in 2016. Despite this growth, solar power averages only 0.7% of total U.S. electricity generation in 2016. Although solar growth has historically been concentrated in customer-sited distributed generation installations, EIA expects that utility-scale solar capacity will increase by more than 60% between the end of 2014 and the end of 2016, with about half of this new capacity being built in California. Wind capacity, which grew by 7.7% in 2014, is forecast to increase by 16.1% in 2015 and by another 6.5% in 2016. Because wind is starting from a much larger base than solar, even though the growth rate is lower, the absolute amount of the increase in capacity is more than twice that of solar: 15 GW of wind versus 6 GW of utility-scale solar between 2014 and 2016.

http://www.eia.gov/forecasts/steo/report/renew_co2.cfm

Thermal energy using renewable plant biomass, energy from solid urban waste, hydrogen cells etc. Out of the five elements of nature (earth, water, air, fire and space) we have utilized water, wind and solar/thermal power. We still have space and earth. Any technology to harness power/energy from these elements? Power from lightening or earth quakes? 

Geothermal heating (for homes & industry) has risen in popularity in the colder climates (Canada), but can also be used for cooling during the summer.

All taxis are now hybrid and rely much less on fossil fuels.

The idea of burning organic remains of pre-existing animals (fossil fuels) to create energy is outrageous. It is like waiting for your relative to die so that you could use the energy from that body to bring your car/truck to work/school/store. In the meantime, you also pollute the air with items that are not normally disposed off by nature in such a way. Take mercury for example. Have you measured how much you have in your body? I know several people who found out horrendous amounts and they have not done anything special to acquire it. Just living on the planet where everyone burns fossil fuels.

You could think twice about burning fossil fuels!