Both are good for biofuel production. But, algae is not economical when compared with plants due to its harvesting cost.

Hi Kunal,

I believe that using either materials for biofuel production has its advantages and disadvantages. However, some experts believe that algae is set to eclipse all other biofuel feedstocks as the cheapest, easiest, and most environmentally friendly way to produce liquid fuel. Companies such as Solix BioSystems (http://solixbiosystems.com/) has already use algae as material for biofuel production. Please read this article "Better Than Corn? Algae Set to Beat Out Other Biofuel Feedstocks" at: http://www.worldwatch.org/node/5391

Biofuel from plants works at an industrial scale, but there are serious environmental constraints.

Biofuel from microalage is still not developed for industrial scale, there are serious dobts about the economic viability of the existing technology. A good review ist here: http://esd.lbl.gov/files/about/staff/nigelquinn/EBI_Algae_Biofuel_Report_2010.10.25.1616.pdf

You can make a biofuel out of anything but whether it is viable is another matter.  Sugarcane, perhaps sugarbeets and fermentation of low quality cereals will all work but all at enormous environmental costs.  Oil Palm oil is really too valuable for the food and hydrocarbon industries as feedstock to simply burn.  The enormous photosynthetic rates of algae are a science fable that I think dates back to Warburg.  It is like the old story that a few litres of algae can provide enough oxygen for an astronaut.  No matter how many times you do the sums and show it cannot work the fable refuses to die.

Algae are a waste of time.  There are those who understand what I say about algal biofuels but simply tell me to shut up and then there those who do not understand the biophysics and so do not understand what I am trying to tell them.  It does not matter how much money you spend or how many chickens you sacrifice on whatever altar you fancy.  Claims that genetic engineering will come to the rescue is also damned foolishness.  You might as well ask a legislature to repeal the Law of Gravity.

Raymond J Ritchie bring up some very good points in the linked manuscript and it is worthwhile to take a look at. Even if we we can make photosynthesis better we will be hampered by the very low density of algae in the water. We need much better harvesting and dewatering approaches (as well as: higher density, more oil per cell etc. etc.).

In addition to all the great answers above, I think the future for green energy would be using both algae and biofuel (biodiesel and cellulosic ethanol), in addition to other renewable sources of energy (solar, wind, wave, etc.).

algae optimists base on higher oil yield in algae culture, algae pessimists base on that the cost to recuperate energy carrier oil from algae are higher than the amount of energy  separated. Hence once the 1g/l algae content can be concentrated with a affordable technology algae will take over plants, but refuse oil containing wastes must be converted to biodiesel under any scenario, and the conversion must be feasible, that is not the case for all the technologies in use

Both can be used for biofuel production but because land and freshwater crisis for coming day promotes a lot opportunity for algae biofuel due to its survival in waste-water as well as marine water too. In coming day as per C-sequestration or food vs fuel, land availability etc will be so much useful for this 3rd generation biofuel i.e. microalgae fuel production.

No. No. No. No.

Algal biofuels will not work.  Is not a technological problem - it is a matter of physics. 

Another paper of mine.

Raymond, your work discusses optimal algal growth in shallow ponds, but does growth have to be "optimized" when talking about harvesting from sources like wastewater?  Isn't the idea not to use more arable land for this, but to use sources which already have naturally occurring growth?  Also, algae growth is fairly rapid, wouldn't multiple harvests in the length of time you use as a "growing season" make more sense for a continuous operation model?

The trouble is that in my calculations I was trying to be generous.  Growth of a continuous optimalised culture is the best you can do - any others will give a lower figure. Semi-continuous culture is about the best that could be practically achieved and that would effectively translate into a down time of about 30%. Yield of batch cultures will be lower on a per day basis simply because productivity will not be optimum for most of the grow-out period so actual productivity on an annual basis would likely be 1/3 to 1/2 of my figures based on a continuous system. 

Useful biofuels from ponds (more energy out than put in) is nonsense on biophysical grounds but lets just suppose it was not. Where to grow massive algal culutures is quite problematic.  For the US about 1 million square km is needed - where is the spare flat land and the water and what to do with the waste stream?  There is also NIMBY.  Try and set up ponds of 1 square km or so anywhere and the local residents will stop it.  Fill in mangroves and saltmarshes? - you have got to be joking. Suppose after years of paperwork you get one approved, where are you going to put the other 999,999 needed?

It is all a silly delusion.  Those algal farms used to make Spirulina and Chlorella cosmic health pills seem very large but each farm does not even have a total of 1km2 of ponds and most of the ponds are empty at any one time (Google maps - I give coordinates of some of them in my papers so you can see them yourself).

Obviously plants. availability of plants are  more  in nature as compared to algae. algae is available only in certain area.

http://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/422/442-886/442-886_pdf.pdf